CN117210856A

CN117210856A - Bimetallic catalyst for water electrolysis hydrogen production and preparation method thereof

Info

Publication number: CN117210856A
Application number: CN202311122460.7A
Authority: CN
Inventors: 宁星杰; 张本树邦; 范峰强; 毕一飘; 赵淑燕; 冯伟民
Original assignee: Tianneng Battery Group Co Ltd
Current assignee: Tianneng Battery Group Co Ltd
Priority date: 2023-08-31
Filing date: 2023-08-31
Publication date: 2023-12-12

Abstract

The invention discloses a bimetallic catalyst for water electrolysis hydrogen production and a preparation method thereof, and relates to the technical field of water electrolysis hydrogen production. The invention provides a bimetallic catalyst for water electrolysis hydrogen production and a preparation method thereof, wherein nano-crystalline iridium and palladium are loaded on a carbon carrier with high specific surface area by a liquid phase reduction method, and the dispersibility and the particle size of bimetallic particles are controlled by carbon loading; the electron transfer between metals is improved through the synergistic effect between the palladium and iridium metals, so that the activity of the catalyst is improved; and then carrying out high-temperature heat treatment on the catalyst by a step heating method, thereby realizing coexistence of iridium oxide amorphous and crystal structures and improving the water electrolysis capacity of the catalyst.

Description

Bimetallic catalyst for water electrolysis hydrogen production and preparation method thereof

Technical Field

The invention relates to the technical field of water electrolysis hydrogen production, in particular to a bimetallic catalyst for water electrolysis hydrogen production and a preparation method thereof.

Background

There is an urgent need to develop economical, efficient and ecologically friendly energy storage and conversion systems for global climate change and energy crisis. Among them, the water electrolysis hydrogen production technology and the hydrogen fuel cell technology have important significance for the worldwide accepted utilization of clean energy carrier-hydrogen energy.

In the water electrolysis hydrogen production, compared with alkaline water electrolysis, the proton exchange membrane water electrolysis has the advantages of high current density, high hydrogen purity, high response speed and the like, and the working efficiency of the PEM water electrolysis hydrogen production technology is higher. Metallic iridium is considered as an OER-optimal catalytic material due to its excellent Oxygen Evolution Reaction (OER) activity and stability in an acidic medium during water electrolysis, but its low reserves and high price seriously hamper its large-scale application, so that it is required to increase the intrinsic activity of active centers during practical application to reduce the use of noble metals.

The rational incorporation of other metals in noble metal systems generally leads to an increase in catalytic activity, because changes in the electron or geometry lead to an adsorptive transfer of bond energy to the catalyst surface reaction intermediate, or to the generation of a synergistic effect of multiple active sites. The structures of the IrCo alloy, the IrCu alloy, the IrRu alloy and the like all show higher than the traditional IrO ₂ These are due to the fact that leaching of the doping element may expose more of the high-index crystal planes, resulting in an improvement of OER performance, essentially due to IrO at the interface _x The structure achieves high OER performance.

Patent application publication No. JP2015534607a discloses an electrolytic electrocatalyst and an electrolytic process, such as the electrolysis of water, more specifically hydrogen at the cathode of a water electrolysis cell or oxygen at the anode of a water electrolysis cell. Are used and applied to water baths containing such electrode catalysts. The electrode catalyst used in the invention comprises a combination of palladium and iridium. After preparing the PdIr alloy catalyst by a chemical reduction method, the method removes hydroxide and oxide on the surface of the catalyst by heat treatment in a hydrogen atmosphere at 150 ℃, and has lower treatmentThe temperature does not cause sintering of the catalyst and loss of specific surface area; however, the heat treatment temperature is too low and the heat treatment is carried out under the anaerobic condition, so that the PdIr catalyst exists mainly in the form of simple substance, especially the metal Ir with main activity and not IrO _x The morphology exists, so that the catalyst activity can be attenuated during long-time operation.

Pyrolysis and liquid phase colloid processes are common processes for preparing Ir nanocrystals. In the preparation process of the pyrolysis method, a certain amount of surfactant is required to be added for dispersing nanocrystals, so that certain organic matters are easily remained on the surfaces of the pyrolyzed nanoparticles, and the activity of the catalyst is influenced; the liquid phase colloid method obtains the nanocrystalline through chemical reaction between the precursor in the solution and other additives, the experimental operation is simple, and the control of the nanocrystalline structure, morphology, size and the like is easy to realize; however, due to the fact that a large amount of alcohol organic solvents are used, the generated nanocrystals have high stability in the solvents, and the defects of serious agglomeration of large-size crystals, difficult collection of products, low yield and the like exist; secondly, when the liquid phase colloid method is used for calcining the nanocrystals at a high temperature, the catalyst is easy to sinter further, and the activity of the catalyst is reduced.

Disclosure of Invention

Based on the defects in the prior art, the invention provides a bimetallic catalyst for water electrolysis hydrogen production and a preparation method thereof. The invention adopts a liquid phase reduction method to prepare the carbon supported palladium iridium bimetallic catalyst, and the carbon black with high specific surface area enhances the high dispersion of palladium and iridium on the carrier, so as to obtain the small-particle-diameter high-activity metal; then adopting stepped heating calcination, and oxidizing elemental iridium into iridium oxide with better durability while removing oxygen-containing groups on the surface of the catalyst; the carbon black with high specific surface makes iridium not easy to agglomerate in the calcining process; compared with iridium, the metal palladium has larger particle size and has more contact surface with carbon black; the iridium metal is mostly attached to the palladium metal, and then exists on the surface of the carrier through palladium-carbon interaction, so that sintering agglomeration is not easy to occur in the high-temperature calcination process.

The specific technical scheme of the invention is as follows:

the preparation method of the bimetallic catalyst for water electrolysis hydrogen production comprises the following steps:

(1) Dissolving an iridium precursor in a solvent 1 to obtain an iridium precursor solution, dissolving a palladium precursor in a solvent 2 to obtain a palladium precursor solution, and uniformly mixing and dispersing the obtained iridium precursor solution and the palladium precursor solution to obtain a mixed solution A;

(2) Uniformly dispersing carbon black, organic alcohol, alkali liquor and a reducing agent to obtain a mixed solution B;

(3) Dropwise adding the mixed solution B obtained in the step (2) into the mixed solution A obtained in the step (1) to perform a reduction reaction, and obtaining a reaction solution after the reaction is finished;

(4) Adding acid liquor into the reaction solution in the step (3) to obtain a reaction solid;

(5) And (3) carrying out stepwise heating calcination on the reaction solid in the step (4) to obtain the bimetallic catalyst for water electrolysis hydrogen production.

Specifically, in the step (1), the iridium precursor is chloroiridic acid, iridium acetylacetonate or iridium acetate,

the solvent 1 is water, and the solvent is water,

the mass fraction of the iridium precursor solution is 5% -20%,

the palladium precursor is palladium acetate,

the solvent 2 is acetone, and the solvent is acetone,

the mass fraction of the palladium precursor solution is 5% -20%.

Dispersing the iridium and palladium precursor solution by using a sand mill, wherein the dispersing time of the sand mill is 30-60min, and cooling water is introduced in the dispersing process.

Preferably, in the step (1), the mass ratio of palladium metal to iridium metal in the mixed solution A is 1:1-5. The mass ratio of iridium metal and palladium metal in the step (1) to the carbon black, alkali liquor and reducing agent in the step (2) is 1:1-10, 1:50-200 and 1:1-10 respectively. The electron transfer between metals is improved through the synergistic effect between the palladium and iridium metals, so that the activity of the catalyst is improved.

In the step (2), the carbon black is acetylene black, the acetylene black is BP2000, EC300J or cabot FCX800,

the organic alcohol is at least one of ethanol, isopropyl alcohol and ethylene glycol,

the mass ratio of the carbon black to the organic alcohol is 1:100-400,

the alkali liquor is at least one of sodium carbonate aqueous solution, sodium bicarbonate aqueous solution and sodium hydroxide aqueous solution, the mass fraction of the alkali liquor is 10% -25%,

the reducing agent is at least one of methanol, formaldehyde and formic acid.

In the step (3), the dropping speed is 5-20ml/min, the temperature of the reduction reaction is 70-90 ℃, and the reaction time is 3-9h. Iridium and palladium are loaded on a carbon carrier with high specific surface area by a liquid phase reduction method.

In the step (4), the acid liquid is at least one of sulfuric acid, nitric acid and phosphoric acid,

the mass ratio of iridium metal and palladium metal in the step (1) to the acid liquor in the step (4) is 1:10-20 respectively.

In the step (5), the step-type temperature-rising calcination is divided into 3 stages:

stage 1: heating to 100-200deg.C at a temperature rising rate of 5-10deg.C, heat treating for 30-90min,

stage 2: heating to 250-350deg.C at 5-10deg.C at stage 1, heat treating for 60-120min,

stage 3: heating to 400-600deg.C at 5-10deg.C at stage 2, heat treating for 90-180min, and cooling.

The stepwise temperature rising calcination method can achieve the coexistence effect of the amorphous and crystalline structures of iridium oxide.

The invention also provides a bimetallic catalyst for water electrolysis hydrogen production prepared by the preparation method.

The invention has the beneficial effects that:

the invention provides a bimetallic catalyst for water electrolysis hydrogen production and a preparation method thereof, wherein nano-crystalline iridium and palladium are loaded on a carbon carrier with high specific surface area by a liquid phase reduction method, and the dispersibility and the particle size of bimetallic particles are controlled by carbon loading; the electron transfer between metals is improved through the synergistic effect between the palladium and iridium metals, so that the activity of the catalyst is improved; and then carrying out high-temperature heat treatment on the catalyst by a step heating method, thereby realizing coexistence of iridium oxide amorphous and crystal structures and improving the water electrolysis capacity of the catalyst.

Drawings

FIG. 1 is an OER performance test pattern for examples 1-6 and comparative example 1.

Fig. 2 is a timing current test pattern for example 4 and comparative example 1.

Fig. 3 is an SEM characterization map of example 4.

Fig. 4 is an SEM characterization map of example 4.

Fig. 5 is an SEM characterization map of comparative example 1.

Fig. 6 is an SEM characterization of comparative example 1.

Detailed Description

Example 1

1. Dissolving iridium acetate in deionized water to prepare 10wt% iridium acetate aqueous solution; palladium acetate is dissolved in acetone to prepare 10wt% palladium acetate acetone solution; 2.57g of iridium acetate aqueous solution, 1.26g of palladium acetate acetone solution and the mass ratio of iridium to palladium metal is 0.7:0.3, dispersing for 30 minutes by a sand mill;

2. dissolving sodium carbonate in an aqueous solution to prepare a 20% sodium carbonate aqueous solution; 0.8g of EC300J carbon black is weighed, 160g of ethanol is placed in a beaker, and 20g of 20% sodium carbonate aqueous solution is added; 1g of reducing agent formic acid; then placing the mixed solution into a sand mill, and performing sand milling and dispersing for 120 minutes;

3. transferring the dispersed carbon black mixed solution into a three-neck flask, placing the three-neck flask into a water bath kettle, setting the reaction temperature of the water bath kettle to be 80 ℃, and magnetically stirring; setting the flow rate of a peristaltic pump to be 5ml/min, and dripping the palladium and iridium precursor mixed solution into a three-neck flask in the reaction process; after all transfer is completed, continuously reacting for 6 hours;

4. naturally cooling the reacted solution, transferring to a large beaker, adding 2g of pure sulfuric acid (the mass fraction is 98%), adding a large amount of deionized water, and stirring to allow the mixture to naturally settle;

5. filter-pressing the settled catalyst, and then placing the catalyst in a vacuum drying oven for vacuum drying for 16 hours at 70 ℃;

6. placing the dried catalyst in a calciner, and then carrying out heating heat treatment; heating to 150 ℃ at a heating rate of 5 ℃/min in stage 1, and then heat-treating at the temperature for 60 minutes; then heating to 300 ℃ continuously at a heating rate of 5 ℃/min, and performing heat treatment for 90 minutes; finally, continuously heating to 450 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 120 minutes; naturally cooling to obtain the required catalyst, and marking Pd _0.3 -Ir _0..7 /C-450。

Example 2

1. Dissolving iridium acetate in deionized water to prepare 10wt% iridium acetate aqueous solution; palladium acetate is dissolved in acetone to prepare 10wt% palladium acetate acetone solution; 1.84g of iridium acetate aqueous solution and 2.1g of palladium acetate acetone solution are weighed, the mass ratio of iridium to palladium metal is 1:1, and the iridium to palladium metal is dispersed for 30 minutes by a sand mill;

6. placing the dried catalyst in a calciner, and then carrying out heating heat treatment; at a temperature rising rate of 5 ℃/min in stage 1Heating to 150 ℃, and then heat-treating at the temperature for 60 minutes; then heating to 300 ℃ continuously at a heating rate of 5 ℃/min, and performing heat treatment for 90 minutes; finally, continuously heating to 450 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 120 minutes; naturally cooling to obtain the required catalyst, and marking Pd _0.5 -Ir _0.5 /C-450。

Example 3

1. Dissolving iridium acetate in deionized water to prepare 10wt% iridium acetate aqueous solution; palladium acetate is dissolved in acetone to prepare 10wt% palladium acetate acetone solution; 1.1g of iridium acetate aqueous solution and 2.94g of palladium acetate acetone solution are weighed, the mass ratio of iridium to palladium metal is 0.3:0.7, and the iridium and palladium metals are dispersed for 30 minutes by a sand mill;

6. placing the dried catalyst in a calciner, and then carrying out heating heat treatment; heating to 150 ℃ at a heating rate of 5 ℃/min in stage 1, and then heat-treating at the temperature for 60 minutes; then heating to 300 ℃ continuously at a heating rate of 5 ℃/min, and performing heat treatment for 90 minutes; finally, continuously heating to 450 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 120 minutes; naturally cooling to obtain the required catalyst, and marking Pd _0.7 -Ir _0.3 /C-450。

Example 4

6. placing the dried catalyst in a calciner, and then carrying out heating heat treatment; heating to 200 ℃ at a heating rate of 5 ℃/min in stage 1, and then heat-treating at the temperature for 60 minutes; then heating to 250 ℃ continuously at a heating rate of 5 ℃/min, and performing heat treatment for 90 minutes; finally, continuously heating to 450 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 120 minutes; naturally cooling to obtain the required catalyst, and marking Pd _0.5 -Ir _0.5 /C-450。

Example 5

6. placing the dried catalyst in a calciner, and then carrying out heating heat treatment; heating to 200 ℃ at a heating rate of 5 ℃/min in stage 1, and then heat-treating at the temperature for 60 minutes; then heating to 250 ℃ continuously at a heating rate of 5 ℃/min, and performing heat treatment for 90 minutes; finally, continuously heating to 500 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 120 minutes; naturally cooling to obtain the required catalyst, and marking Pd _0.5 -Ir _0.5 /C-500；

Example 6

6. placing the dried catalyst in a calciner, and then carrying out heating heat treatment; heating to 200 ℃ at a heating rate of 5 ℃/min in stage 1, and then heat-treating at the temperature for 60 minutes; then heating to 250 ℃ continuously at a heating rate of 5 ℃/min, and performing heat treatment for 90 minutes; finally, continuously heating to 550 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 120 minutes; naturally cooling to obtain the required catalyst, and marking Pd _0.5 -Ir _0.5 /C-550。

Comparative example 1

2. dissolving sodium carbonate in an aqueous solution to prepare a 20% sodium carbonate aqueous solution; 160g of ethanol is weighed into a beaker, and 20g of 20% sodium carbonate aqueous solution is added; 1g of reducing agent formic acid; then placing the mixed solution into a sand mill, and performing sand milling and dispersing for 120 minutes;

3. transferring the dispersed mixed solution into a three-neck flask, placing the three-neck flask into a water bath kettle, setting the reaction temperature of the water bath kettle to be 80 ℃, and magnetically stirring; setting the flow rate of a peristaltic pump to be 5ml/min, and dripping the palladium and iridium precursor mixed solution into a three-neck flask in the reaction process; after all transfer is completed, continuously reacting for 6 hours;

6. placing the dried catalyst in a calciner, and then carrying out heating heat treatment; heating to 150 ℃ at a heating rate of 5 ℃/min in stage 1, and then heat-treating at the temperature for 60 minutes; then heating to 300 ℃ continuously at a heating rate of 5 ℃/min, and performing heat treatment for 90 minutes; finally, continuously heating to 450 ℃ at a heating rate of 5 ℃/min, and performing heat treatment for 120 minutes; naturally cooling to obtain the required catalyst, and marking Pd _0.5 -Ir _0.5 -450。

Detection example 1

The catalysts prepared in examples 1 to 6 and comparative example 1 were subjected to electrochemical performance test under the same conditions as follows: accurately weighing 5mg of the catalyst in a 50mL brown glass bottle, and adding 5mL of prepared Nafion isopropanol solution (Nafion mass fraction is 0.13%) into the weighed catalyst; ultrasonic wave is carried out for 30min, so that the slurry is uniformly mixed; transferring 5 mu L of the dispersed slurry by a liquid transferring gun, and uniformly dripping the slurry onto the surface of a smooth and clean disc electrode to completely dry the disc electrode under an infrared lamp to serve as a working electrode; the electrodes are placed in an electrolytic cell to form a three-electrode system. Wherein the reference electrode is a calomel electrode, the counter electrode is a Pt wire electrode, and the electrolyte is O ₂ Saturated 0.5mol/L H ₂ SO ₄ A solution.

The catalyst coated working electrode was immersed in electrolyte at a constant temperature of 25 c, cyclic voltammetric scan was performed at 200mV/s to activate the electrode, then the disk electrode was adjusted to 1600rpm, scanning was performed from low to high potential with a scan rate of 5mV/s, and each sample was tested 3 times. The test voltage ranges from 1.0 to 1.6V (Vs RHE). The RHE electrode is a reversible hydrogen electrode, a conventional electrode in electrochemical testing. Read at 10mA/cm ² The voltage values were tested at current density to specifically evaluate the Oxygen Evolution Reaction (OER) activity of the catalyst. The test results are shown in FIG. 1.

From the test patterns, the OER performance of the catalysts of examples 1-5 is better than that of the catalyst of comparative example 1; by conversion at 10mA/cm ² At current density, example 345mV (relative to RHE) and comparative example 1 395mV (relative to RHE), the overpotential was reduced by 50mV, which illustrates the Pd prepared in example 4 _0.5 -Ir _0.5 The catalyst/C-450 has better OER performance.

In water electrolysis, the catalyst performance is generally related to its structure, particle size, and degree of dispersion; for comparative example 1, the liquid phase method is adopted to reduce palladium iridium bimetallic, and then high temperature heat treatment is carried out, so that agglomeration phenomenon can occur in the preparation process, the particle size of the generated metal particles is larger, and the uniformity of the particle size is poor; in the embodiment 1-embodiment 4, bimetal is loaded on a carbon carrier, and palladium iridium metal particles are highly dispersed through the interaction of the carrier with high specific surface area and the metal, so that no obvious agglomeration phenomenon exists, the particle size is smaller, more active sites are exposed in the water electrolysis process, and the OER activity of the palladium iridium metal particles is further improved.

Detection example 2

The catalysts prepared in example 4 and comparative example 1 were subjected to a chronoamperometric durability test under the same conditions; coating the catalyst working electrode according to the method; immersing the catalyst-coated working electrode in 0.5mol/L H at a constant temperature of 25 DEG C ₂ SO ₄ The revolution of the disk electrode is regulated to 1600rpm by the solution electrolyte; setting the working voltage of the timing current to be 1.65V (compared with the RHE electrode), and taking 6 hours to examine the change condition of the working electrode current with time under the constant voltage condition. The results are shown in FIG. 2.

As can be seen from the graph, the initial operating current of example 4 and comparative example 1 are different, and example 4 has more excellent OER activity, so that the initial operating current is significantly greater than that of the catalyst of comparative example 1; under the action of constant voltage, the working current of the two catalysts is gradually reduced; when the comparative example 1 is about 5000s, the working current of the catalyst tends to be gentle, which shows that the activity of the catalyst is greatly attenuated; in example 4, the working current is approximately parallel to that of comparative example 1 after 1800s of constant voltage, and the constant voltage acting time is obviously better than that of the catalyst of comparative example 1, which shows that the catalyst prepared by the invention has better water electrolysis stability than that of the catalyst of comparative example 1.

Detection example 3

The catalysts prepared in example 4 and comparative example 1 were subjected to physical characterization of SEM materials under the same conditions, and the results are shown in fig. 3 to 6 below.

As can be seen from fig. 3 and 5, example 4 has a better metal dispersity and a smaller particle size than comparative example 1 under the same electron microscope magnification; comparative example 1 exhibited a certain flake shape under the lens, and the structure was different from that of the pellet shape of example 4.

In fig. 4, example 4 shows a certain number of spherical particles under a sponge-like structure, which may be caused by amorphous state transition of iridium oxide under high temperature treatment; whereas in comparative example 1 of fig. 6, the metal particles were almost entirely of a sponge structure; related literature reports that iridium oxide is mainly composed of amorphous and crystalline structures; the crystal structure is mostly in a rutile state, and has higher durability compared with amorphous iridium oxide; the amorphous Ir oxide has more unsaturated bonds, which is favorable for the adsorption of reactants; in the water electrolysis process, the iridium oxide with amorphous and crystal structures exists at the same time in a certain proportion, and Ir is reacted under the combined action of the iridium oxide and the iridium oxide ³⁺ 、Ir ⁴⁺ And Ir ⁵⁺ And cyclic conversion is realized, so that a rapid OER process is realized.

Claims

1. The preparation method of the bimetallic catalyst for water electrolysis hydrogen production is characterized by comprising the following steps of:

2. The method for preparing a bimetallic catalyst for hydrogen production by water electrolysis according to claim 1, wherein in the step (1), the iridium precursor is chloroiridic acid, iridium acetylacetonate or iridium acetate,

the solvent 1 is water, and the solvent is water,

the mass fraction of the iridium precursor solution is 5% -20%,

the palladium precursor is palladium acetate,

the solvent 2 is acetone, and the solvent is acetone,

the mass fraction of the palladium precursor solution is 5% -20%.

3. The method for producing a bimetallic catalyst for the production of hydrogen by water electrolysis according to claim 1, wherein in the step (1), the mass ratio of palladium metal to iridium metal in the mixed solution a is 1:1-5.

4. The method for preparing a bimetallic catalyst for water electrolysis hydrogen production as claimed in claim 1, wherein the mass ratio of iridium metal and palladium metal in the step (1) to the carbon black, alkali liquor and reducing agent in the step (2) is 1:1-10, 1:50-200, 1:1-10.

5. The method for producing a bimetallic catalyst for hydrogen production by water electrolysis according to claim 1, wherein in the step (2), the carbon black is acetylene black, and the acetylene black is BP2000, EC300J or Kabote FCX800,

the mass ratio of the carbon black to the organic alcohol is 1:100-400,

the reducing agent is at least one of methanol, formaldehyde and formic acid.

6. The method for producing a bimetallic catalyst for hydrogen production by water electrolysis according to claim 1, wherein in the step (3), the dropping rate is 5 to 20ml/min, the temperature of the reduction reaction is 70 to 90 ℃, and the reaction time is 3 to 9 hours.

7. The method for producing a bimetallic catalyst for the production of hydrogen by water electrolysis according to claim 1, wherein in the step (4), the acid solution is at least one of sulfuric acid, nitric acid and phosphoric acid,

the mass ratio of iridium metal and palladium metal in the step (1) to the acid liquid in the step (4) is 1:10-20.

8. The method for producing a bimetallic catalyst for hydrogen production by water electrolysis according to claim 1, wherein in the step (5), the step-wise temperature-raising calcination is divided into 3 stages:

9. A bimetallic catalyst for hydrogen production by water electrolysis prepared by the method of any one of claims 1 to 8.