Method for preparing surface amorphous methanol electrooxidation catalyst through electrodeposition

Abstract

The invention provides a method for preparing a surface amorphous methanol electrooxidation catalyst through electrodeposition, and belongs to the technical field of catalysts. The Pt-Ag bimetallic methanol electrooxidation catalyst prepared by the invention has a special surface amorphous structure, shows very excellent catalytic stability for methanol electrooxidation reaction, is adjustable in component and controllable in structure, can effectively give consideration to catalyst performance and production cost through systematic optimization of synthesis parameters, and is suitable for industrial production. And the practical application of the direct methanol fuel cell is facilitated. By enlarging the size of the electro-deposition substrate, the Pt-Ag bimetallic methanol electro-oxidation catalyst which is loaded by the large-size substrate and has the surface amorphous structure can be obtained, and a solid foundation is laid for subsequent large-scale application.

Description

Technical Field

[0001] This invention belongs to the field of catalyst technology and relates to a method for preparing amorphous methanol electro-oxidation catalysts by electrodeposition. Background Technology

[0002] In the context of energy transition, developing novel and efficient energy catalysts to promote the practical application of clean energy is of paramount importance. Methanol, as an important low-carbon energy carrier, boasts a mass energy density ten times that of lithium batteries and a volumetric energy density nine times that of compressed hydrogen (at 20 MPa). Furthermore, its liquid state at room temperature facilitates transportation and storage, making it a promising candidate for practical applications. Currently, converting methanol into electricity through direct methanol fuel cell technology is a crucial pathway for methanol energy utilization. However, the poor stability of its anode methanol electrooxidation catalyst is a significant problem, severely hindering the practical application of direct methanol fuel cell technology. Therefore, to accelerate the efficient utilization of methanol energy across multiple scenarios, it is essential to develop new methods to prepare highly stable methanol electrooxidation catalysts. Summary of the Invention

[0003] In view of this, the present invention provides a method for preparing amorphous methanol electro-oxidation catalysts by electrodeposition. The catalyst material has the characteristics of amorphous surface structure, low cost, and high stability, which will strongly promote the practical application of direct methanol fuel cells.

[0004] The present invention provides a method for preparing a Pt-Ag bimetallic catalyst with a surface amorphous structure, comprising the following steps: (1) functionalizing an electrochemically deposited substrate with an acidic or alkaline solution to obtain a functionalized substrate;

[0005] (2) Dissolve and disperse Pt metal precursors and Ag metal precursors in different proportions in a solvent to obtain a liquid system; place the functionalized substrate described in step (1) in the liquid system and perform electrodeposition; remove the deposition electrode to obtain a supported Pt-Ag catalyst with a surface amorphous structure.

[0006] Preferably, the electrochemical deposition substrate in step (1) includes nickel foam, carbon paper, or titanium felt, etc.

[0007] Preferably, the functionalization process in step (1) includes placing the electrochemically deposited substrate in an acidic or alkaline solution with a pH of 0 to 14 for 0.5 to 17 hours.

[0008] Preferably, the Pt metal precursor in step (2) can be chloroplatinate, chloroplatinic acid, etc.;

[0009] The Ag metal precursor can be silver nitrate, silver acetate, etc.

[0010] Preferably, the electrodeposition voltage in step (2) is below 0V and the holding time is 0 to 360,000 seconds.

[0011] Preferably, before the electrodeposition in step (2), the process further includes dissolving the core metal precursor, placing the functionalized substrate in the core metal precursor solution, performing a first electrodeposition, placing the electrode obtained after the first electrodeposition in the liquid system for a second electrodeposition, washing with water and removing the electrode to obtain Pt-Ag catalysts with different core-supported types and surface amorphous structures.

[0012] Preferably, the deposition voltage of the first electrodeposition and the second electrodeposition is below 0V, and the holding time is 0 to 360,000 seconds.

[0013] Preferably, the core metal precursor is an inexpensive 3d transition metal salt.

[0014] The present invention also provides a Pt-Ag bimetallic catalyst with an amorphous surface structure prepared by the aforementioned preparation method.

[0015] The present invention also provides the application of the Pt-Ag bimetallic catalyst with amorphous surface structure in the electro-oxidation catalysis of methanol.

[0016] This invention provides a method for preparing a Pt-Ag bimetallic catalyst with an amorphous surface structure via electrochemical deposition. The Pt-Ag bimetallic catalyst prepared by this method possesses a unique amorphous surface structure, enabling highly stable catalysis for the electrooxidation reaction of methanol. The amorphous layer on the surface of the Pt-Ag bimetallic catalyst has an adjustable Pt:Ag ratio within the range of 100:1 to 1:100. In this invention, the catalyst core has a tunable composition, effectively compatible with inexpensive 3d transition metals such as Ru, Ni, and Co.

[0017] Beneficial effects:

[0018] (1) The Pt-Ag bimetallic methanol electro-oxidation catalyst prepared in this invention has a special surface amorphous structure, exhibits excellent catalytic stability for methanol electro-oxidation reaction, and its composition is adjustable and its structure is controllable. Through systematic optimization of synthesis parameters, it can effectively balance catalyst performance and production cost, which is very beneficial for promoting the practical application of direct methanol fuel cells.

[0019] (2) By enlarging the size of the electrodeposition substrate, this invention can obtain a Pt-Ag bimetallic methanol electro-oxidation catalyst with a surface amorphous structure supported by a large-size substrate, which lays a solid foundation for subsequent large-scale application. Attached Figure Description

[0020] Figure 1 The graph shows the methanol electro-oxidation performance of the Pt-Ag bimetallic catalyst and the commercial Pt / C catalyst.

[0021] Figure 2 This refers to the change in the Pt-Ag bond length in the Pt-Ag catalyst during the reaction;

[0022] Figure 3 A scanning transmission electron microscope image of a Pt-Ag bimetallic catalyst with an amorphous surface structure;

[0023] Figure 4 Scanning transmission electron microscopy (STEM) image of a Pt-Ag bimetallic catalyst with an amorphous surface structure prepared using a large-size substrate.

[0024] Figure 5 Scanning transmission electron microscopy (STEM) images of Pt-Ag bimetallic catalysts with amorphous surface structures and different surface Pt:Ag ratios.

[0025] Figure 6 Scanning transmission electron microscopy (STEM) images of Pt-Ag bimetallic catalysts with different core compositions and amorphous surface structures. Detailed Implementation

[0026] Unless otherwise specified in the following examples, the conditions were performed under standard conditions or as recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0027] Example 1

[0028] A supported Pt-Ag bimetallic catalyst with an amorphous surface structure is disclosed. The carbon paper substrate is functionalized with acid or alkali (hydrochloric acid solution, sulfuric acid solution, or sodium hydroxide solution, potassium hydroxide solution, pH=14). The Pt precursor is chloroplatinic acid, and the Ag precursor is silver nitrate, with a Pt:Ag ratio of 1:3. During synthesis, the disordered surface atomic arrangement is induced by associated hydrogen gas, effectively achieving surface amorphization of the Pt-Ag bimetallic catalyst (e.g., ...). Figure 3 (As shown).

[0029] The preparation method of the above-mentioned supported Pt-Ag bimetallic catalyst with amorphous surface structure is as follows: First, Pt salt and Ag salt are dissolved in potassium hydroxide solvent at pH=14. Then, the substrate electrode is placed in this liquid system, and the deposition voltage is set to -0.25V and maintained for 0-360000 seconds. Afterward, the deposited electrode is removed and washed with water to obtain the supported Pt-Ag catalyst with amorphous surface structure.

[0030] Example 2

[0031] A supported Pt-Ag bimetallic catalyst with an amorphous surface structure was prepared using a large-size substrate. The large-size carbon paper substrate was functionalized with acid or alkali (hydrochloric acid solution, sulfuric acid solution, or sodium hydroxide solution, potassium hydroxide solution, pH=14). The Pt precursor was chloroplatinic acid, and the Ag precursor was silver nitrate, with a Pt:Ag ratio of 1:3. During the synthesis process, the disordered surface atomic arrangement was induced by associated hydrogen gas, effectively achieving surface amorphization of the Pt-Ag bimetallic catalyst (e.g., ...). Figure 4 (As shown).

[0032] The preparation method of the supported Pt-Ag bimetallic catalyst with an amorphous surface structure using a large-size substrate is as follows: First, Pt salt and Ag salt are dissolved in potassium hydroxide solvent at pH=14. Then, the large-size substrate electrode is placed in this liquid system, and the deposition voltage is set to -0.25V and maintained for 0-360000 seconds. Afterward, the large-size deposition electrode is removed and washed with water to obtain the supported Pt-Ag catalyst with an amorphous surface structure.

[0033] Example 3

[0034] A supported Pt-Ag bimetallic catalyst with amorphous surface structure and different surface Pt:Ag ratios was developed. The carbon paper substrate was functionalized with acid or alkali (hydrochloric acid solution, sulfuric acid solution, or sodium hydroxide solution, potassium hydroxide solution, pH=14). The Pt precursor was chloroplatinic acid, and the Ag precursor was silver nitrate, with a Pt:Ag ratio of 1:1. During synthesis, the disordered surface atomic arrangement was induced by associated hydrogen gas, effectively achieving surface amorphization of the Pt-Ag bimetallic catalyst (e.g., ...). Figure 5 (As shown).

[0035] The preparation method of the above-mentioned supported Pt-Ag bimetallic catalysts with different surface Pt:Ag ratios and amorphous surface structures is as follows: First, Pt salts and Ag salts with different Pt:Ag ratios are dissolved in potassium hydroxide solvent at pH=14. Then, the substrate electrode is placed in this liquid system, and the deposition voltage is set to -0.25V and maintained for 0-360000 seconds. Afterward, the deposited electrode is removed and washed with water to obtain the supported Pt-Ag catalyst with an amorphous surface structure.

[0036] Example 4

[0037] A Pt-Ag catalyst with different core components and an amorphous surface structure was developed. The carbon paper substrate was functionalized with acid or alkali (hydrochloric acid solution, sulfuric acid solution, or sodium hydroxide solution, potassium hydroxide solution, pH=14). The Pt precursor was chloroplatinic acid, the Ag precursor was silver nitrate, and the Pt:Ag ratio was 1:1. The Ru precursor was a Ru salt. During synthesis, the disordered surface atomic arrangement was induced by associated hydrogen gas, effectively achieving surface amorphization of the Pt-Ag bimetallic catalyst (e.g., ...). Figure 6 (As shown).

[0038] The preparation method of the above-mentioned Pt-Ag catalysts with different core components and amorphous surface structures is as follows: Ru salt is dissolved in potassium hydroxide solvent at pH=14, with continuous stirring during the process. After the Ru salt is completely dissolved, the substrate electrode is placed in the liquid system, and the deposition voltage is set to -0.25V, maintained for 0-360000 seconds. Afterwards, the deposited electrode is removed and washed with water. The electrodeposited substrate is then placed in a solution containing reduced amounts of Pt and Ag salts, and the deposition voltage is set to -0.25V, maintained for 0-360000 seconds. After washing with water, the Ru metal core-supported Pt-Ag catalyst with an amorphous surface structure is obtained.

[0039] Stability testing was conducted using the chronoamperometry method. A voltage value was set, and the current retention at that voltage was observed. The experiment tested the catalyst's stability in the electro-oxidation of methanol, specifically in 1M KOH and 1M methanol solutions. The results showed that the catalyst exhibited excellent stability. The catalyst described in Example 1 demonstrated excellent catalytic stability for the electro-oxidation reaction of methanol. Specifically, at a test voltage of 0.86V, after one hour of testing, the output current of the catalyst decreased by only about 7% (e.g., ...). Figure 1 As shown), in contrast, the price reduction of commercial Pt / C catalyst (40% commercial Pt / C catalyst, produced by Johnson Matthey, UK) was as high as 98% (e.g. Figure 1 (As shown).

[0040] By assembling a Pt-Ag bimetallic catalyst with an amorphous surface structure as the anode catalyst into a direct methanol fuel cell, the resulting device can operate at 50 mA cm⁻¹. -2 It has been operating stably for over 120 hours under output current density conditions, demonstrating great potential for practical applications.

[0041] In-situ synchrotron radiation characterization results show that the surface active sites of the Pt-Ag bimetallic catalyst with an amorphous surface structure are mobile during the reaction (e.g., Figure 2As shown in the figure, this is the key to the excellent electro-oxidation stability of the catalyst in methanol. Thanks to this, the OH intermediates adsorbed at Ag sites in the amorphous layer on the surface are more likely to react with the carbon-containing intermediates adsorbed at Pt sites, thereby effectively inhibiting the accumulation of toxic carbon-containing intermediates on the catalyst surface, avoiding catalyst poisoning and deactivation, and thus greatly improving the stability of the catalyst.

[0042] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a Pt-Ag bimetallic catalyst having a surface amorphous structure, characterized by, The method comprises the following steps: (1) functionalizing the electrochemical deposition substrate with an acidic or basic solution to obtain a functionalized substrate; (2) dissolving and dispersing Pt metal precursors and Ag metal precursors in different proportions in a solvent to obtain a liquid system; placing the functionalized substrate of step (1) in the liquid system to perform electrodeposition, and taking out the deposited electrode to obtain a supported Pt-Ag catalyst with surface amorphous structure.

2. The preparation method according to claim 1, characterized in that, The electrochemical deposition substrate of step (1) comprises a nickel foam, carbon paper and titanium felt.

3. The method of claim 1 or 2, wherein the method further comprises, The functionalization treatment of step (1) comprises placing the electrochemical deposition substrate in an acidic or basic solution with a pH value of 0-14 for treatment, and the treatment time is 0.5-17 h.

4. The preparation method according to claim 1, characterized in that, The Pt metal precursor of step (2) comprises chloroplatinic acid salt or chloroplatinic acid. The Ag metal precursor comprises silver nitrate or silver acetate.

5. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. The deposition voltage of the electrodeposition of step (2) is 0 V or less, and the holding time is 0-360,000 s.

6. The method of claim 1, wherein the step of forming the first and second layers is performed by a process selected from the group consisting of: sputtering, evaporation, and chemical vapor deposition. Before the electrodeposition of step (2), the method further comprises dissolving a core metal precursor, placing the functionalized substrate in the core metal precursor solution to perform first electrodeposition, placing the deposited electrode obtained after the first electrodeposition in the liquid system to perform second electrodeposition, and taking out after water washing to obtain a different core supported Pt-Ag catalyst with surface amorphous structure.

7. The preparation method according to claim 6, characterized in that, The deposition voltage of the first electrodeposition and the second electrodeposition is 0 V or less, and the holding time is 0-360,000 s.

8. The preparation method according to claim 6, characterized in that, The core metal precursor is a cheap 3d transition metal salt.

9. A Pt-Ag bimetallic catalyst with surface amorphous structure prepared by the preparation method of any one of claims 1-9.

10. Application of the Pt-Ag bimetallic catalyst with surface amorphous structure of claim 9 in methanol electro-oxidation catalysis.

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