TW202023953A - Method for depositing metal oxide film in liquid environment - Google Patents

Abstract

A method for depositing a metal oxide film in a liquid environment, comprising steps of: (S1) dissolving an oxidizing agent in solvent with hydrogen bond to form a solution, and (S2) placing a substrate into the solution for performing a deposition reaction to deposit a metal oxide hydroxide film on the substrate, wherein the oxidizing agent is potassium permanganate, potassium chromate, or potassium dichromate, a reaction temperature of the deposition reaction ranges from 1 to 99 degrees Celsius, and a reaction pressure environment of the deposition reaction is an atmospheric pressure environment.

Description

Method for depositing metal oxide film in liquid phase environment

The present invention relates to a method for producing a metal oxide film, in particular to a method for electrolessly depositing a metal oxide film in a liquid phase environment.

Large-size ultra-thin multi-component deposition (<10nm) on flexible plastic substrates is very meaningful to engineers and scientists, but it is usually affected by island discontinuities and element separation, and cannot be performed by electroplating. Transition metal oxide films with uniform thickness and continuous coverage have proven to be indispensable in various modern devices and structures including flexible and wearable electronic devices.

Complete chemical and physical deposition (such as chemical vapor deposition, evaporation, sputtering, atomic layer deposition, etc.) requires high standard operating conditions (such as fine chemicals, high vacuum/energy consumption, expensive instruments, etc.), but the supply is limited The scale of production. Solutions such as processable deposition have emerged due to its low cost and easy operation to explore low temperature, large-scale manufacturing and complex 3D structures on plastic/soft material substrates with low thermal durability.

Many typical solution processable depositions (such as drop casting, sol-gel, spray/dip coating/spin coating, etc.) require pyrolysis to remove an organic residue and promote film adhesion. However, they are not suitable for amorphous/sub-crystalline Stable deposition and soft/flexible substrate. Electrodeposition can be considered as an alternative to avoid pyrolysis, but generally requires a highly conductive substrate. The disadvantage of pinhole formation is that it hinders the rapid deposition rate of ultra-thin coatings, and the uneven multi-element deposition due to the different deposition potentials of various elements also limits its control over the formation of active sites and electrocatalytic charge transport resistance.

Earth-rich transition metal oxide films with easy deposition are ideal candidates for effective oxygen evolution reaction (OER) at a reasonable cost. It is worth noting that some studies have shown that amorphous transition metal oxides, including the intermediate state existing in the electrocatalytic process, are more Have greater activity.

However, due to the thermal decomposition step that usually involves solution processable deposition, it is not suitable for flexible plastic substrates, and secondly, amorphous products cannot be obtained. Only a few examples of amorphous oxide coatings have been successfully reported, but their high resistivity can also cause difficulties in electrocatalysis

One object of the present invention is to provide a method for depositing metal oxide films in a liquid phase environment, which utilizes the liquid phase environment to deposit multiple metal oxide films on different substrates, so as to meet the demand for mass production.

To achieve the above objective, the present invention provides a method for depositing a metal oxide film in a liquid phase environment, which includes the steps of: (S1) dissolving an oxidant in a hydrogen-bonded solvent to form a solution; and (S2) A substrate is put into the solution to perform a deposition reaction, so that a metal oxide hydroxide film is deposited on the substrate; wherein the oxidant is potassium permanganate, potassium chromate or potassium dichromate, one of the deposition reactions The reaction temperature ranges from 1 to 99 degrees Celsius, and a reaction pressure environment for the deposition reaction is an atmospheric pressure environment.

In an embodiment of the present invention, in step (S1), a reducing agent and the oxidizing agent are mixed according to a molar ratio of a reducing agent to an oxidizing agent and dissolved in the hydrogen-bonded solvent to form the solution.

In an embodiment of the present invention, the reducing agent is selected from the group consisting of divalent cobalt compounds, divalent iron compounds, divalent nickel compounds, divalent manganese compounds, and first transition metal ion compounds.

In an embodiment of the present invention, one of the molar ratios of the reducing agent to the oxidizing agent ranges from 9:1 to 1:3.

In an embodiment of the present invention, in step (S1), an additive containing an anion is added to the solution, and the anion of the additive is selected from metal salt ions.

In an embodiment of the present invention, after step (S2), the method further includes the step of: (S3) subjecting the metal oxyhydroxide film to a calcining process in a calcining temperature range and a gas environment, To produce a metal oxide calcined film; wherein the calcining temperature range is 250 to 800 degrees Celsius.

In an embodiment of the present invention, the gas in the gas environment is in the atmospheric environment air.

In an embodiment of the present invention, the gas in the gas environment is argon, nitrogen or oxygen.

In an embodiment of the present invention, a duration of the calcining process ranges from 1 to 12 hours.

In an embodiment of the present invention, the substrate is selected from silicon crystal materials, carbohydrates, glass materials, foamed nickel, metal materials, metal oxides, organics, high molecular polymers, carbon materials and glassy carbon electrode materials. A group formed by.

In an embodiment of the present invention, the hydrogen-bonded solvent is deionized water with an impedance value of 18.2 megohm ‧ cm.

S1‧‧‧Mixing steps

S2‧‧‧Deposition step

S3‧‧‧Caking steps

Figure 1: A schematic flow diagram of a method for depositing a metal oxide film in a liquid phase environment according to an embodiment of the present invention.

Figures 2 to 10: Schematic diagrams (1) to (9) of the deposition procedure and identification of CMOH acetate according to an embodiment of the present invention; where: Figure 2 is the immersion of a transparent FTO substrate in Co(OAc) ₂ and KMnO ₄ Figure 3 shows the FTO immersion for 15 minutes; Figure 4 shows the removal of the FTO substrate after complete deposition (darker contrast area). The processes of Figures 2 to 4 proceed in sequence; Figure 5 is SEM Image; Figure 6 is the AFM data of the thin film; Figure 7 is the grazing angle XRD pattern of thin and thick CMOH deposited by Co(OAc) ₂ and CoSO ₄ respectively; Figure 8 is the HR-TEM image of CMOH Figure 9 is the HR-TEM image of CMO after annealing at 500°C; Figure 10 is the TEM image of CMOH after 1000 OER test cycles. Among them, the illustrations in Figures 8 to 10 are the corresponding Fourier transform modes of the CMOH region.

Figures 11 to 18: Schematic diagrams (1) to (8) of deposition conditions testing of an embodiment of the present invention; among them: Figure 11 is a photo of simultaneous deposition on six separate FTO substrates; Figure 12 is from Figure 11 shows multiple products of six coated FTO films with uniform coating comparison; Figure 13 is a schematic diagram of large-scale deposition of CMOH in a highly ordered array on a 100cm ² FTO film; Figure 14 The picture shows the CMOH deposition (RT) at room temperature to 100 degrees; picture 15 is the UV-vis spectral transparency diagram of the CMOH coating shown in picture 14; picture 16 is through Scotch tape The CMOH adhesion test picture after peeling off for more than 100 cycles; picture 17 is the cross-sectional profile picture of the CMOH coating on the silicon (Si) array trench; pictures 18a to 18f are the test pictures of any substrate deposition; Among them, picture 18a is CMOH coated on 3D porous Ni foam, and compares bare nickel (Ni) foam; picture 18b is uniformly deposited on the cylindrical surface of the spiral pair; picture 18c is CMOH coating, passed The mask transfers the large-scale and complex pattern to a 100cm ² glass substrate; picture 18d shows the CMOH coated with PET, and no obvious cracks are observed after 100 cycles of bending and folding; picture 18e shows CMOH-coated curved wood Surface; Figure 18f shows that CMOH is coated on the metal surface of copper (Cu) foil.

Figures 19 to 24: Schematic diagrams (1) to (6) of the spectrum and distribution of CMOH according to an embodiment of the present invention; among them: Figure 19 is a 2p XPS data map of Co for uncalcined coating; Figure 20 shows the XPS data of 2p for Mn with unsintered coating; Figure 21 shows the XPS data of 1s for O with unsintered coating; Figure 22 shows the absorption edge of Co's K layer XAS spectrum; Figure 23 is the XAS spectrum of the absorption edge of the K layer of Mn; Figure 24 is the vertical component distribution of the film.

Figures 25 to 29 are schematic diagrams (1) to (5) of film growth of QCM with different precursor formulations according to an embodiment of the present invention, in which all tests are performed under the same preparation conditions; Among them: Figure 25 is a comparison between cobalt or manganese precursors only and the mixing conditions of the two precursors; Figure 26 is a comparison of cobalt precursors with different anions; Figure 27 is the effect of other coordination groups on the growth of CMOH Figure; Figure 28 is a cross-sectional SEM image and EDXS distribution map of CMOH prepared by CoSO4; Figure 29 is multiple CVs of cobalt precursors with different anions and coordination groups (Cyclic Fuan method), Explore its redox behavior.

Figures 30 to 33 are schematic diagrams (1) to (4) of research and analysis of MD simulation of CMOH growth according to an embodiment of the present invention; among them: MD simulation of CMOH growth in Figure 30 (a) to ( f), where (a) and (b) are diagrams of the simulation units of the sulfate system and the acetate system. After connection, the simulation is performed to remove all unreacted Co ²⁺ and MnO ₄ ^- ions, and the counter ion ( OAc ^-, sO ₄ ^2-) and a solvent (H ₂ O) to make (MnO ₄₎ -Co complex clearly presented; (c) a reaction vessel (a) and (b) the colloidal precipitate (MnO4) -Co complex enlarged view; (d) in (e) sulfate system and (f) acetate system deposited on the surface of the SnO ₂ substrate connected (MnO ₄ )-Co composite (CMOH film) Enlarged view; Figure 31 is a diagram of the Co-O-Mn bond numbers of the colloidal complex analyzed from the reaction tanks in (a) and (b) in Figure 30; Figure 32 is a diagram from (e) in Figure 30 ) And (f) the Co-O-Mn bond number diagram of the surface-linked complexes analyzed; Figure 33 shows the use of acetate (acetate O) and sulfate (sulfate O) ion O atoms to Co ^{2 +} Ion is analyzed by RDF.

Figures 34 to 39 are schematic diagrams (1) to (6) of the electrocatalytic oxygen evolution of the CMOH coating on the FTO of an embodiment of the present invention; among them: Figure 34 shows the presence of amorphous CMOH and calcined CMO with standard RuO2 Comparison under 0.1M KOH, where the illustration is an enlarged view; Figure 35 is a comparison of the Tafo diagrams of the materials in Figure 34; Figure 36 is the current density-potential curve of CMOH coatings prepared with different Co-Mn ratios; Figure 37 is the current density-time diagram, with To compare the stability; Figure 38 is a comparison diagram of stability between amorphous and crystalline coatings; Figure 39 is a comparison diagram of different cobalt precursor coatings.

Figures 40 to 43 are comparison diagrams (1) to (4) of current density-potential curves of amorphous CMOH coated on a typical substrate of OER according to an embodiment of the present invention; among them: Figure 40 is a Ni foam Comparison diagram of current density-potential curves; Picture 41 is a diagram of current density-potential curve comparison of Cu foil; Picture 42 is a diagram of current density-potential curve comparison of carbon cloth; Picture 43 is the current of glassy carbon electrode (GCE) Comparison of density-potential curves.

Figures 44 to 47 are schematic diagrams (1) to (4) of EDXS results of CMOH acetate according to an embodiment of the present invention; among them: Figure 44 is an SEM image of CMOH, in which the selected area is highlighted with a dotted line for element Distribution analysis; Figure 45 shows the EDXS results showing the signals of Co and Mn, atomic ratio Co/Mn=3.08; Figures 46 and 47 respectively show the analysis results of the element distribution of Co and Mn corresponding to the dotted area in Figure 44.

Figure 48 shows the Raman spectrum of CMOH according to an embodiment of the present invention showing a broad band at 599 cm ^-1 , indicating the presence of amorphous cobalt oxide, and showing the Raman signal of crystalline Co ₃ O ₄ for comparison.

Figure 49 shows the GIXRD pattern of CMOH sulfate after calcining at 500°C in an embodiment of the present invention, which shows that it corresponds to the Co ₃ O ₄ phase.

Figure 50 is an embodiment of the present invention to identify the CMOH cross-section under HR-TEM. See also Figure 8 in this article. The I label in the film area shows most of the EDXS signals of Co and Mn. The upper left illustration shows that it corresponds to "I" FFT mode with amorphous characteristics. The area marked by "II" of FTO shows strong Sn signal, corresponding to high-resolution TEM image (Bottom right inset) shows the lattice of (110) corresponding to FTO, and the Ga signal is attributed to the Ga ion beam in FIB.

Figure 51 is an example of the AFM results of acetate CMOH grown at 60 minutes, showing that the thickness of the film prepared at 80°C is about 11 nanometers (nm).

Figures 52 to 54 are the XPS data of crystalline CMO acetate after annealing at 500°C according to an embodiment of the present invention; among them: Figure 52 is the XPS data of 2p of Co; Figure 53 is the XPS data of 2p of Mn Figure; Figure 54 shows the XPS data of O's 1s.

Figures 55 to 56 are photos of only Co(OAc) ₂ and KMnO ₄ deposited on non-metallic substrates of wood (Figure 55) and PET (Figure 56) according to an embodiment of the present invention. The arrows in Figure 55 indicate the boundary between the deposited and non-deposited regions for comparison. These results indicate that only Co(OAc) 2 deposition does not form a thin film, while only KMnO ₄ deposition can observe a thin coating.

Figure 57 is a Faraday efficiency test of an acetate CMOH film according to an embodiment of the present invention. After 4 hours of oxygen release, the Faraday efficiency of the film is close to 100%.

Figure 58 is a Tafel diagram of acetate CMOH samples prepared with different Co/Mn precursor ratios at 80°C for 15 minutes in an embodiment of the present invention. The Tafel slopes are summarized in the table of the same figure. .

Figure 59 shows the XPS data of CMOH _7/1 cobalt (Co/Mn precursor ratio is 7/1) showing that it is compared with CMOH _3/1 (Co/Mn precursor ratio is 3/1) The high similarity indicates that Co ^{3+ is} still the main type of CMOH film.

Figure 60 shows the ultraviolet-visible spectra of CMOH acetate deposited at 80°C with different deposition times in an embodiment of the present invention.

Figure 61 is a calibration curve corresponding to Figure 60 with absorbance at 550 nm.

Figures 62 to 65 show the identification of amorphous iron manganese oxide and ternary iron cobalt manganese oxide coatings on SiO ₂ /Si wafers in an embodiment of the present invention. The SEM results show that these two coatings ( The iron-manganese oxide in Figure 62 and the iron-cobalt-manganese oxide in Figure 63 are highly smooth and crack-free; their EDXS results are shown in Figures 64 and 65, respectively, and the corresponding Fe : Mn=2.39:1 and Fe:Co:Mn=1:2.11:0.77; the illustrations in Figures 62 and 63 show photographs of the appearance of the film on the FTO.

Figures 66a, 66b, and 66c are photographs of the sample results of a calcined metal oxide film according to an embodiment of the present invention at 400, 600, and 800 degrees Celsius, respectively.

Figures 67a and 67b are photographs of the results of a sample of different organic polymers on a substrate according to an embodiment of the present invention.

Figures 68a to 68c are photographs of the results of samples with a substrate of different organic substances according to an embodiment of the present invention.

Figures 69a to 69c are photographs of the results of samples with a substrate of different carbon materials according to an embodiment of the present invention.

Figure 70 is a photograph of the results of a sample with a carbohydrate base material according to an embodiment of the present invention.

In order to make the above and other objectives, features, and advantages of the present invention more obvious and understandable, the following will specifically cite the preferred embodiments of the present invention, together with the accompanying drawings, and describe in detail as follows. Furthermore, the directional terms mentioned in the present invention, such as up, down, top, bottom, front, back, left, right, inside, outside, side, surrounding, center, horizontal, horizontal, vertical, vertical, axial, The radial direction, the uppermost layer or the lowermost layer, etc., are only the direction of reference to the attached drawings. Therefore, the directional terms used are used to describe and understand the present invention, rather than to limit the present invention.

Please refer to Fig. 1, the method for depositing a metal oxide film in a liquid phase environment according to an embodiment of the present invention is a method for producing a metal oxide film, which may include the following steps: (S1) dissolving an oxidant in a container Hydrogen bond solvent to form a solution; and (S2) placing a substrate into the solution to perform a deposition reaction, so that a thin film of metal oxide hydroxide is deposited on the substrate; wherein the oxidizing agent is potassium permanganate ( KMnO ₄ ), potassium chromate (K ₂ CrO ₄ ) or potassium dichromate (K ₂ Cr ₂ O ₇ ), a reaction temperature range of the deposition reaction is 1 to 99 degrees Celsius (°C), one of the deposition reactions The reaction pressure environment is an atmospheric pressure environment. The following examples illustrate some embodiments of the above method of the present invention, but are not limited thereto.

For example, the hydrogen-bonded solvent can be water or its analogues, such as alcohol. It can be understood that water and alcohol have hydrogen bonds and are mutually soluble, and the boiling point of water and alcohol is slightly There are differences (for example, water is about 100°C, and alcohol is about 78.4°C). The choice of other available solvents can be understood by those with ordinary knowledge in the relevant technical field, and will not be repeated here. In the following, only water is used as an example to illustrate the implementation in an aqueous environment. For example, the water can also be selected as deionized (DI) water with an impedance value of 18.2 megohm ‧ cm to promote the quality of the reaction , But not limited to this.

In one embodiment, in step (S1), an additive containing an anion is added to the solution. The anion of the additive may be selected from metal salt ions. For example, the metal may include Co, Ni, Fe, Mn, V, Ti, Cr, Cu, Zn, the salts can be nitrate salts, sulfate salts, acetate salts, halogen salts, etc. of the aforementioned metals; specifically, the anions of the additives can be selected as acetate, sulfate , Sulfite, nitrate, halogen anion, thiosulfate, bisulfate, sulfite, bisulfite, persulfate, arsenate, arsenite, borate, bicarbonate ion, carbonate , Hydroxide, perchlorate, chlorite, hypochlorite, chlorate, nitrite, acetylacetonate or ethylenediaminetetraacetic acid and other anions, but not limited to this. In this way, with different concentrations of the solution and different film growth times (such as 5 minutes to more than 24 hours), it can be used to control the film thickness (<10 nm), so that the producer can control different film thicknesses and growth rates.

In one embodiment, in step (S1), a reducing agent and the oxidizing agent may be mixed according to a molar ratio of the reducing agent and the oxidizing agent and dissolved in the hydrogen-bonded solvent (such as water) to form the solution For example: the reducing agent can be selected from divalent cobalt (Co ²⁺ ) compounds, divalent iron (Fe ²⁺ ) compounds, divalent nickel (Ni ²⁺ ) compounds, and divalent manganese (Mn ²⁺ ) compounds And the first transition metal ion compound; a range of the molar ratio of the reducing agent to the oxidizing agent can be selected from 9:1 to 1:3.

For example, the divalent cobalt compound can be selected from cobalt acetate (Co(CH ₃ COO) ₂ ), cobalt sulfate (CoSO ₄ ), cobalt nitrate (Co(NO ₃ ) ₂ ), cobalt chloride (CoCl ₂ ) Or cobalt acetone (C ₁₅ H ₂₁ CoO ₆ ); the divalent iron compound can be selected from ferrous acetate (Fe(CH ₃ COO) ₂ ), ferrous sulfate (FeSO ₄ ) or ferrous nitrate (Fe(NO ₃ ) ₂ ); the divalent nickel compound can be selected from nickel sulfate (NiSO ₄ ), nickel nitrate (Ni(NO ₃ ) ₂ ) or nickel chloride (NiCl ₂ ); the divalent manganese compound can be selected from manganese acetate ( Mn(CH ₃ COO) ₂ ) or manganese sulfate (MnSO ₄ ); the first transition metal ion compound can be selected from vanadium, titanium, chromium, copper, and zinc ions, but is not limited thereto.

In one embodiment, a reaction time of the deposition reaction can range from 5 minutes (min.) to 24 hours (hr.), and the reaction time can also be extended indefinitely as required.

The following further examples illustrate and show some implementation aspects and test results of the foregoing method embodiments of the present invention, but are not limited thereto.

In order to increase the inherent conductivity and reduce the charge transport barrier (barrier), it is a challenging but effective strategy to realize a multi-component metal oxide coating with mixed valence and uniform distribution to enhance the electronic jumping process and thus the conductivity . Therefore, ultra-thin, highly continuously deposited amorphous multi-component metal oxides are the best and ideal model for OER electrocatalysts. A simple and scalable method will be reported here to achieve ultra-thin amorphous multi-component metal oxide coatings on any substrate (including flexible plastics) under environmental conditions. The ultra-thin coating has high continuity and element uniformity on the centimeter-level surface, and the thickness is 6 to 10 nanometers (nm). Since KMnO ₄ is a strong dyeing agent on various surfaces (such as fabrics, plastics, and even human skin), this property of KMnO ₄ can be used to achieve strong film adhesion on any substrate without pyrolysis treatment. The interaction of Co(OAc) ₂ and KMnO ₄ leads to self-limited redox-coupled film growth (self-limited redox-coupled film growth) dominated by a variety of ligand coordination effects. For electrocatalytic OER applications, amorphous CMOH shows excellent activity and durability to its crystalline counterpart and benchmark RuO ₂ . The following examples illustrate the experimental part.

Preparation of CMOH film:

The reaction mixture (18.2) MU cm) for deposition is prepared by dissolving the cobalt precursors (ie Co(OAc) ₂ , CoSO ₄ and Co(NO ₃ ) ₂ ) and KMnO ₄ in deionized (DI) water, typically The Co/Mn Mohr ratio is 3/1. This process demonstration example uses fluorine-doped tin oxide (FTO) glass. The deposition area can usually be patterned by photoresist or mask masking. It is also deposited on copper foil, Ni foam, carbon cloth, glass carbon electrode (GCE), SiO ₂ /Si wafer and glass. In a typical deposition, the substrate is placed in a reaction mixture of KMnO ₄ and Co(OAc) ₂ and stirred at 80° C. and 500 rpm for 15 minutes. The subscript of CMOH represents the anion of the cobalt precursor used in the deposition. CMOH without a specific subscript refers to Co(OAc) ₂ deposition. After deposition, the coating was rinsed with deionized water, and the nail-polish mask was removed with acetone. CMOH annealing was performed at 500° C. under argon for 1 hour to obtain a cobalt manganese oxide (CMO) film. The temperature-dependent CMOH deposition was performed at room temperature, 50°C, 80°C, and 95°C, respectively.

Prepare reaction mixtures with different Co/Mn molar ratios (Co:Mn=1:3, 1:1, 3:1, 5:1, 7:1, and 9:1). For the redox deposition of the iron manganese oxide coating, Fe(OAc) ₂ (Acros Organics) was used as the precursor, and the iron (Fe)/manganese (Mn) molar ratio in the reaction mixture was 3/1. In the synthesis of the ternary metal oxide film, Co(OAc) ₂ , Fe(OAc) ₂ and KMnO ₄ are mixed with the ratio of iron (Fe)/cobalt (Co)/manganese (Mn) of 1/2/1.

Electrochemical measurement:

其中f₀是QCM的基本共振頻率，ρ _a 是石英密度(2.648g cm^-3)，G _a 是石英晶體剪切模量(2.947×10¹¹g cm^-1 s^-2)，A是QCM的有效電極面積。對於所有QCM測量，將Au/石英基板保持在去離子水中直至頻率達到平衡。之後，Co與Mn前驅物是小心地注入系統以引發塗層生長。還在QCM中測試純Co(OAc)₂和KMnO₄作為對照樣本。研究抗衡離子、鈷前驅物的影響Co(OAc)₂、CoSO₄及Co(NO₃)₂的不同陰離子均為在相同的沉積條件下使用。醋酸鈉(Acros Organics)被用來作為醋酸根陰離子的來源。 Use the three-electrode system on the CHI 614D electrochemical analyzer to obtain electrochemical results. FTO glass with CMOH coating is used as the working electrode, in which a platinum (Pt) plate and mercury (Hg)/HgO (mercury oxide) are used as the counter and reference electrodes, respectively. The OER activity was evaluated by linear sweep voltammetry (LSV), and the sweep rate was 5 mVs ^-1 at 0.1 M KOH. All overpotentials (η) are recorded at 10 mA cm ^-2 . The potential provided in this article is based on the reversible hydrogen electrode (RHE), following the equation: ERHE=E _Hg/HgO +0.098+0.059×pH (1) Use a gas chromatograph (GC) equipped with a thermal conductivity detector (TCD) Obtain the Faraday efficiency (FE) to analyze the amount of molecular oxygen. FE is obtained from the ratio of O ₂ measured value/O ₂ theoretical value, where the theoretical value of O ₂ is integrated with the current time (it) curve. A quartz crystal microbalance (QCM/CHI 401) is used to monitor the in situ growth of the CMOH coating at room temperature. The fundamental resonance frequency of QCM is 8 megahertz (MHz). Using the Sauerbrey equation to calculate the weight change is:

Where f ₀ is the fundamental resonance frequency of QCM, ρ _a is the quartz density (2.648g cm ^-3 ), G _a is the quartz crystal shear modulus (2.947×10 ¹¹ g cm ^-1 s ^-2 ), and A is the QCM Effective electrode area. For all QCM measurements, keep the Au/quartz substrate in deionized water until the frequency reaches equilibrium. Afterwards, Co and Mn precursors are carefully injected into the system to initiate coating growth. Pure Co(OAc) ₂ and KMnO _{4 were} also tested in QCM as control samples. Study the influence of counterion and cobalt precursor Co(OAc) ₂ , CoSO ₄ and Co(NO ₃ ) ₂ different anions are all used under the same deposition conditions. Sodium acetate (Acros Organics) is used as the source of acetate anions.

Characteristic description:

Scanning electron microscope (SEM) images were obtained using FEI Inspect F50 and Zeiss Supra 55 Gemini with an acceleration voltage of 10-20 kV. X-ray photoelectron spectroscopy (XPS) measurement was performed on the PHI 5000 virtual probe (VersaProbe). The film composition distribution was studied by Arsputtering XPS, and the removal rate was 3 nanometers (nm) per minute (min) ^-1 . Grazing incidence X-ray diffraction (GIXRD) is used to identify thin CMOH coatings with a glancing angle of 1 degree on a Bruker D8 Advance diffractometer with an X-ray source of CuKα. FEI EO Tecnai F20 G2 was used to collect field emission transmission electron microscope (FE-TEM) images at 120 kV. A focused ion beam (FIB) was used to prepare the TEM foil using SMI 3050. First, the CMOH/FTO sample is coated with platinum (Pt) and subsequent carbon layers, and then ion beam cutting and thinning are performed. The samples were analyzed by energy dispersive X-ray spectroscopy (EDXS) under SEM and TEM. Raman spectra were obtained using a WITec confocal Raman microscope with a 532nm wavelength laser source. The CMOH sample was deposited on a gold substrate to enhance the Raman signal through surface enhanced Raman scattering. X-ray absorption spectroscopy (XAS) was collected and transmitted in the 17C1 mode of the National Synchrotron Radiation Research Center (NSRRC) in Taiwan. The roughness of the CMOH film was analyzed by AFM (Bruker Dimension Edge) in contact mode. Conduct conductivity measurement using a four-point probe on Quatek 5601Y Sheet Resistivity Meter. A Jasco V-630 UV visible spectrometer was used to obtain the UV-vis spectrum. PerkinElmer ELAN 6100 DRC Plus was used for inductively coupled plasma mass spectrometry (ICP-MS) measurement for elemental analysis. In order to determine the Co/Mn ratio, the CMOH sample was dissolved in a solution consisting of HNO ₃ (60%) and H ₂ O ₂ (35%) in a volume ratio of 2:1. In order to study the problem of element dissolution, the electrolyte solution (0.1M KOH) was scanned by OER cycles for 10,000 times, and then the content of Co and Mn was determined by ICP-MS.

Simulation of CMOH deposition behavior:

A molecular dynamics (MD) simulation was performed to study the growth of CMOH film on the FTO surface. Study the deposition of Co(OAc) ₂ and CoSO ₄ . In acetate form the MD system comprises a reaction vessel 1500 parts by Co ^2+, 3000 parts of OAc ^-, 500 parts of MnO ₄ ^-, 500 parts 2000 parts of K ⁺ and H ₂ O (solvent), and the composition systems include the sulfate 1500 parts of Co ^2+, 1500 parts of SO ₄ ^2+, 500 parts of MnO ₄ ^-, 500 parts 2000 parts of K ⁺ and H ₂ O. A crystalline tin oxide (SnO ₂ , 100×100×8Å ³ ) substrate was built to mimic FTO glass for deposition. All simulations are calculated using Material Studio software. The COMPASS force field and NVT ensemble (ensemble) are suitable for simulation. The density of the liquid phase in each system is set to 1.0 g cm ^-3 . The initial temperature of the MD simulation is 298K until thermal equilibrium is reached; then the temperature is further increased to 353K. This temperature setting corresponds to the actual reaction temperature. Between the Co ²⁺ and O (i.e., (MnO ₄₎ -Co complex) ^- Analysis on the surface of SnO ₂ Co ²⁺ and Mn ⁷⁺ (in MnO ₄ ^-) is the distance between the O, and MnO ₄ the distance. It is believed that the distance between the metal cation and O shorter than 3.0 is due to the formation of bonds to generate precipitates. This connection process repeats five times every 75 picoseconds (picosecond). The following examples illustrate the results and discussion.

Deposition and identification of CMOH coating:

Under multiple environmental conditions, a solution-treated binary CMOH film is deposited in a single-step redox process. The aqueous reaction mixture is prepared by dissolving various Co(II) precursors with KMnO ₄ (as a metal-containing oxidizing agent) without adding any additives (such as organic solvents, surfactants, polymers, etc.). In order to clearly demonstrate the thin film deposition, transparent FTO was selected as the substrate, as shown in Figures 2-10. The one-step CMOH deposition produced by the Co(OAc) ₂ precursor (ie, CMOH acetate) can be completed by immersing the original FTO in the reaction mixture for a period of time, and then taking it out after complete deposition (Figures 2 to 4) . Neither an inert environment nor fine operation is required. As demonstrated by EDXS, the uniform distribution of cobalt and manganese can achieve uniform dull contrast (Figures 44 to 47). ICPMS analysis confirmed that the composition ratio of Co/Mn=2.92 (as shown in Table 1), which is similar to the selected area composition of 3.08 obtained by EDXS. Compared with other solution-based depositions, homogeneous binary element distribution usually requires specific reaction conditions due to potential mismatches in properties (such as hydrolysis rate, K _sp constant, thermal stability, etc.) between precursors. The fixed electron exchange stoichiometry that relies on redox synthesis provides reliable composition uniformity for the deposition of multiple precursors. Unlike typical dip coating or polymer assisted deposition, the method disclosed herein does not require thermal annealing to eliminate organic/polymer components and consolidate coating adhesion, thereby preserving amorphous characteristics. The SEM image of the CMOH thin film deposited on the SiO ₂ wafer (Figure 5) shows a smooth and highly continuous coating with a root mean square (RMS) value of 3.16 nm obtained using AFM (No. 6 Figure). The GIXRD patterns of samples deposited with Co(OAc) ₂ and CoSO ₄ precursors (CMOH sulfate) showed no diffraction peaks, indicating the amorphous characteristics of the CMOH coating (Figure 7). The Raman spectra of CMOH acetate shows a broad band at 599 cm (cm) ^-1 (Figure 48), which is also consistent with the presence of amorphous cobalt oxide. The signal of amorphous manganese oxide is due to their relative comparison. Small and difficult to identify (<25%), significant peak broadening, and Raman wavenumber similar to cobalt oxide. By annealing the sulfate CMOH at 500°C for 1 hour, the coating appeared to correspond to the crystals of the spinel Co ₃ O ₄ phase, representing cobalt manganese oxide (CMO sulfate) (Figure 49). To further verify the film crystallinity, the focused ion beam (FIB) cutting of acetate CMOH was identified by high-resolution TEM. The TEM image of the uncalcined CMOH acetate clearly shows the amorphous features without any ordered lattice fringes (Figures 8 and 50), which is consistent with the amorphous deposition shown in Figure 7. The cross-section of the coating is highly continuous and without pinholes/voids, and the main thickness is 6-10nm, which is equivalent to the thickness of 11nm under AFM (Figure 51). At this thickness, the multiple coatings reported to be manufactured by physical deposition are still discontinuous. The annealed acetate CMO film has a lattice with a d-spacing of 0.244 nm, corresponding to the (311) plane of the spinel Co ₃ O ₄ (Figure 9). The conductivity of the film is summarized in Table 2, which indicates that the CMOH coating exhibits a sheet resistance in the range of 7.4×10 ⁷ to 13.0×10 ⁷ (Ω□ ^-1 , ohms per square). Annealed CMO generally shows a smaller sheet resistance (as low as 0.469×10 ⁷ ohms per square) than amorphous CMOH. Sulfate CMOH is slightly more conductive than acetate CMOH. The effect of different Co/Mn ratios on the sheet resistance is not significant. The controlled manganese oxide coating sample had a sheet resistance exceeding the measurement limit, indicating that a uniform binary oxide coating exhibited a sheet resistance much lower than a single oxide.

Large-scale manufacturing and performance of CMOH:

Through simple operating procedures, an attempt was made to achieve high-volume manufacturing by simultaneously impregnating multiple substrates in a batch of reaction mixtures. Figure 11 shows the success of parallel deposition on FTO to produce six separate, uniform and well-defined CMOH acetate coatings, which are more effective than traditional deposition (such as spin coating). In addition, shape and size specific deposition can be controlled by masking technology. Figure 13 shows the realization of a large 10×10 cm ² square deposition array transferred from a resin-based mask. All map units of CMOH have clear definitions in terms of shape and separation distance, and show highly similar contrast. Scalable and throughput redox deposition is very practical for mass production.

It is worth noting that the coated CMOH also shows high visible light transparency. By changing the deposition temperature (Figure 14), as the temperature increases, the coating contrast becomes darker, indicating that a thicker coating is formed. The transparency (at 550nm) of CMOH deposited at room temperature, 50°C, 80°C and 95°C was measured to be 99.2%, 98.4%, 97.4% and 95.2%, respectively (Figure 15). CMOH at room temperature forms a thin, uniform, almost invisible coating (see the arrow in Figure 14). Since binary metal oxides have recently received attention as materials for transparent OER active films, this property has become relevant. Film adhesion is a key issue, especially for low temperature deposition. As shown in Figure 16, Scotch-tape was used to perform a 100-cycle peel test on CMOH. No obvious film peeling or breakage was observed. This strong adhesion is comparable to annealed crystalline CMO samples, which allows CMOH to be used directly in amorphous form. The step coverage study shows that the CMOH coating can be deposited along the top, sidewalls and bottom of the SiO ₂ trench with thicknesses of 9.1nm, 9.5nm and 10.1nm respectively (Figure 17); therefore, it can be expected that the 3D complex structure and porous Strongly adhered uniform CMOH deposition on the tunnel. As shown in Figures 18a to 18f, the deposition of CMOH on complex 3D structures (Ni foam) and cylindrical materials (spiral pairs) is further successfully demonstrated. On different types of surfaces, including hard glass, soft plastics (polyethylene terephthalate, PET), wood and metal foil (Cu), CMOH deposition shows strong adhesion and high uniformity (18a) To 18f). In particular, after 100 cycles of testing under 180° folding, the coating on PET can completely tolerate bending strain without obvious film breakage, and has excellent adhesion and mechanical properties.

Redox interaction:

In order to verify the basic principle of CMOH formation, the oxidation state of cobalt and manganese was studied. In the XPS spectrum (Figure 19), the binding energy of Co 2p _1/2 at 796.2eV, the binding energy of 2p _3/2 at 781.1eV and the satellite peak at 790.8eV show the presence of Co(III). The XPS data also shows that the signals of Mn 2p _3/2 and 2p _1/2 are 641.8 and 654.2 eV, respectively, and Mn ³⁺ and Mn ^{4+ are} almost indistinguishable (Figure 20). In the O 1s spectrum, a strong hydroxide signal can be observed at 532.0 eV, and a weak signal of O ^2- at 530.0 eV (Figure 21), showing a similar ratio to the metal oxyhydroxide species. After the film is annealed at 500°C, the hydroxide signal is significantly reduced due to the conversion of amorphous oxyhydroxide to crystalline oxide, while the O ^2- signal is much stronger (Figures 52 to 54). Therefore, the presence of Co(III) and hydroxide/oxide signals is expressed as CoOOH. Further conduct X-ray near edge structure studies of CMOH to confirm the oxidation states of Co and Mn. The K-edge signal of Co (Figure 22) was observed at 7728.6eV, which corresponds to the reported octahedral Co(III) at 7729eV, which is further consistent with the XPS data. The K-layer absorption edge spectrum of Mn (Figure 23) shows a peak at 6563 eV, which is almost the same as the peak of MnO ₂ at 6562.2 eV, instead of Mn(III) at 6554.2 eV. Therefore, the results clearly confirm the existence of Co ³⁺ and Mn ⁴⁺ in the CMOH coating. Since elemental analysis highly agrees that the ideal redox stoichiometry between Co ²⁺ and Mn ⁷⁺ is 3:1 (that is, 2.86 to 3.03, see Table 1), it is obvious that the redox-driven CMOH deposition can be expressed as Co _1-x Mn _3x/4 OOH. Thus, the net redox equation is as _{^{follows: 9Co 2+ (aq) + 3MnO}} 4 - (aq) 14H 2 O (1) → Co 9 Mn 3 O 26 H 13 (s) + 15H + (aq) (3) The film composition distribution of CMOH obtained by XPS (Figure 24) shows a uniform Co:Mn Mohr ratio from top to bottom (ie, an average of 3.30), which corresponds to the redox coupled film growth, as shown in equation (3 ) Shown. The depth profile study shows that the residual signal of sulfur and carbon is less than 0.01%.

Coating formation process:

QCM was performed to monitor the in-situ growth load quality and film growth of CMOH on gold (Au)/quartz substrate. First, a control experiment of deposition was performed with the precursor Co(OAc) ₂ or KMnO ₄ . The distribution graph in Fig. 25 shows that the mass load does not increase in the case of Co(OAc) _2- only, while the obvious film formation can be observed in the case of KMnO ₄ only. In addition, deposition tests on carbon-based and transparent substrates also show that only KMnO ₄ deposition can contribute to the formation of thin films (see Figures 55 to 56). This further confirms that the strong oxidation dyeing ability of KMnO ₄ is essential for film formation and fixation on the substrate. For the test combining Co(OAc) ₂ and KMnO ₄ . The QCM depiction indicates that the mass load is faster and larger than the previous two control experiments, verifying the redox nucleation.

Since Co ²⁺ is a mixture of species preponderance of reaction with the matrix-anchored ₄ MnO ^- attraction between the anion and cation may facilitate reduction of Co ²⁺ site interact to form an oxide coating on the substrate surface CMOH. Although there have been reports on the preparation of cobalt oxyhydroxide (such as the interaction of Co ²⁺ and S ₂ O ₈ ^2- with CoOOH) through a redox route, few people have realized their film deposition. Through the redox interaction with KMnO ₄ , the successful incorporation of cobalt into the film was revealed for the first time. Theoretically, each Mn ⁷⁺ will directly transfer the charge to three adjacent Co ²⁺ ions, so that it is possible to build an interconnection network of multiple Co atoms and a Mn through oxygen bridge bonding. As a result, this network-like nucleation may facilitate the formation of continuous coatings, even at ultra-thin scales of a few nanometers, rather than island-like discontinuous depositions often observed in physical vapor deposition. Therefore, it is proposed that KMnO ₄ plays a dual role of surface anchoring oxidant and cobalt-fixing agent in the process of binary oxide deposition.

Oxide deposition process:

The influence of precursor anion on deposition In order to study the control parameters of film thickness, it is worth noting that the film growth is highly dependent on the counterion of the cobalt precursor. Under the same conditions, as shown in Figure 26, the CoSO ₄ and Co(NO ₃ ) ₂ precursors show a general trend that the thickness of CMOH is proportional to the deposition time. They deposition rate (CoSO ₄ to _{^{0.059mg min -1, Co (NO 3}} ) 2 was 0.086mg min ^-1) ratio of _{Co (OAc) 2- (0.0097mg min} -1) 6-9 times faster. In fact, CoSO ₄ and Co(NO ₃ ) ₂ deposition can continue for more than a few hours to produce thicker coatings. On the other hand, Co(OAc) _2- deposition grows linearly in the first 50 minutes and then saturates at 60 minutes, with a maximum load mass of 2.97 mg cm ^-2 (Figure 26). This self-limiting phenomenon was also observed at different deposition temperatures of CMOH acetate. The results clearly show that the resulting deposition thickness varies according to the precursor anion. As shown in Figure 28, the cross-sectional SEM image of CMOH sulfate was deposited for 2 hours, which is characterized by a uniform element distribution with a thickness of 180 nm, without cracks or pinholes/voids. Together with the ultra-thin thickness of CMOH acetate, the thickness of the film can be controlled from a few nanometers to sub-microns through the precursor anion. In order to reduce the electrocatalytic interface barrier, the Co(OAc) ₂ deposition method was used to prepare ultra-thin CMOH acetate for later OER research. In order to further study the influence of anions, a control experiment was conducted by adding acetate ions to the CoSO ₄ deposition (Figure 27). Adding two equivalents of acetate ions, the amount of which is equivalent to the amount of Co(OAc) ₂ , produces almost the same saturation time and coating quality as Co(OAc) ₂ deposition. However, the addition of an acetate ion equivalent, which corresponds to half of Co(OAc) ₂ , appeared to be similar to CoSO _4- deposition but saturation was not observed. In addition, the load mass is located between CoSO ₄ and Co(OAc) ₂ deposition. These phenomena clearly indicate that self-limiting film growth is due to the presence of acetate anions. The film growth inhibition of the combination of Fe ₂ (SO ₄ ) ₃ and Ni(OAc) ₂ anions was observed. In fact, acetate anion can be used as a buffer to affect pH conditions and deposition. Their research on pH changes is partially valid, but a comprehensive understanding of the saturated growth of binary Fe-Ni oxides is still uncertain. Since the acetate anion has a stronger intrinsic coordination ability than the other two, the coordination effect of the coordination group is most likely to rationalize the anion influence. In order to verify the coordination effect, the hexadentate ligand of ethylenediaminetetraacetic acid (EDTA) was added as a stronger ligand than acetic acid for comparison. No coating formation was observed in the presence of EDTA (Figure 27), indicating that its ability to coordinate with Co ²⁺ significantly affected CMOH deposition. Therefore, compare the oxidation potential of EDTA- and acetate coordinated Co (2) under deposition conditions. The oxidation potentials of Co ²⁺ /Co ^{3+ in the} presence of acetate and sulfate anions are 1.55 and 1.63V, respectively ((I) and (V) in Figure 29). By adding acetate coordination groups to cobalt sulfate (Moore ratio of 2 to 1, see (II) and (III) in Figure 29), the oxidation potential of Co ²⁺ /Co ³⁺ is reduced, and finally it is combined with Co(OAc ) _{2 is} similar. On the other hand, the addition of stoichiometric sodium sulfate to Co(OAc) ₂ showed no significant change in the Co ²⁺ oxidation peak. By adding EDTA to CoSO ₄ , it has been observed that the oxidation potential of Co ²⁺ /Co ³⁺ drops sharply to 0.67 V ((IV) in Figure 29). This drop in oxidation potential of Co ²⁺ should make redox deposition easier and more spontaneous. However, the observed absence of CMOH indicates that the coordination effect determines the growth of deposition rather than the change of redox potential. The EDTA ligand tightly captures Co ²⁺ and can keep the coordinated Co ²⁺ away from the substrate to maintain film growth. Compared with EDTA, the relatively unstable and weak coordination ability of acetate can lead to inhibition of deposition rather than complete stop. The addition of coordination ligands may also establish a new balance of CMOH deposition. Therefore, the precursor anion effect can be mainly attributed to the ligand coordination ability. As a result, by appropriately selecting the ligand additives, the thickness can be precisely controlled.

Simulation study of CMOH growth:

Figures 30 to 33 show the MD simulation study of the (MnO ₄ )-Co complex, which produces oxidation in the deposition of sulfate ((a) in Figure 30) and acetate ((b) in Figure 30) Reduction reaction. O, Co, and Mn are expressed in different gray scales. Describe and study two different (MnO ₄ )-Co complexes, one forms a colloidal precipitate in the solution ((c) in Figure 30), and the other binds to the SnO ₂ substrate (Figure 30) (D)) is deposited as a thin film. It was observed that the amount of colloidal complex in the sulfate solution was greater than the amount of colloidal complex in the acetate solution. By correlating the number of (MnO ₄ )-Co colloidal complexes formed with the simulation time (Figure 31), it was found that the formation rate in the sulfate solution was higher than that in the acetate solution. It was found that the saturated amount of (MnO ₄ )-Co colloidal complex in the acetate solution was 480. Since the total number of Co ions in the initial stage is 1500, about one third of the Co ions in the acetate solution form colloidal complexes. For the ions in the sulfate solution, the maximum number of colloidal complexes at the end of the simulation time is 780, which is greater than half of the number of Co ions. Co ions not only bond with the oxygen in MnO ₄ , but also bond with the oxygen on the surface of SnO ₂ to form a deposit (see (e) (sulfate system) in Figure 30 and (f) (Acetate) in Figure 30 system)). Similarly, the number of surface-attached complexes in the sulfate solution is greater than that in the acetate solution. During the simulation time period, the number of surface-attached complexes in the acetate solution is saturated, but not saturated in the case of sulfate (Figure 32). These simulation results are consistent with the experimental observation results of CMOH deposition controlled by the above ligand. In order to further study the formation of (MnO ₄ )-Co complexes, calculate the radial distribution function (RDF) (g _Co-O (sulfate)) of Co ion and O in sulfate ion and O (g _Co-O (acetate)). In Figure 33, g _Co-O (acetate) has a peak around 3.5 Å, while Co-O (sulfate) has no corresponding peak. This means that the acetate anion closely surrounds the Co ions with high local density instead of being evenly dispersed throughout the solution pool. This accumulation of acetate ions restricts the coordination of Co ²⁺ with other oxygen atoms (such as O of the SnO ₂ substrate), and can also accumulate a large negative charge barrier to repel MnO ₄ anions to promote redox interactions. The significantly inhibited CMOH deposition can also be explained by changes in ligands from acetate to EDTA.

Electrocatalysis of OER:

Figure 34 shows a comparison of the linear sweep voltammogram (LSV) of amorphous acetate CMOH and crystalline acetate CMO deposited on FTO under 0.1M KOH. When FTO needs to be as high as 1.9V, no obvious OER activity is observed. The OER onset and overpotential (η at 10mA cm ^-2 ) of amorphous CMOH are 1.28V and 390mV, respectively. The crystalline CMO showed a higher onset potential than CMOH at 1.47V, and η was 460mV. At an overpotential of 400mV, the current density of CMOH is 11.60mA cm ^-2 , which is 4.7 times that of CMO. Compared with the benchmark RuO ₂ , CMOH has a smaller starting potential of 180mV and an overpotential of 200mV. In Figure 35, CMOH exhibits favorable OER kinetics, which has a smaller Tafel slope of 60.9 mV dec ^-1 than CMO (72.8 mV dec ^-1 ). The measured Faraday efficiency of CMOH is close to 100%, indicating that no side electrochemical reaction occurred during OER (Figure 57). Generally, higher electrical conductivity makes higher electrocatalytic performance possible. Although amorphous CMOH has lower conductivity, it exhibits higher OER performance than crystalline CMO (Table 2), which clearly shows the inherent OER advantage of amorphous materials over crystalline materials. The comparison of OER performance with the reported thin coatings is summarized in Table 4.

Metal oxyhydroxide (such as CoOOH, NiOOH) has been recognized as an inclusive substance of OER. Thin amorphous metal oxyhydroxides are usually obtained from the electrochemical conversion of metal hydroxides as a precatalyst during OER, rather than produced by direct deposition. Electrochemical adjustments are required to convert crystalline metal hydroxides to oxyhydroxides to increase OER activity. It was found that CMOH does not require significant electrochemical activation to improve OER performance (Figure 34) because it may already be in the form of oxyhydroxide. In order to study the optimal composition, coatings with different Co/Mn ratios were prepared by changing the precursor ratio in the initial reaction mixture (see Table 1). By increasing the content of the cobalt precursor, a coating with a larger Co/Mn ratio is usually produced. Due to redox interactions, the Co/Mn ratio of the coating shows a smaller change (ie, 2.92 to 5.72) compared to the reaction mixture in the range of 3/1 to 9/1. The Co/Mn precursor ratio is 7/1, with the most active coating (CMOH _7/1 ) (Figure 36, Figure 58 and Table 3). The cobalt XPS data of CMOH _7/1 (Figure 59) shows a high similarity to CMOH _3/1 , indicating that Co ³⁺ is still the main species of the film, rather than Co ²⁺ . This may also indicate that Co ³⁺ is the active substance of OER rather than the Mn site. Compared with the ideal redox stoichiometry and binary composition, the relatively low Mn content in CMOH _7/1 may indicate that Mn ³⁺ is replaced by Co ³⁺ , and cation vacancies are generated in the framework of the film due to charge compensation. A small amount of these defects can increase the conductivity of the material and improve the catalytic activity, as observed in CMOH _7/1 (see Table 2), but a large number of defects will weaken the structural stability. The activity of Co/Mn=9/1 will be significantly reduced. Therefore, because even higher cation vacancies collapse the CMOH framework, incomplete film formation is observed.

The OER stability test of the it curve (Figure 37) was continuously performed for 60,000 seconds at a current density of 10 mA cm ^-2 . No significant decrease in current density of CMOH (<2%) was observed, while CMO showed a decrease of 18% in current density. RuO ₂ showed a more serious current density reduction of 67%, much greater than CMOH and CMO. In addition, compare the cyclic LSV test with 10,000 scans. Amorphous CMOH showed almost the same curve as the first run (Figure 38), while crystalline CMO showed a 16% decrease in current density and a 16mV increase in overpotential. The benchmark RuO ₂ showed a greater current density decay of 18% and an overpotential increase of 44mV after the test. In fact, both CMOH and CMO are more stable than RuO ₂ in the entire cycle test. In the TEM identification, the CMOH remained amorphous after 10,000 cycles without any crystalline characteristics (Figure 10), indicating that although there may be local structural rearrangements during OER, there is atypical oxygen evolution activity and stability Is due to the amorphous characteristics. The dissolution study was further conducted by sampling the OER electrolyte solution (0.1M KOH) after 10,000 cycles. ICPMS data show that crystalline CMO coating releases Co and Mn twice as much as amorphous CMOH, which can explain the poor stability of CMO over time compared with CMOH (Figure 37). The spinel phase is considered a structure that is unfavorable for conversion to oxyhydroxide. The crystalline spinel CMO with a rigid ordered coordination environment may limit the flexibility of structural changes. The high lattice stress caused by the phase transition increases the possibility of irreversible bond breaking, leading to the observed dissolution of Co and Mn. In contrast, disordered amorphous CMOH is more flexible in structure to tolerate a greater degree of structural rearrangement, including Co ^3+/4+ exchange in the OER mechanism.

The influence of thickness on OER was studied by changing the deposition time and different precursors of Co(OAc) ₂ and CoSO ₄ . As shown in Figure 39, the Co(OAc) ₂ coating generally exhibits better activity than the CoSO ₄ coating under the same deposition time. The almost identical OER activity between Co(OAc) ₂ coatings between 15 and 60 minutes consists of the observed self-limiting growth and negligible thickness differences (see also Figures 60 to 61). In the case of CoSO ₄ coating, longer deposition time leads to weaker OER performance and is closely related to its sharp thickness difference. Since the ultra-thin coating promotes charge transport in electrocatalysis, controlling the thickness of CMOH through the coordination effect of ligand groups may be a promising way to manipulate OER performance.

OER on various substrates:

The substrate is universally deposited and easy to operate. Ultra-thin CMOH is tested on various substrates commonly used in OER, including metal foil (Cu foil), carbon cloth, 3D Ni foam and glassy carbon electrode (GCE). As shown in Figures 40 to 43, the electrochemical results usually show excellent OER enhancement compared with uncoated substrates, indicating (1) strong interfacial contact between CMOH and the substrate used for electrocatalysis, And (2) Abnormal OER activity of amorphous CMOH coating. It is worth noting that the LSV curve of the bare Ni foam shows an oxidation peak at 1.34V, which corresponds to the Ni transition (II)/(III). However, the CMOH coating on Ni foam does not reflect the Ni(II)/(III) signal, but it exhibits an OER starting potential of 1.234V, which is very close to the theoretical value (1.23V), and has a small value of 0.31mV. The overpotential. Table 3 summarizes the improved OER performance. The 3V electrolysis setting was performed by connecting two commercial batteries in series (1.5V each), and the operation video clip showed that only the CMOH coated area, not the uncoated area, showed violent O ₂ bubbling. Compared with CMOH-coated electrodes, commercial raw carbon rods and platinum (Pt) wires are relatively weak in O ₂ production under the same conditions. These results confirm that CMOH is responsible for oxygen release and has excellent OER activity on substrates, including copper foil and Ni foam with high conductivity and electrocatalytic activity.

Ternary oxide film deposition:

According to the above-mentioned deposition principle, various thin film compositions are explored by replacing Co ²⁺ with other transition metals (such as Fe ²⁺ ). The preliminary results show that the Fe/Mn ratio of the iron-manganese oxide coating is 2.39, which indicates the feasibility of various metal oxide combinations through the redox scheme. In addition, with the presence of Co ²⁺ , Fe ²⁺ and KMnO ₄ , ternary iron-cobalt-manganese oxide coatings on FTO have been successfully produced, where their composition ratio is similar to the precursor ratio (Fe: Co: Mn =1: 2.11: 0.77), see figures 62 to 65). For Co ²⁺ and Fe ²⁺ , the metal ion fixation effect of KMnO ₄ was observed again. According to previous work, the metal-containing oxidant KMnO ₄ in the redox synthesis may be replaced by other metal oxoates (ie K ₂ Cr ₂ O ₇ ), not limited to KMnO ₄ . Therefore, the realization of various combinations of multi-component amorphous coatings can be systematically studied through this redox scheme.

In summary, the above-mentioned scalable, solution-processable, multi-component ultra-thin metal oxide coating solution can realize non-porous, continuous and universal substrate deposition. The formation of redox-coupled films has proven to be essential for film growth, fixation and uniform element distribution. As no longer needed For pyrolysis treatment, this solution is a suitable substitute for amorphous deposition and substrates with low heat resistance. The thickness and composition of CMOH can be controlled by ligand selection. This advantage can be used to manufacture wearable semiconductor devices, such as gate material deposition. For the evolution of oxygen, new explorations of multi-component amorphous metal oxides (for example, more than four different metals) can be pursued to obtain higher durability and efficiency. The high transparency and film integrity of the redox protocol can open up new ways for light-assisted PEC applications.

In addition, in one embodiment, after step (S2), the method of the above-mentioned embodiment of the present invention may further include the step: (S3) making the metal oxyhydroxide film in a calcining temperature range and a gas environment Carry out a calcining process to produce a metal oxide calcined film; wherein the calcining temperature can range from the phase transition temperature to below the physical limit temperature of the material, for example: 250 to 800 degrees Celsius (for example, 66a) , 66b, 66c show samples completed at 400, 600, and 800 degrees Celsius respectively); the gas in the gas environment can be air, argon (Ar), nitrogen (N) or oxygen (O ₂ ); A duration of the calcining process can be selected from 1 to 12 hours according to requirements.

In one embodiment, the substrate may be selected from a group consisting of the following objects, such as silicon crystal plates, high molecular organic polymers (such as the plastic plate shown in Figure 67a or the plastic plate shown in Figure 67b) Rubber balloons, etc.), organic materials (e.g. wood as shown in figure 68a, plastic plates as shown in figure 68b, rubber balloons as shown in figure 68c, etc.), carbon materials (e.g. graphene as shown in figure 69a, Carbon cloth shown in Figure 69b, carbon/plastic composite substrate shown in Figure 69c, etc.), carbohydrates (such as wood shown in Figure 70 or biocellulose such as artificial leather, but not limited to this) , Glass material, foamed nickel, metal material, metal oxide and glassy carbon electrode material, but not limited to this; for example: the glass material can be further selected from FTO (Fluorine-doped Tin Oxide) conductive glass plate or ITO ( Indium Tin Oxide) conductive glass plates, etc., but not limited to this.

It is particularly noteworthy that the above-mentioned embodiments of the present invention are particularly related to electroless deposition of metal oxide films on various substrates (especially plastic organic substrates, such as polyethylene terephthalate, Polyurethane, polymethyl methacrylate, polyethylene naphthalate, polycarbonate, etc.) methods have at least the following advantages: metal oxide hydroxide and metal oxide films are in an ultra-thin state Still continuous, a few nanometers of thickness can be formed into a film, for example: 5nm; in addition, metal oxide hydroxide and metal oxide films have high activity in the oxygen evolution reaction. Stability; In addition, metal oxide hydroxide and metal oxide films have strong adhesion to FTO, ITO conductive glass, silicon wafers, wood, glass, nickel foam, plastics, metal substrates, carbon materials, and glass carbon electrodes , It has low interface resistance with conductive substrates. In addition, metal oxide hydroxide films can be evenly plated on complex substrates because of the high solution permeability and can be plated on substrates with low environmental tolerance (low pressure, high temperature, insulator), Because the low temperature and room pressure reflect the conditions; the metal oxide hydroxide film does not need to add surfactants, no vacuum environment, no expensive equipment, low cost, low pollution; in addition, metal oxide hydroxide and metal oxide film elements Uniform distribution (redox electron measurement), smooth surface, uniform thickness and excellent step coverage efficiency (solution permeability); in addition, metal oxide hydroxide and metal oxide films have good light transmittance and uniform appearance; Metal oxyhydroxide films have flexible properties; in addition, metal oxyhydroxide and metal oxide films can be used for large-scale coating and pattern transfer replication; in addition, metal oxyhydroxide and metal oxide films can be precisely controlled in composition The ratio between metals; in addition, the metal oxide hydroxide film structure is amorphous; in addition, the metal oxide film structure is crystalline.

Although the present invention has been disclosed in the preferred embodiments, it is not intended to limit the present invention. Anyone familiar with the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the present invention The scope of protection shall be subject to the scope of the attached patent application.

S1‧‧‧Mixing steps

S2‧‧‧Deposition step

S3‧‧‧Caking steps

Claims (11)

A method for depositing a metal oxide film in a liquid phase environment includes the steps of: (S1) dissolving an oxidizing agent in a hydrogen-bonded solvent to form a solution; and (S2) placing a substrate in the solution to perform a The deposition reaction causes a metal oxide hydroxide film to be deposited on the substrate; wherein the oxidant is potassium permanganate, potassium chromate or potassium dichromate, and a reaction temperature of the deposition reaction ranges from 1 to 99 degrees Celsius , A reaction pressure environment of the deposition reaction is an atmospheric pressure environment. The method for depositing a metal oxide film in a liquid phase environment as described in claim 1, wherein in step (S1), a reducing agent and the oxidizing agent are mixed according to a molar ratio of the reducing agent to the oxidizing agent and dissolved in the A solvent with hydrogen bonds to form the solution. The method for depositing a metal oxide thin film in a liquid phase environment according to claim 2, wherein the reducing agent is selected from the group consisting of divalent cobalt compounds, divalent iron compounds, divalent nickel compounds, divalent manganese compounds and first A group of transition metal ion compounds. The method for depositing a metal oxide film in a liquid phase environment as described in claim 2, wherein one of the molar ratios of the reducing agent to the oxidizing agent ranges from 9:1 to 1:3. The method for depositing a metal oxide thin film in a liquid phase environment as described in claim 1, wherein in step (S1), an additive containing an anion is added to the solution, and the anion of the additive is selected from metal salts ion. The method for depositing a metal oxide film in a liquid phase environment as described in claim 1, wherein after step (S2), the method further includes the step: (S3) making the gold The oxidized hydroxide film undergoes a calcining process in a calcining temperature range and a gas environment to produce a metal oxide calcined film; wherein the calcining temperature range is 250 to 800 degrees Celsius. The method for depositing a metal oxide film in a liquid phase environment as described in claim 6, wherein the gas in the gas environment is air in the atmospheric environment. The method for depositing a metal oxide film in a liquid phase environment as described in claim 6, wherein the gas in the gas environment is argon, nitrogen or oxygen. The method for depositing a metal oxide film in a liquid phase environment as recited in claim 6, wherein a duration of the calcining process ranges from 1 to 12 hours. The method for depositing a metal oxide film in a liquid phase environment according to claim 1, wherein the substrate is selected from silicon crystal materials, carbohydrates, glass materials, foamed nickel, metal materials, metal oxides, organic materials, A group consisting of high molecular organic polymers, carbon materials and glassy carbon electrode materials. The method for depositing a metal oxide film in a liquid phase environment as described in claim 1, wherein the hydrogen-bonding solvent is deionized water with a resistance value of 18.2 megohms ‧ cm.

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