KR20220081940A - Transition metals doped rhenium selenide nanosheet having enhanced catalytic activity on hydrogen evolution reaction and preparation method thereof - Google Patents

Abstract

The present invention relates to a rhenium selenide nanosheet doped with a transition metal having excellent hydrogen evolution reaction (HER) activity and a method for preparing the same.

Description

Transition metal doped rhenium selenide nanosheet having enhanced catalytic activity on hydrogen evolution reaction and preparation method thereof

The present invention relates to a rhenium selenide nanosheet doped with a transition metal having excellent hydrogen evolution reaction (HER) activity and a method for preparing the same.

In order to overcome severe environmental destruction such as resource depletion and global warming and air pollution caused by the rapidly increasing consumption of fossil fuels, the next generation of alternative energy sources must be found, which is the biggest challenge that mankind must solve in the present age. Hydrogen energy is environmentally friendly as it burns cleanly in the air. In addition, it is not ubiquitous in the region, so it is an energy suitable for the next-generation energy mentioned above. The method of decomposing water with solar energy, which is the most abundant and pollution-free on earth, is evaluated as the most eco-friendly and economical hydrogen production method. Currently, the reforming reaction mainly used for hydrogen production uses natural gas or petroleum, so there is a limit, but water is an abundant resource. Therefore, it can be said that hydrogen production through water cracking is the most suitable method in the long term.

Water electrolysis refers to a reaction in which water is decomposed into hydrogen and oxygen when electricity is applied. That is, when a voltage is applied to the electrode material, an electrochemical oxidation-reduction reaction occurs. At this time, oxygen is generated at the anode and hydrogen is generated at the cathode. The process of decomposing water to produce hydrogen and oxygen is an endothermic reaction due to a large increase in free energy and corresponds to an involuntary reaction. Therefore, in order to proceed with the water decomposition reaction, a potential corresponding to 1.23 V must be externally applied, but in reality, an overvoltage higher than the ideal potential is applied depending on the electrode catalyst. Water electrolysis is also the simplest method to produce hydrogen, and because water is used as a raw material, it can be easily mass-produced and high-purity hydrogen can be obtained. However, when hydrogen is produced by water electrolysis, power consumption may increase, so it is difficult to put into practical use. To this end, it is necessary to develop a system that increases the efficiency of hydrogen production through water electrolysis and to study the electrode catalyst manufacturing technology with high activity for hydrogen generation. The most representative thing that determines the performance in water electrolysis is the electrocatalyst, and the phenomenon in which hydrogen is generated through the catalyst is called the Hydrogen Evolution Reaction (HER). The required voltage and performance are determined according to the electrode material and surface condition. The reversible electrochemical reaction on the electrode surface is as follows.

H ⁺ (aq) + e- → 1/2H ₂ (g), E° = 0V vs. SHE

Based on the hydrogen reduction electrode, hydrogen is generated when the voltage is 0V. When hydrogen is generated on the electrode surface, it occurs through three mechanisms. Basically, hydrogen ions are reduced and adsorbed on the electrode surface in the form of hydrogen atoms (Volmer reaction). Here, it is divided into two paths. Hydrogen is generated by the bonding between the adsorbed hydrogen atom and the hydrogen ion in the solution (Heyrowsky reaction) or the bonding between the adsorbed hydrogen atoms (Tafel reaction). In addition, the Tafel slope is used as a value to investigate the mechanism of the hydrogen evolution reaction. Equations related to factors affecting hydrogen catalytic activity are as follows.

η = b log( j/j _o )

In the above formula, η: overvoltage, b: Tafel slope, j: current density, j _o : means exchange current density, based on this, an ideal hydrogen catalyst has a low Tafel slope and high exchange current density have

The factor that has the greatest influence on catalytic activity is overvoltage. The overvoltage is the factor that contributes the most to the charge transfer reaction, and the overvoltage value depends on the speed and whether or not the energy barrier is overcome in catalyst activation. The better the catalyst activation, the lower the overvoltage value. In the case of commercially available platinum electrodes, the voltage when hydrogen is generated is almost 0V. However, research on hydrogen catalysts to minimize the overvoltage as much as the platinum electrode is in progress while compensating for the disadvantages of the platinum electrode. In order to satisfy the development of a hydrogen catalyst, it must be a material with advantages of low cost and abundance that can compensate for the disadvantages of platinum, and it must have good catalytic activity that can replace platinum.

KR 10-1495755 B1

Accordingly, the present inventors made intensive efforts to develop an inexpensive nanomaterial catalyst that can replace platinum (Pt) , which is an expensive noble metal hydrogen evolution catalyst. As a result, rhenium selenium doped with a transition metal using solvothermal synthesis. In the case of manufacturing the aged nanosheet, after confirming that it has excellent HER performance, the present invention was completed.

An object of the present invention is to provide a rhenium selenide nanosheet doped with a transition metal having excellent hydrogen evolution reaction (HER) activity.

Another object of the present invention is to provide a method for preparing a rhenium selenide nanosheet doped with a transition metal having the excellent hydrogen evolution activity.

In order to achieve the above object,

the present invention

An object of the present invention is to provide a rhenium selenide nanosheet doped with a transition metal having excellent hydrogen evolution activity.

In the rhenium selenide nanosheet doped with a transition metal according to the present invention, the transition metal is nickel (Ni), cobalt (Co), iron (Fe), copper (Cu) or manganese (Mn), preferably nickel (Ni) or cobalt (Co), more preferably nickel (Ni).

In the rhenium selenide nanosheet doped with a transition metal according to the present invention, the doping concentration of the transition metal is 5% based on rhenium.

In the rhenium selenide nanosheet doped with the transition metal according to the present invention, the HER performance (10 mAcm ^-2 ) of the rhenium selenide nanosheet doped with the transition metal is 100 mV or less. For example, the HER performance (10 mAcm ^-2 ) of the rhenium selenide nanosheet doped with the transition metal may be 100 mV or less, preferably 90 mV or less, and more preferably 85 mV or less.

In the rhenium selenide nanosheet doped with the transition metal according to the present invention, the Tafel slope of the rhenium selenide nanosheet doped with the transition metal is 70 mV/dec or less. For example, the Tafel slope of the rhenium selenide nanosheet doped with the transition metal may be 70 mV/dec or less, preferably 65 mV/dec or less, and more preferably 60 mV/dec or less.

The present invention also

(A) NH ₄ ReO ₄ , (PhCH ₂ ) ₂ Se ₂ , TM (Transition metal) acetylacetonate was added to oleylamine (C ₁₈ H ₃₅ NH ₂ , OAm) and stirred; and

(B) performing a solvothermal process on the stirred solution to prepare a transition metal-doped rhenium selenide nanosheet, excellent hydrogen evolution reaction using solvothermal synthesis An object of the present invention is to provide a method for preparing a rhenium selenide nanosheet doped with an active transition metal.

In the method of manufacturing a rhenium selenide nanosheet doped with a transition metal according to the present invention, the transition metal is nickel (Ni), cobalt (Co), iron (Fe), copper (Cu) or manganese (Mn), preferably The following is characterized in that nickel (Ni) or cobalt (Co), more preferably nickel (Ni).

In the method for manufacturing a rhenium selenide nanosheet doped with a transition metal according to the present invention, the doping concentration of the transition metal is 5% based on rhenium.

In the method for manufacturing a rhenium selenide nanosheet doped with a transition metal according to the present invention, the HER performance (10 mAcm ^-2 ) of the rhenium selenide nanosheet doped with the transition metal is 100 mV or less. For example, the HER performance (10 mAcm ^-2 ) of the rhenium selenide nanosheet doped with the transition metal may be 100 mV or less, preferably 90 mV or less, and more preferably 85 mV or less.

In the method of manufacturing a rhenium-selenide nanosheet doped with a transition metal according to the present invention, the Tafel slope of the rhenium-selenide nanosheet doped with the transition metal is 70 mV/dec or less. For example, the Tafel slope of the rhenium selenide nanosheet doped with the transition metal may be 70 mV/dec or less, preferably 65 mV/dec or less, and more preferably 60 mV/dec or less.

The rhenium selenide nanosheet doped with a transition metal according to the present invention has excellent hydrogen generating activity and can provide a catalyst for hydrogen generating reaction in a cheaper and simpler way than a conventional platinum catalyst.

1(a) shows NH ₄ ReO ₄ , (PhCH ₂ ) ₂ Se ₂ , TM acetylacetonate (TM (acac)2 or 3) and TM using solvothermal synthesis using oleylamine (OAm) as reagent. - Shows a schematic diagram for a method for synthesizing doped ReSe ₂ . Figure 1 (b) of ReSe ₂ HRTEM images are shown. Figure 1(c) shows lattice-resolved TEM and corresponding fast Fourier transform (FFT) images for the basal plane. 1(d) shows HAADF-STEM images and EDX element mapping/spectra of Re (M shell), Mn or Ni (K shell) and Se (L shell).
Figure 2(a) shows a TEM image of rhenium selenide and rhenium selenide doped with a transition metal. FIG. 2( b ) shows HAADF-STEM images and EDX element mapping/spectrum of Fe-ReSe _{2 ,} Co-ReSe _{2 ,} Cu-ReSe ₂ . Figure 2 (c) is rhenium selenide and transition metal doped rhenium selenide of The SEM EDX element spectrum is shown.
Figure 3 (a) is of rhenium selanide An atomic-resolution HAADF-STEM image is shown. 3(b), 3(c), 3(d), 3(e) and 3(f) show the Mn, Fe, Co, Ni, Cu-doped rhenium selenide, respectively. An atomic-resolution HAADF-STEM image and electron energy loss spectroscopy (EELS) are shown.
4 shows an X-ray diffractometer (XRD) pattern of rhenium selenide and rhenium selenide doped with a transition metal.
5(a), 5(b), and 5(d) show Re 4f, Se 3d and metals (Mn, Fe, Co, Ni, Cu of rhenium selenide ₂ doped with rhenium selenide and a transition metal, respectively) ) Fine-scan results of x-ray photoelectron spectroscopy (XPS) for 2p are shown. 5( c ) is a Valence band spectrum of rhenium selenide and rhenium selenide doped with a transition metal. 5(e) is XANES data of rhenium selenide and rhenium selenide doped with a transition metal. FIG. 5(f) is EXAFS data of rhenium selenide and rhenium selenide doped with a transition metal. 5( g ) is EXAFS data of Co K-edge, Ni K-edge, and Cu K-edge of rhenium selenide doped with Co, Ni, and Cu.
6 is Raman data of rhenium selenide and rhenium selenide doped with a transition metal.
Figure 7(a) is a transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni as a catalyst for HER in H ₂ -saturated 0.5 MH ₂ SO ₄ (pH 0)). LSV curves (scan rate: 2 mVs ^-1 ) for -ReSe ₂ and Cu-ReSe ₂ ) are shown. 7(b) shows a Tafel plot derived from the LSV curve at a low potential corresponding to the activation-control region using the Tafel equation η=blog(J/J ₀ ), where η is the overvoltage and b is the Tafel slope ( mV dec ^-1 ), J represents the measured current density, and J ₀ represents the exchange current density. 7(c) and 7(d) show rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ ) doped with a transition metal for HER in H ₂ -saturated 0.5 M KOF (pH 14). , show LSV curves and Tafel plots as catalytic performance of Ni-ReSe ₂ and Cu-ReSe ₂ ), respectively. 7(e) shows η _J=10 (left axis) and Tafel slope (right axis). 7(f) shows the TOF at 125 mV. Figure 7(g) shows the LSV curves of Ni-ReSe ₂ for the 1st and 2000th cycles in 0.5 MH ₂ SO ₄ and 1 M KOH and CA at η _J=10 for 12 h. 7(h) shows data comparing η _J=10 of Ni-ReSe ₂ with a conventionally known catalyst in 0.5 MH ₂ SO ₄ and 1 M KOH.
8 shows the results of electrochemical impedance spectroscopy (EIS) analysis of rhenium selenide and rhenium selenide doped with a transition metal according to an embodiment of the present invention.
9 is a graph showing a cyclic voltammetry (CV) curve analysis result of rhenium selenide and rhenium selenide doped with a transition metal according to an embodiment of the present invention. The current density at 0.15 V is plotted according to the scan rate to indicate the double-layer capacitance (Cdl) value from the slope.

Hereinafter, the present invention will be described in more detail through examples. However, these are only for describing the present invention in more detail, and the scope of the present invention is not limited thereto.

<Example>

Example 1. Rhenium selenide doped with transition metal (TM-ReSe ₂ ) Preparation of Nanosheets

Transition metal-doped rhenium selenide (TM-ReSe ₂ TM is Mn, Fe, Co, Ni and Cu) nanosheets were prepared by solvothermal synthesis according to the method shown in FIG. 1(a). The doping concentrations of the five TM-doped ReSe ₂ samples (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) were 5% ([TM]/[Re]=0.05). ) was adjusted.

<Experimental example>

Experimental Example 1. Confirmation of form, crystal structure and electronic structure of rhenium selenide doped with transition metal according to the present invention

1-1. HRTEM image analysis

HRTEM (high-resolution transmission) of the transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanosheets prepared in Example 1 electron microscope) image analysis was performed. As a result, it was confirmed that the thickness of the rhenium selenide (ReSe ₂ ) nanosheet was 2 nm on average, and the interlayer distance (d ₀₀₁ ) was 6.5 Å, which is close to the value of ReSe ₂ on 1T″ (6.3899 Å) (Fig. 1(b)). )). Average of rhenium selenide (ReSe ₂ ) and transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanosheets through TEM images It was confirmed that all of them were similar in size in the form of flowers of approximately 148 nm (Fig. 2(a)).

1-2. Lattice resolution TEM and FFT image analysis for the basal plane

Lattice resolution TEM of the basal surface of the transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanosheets prepared in Example 1 and FFT (fast-Fourier transformed) image analysis was performed. As a result, since the b-beam is projected perpendicular to the base plane, the FFT image exhibited a quasi-hexagonal pattern formed by (200), (020) and (220) reflections with the domain axes approximately [001]. In practice, the angle γ (between the a and b axes) is 118.94°, which is close to the 120° value of the hexagonal unit cell, and the distance (d ₂₀₀ ) between adjacent (200) faces is 2.9 Å, which is the reference value ( 2.8881 Å) was confirmed (FIG. 1(c)).

1-3. HAADF-STEM and EDX image analysis

_{HAADF - STEM ( high-} Angle annular dark-field imaging-scanning transmission electron microscope) image analysis and EDX (energy-dispersive X-ray spectroscopy) elemental mapping and spectra were measured. As a result, it was confirmed that the transition metals Mn, Fe, Co, Cu, Ni elements, rhenium (Re) elements, and selenium (Se) elements were uniformly distributed in the rhenium selenide nanosheets doped with the transition metal (FIG. 1). (d), FIG. 2(b)). It was also confirmed that approximately 5% of the transition metal was present through the SEM EDX element spectrum (FIG. 2(c)).

3 is an atomic-level HAADF-STEM image of the basal plane of rhenium selenide. 1D chains of diamond-shaped Re ₄ clusters linked along the b-axis (see the red line) were clearly observed. In this image, the lighter Se atom (Z = 34) is difficult to distinguish. A uniform red color in the contour plot for the indicated area of the STEM image indicates Re atoms. In contrast, rhenium selenide doped with a transition metal had weaker or stronger Re positions for TM substitution and adatom, respectively. 3 (b) and (c) are HAADF-STEM images of Mn-ReSe ₂ and Fe-ReSe ₂ , respectively. The weak Re strength is when light Mn and Fe atoms (Z = 25 and 26, respectively) are substituted for heavy Re atoms (Z = 75). In the data for the intensity profile along the dotted line and the indicated region of the STEM image, the TM atom is substituted at the Re position with the weaker intensity. The reason that the intensity of the Re position appears brighter is because of the adsorbed atom with the atom at the corresponding position. The EELS data confirmed that the atoms of Mn and Fe exist as single atoms in the doping site. That is, a spectrum was obtained with a probe size of 1.0 Å, and when the L _2,3 -ionization edge of Mn or Fe was measured, it was confirmed that the atom was present at the doped position and not the atom immediately adjacent to it. Unlike Mn-ReSe ₂ and Fe-ReSe ₂ , Co-ReSe ₂ and Ni-ReSe ₂ were confirmed to exist as adsorbent atoms. The part showing strong intensity in the contour plot is because another adsorbed atom exists at the Re atom position. The EELS data confirmed that Co and Ni also exist as single atoms. In the case of Cu-ReSe ₂ , it was confirmed that about 2-4 Cu atoms were clustered together and adsorbed. The stronger strength than other metals is because two or more coppers are agglomerated, and the EELS data also confirmed that they are more agglomerated than other metals.

1-4. Crystallinity confirmation by XRD

4 is rhenium selenide (ReSe ₂ ) prepared in Example 1 and rhenium selenide doped with a transition metal (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ , and Cu-ReSe ₂ ) X-ray diffraction analysis (X-ray diffractometer, XRD) results of nanosheets are shown. Rhenium selenide and rhenium selenide doped with a transition metal were found to be composed of ReSe ₂ on 1T″ (JCPDS No. 74-0611; a = 6.716 Å, b = 6.728 Å, c = 6.728 Å, and υ = 104.90°). Confirmed.

1-5. Electronic structure analysis through XPS, XANES, EXAFS

Rhenium selenide (ReSe ₂ ) prepared in Example 1 and rhenium selenide doped with a transition metal (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nano Fine-scan X-ray photoelectron spectroscopy (Fine-scan X-ray photoelectron spectroscopy) was performed for qualitative and quantitative analysis of the catalyst surface on the sheet, and the results are shown in FIGS. 5(a), 5(b) and 5(d). indicated.

As shown in FIGS. 5(a), 5(b) and 5(d), Re4f _7/2 of rhenium selenide (ReSe ₂ ) has a peak at 41.7 eV, which is a higher binding energy than 40.3 eV, which is the value of metal Re. appear. When the transition metal is doped, the peak of Re 4f is redshifted. In the case of Se 3d, like Re 4f, when a transition metal is doped, it becomes redshifted. The valence band maximum (VBM) data is 0.65 eV for rhenium selenide (ReSe ₂ ), but 0.50 eV for Mn and Fe. In the case of Co, Ni, and Cu, the value decreases to 0.36 eV. This is similar to the data of Re 4f and Se 3d. Through the 2p data of the transition metal, it was confirmed that the TM-Se bond is almost similar to the metal, and in the case of Cu, it was confirmed that it is in an oxidized state rather than other metals. The redshift of the binding energy may be due to the increased conductivity due to the addition of the doping state of the transition metal at the nearest Fermi level (E _f ). As it moved from Mn to Cu, it was confirmed that the electronic structure of ReSe ₂ became more metallic due to the increase of d electrons.

In addition, X-ray absorption near edge structure (XANES) analysis and Fourier-transform extended X-ray absorption fine structure (FT EXAFS) were analyzed and the results were is shown in Figure 5 (e). 5(e) is XANES data of Re L ₃ -edge. The intensity of rhenium selenide doped with a transition metal is lower than that of rhenium selenide, which can be explained by the increase in electron density due to doping with the transition metal. . As the transition metal moves from Mn to Cu, the intensity decrease becomes larger, which is closely related to the redshift of the XPS peak.

In addition, X-ray absorption near edge structure (XANES) analysis and Fourier-transform extended X-ray absorption fine structure (FT EXAFS) were analyzed and the results were is shown in FIG. 5(f). According to the EXAFS data, for ReSe ₂ , the shortest bond length among Re-Se bonds is 2.40 Å, and the shortest bond length among Re-Re bonds is 2.84-2.85 Å. From this, it can be confirmed that it is ReSe ₂ on 1T″. The XANES data of the K-edge of the transition metal confirmed that Co-Se (2.38 Å) and Ni-Se (2.41 Å) were single atoms because there was no bonding between Co-Co and Ni-Ni. In the case of Cu, a bond between Cu-Se and Cu-O was observed.

1-6. Raman analysis

Rhenium selenide (ReSe ₂ ) prepared in Example 1 and rhenium selenide doped with a transition metal (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nano Raman analysis was performed on the sheet, and the results are shown in FIG. 6 . 6 shows the same Raman peak corresponding to 1T″ phase ReSe ₂ . Many peaks arise from the complexity of the lattice oscillations of 1T″-phase ReSe ₂ , consistent with previous studies. The peak at 125 cm ^-1 is the Eg-like vibration mode (in-plane vibration), and the peaks at 160 and 174 cm ^-1 are the Ag-like vibration mode (out-of-plane vibration).

Experimental Example 2. Confirmation of electrochemical properties of rhenium selenide doped with transition metal according to the present invention

2-1. Electrochemical test method

4 mg of the transition metal-doped rhenium selenide (Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ ) nanosheet sample prepared in Example 1 was mixed with carbon black ( Vulcan XC-72) was mixed with 1 mg, and then dispersed in a solution consisting of 20 μl of a 5 wt% Nafion solution and 980 μl of isopropyl alcohol to prepare a catalyst ink. On the other hand, purchasing a Pt/C catalyst material (manufacturer: sigma-aldrich) in which standardized 20 wt% of nano-sized platinum is dispersed in carbon black and using it instead of the rhenium selenide nanosheet containing the transition metal Except for this, a catalyst ink was prepared in the same manner as above. Electrochemical experiments were conducted with a three-electrode cell composed of a working electrode, a reference electrode, and a counter electrode. Ag/AgCl (4M KCl, manufacturer: Pine Co.) was used as a reference electrode, and a graphite rod (diameter 6 mm) was used as a counter electrode. As a working electrode, 18 μl of the above catalyst ink was added dropwise to a glassy carbon electrode (area: 0.1963 cm ² ), which is a rotating disk electrode (RDE), and dried sufficiently before use.

In the hydrogen evolution reaction (HER) experiment, each was purged with high-purity hydrogen gas, and the gas flow rate was 20 sccm (mL min ^-1 ). The voltage used for measurement was converted based on a reversible hydrogen electrode (RHE).

The conversion formula for the reversible hydrogen electrode (RHE) at the hydrogen ion concentration index (pH) 0 (0.5MH ₂ SO ₄ ) follows the formula below. E (vs. RHE) = E (vs. SCE) + E _SCE (=0.278V) + 0.0592 pH=E(vs.SCE) + 0.278V

The conversion formula for the reversible hydrogen electrode (RHE) at the hydrogen ion concentration index (pH) 14 (1M KOH) follows the formula below. E(vs. RHE) =E(vs.Ag/AgCl) + 1.007V

During the measurement, the rotating electrode (RDE) was rotated at a speed of 1600 RPM (Revolutions per minute), and the hydrogen evolution reaction (HER) activity was measured by linear sweep voltammetry (LSV).

When measuring the linear scanning potential (LSV), the hydrogen evolution reaction (HER) was measured at a scan rate of 5 mV s ^-1 from 0 V to 0.8 V based on the reversible hydrogen electrode (RHE).

2-2. result

7(a) shows the LSV curve measured at pH 0, where the potential was based on the reversible hydrogen electrode (RHE). For the overvoltage required to obtain a current density of 10 mAcm ^-2 (η _J=10 ), 143 in ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ respectively, 132, 115, 104, 82, and 126 mV.

7(b) is a Tafel plot in the low potential region, η(V) vs. It represents log [J(mAcm ^-2 )]. Tafel slope (b) is 62, 62, 59, 56, 54, 58, and 30 mV in ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ , respectively. As dec ^-1 , it was confirmed that HER catalytic activity was increased when TM was doped into ReSe ₂ . In particular, in the case of Ni-ReSe ₂ η _{J = 10} and b values close to Pt / C, it was confirmed that the most excellent catalytic activity among the two-dimensional transition metal chalcogen compound doped with the transition metal.

7(c) shows that at pH 14, LSV curves of 256, 197 at ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ for η _J=10 , 221, 138, 109, and 179 mV. Tafel plots show the corresponding b of 146, 116, 133, 99, 81 and 115 mV dec ^-1 in ReSe ₂ , Mn-ReSe ₂ , Fe-ReSe ₂ , Co-ReSe ₂ , Ni-ReSe ₂ and Cu-ReSe ₂ , respectively. values are shown (Fig. 7(d)) . In particular, it was confirmed that the b value of Ni-ReSe ₂ was closest to the value of Pt/C (35 mV dec ^-1 ).

7(e) shows η _J=10 and b values, and it was found that the HER performance was maximally improved at pH 0 to 14 when Ni was doped into ReSe ₂ . Overall, the positive effect of TM doping on HER catalytic performance at pH 0 followed the order Ni>Co>Fe>Cu>Mn, and at pH 14, it was confirmed that Ni>Co>Cu>Mn>Fe.

Figure 7(f) is a plot of the TOF values calculated using the LSV curve for each catalyst at 125 mV. The active surface area is the capacitance measured based on the CV curve in the range of -0.2 to 0.6V at pH 7. and estimated. For Ni-ReSe ₂ , values of turn of frequency (TOF) at pH 1 to 14 were estimated to be 2.5 and 0.91 s ⁻¹ , respectively.

7( g ) shows that the LSV curve of Ni-ReSe ₂ shows little change at pH 0 to 14 even after 2000 cycles (80 h).

7(h) is a comparison of the catalytic performance of Ni-ReSe ₂ with the conventionally known performance at η _J=10 , and it was confirmed that the HER catalytic effect was the most excellent.

8(a) and 8(b) are electrochemical impedance spectroscopy (EIS) data of ReSe ₂ doped with a transition metal. A Nyquist plot was performed, and the real and imaginary resistances were shown while decreasing 0.1 Hz at 100 kHz with -0.15 V as an alternating current. By fitting the curve with the electric circuit inserted in the graph, the charge transfer resistance (Rct) can be obtained. It can be obtained from the position where the hemispherical curve intersects the x-axis, and the smaller it is, the better the catalyst activity is. The charge transfer resistance follows the order of Ni<Co<Fe<Cu<Mn<ReSe ₂ at pH 0 and Ni<Co< Cu <Mn <Fe < ReSe ₂ at pH 14.

9 is a cyclic voltammetry (CV) curve data of 0.1-0.2 V region. The CV curve was measured as the scan speed was increased from 20 mV/s to 100 mV/s. The double-layer capacitance (Cdl) can be obtained from the slope by plotting the current density at 0.15 V as a function of the scan rate. At pH 0, Ni>Co>Fe>Mn> Cu <ReSe ₂ Follows the order, and at pH 14, Ni>Co>Cu>Mn>Fe> ReSe ₂ It was confirmed. This can be expected to maximize the surface area of Ni-ReSe ₂ .

As described above in detail a specific part of the content of the present invention, for those of ordinary skill in the art, this specific description is only a preferred embodiment, and it is clear that the scope of the present invention is not limited thereby. something to do. Accordingly, it is intended that the substantial scope of the present invention be defined by the appended claims and their equivalents.

Claims (5)

As a rhenium selenide nanosheet doped with a transition metal having excellent hydrogen evolution activity,
The transition metal is nickel (Ni), cobalt (Co), iron (Fe), copper (Cu) or manganese (Mn), characterized in that the transition metal doped rhenium selenide nanosheet.
According to claim 1,
The doping concentration of the transition metal is characterized in that 5% based on rhenium, the transition metal doped rhenium selenide nanosheet.
A method for preparing rhenium selenide nanosheets doped with a transition metal having excellent hydrogen evolution activity using solvothermal synthesis, the method comprising:
(A) NH ₄ ReO ₄ , (PhCH ₂ ) ₂ Se ₂ , TM (Transition metal) acetylacetonate was added to oleylamine (C ₁₈ H ₃₅ NH ₂ , OAm) and stirred; and
(B) subjecting the stirred solution to a solvothermal process to prepare a transition metal-doped rhenium selenide nanosheet,
The transition metal is nickel (Ni), cobalt (Co), iron (Fe), copper (Cu) or manganese (Mn), characterized in that the method.
4. The method of claim 3,
The method, characterized in that the doping concentration of the transition metal is 5% based on rhenium.
4. The method of claim 3,
HER performance (10 mAcm ^-2 ) and Tafel slope of the rhenium selenide nanosheet doped with the transition metal is characterized in that it is 100 mV or less and 70 mV/dec or less, respectively.

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