CN117867564A - An alkaline water electrolysis/hydrogen oxidation bifunctional hydrogen electrode supported Ir cluster catalyst - Google Patents

Abstract

The invention provides an alkaline water electrolysis/hydrogen oxidation bifunctional hydrogen electrode supported Ir-based catalyst, expressed as Ir/ _V2O3 , wherein nano Ir clusters are supported on _V2O3 carriers, the size of the nano Ir clusters is _1-3nm , and the Ir loading amount is _0.5-1.0wt %. The invention prepares Ir clusters Ir/ _V2O3 supported on vanadium _trioxide , which have good alkaline HOR/HER electrocatalytic activity, high utilization efficiency of active center Ir, and stable catalyst structure. The catalyst performs reversible hydrogen oxidation reduction in alkaline electrolyte, thereby performing water electrolysis and hydrogen oxidation. The invention uses Ir clusters as catalytic active centers and vanadium trioxide as active intermediate adsorbent, and the electrocatalytic HOR/HER performance is significantly improved, and the catalytic effect is long-lasting.

Description

An alkaline water electrolysis/hydrogen hydroxide bifunctional hydrogen electrode loaded with Ir cluster catalyst

Technical Field

The invention belongs to the field of catalyst materials, and in particular relates to an alkaline water electrolysis/hydrogen oxidation bifunctional hydrogen electrode loaded Ir cluster catalyst.

Background technique

In recent years, the problem of energy shortage has become increasingly prominent. The economic system based on traditional fossil energy has increasingly exposed more environmental problems such as dust, haze, air pollution, water pollution, and ozone layer holes. There is an urgent need for the emergence of clean energy to replace traditional fossil energy. The hydrogen economy with hydrogen energy as the carrier is an energy-saving, environmentally friendly and efficient emerging energy economic system. Hydrogen energy is a clean energy source derived from water decomposition, and the final product of its use is also water. The sustainable method of obtaining hydrogen is electrocatalytic/photocatalytic water splitting. In this reaction, the reaction of the hydrogen electrode includes hydrogen oxidation reaction (HOR) and hydrogen evolution reaction (HER). Affected by the alkaline exchange membrane and the counter electrode oxygen reduction (ORR)/oxygen evolution reaction (OER), alkaline hydrogen fuel cells and water electrolyzers have attracted widespread attention as alternatives to proton exchange membrane fuel cells/electrolyzers. In fact, the kinetic reaction rate of Pt-based catalysts HOR/HER under alkaline conditions is 2 orders of magnitude lower than that under acidic conditions, which is also one of the problems of slow kinetics that HOR/HER needs to overcome under alkaline conditions.

From the volcano plot of calculated hydrogen adsorption energy and experimentally measured exchange currents based on different transition metals and noble metals, Ir is considered to be one of the most promising Pt substitutes in HOR/HER reactions, with a relatively suitable hydrogen adsorption energy. However, the performance of Ir-based catalysts for alkaline HOR/HER reported so far is not sufficient for practical electrocatalytic applications for two reasons: 1) Ir is less abundant in nature and its price is 5 to 10 times that of Pt, so its cost as a substitute for Pt is high; 2) When the Ir content in the catalyst is low, its electrocatalytic activity does not meet the requirements of practical electrocatalytic applications, and the use of Ir needs to be increased. In summary, there are many challenges for Ir-based catalysts to replace alkaline electrocatalytic HOR/HER. Therefore, the development of low-loaded, stable Ir-based catalysts is a promising approach to replace commercial Pt/C catalysts.

Since catalysis is a surface reaction, the surface atoms of metal-based catalysts are far more important than the bulk atoms, and the size of the metal limits the content of surface atoms in the component. In order to improve the utilization efficiency of precious metal-based catalysis, it is very important to develop precious metal-based catalysts with high dispersion and large surface atom ratio. Single-atom catalysts have discrete metal centers and can theoretically achieve 100% metal utilization. However, they cannot provide multiple metal atom sites, and the adsorption of active intermediates is relatively simple, which is not suitable for the regulation of multiple adsorptions of H* and OH* at the same time; in addition, since the system is anchored on the metal oxide carrier, the single atom loses some of the metal properties required for effective adsorption and activation of specific catalytic reactions, which is also one of the reasons for the attenuation of the reaction performance of single-atom catalysts. Metal clusters have both metallic properties and high surface atom content due to their rich and unique physical and chemical properties, showing broad application prospects in materials, energy, environment and other fields, so cluster metal catalysts can be selected as active components.

Supported catalysts are mainly divided into precious metal catalyst systems and non-precious metal catalyst systems based on transition metal oxides. Although precious metal catalyst systems have excellent low-temperature catalytic effects, their high prices limit their large-scale application in industrial production. In transition metal oxide systems, vanadium/titanium/cerium oxides (MO _x ) have the advantages of multi-valence and structural variability, and can exhibit excellent catalytic oxidation ability at room temperature, which has attracted widespread attention from researchers. By adjusting the valence state of Ir through different interactions between different substrates and Ir, the optimal Ir-based catalyst is explored.

Wang Yong's research group at Zhejiang University reported an IrO ₂ /V ₂ O ₅ catalyst (Document 1: Adv. Sci. 2022, 9, 2104636; Document 2: CN114289017A), which achieved full water splitting under full pH conditions by constructing a strong oxide-support interaction. In this patent, the Ir/V ₂ O ₃ catalyst we constructed is mainly for the anode reaction of alkaline membrane fuel cells, namely the hydrogen oxidation reaction (HOR) and the alkaline water electrolysis hydrogen reaction (HER) bifunctional catalyst. Compared with V ₂ O ₅ , by utilizing the variable valence of V ₂ O ₃ , the electrons of Ir are regulated, so that it can better catalyze the redox reaction. Secondly, due to the different nature of its catalytic reaction, the loading amount of Ir clusters in Ir/V ₂ O ₃ is about 3% of IrO ₂ /V ₂ O ₅ , which is two orders of magnitude different.

Metal nanoclusters, with _particle sizes between metal atoms and nanoparticles, have unique physical and chemical properties, which have aroused widespread interest among researchers. By regulating the electronic structure of nanoclusters, Ir clusters were used as catalytic active centers loaded on _V2O3 carriers for electrocatalytic alkaline HOR/HER, which has not been reported before.

Summary of the invention

In order to solve the defects of the prior art in alkaline electrocatalytic hydrogen reaction HOR/HER, such as low Pt utilization rate, low catalytic activity and short catalytic life, the present invention proposes a supported catalyst using Ir clusters as catalytic active centers, and obtains a composite material with high catalytic activity, stable structure and long service life, which is used for alkaline electrocatalytic HOR/HER. Due to its ultra-low loading and stability, it is a new alkaline electrocatalytic HOR/HER composite catalyst material that is expected to be industrialized.

The present invention achieves the above object through the following technical solutions:

The first object of the present invention is to provide an alkaline water electrolysis/hydrogen oxidation bifunctional hydrogen electrode supported Ir-based catalyst Ir/ _V2O3 , wherein nano-Ir clusters are supported on _{a V2O3} carrier, the size of the nano-Ir clusters is 1-3nm, _and the Ir loading is 0.5-1.0wt%. For example, the Ir loading is 0.66wt%. The bifunctionality means that the catalyst can catalyze hydrogen evolution reaction and hydrogen oxidation reaction.

Furthermore, the supported Ir-based catalyst Ir/V ₂ O ₃ is a nanorod structure, the nanorod has a diameter of 50-500 nm and a length of 200 nm to 3 μm; preferably, the nanorod has a diameter of 100-300 nm and a length of 500 nm-2 μm.

The inventors have found that the size of nano Ir clusters has an important influence on the catalyst activity and catalyst stability. Generally, when preparing a supported Ir catalyst, the preparation conditions of high temperature calcination will make the precious metal Ir easily agglomerate to form nanoparticles. It is generally believed that catalysis is a surface reaction. Clusters aggregate into particles, which reduces the utilization rate of surface atoms. The performance will be slightly increased, but the utilization rate of atoms will be seriously reduced, resulting in an increase in cost. The prior art uses a catalyst in a single-atom dispersed state, but it is not suitable for electrolysis of water, that is, it is not suitable for the regulation of simultaneous adsorption of H* and OH*; in addition, the catalytic activity of the single-atom catalyst will decay rapidly, which is not suitable for industrial electrolysis of water. The present invention regulates the size of nano Ir clusters by means of tubular furnace calcination regulation, load content regulation, XRD crystal diffraction, electron microscopy technology characterization, etc., and is loaded on _V2O3 with surface _defects .

The inventors also found that the Ir/ _{V2O3 supported} catalyst has significantly improved catalytic activity and catalytic stability. However, nano-Ir clusters of the same size supported on other metal oxide supports, such as Ir/ _TiO2 and Ir/ _CeO2 , fail to show the significantly improved catalytic activity and/or catalytic stability of _the Ir/ _V2O3 of the present invention.

Furthermore, the alkaline water electrolysis/hydrogen oxidation bifunctional hydrogen electrode supported Ir-based catalyst Ir/V ₂ O ₃ provided by the present invention has the following XRD derivative spectrum characteristic peaks: 24.5±0.2°, 33.2±0.2°, 36.6±0.2°, 41.6±0.2°, 50.3±0.2°, 54.3±0.2°, 63.8±0.2°, 66.0±0.2°, 71.0±0.2.

The present invention also provides a method for preparing the alkaline water electrolysis/hydrogen oxidation bifunctional hydrogen electrode supported Ir-based catalyst Ir/V ₂ O ₃ , comprising the following steps:

(S1) dissolving a soluble vanadium source in water, adding acid to adjust the pH to 2-3, reacting at 150-180°C, washing, centrifuging, grinding the obtained solid, and calcining at 260-300°C under a reducing atmosphere to obtain nanorod-shaped vanadium oxide

(S2) adding iridium salt to the dispersion of nanorod-shaped vanadium oxide, stirring continuously until the solution volatilizes, calcining the obtained solid in a reducing atmosphere, cooling, washing, and drying to obtain an Ir-supported catalyst in which Ir nanoclusters are supported on V ₂ O ₃ .

Furthermore, in step (S1), the soluble vanadium source is NH ₄ VO 3, the soluble vanadium source is dissolved in water, and the amount of the soluble vanadium source and water is such that the metal V concentration in the solution is 0.1-0.3 M; the reducing atmosphere is a 5-10 vol% hydrogen atmosphere (such as a hydrogen/argon mixed gas), and the calcination time is 2-3 h; the acid is an organic acid or an inorganic acid, such as hydrochloric acid, acetic acid, or formic acid.

Calcinate at 260-300℃ for 2-3h in a reducing atmosphere. In this state, vanadium oxide is not reduced to V ₂ O ₃ . The calcination temperature should not be higher, and the calcination time should not be longer, otherwise vanadium oxide may be reduced to V ₂ O ₃ . The purpose of calcination is to make it have good crystallinity, and at the same time, it can produce certain defects, which is conducive to anchoring Ir. In the case of hydrogen and heating power source, some lattice O atoms in vanadium oxide will interact with H2, generate water from it, and separate from VO2 (because it is still a VO2 carrier after calcination, and V2O3 is not generated). Secondly, for the anchoring of Ir, it is more inclined to produce vacancies, which is conducive to the embedding of atoms into the carrier.

Furthermore, in step (S2), the solvent of the dispersion of nanorod-shaped vanadium oxide is alcohol, water or a mixed solvent of alcohol and water, the alcohol is selected from at least one of methanol, ethanol and isopropanol, the mass concentration of the dispersion of nanorod-shaped vanadium oxide is 1-50 mg/mL, preferably 5-10 mg/mL; the diameter of the nanorod-shaped vanadium oxide is 50-500 nm, and the length is 200 nm to 3 μm; preferably, the diameter is 100-300 nm, and the length is 500 nm-2 μm.

Furthermore, the iridium salt is selected from at least one of chloroiridic acid hexahydrate, potassium hexachloroiridate, and iridium trichloride.

Furthermore, the mass ratio of the iridium salt to the nanorod-shaped vanadium oxide is 2-5:50.

Furthermore, the continuous stirring until the solution evaporates to obtain a solid is continuous stirring at 50-70°C.

Furthermore, the reducing atmosphere of step (S2) is the same as that of step (S1), which is a 5-10 vol% hydrogen atmosphere (such as a hydrogen/argon mixed gas); the calcination is performed at 400-600°C for 1-3 hours; the cooling is performed naturally to room temperature; the washing is performed alternately with deionized water and ethanol; the drying is not particularly limited, such as oven drying or vacuum drying.

The inventor unexpectedly found that only when the Ir clusters of suitable size are loaded on the vanadium trioxide carrier, the obtained composite material has the highest catalytic activity for the alkaline electrocatalytic HOR/HER supported Ir-based catalyst. Ir clusters of other sizes, or Ir clusters loaded on other metal oxide carriers, cannot achieve the catalytic activity effect of Ir/ _V2O3 of the present invention. The possible reason is that the Ir clusters and vanadium _trioxide have a unique electronic structure interaction. The unique structure and the adsorption capacity of the carrier for the active intermediate OH* in the alkaline electrocatalysis are in a more suitable position, and the vanadium trioxide can more easily capture OH* in the alkaline solution and be used for the catalytic desorption of Ir. The high HOR/HER mass activity (10.14A mg ^-1 _/ 14.76A mg ^-1 , when the overpotential is 50mV) of the Ir/ _V2O3 of the present invention cannot be achieved with other Ir clusters.

The third object of the present invention is to provide the use of the alkaline electrocatalytic HOR/HER supported catalyst under alkaline conditions. The supported catalyst based on Ir clusters provided by the present invention has high Ir utilization efficiency, high catalytic activity, and the catalyst can remain stable for a long time and has a long service life. Hydrogenation and hydrogen reduction can be catalyzed at room temperature, and the product is non-toxic and harmless, and does not cause secondary pollution.

The fourth object of the present invention is to provide a method for electrolyzing water, wherein the hydrogen electrode adopts the _above alkaline water electrolysis/hydrogen oxidation bifunctional hydrogen electrode supported Ir-based catalyst Ir/ _V2O3 as a catalyst for HOR/HER. Compared with the prior art, the present invention has the following beneficial effects:

The present invention prepares _an Ir cluster Ir/ _V2O3 supported on vanadium trioxide, which has good alkaline HOR/HER electrocatalytic activity, high utilization efficiency of active center Ir, and stable catalyst structure. The catalyst performs reversible hydrogen oxidation reduction in an alkaline electrolyte, thereby performing water electrolysis and hydrogen oxidation. The present invention uses Ir clusters as catalytic active centers and vanadium trioxide as an active intermediate adsorbent, significantly improves electrocatalytic HOR/HER performance, and has a long-lasting catalytic effect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a scanning electron microscope image (SEM) of the VO ₂ carrier prepared in Preparation Example 1.

FIG. 2 is a scanning electron microscope image (SEM) of the VO ₂ carrier prepared in Preparation Example 2.

FIG3 is a spherical aberration corrected high resolution transmission electron micrograph (AC-HRTEM) of the Ir supported on V ₂ O ₃ catalyst prepared in Example 1. FIG.

FIG. 4 is a transmission electron microscope image (TEM) of the catalyst prepared in Example 4.

FIG5 is a transmission electron microscope image (TEM) of the catalyst prepared in Example 5.

FIG. 6 is a transmission electron microscope image (TEM) of the TiO ₂ support prepared in Comparative Example 1.

FIG. 7 is a transmission electron microscope (TEM) and a spherical aberration corrected high-resolution transmission electron microscope image (AC-HRTEM) of Ir loaded on TiO ₂ (Ir/TiO ₂ ) in Comparative Example 2.

FIG8 is a transmission electron microscope image (TEM) of the CeO ₂ carrier prepared in Comparative Example 3.

FIG. 9 is a spherical aberration corrected high resolution transmission electron micrograph (AC-HRTEM) of Ir loaded on CeO ₂ (Ir/CeO ₂ ) in Comparative Example 4. FIG.

FIG10 is a TEM image of the catalyst prepared in Comparative Example 7.

FIG. 11 is an X-ray diffraction spectrum of three catalysts: Ir/V ₂ O ₃ of Example 1, Ir/TiO ₂ of Comparative Example 2, and 4Ir/CeO ₂ of Comparative Example.

Detailed ways

To make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme of the present invention will be described in detail below. The following examples are convenient for better understanding of the present invention, but are not intended to limit the present invention. The experimental methods in the following examples are conventional methods unless otherwise specified.

In the embodiments of the present invention, "parts" are parts by mass unless otherwise specified, and "%" are percentages by mass unless otherwise specified.

Preparation Example 1

Preparation of VO ₂ : 0.234 g _{NH 4} VO ₃ was dissolved in 20 ml deionized water, the solution was stirred at room temperature until it turned bright yellow, 0.4 ml HCOOH was added dropwise to make its pH at 2.6, stirred until it turned orange-yellow, and the solution was uniform, and finally transferred into a 50 ml reactor, reacted in an oven at 180°C for 48 hours, washed with deionized water 2-3 times after cooling, centrifuged, and the obtained solid powder was dried in a vacuum freeze drying oven. The obtained VO ₂ was ground with an agate mortar, and finally calcined at 300°C in a 5% hydrogen-argon mixed atmosphere to obtain nanorod-shaped vanadium oxide (VO ₂ ), in which the vanadium oxide was not reduced to V ₂ O ₃ , but crystallized into a rod-shaped structure, and further oxidation was avoided.

Figure 1 is a scanning electron microscope (SEM) image of the VO ₂ carrier prepared in Preparation Example 1. It can be seen that the rod-shaped VO ₂ prepared in Preparation Example 1 has a nanorod diameter of 100-300 nm and a length of 500 nm-2 μm.

Preparation Example 2

Other conditions and operations are the same as those in Preparation Example 1, except that the vanadium oxide after hydrothermal synthesis is not reduced at 300°C and 5% hydrogen. Figure 2 is a scanning electron microscope image (SEM) of the VO ₂ carrier prepared in Preparation Example 2, from which it can be seen that the vanadium oxide is not well crystallized and is mostly in an amorphous state.

Example 1

The solvent of the hexahydrate chloroiridic acid solution is deionized water, and the concentration of the hexahydrate chloroiridic acid solution is 80 mg/mL; 0.025 mL of the hexahydrate chloroiridic acid solution is added dropwise to the deionized water in which 50 mg of the rod-shaped VO2 prepared in Preparation Example ₁ is dissolved; the solution is stirred at 65°C until the solution volatilizes, and the obtained solid is heated at a rate of 5°C per minute in a 5% hydrogen-argon mixed atmosphere, and the temperature is increased to 500°C and kept constant for 2 hours, and then naturally cooled, washed with deionized water and ethanol, and vacuum dried at 0.01 MPa and 70° _C to obtain a final supported catalyst Ir/ _V2O3 ; through inductively coupled plasma emission spectrometer (ICP) testing, the Ir loading amount in the composite _catalyst Ir/ _V2O3 prepared in Example 1 is 0.66wt%.

FIG3 is a spherical aberration corrected high resolution transmission electron micrograph (AC-HRTEM) of the Ir-supported V ₂ O ₃ catalyst prepared in Example 1. It can be seen from the figure that the Ir clusters are uniformly dispersed on the V ₂ O ₃ carrier and have a size of 1.6 nm±0.2 nm.

Example 2

Other conditions and operations are the same as those in Example 1, except that _VO2 is prepared as in Preparation Example 2.

Example 3

Other conditions and operations were the same as those in Example 1, except that the calcination temperature was changed from 500° C. to 400° C. in the programmed temperature-controlled calcination furnace.

Example 4

Other conditions and operations are the same as those in Example 1, except that the calcination temperature in the programmed temperature-controlled calcination furnace is changed from 500° C. to 600° C. FIG4 is a TME diagram of the catalyst obtained in Example 4, from which it can be seen that the Ir clusters are supported on vanadium oxide, the overall morphology of the catalyst is more irregular than that in Example 1, and the size of the Ir clusters is about 3 nm, which reduces the utilization rate of Ir.

Example 5

Other conditions and operations are the same as those in Example 1, except that the amount of chloroiridic acid hexahydrate added is 0.065 mL. According to the inductively coupled plasma emission spectrometer (ICP) test, the Ir loading in the composite catalyst prepared in this example is 1.3 wt %. FIG5 is a TEM image of the catalyst prepared in Example 5. Ir clusters are dispersed on the V ₂ O ₃ carrier, and the size is about 3 nm ± 1 nm.

Example 6

Other conditions and operations were the same as those in Example 1, except that 50 mg VO ₂ was dispersed in 10 mL ethanol, 0.025 mL chloroiridic acid hexahydrate was added dropwise, and the stirring step was accelerated at 65° C. The Ir loading in the composite catalyst prepared in this example was 0.7 wt %.

Example 7

Other conditions and operations are the same as those in Example 1, except that the 65°C stirring to dry step is changed to room temperature stirring for 24 hours, and the loading is impregnated and tested by inductively coupled plasma emission spectrometry (ICP). The Ir loading in the composite catalyst prepared in this example is 0.58 wt%.

Comparative Example 1

The other conditions and operations are the same as those in Example 1, except that VO ₂ is replaced by TiO ₂ to make the Ir loading amount consistent. The preparation method of TiO ₂ is as follows: 1 ml of TiCl ₄ and 35 ml of ethylene glycol are stirred at room temperature for 10 min, 1 ml of deionized water is slowly added to the system, stirred until the solution becomes uniform yellow, transferred into a reaction kettle, reacted at 150°C for 5 h, the white precipitate obtained at the end is washed with deionized water and ethanol for 2 to 3 times, dried in a vacuum freeze dryer, and the obtained dry sample is calcined at 250°C, 5% hydrogen-argon mixed gas, for 2 h to obtain a defective layered TiO ₂ carrier for use.

FIG6 is a transmission electron microscope image (TEM) of the TiO ₂ carrier prepared in Comparative Example 1. It can be seen that the TiO ₂ has a layered structure.

Comparative Example 2

Other conditions and operations were the same as those in Comparative Example 1, except that to make the Ir clusters of uniform size, 0.065 ml of 80 mg/ml chloroiridic acid hexahydrate solution was added to 50 mg TiO2 dispersed in ₁₀ ml of deionized water.

FIG. 7 shows the transmission electron microscopy (TEM) and spherical aberration corrected high resolution transmission electron microscopy (AC-HRTEM) images of Ir loaded on TiO ₂ (Ir/TiO ₂ ) in Comparative Example 2. It can be seen from the figure that the Ir clusters are uniformly dispersed on the titanium oxide support and have a size of 1.6 nm±0.2 nm.

Comparative Example 3

Other conditions and operations are the same as those in Example 1, except that VO ₂ is replaced by CeO ₂ to make the Ir loading amount consistent. The preparation method of CeO ₂ is as follows: 1.5 g Ce(NO ₃ ) ₂ ·6H ₂ O is dissolved in 40 mL of deionized water and stirred evenly, 4.0 g NaOH is added thereto, and the solution is stirred vigorously to make it uniform, and then transferred into a 100 ml reactor and placed at 130° C. for 18 h for hydrothermal reaction, and the obtained yellow powder is washed with deionized water for 2 to 3 times, dried in an oven at 60° C., and then calcined at 300° C., 5% hydrogen-argon mixed gas, for 2 hours to obtain a cerium oxide carrier with oxygen defects for use.

FIG8 is a transmission electron microscope image (TEM) of the CeO ₂ carrier prepared in Comparative Example 3. It can be seen that CeO ₂ is a rod-like structure.

Comparative Example 4

Other conditions and operations were the same as those in Comparative Example 3, except that to make the size of the Ir clusters uniform, 0.195 ml of 80 mg/ml chloroiridic acid hexahydrate solution was added to 50 mg _CeO2 dispersed in 10 ml of deionized water.

FIG9 is a spherical aberration corrected high resolution transmission electron micrograph (AC-HRTEM) of Ir loaded on CeO ₂ (Ir/CeO ₂ ) in Comparative Example 4. It can be seen from the figure that the Ir clusters are uniformly dispersed on the cerium oxide carrier and have a size of 1.6 nm±0.2 nm.

Comparative Example 5

A commercial Ir/C with a mass fraction of 5 wt% was used as a comparative catalyst for the catalyst.

Comparative Example 6

Commercial Pt/C with a mass fraction of 20 wt% was used as a comparative catalyst for the catalyst.

Comparative Example 7

Other conditions and operations are the same as those in Example 1, except that the amount of chloroiridic acid hexahydrate added is 0.195 mL. The Ir loading in the composite catalyst prepared in this example is 10.2 wt % as measured by inductively coupled plasma emission spectrometer (ICP). As shown in FIG10 , which is a TEM image of the catalyst prepared in Comparative Example 7, the Ir cluster aggregation phenomenon is aggravated, resulting in low Ir atomic utilization.

Figure 11 is the X-ray diffraction patterns of the three catalysts, Ir/V ₂ O ₃ of Example 1, Ir/TiO ₂ of Comparative Example 2, and 4Ir/CeO ₂ of Comparative Example. It is found that after high-temperature hydrogen reduction, compared with the standard card, vanadium oxide is rhombohedral V ₂ O ₃ , titanium oxide is tetragonal TiO ₂ , and cerium oxide is cubic CeO ₂ .

Application Examples

The catalyst performance of the above-mentioned embodiments and comparative examples was tested, specifically: the test was carried out in a standard three-electrode system, with a carbon rod as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and the prepared Ir _{/ V2O3} as the working electrode (HOR: the material was dropped on a glassy carbon electrode; HER: the material was dropped on a hydrophilic carbon paper), all data were calibrated to the potential relative to the standard hydrogen electrode (RHE), and the electrolyte was IR corrected by 95%.

The calibration formula is:

E _(RHE) = E _(SCE) + 0.0591*pH + 0.24-0.95*I*R

1. Current density is the value of current density when the overpotential is 50mV.

2. Overpotential η ₁₀ is the magnitude of the overpotential when the current density is 10mAcm ^-2 .

Table 1 Catalyst performance indicators

Combined with the transmission electron microscopy characterization results of the catalyst, it can be known that the catalytic activity of the catalyst is related to the interaction between the active site and the carrier. In the same Ir loading or the same Ir size supported catalyst, the more Ir loading, the larger the size. In alkaline HOR/HER, since the intermediate product may be involved in OH*, the catalytic kinetics of the catalyst adsorbed at a single point are slow. By loading it on a transition metal oxide, the electronic regulation of the Ir cluster is promoted and more intermediate adsorption sites are added. Literature shows that vanadium oxide can be used as a supercapacitor with a variety of variable valence states. The present invention has innovatively discovered that vanadium trioxide can well regulate the electrons of Ir clusters so that it has significantly improved electrocatalytic HOR/HER activity, while Ir clusters loaded on other transition metal oxide carriers and NC materials do not achieve the same excellent catalytic activity. This may be due to the unique electronic regulation of Ir clusters by _{V2O3 ,} and the appropriate adsorption strength _{of V2O3} on the active intermediate OH*. After catalysis at the Ir cluster site, the intermediate can be quickly desorbed. However, due to their single active site, Ir single atom catalysts are unlikely to regulate the binding mode of adsorbed intermediates during the reaction and lack different synergistic interactions. Ir nanoparticles also reduce the utilization of surface Ir atoms. In certain reactions, such as alkaline HOR/HER electrocatalysis, the catalytic activity is not as good as that of supported Ir clusters (Ir/V ₂ O ₃ ) with regulated electronic structures.

Claims (10)

1. An alkaline electrolyzed water/hydrogen hydroxide bifunctional hydrogen electrode supported Ir-based catalyst expressed as Ir/V ₂ O ₃ Characterized in that the nanometer Ir cluster is loaded on V ₂ O ₃ On the carrier, the size of the nano Ir cluster is 1-3nm, and the load of Ir is 0.5-1.0wt%.

2. The supported Ir-based catalyst according to claim 1, characterized in that the catalyst is of a nanorod-like structure, the nanorod having a diameter of 50-500nm and a length of 200nm to 3 μm; preferably, the nanorods have a diameter of 100-300nm and a length of 500nm-2 μm.

3. The supported Ir-based catalyst according to claim 1, characterized in that the catalyst has the following XRD derivative pattern characteristic peaks: 24.5.+ -. 0.2 °, 33.2.+ -. 0.2 °, 36.6.+ -. 0.2 °, 41.6.+ -. 0.2 °, 50.3.+ -. 0.2 °, 54.3.+ -. 0.2 °, 63.8.+ -. 0.2 °, 66.0.+ -. 0.2 °, 71.0.+ -. 0.2.

4. A method for preparing the basic electrolyzed water/hydrogen hydroxide bifunctional hydrogen electrode supported Ir-based catalyst according to any one of claims 1-3, comprising the steps of:

(S1) dissolving a soluble vanadium source in water, adding acid to adjust the pH value to 2-3, fully reacting at 150-180 ℃, washing, centrifuging, grinding the obtained solid, and calcining at 260-300 ℃ in a reducing atmosphere to obtain nano rod-shaped vanadium oxide;

(S2) adding iridium salt into the dispersion liquid of the nano rod-shaped vanadium oxide, continuously stirring until the solution volatilizes to obtain a solid, calcining the solid in a reducing atmosphere, cooling, washing and drying to obtain Ir nanoclusters loaded on V ₂ O ₃ Ir supported catalyst of (C).

5. The method according to claim 4, wherein in the step (S1), the soluble vanadium source is NH ₄ VO ₃ The soluble vanadium source is dissolved in water, and the use amount of the soluble vanadium source and the water is that the concentration of metal V in the solution is 0.1-0.3M; the reducing atmosphere is 5-10vol% hydrogen atmosphere, and the calcination time is 2-3h; the acid is an organic or inorganic acid such as hydrochloric acid, acetic acid, formic acid.

6. The method according to claim 4, wherein in the step (S2), the dispersion of the nano rod-shaped vanadium oxide is an alcohol, water or an alcohol-water mixed solvent, wherein the alcohol is at least one selected from methanol, ethanol and isopropanol, and the mass concentration of the dispersion of the nano rod-shaped vanadium oxide is 1-50mg/mL, preferably 5-10mg/mL; the diameter of the nano rod-shaped vanadium oxide is 50-500nm, and the length is 200nm to 3 mu m; preferably, the diameter is 100-300nm and the length is 500nm-2 μm.

7. The method according to claim 4, wherein in the step (S2), the iridium salt is at least one selected from the group consisting of chloroiridic acid hexahydrate, potassium chloroiridate and iridium trichloride.

8. The method according to claim 4, wherein in the step (S2), the mass ratio of iridium salt to nano rod-like vanadium oxide is 2 to 5:50; and/or

Continuously stirring until the solution volatilizes to obtain a solid, wherein the solid is continuously stirred at 50-70 ℃; and/or

The calcination is carried out at 400-600 ℃ for 1-3h.

9. Use of the supported Ir-based catalyst according to any one of claims 1-3 for HOR/HER under basic conditions.

10. A method for electrolyzing water, characterized in that the hydrogen electrode adopts the alkaline electrolyzed water/hydrogen hydroxide bifunctional hydrogen electrode supported Ir-based catalyst as claimed in any one of the preceding claims 1-3.