Preparation method of an electrocatalytic hydrogen evolution catalyst Pt / GaN

Abstract

The application belongs to the technical field of preparation of electrocatalytic hydrogen evolution catalysts, and discloses a preparation method of an electrocatalytic hydrogen evolution catalyst Pt / GaN. First, gallium nitride nanoparticles are loaded on the surface of an electrode, and then, through cyclic voltammetry, platinum is uniformly electrodeposited on the surface of the gallium nitride from an electrolyte containing chloroplatinic acid to prepare the catalyst Pt / GaN. The mass percentage of Pt in the catalyst is only 2.2-5.4%, which greatly improves the catalytic activity of the catalyst while reducing the Pt loading. From the entire preparation process, the application breaks through the limitation that the traditional platinum loading method cannot accurately control the particle size growth. The particle size of Pt in the catalyst is between 2-5 nm. On the other hand, the method has the advantages of easy availability of raw materials and environmental protection without pollution.

Description

Technical Field

[0001] This invention belongs to the field of preparation technology of electrocatalytic hydrogen evolution catalysts, specifically relating to a method for preparing a Pt / GaN electrocatalytic hydrogen evolution catalyst. Background Technology

[0002] Hydrogen has a high energy density, and its combustion product is water. With a wide range of applications, hydrogen is an ideal energy carrier. Electrocatalytic water splitting for hydrogen production is one of the most promising hydrogen production solutions. Among these, alkaline water splitting has significant value due to the cost advantages of related equipment. Pt-based materials are the most promising hydrogen evolution catalysts, but they face the problem of insufficient catalytic performance under alkaline conditions. Developing effective substrates to address the insufficient water splitting capacity of Pt under alkaline conditions is a key aspect of Pt-based electrocatalysts for hydrogen evolution. However, utilizing readily available substrate materials and exploring simpler electrocatalyst preparation techniques remains a challenge. Summary of the Invention

[0003] In order to overcome the shortcomings of the existing technology, the purpose of this invention is to provide a method for preparing the electrocatalytic hydrogen evolution catalyst Pt / GaN.

[0004] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0005] A method for preparing an electrocatalyst for hydrogen evolution, Pt / GaN, comprises the following steps:

[0006] (1) Preparation of the working electrode: GaN nanoparticles were weighed at room temperature and ultrasonically dispersed in ethanol to obtain a dispersion. The dispersion was then uniformly dropped onto the surface of a glassy carbon electrode or a carbon paper electrode and allowed to dry naturally in air to serve as the working electrode. The GaN loading on the working electrode was 0.2-0.5 mg / cm³. 2 ;

[0007] (2) Preparation of electrolyte: Dissolve the Pt source precursor in a 0.3-0.7M sulfuric acid solution to obtain an electrolyte. The concentration of the Pt source precursor in the electrolyte is 100-300 μmol / L. Inert gas is introduced into the electrolyte to remove the air and the inert gas atmosphere is maintained by continuous gas flow.

[0008] (3) Electrodeposition reaction: The Ag / AgCl reference electrode, graphite rod counter electrode and working electrode prepared in step (1) are placed in the electrolyte obtained in step (2), and cyclic voltammetric electrochemical scanning is performed at a scanning rate of 5-20 mV / s between -0.1V and -0.6V, with 100-200 cycles.

[0009] (4) Rinse the electrolyte on the surface of the glassy carbon electrode or carbon paper electrode with ethanol, then put the glassy carbon electrode or carbon paper electrode into ethanol and sonicate it. Collect the sample multiple times, and finally dry the collected sample to obtain the Pt / GaN catalyst.

[0010] Preferably, in step (1), the raw material ratio is GaN nanoparticles: ethanol = (1-3) mg: (200-500) μL.

[0011] Preferably, in step (1), the volume concentration of the ethanol is ≥95%.

[0012] Preferably, the Pt source precursor is H2PtCl6·6H2O.

[0013] In this invention, gallium nitride nanoparticles are prepared according to existing technology; in step (1), the purchased glassy carbon electrode or carbon paper electrode needs to be pretreated before use: the glassy carbon electrode needs to be polished and cleaned; the carbon paper electrode needs to be treated with concentrated sulfuric acid to remove the grease and impurities on the surface.

[0014] Beneficial effects: The catalyst of this invention uses GaN as a substrate and supports highly dispersed Pt nanoparticles on a gallium nitride matrix. Although the mass percentage of Pt in the obtained catalyst is only 2.2-5.4%, this invention greatly improves the catalytic activity of the catalyst while reducing the Pt loading. In terms of the entire preparation process, this invention overcomes the limitation of traditional platinum-supported methods in that they cannot precisely control the particle size growth. The Pt particle size in the catalyst of this invention is between 2-5 nm. On the other hand, the method of this invention has the advantages of readily available raw materials and being environmentally friendly and pollution-free. Attached Figure Description

[0015] Figure 1 Characterization results of GaN nanoparticles and Pt / GaN catalyst prepared in Example 1: (a) TEM image of GaN nanoparticles, (b) HRTEM image of GaN nanoparticles, (c) TEM image of Pt / GaN catalyst, (d) HRTEM image of Pt / GaN catalyst.

[0016] Figure 2 LSV curves of the catalysts prepared in Examples 1-2 and Comparative Examples 1-3, and commercial 20wt% Pt / C catalysts. Detailed Implementation

[0017] To make the present invention clearer and more explicit, the present invention will be further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0018] Example 1

[0019] A method for preparing an electrocatalyst for hydrogen evolution, Pt / GaN, comprises the following steps:

[0020] (1) Preparation of GaN nanoparticles by tube furnace sintering, the specific process is as follows:

[0021] First, 1.28g of hydrated gallium nitrate (Ga(NO3)3-xH2O) and 0.63g of melamine (C3H6N6) were thoroughly ground and mixed. Then, the mixture was placed in a tube furnace, purged with high-purity argon at 60°C for 30 min, heated to 800°C at a heating rate of 2°C / min, and held at that temperature for 1 h. Next, the mixture was sintered in air at 560°C for 2 h, and finally, pale yellow GaN nanoparticles were obtained.

[0022] (2) Preparation of working electrode: At room temperature, 3 mg of GaN nanoparticles obtained in step (1) were weighed using an electronic balance and dispersed in 500 μL of anhydrous ethanol. The mixture was then sonicated for 40 min to completely disperse the particles and obtain a dispersion. 5.4 μL of the dispersion was evenly added to the polished and cleaned glassy carbon electrode (3 mm in diameter) using a pipette and allowed to dry naturally in the air to serve as the working electrode.

[0023] (3) Preparation of electrolyte: Dissolve H2PtCl6·6H2O in 0.5M sulfuric acid solution to obtain electrolyte. The concentration of H2PtCl6·6H2O in the electrolyte is 100μmol / L. Inert gas is introduced into the electrolyte to remove the air and the inert gas atmosphere is maintained by continuous gas introduction.

[0024] (4) Electrodeposition reaction: The Ag / AgCl reference electrode, graphite rod counter electrode, and working electrode prepared in step (2) are placed in the electrolyte obtained in step (3), and cyclic voltammetric electrochemical scanning is performed at a scanning rate of 5 mV / s between -0.1V and -0.6V (vs. Ag / AgCl reference electrode), with 100 cycles.

[0025] (5) Rinse the electrolyte on the surface of the glassy carbon electrode with anhydrous ethanol, then place the glassy carbon electrode in anhydrous ethanol and sonicate it. Collect samples multiple times, and finally dry the collected samples to obtain the Pt / GaN catalyst.

[0026] Example 2

[0027] The difference from Example 1 is that in step (3), the concentration of H2PtCl6·6H2O in the electrolyte is 300 μmol / L; all other aspects are the same as in Example 1.

[0028] Comparative Example 1

[0029] The difference from Example 1 is that in step (3), the concentration of H2PtCl6·6H2O in the electrolyte is 500 μmol / L; all other aspects are the same as in Example 1.

[0030] Comparative Example 2

[0031] The difference from Example 1 is that in step (3), the concentration of sulfuric acid solution is 0.05M; all other aspects are the same as in Example 1.

[0032] Comparative Example 3

[0033] The difference from Example 1 is that in step (4), the voltage range of the cyclic voltammetric electrochemical scan is -0.5V to 0.2V; all other aspects are the same as in Example 1.

[0034] Product structure characterization

[0035] Figure 1 Characterization results of the GaN nanoparticles and Pt / GaN catalyst prepared in Example 1: (a) TEM image of GaN nanoparticles, (b) HRTEM image of GaN nanoparticles, (c) TEM image of Pt / GaN catalyst, (d) HRTEM image of Pt / GaN catalyst. Figure 1 (a)-(b) show lattice fringes belonging to the (100), (101), and (102) crystal planes of GaN, indicating that GaN has good crystallinity. Figure 1 (c)-(d) show lattice fringes belonging to the (111) plane of Pt, with a lattice spacing of d = 0.22 nm and a highly dispersed distribution on the substrate. The particle size of Pt is 2-5 nm, indicating the successful synthesis of the Pt / GaN catalyst.

[0036] Table 1 shows the ICP-MS test results of the catalysts prepared in Examples 1-2. It indicates that the mass percentage of Pt in the catalysts obtained in this invention is 2.2-5.4%.

[0037] Table 1. Metal element content determined by ICP-MS

[0038]

[0039] Performance testing

[0040] The samples were characterized for electrocatalytic hydrogen evolution using an electrochemical workstation (CHI 760E). The electrolyte was 1 mol / L potassium hydroxide. A carbon rod was used as the counter electrode, Hg / HgO as the reference electrode, and the working electrode was a carbon paper-supported catalyst. Hydrogen evolution was tested using linear sweep voltammetry (LSV). The working electrode was prepared as follows: the catalysts prepared in Examples 1-2 and Comparative Examples 1-3, and the commercial 20 wt% Pt / C catalyst were used as dispersants to prepare dispersions. The dispersions were then uniformly added dropwise to a 0.25 cm³ solution. 2 The carbon paper surface was allowed to dry naturally in air to obtain the working electrode, with a catalyst loading of 0.5 mg / cm³. 2 .

[0041] The LSV curves from the test are shown below. Figure 2 .from Figure 2 (a) It can be seen that the catalyst prepared in this invention has a performance of 10 mA / cm². 2 The overpotentials at the time of application (24 mV in Example 1; 41 mV in Example 2) were lower than those of a commercial 20 wt% Pt / C catalyst (62 mV), demonstrating that the samples of this invention exhibit excellent electrocatalytic hydrogen evolution performance despite low platinum content. Figure 2 (b) It can be seen that the concentration of the Pt precursor solution, the concentration of concentrated sulfuric acid, and the deposition voltage window all affect the performance of the final catalyst, especially the catalyst deposited under 0.05M sulfuric acid has the worst performance. Therefore, after a series of experiments, this invention has developed a suitable method for preparing the electrocatalytic hydrogen evolution catalyst Pt / GaN.

Claims

1. A method for preparing a Pt / GaN electrocatalyst for hydrogen evolution, characterized in that, The steps are as follows: (1) Preparation of the working electrode: GaN nanoparticles were weighed at room temperature and ultrasonically dispersed in ethanol to obtain a dispersion. The dispersion was then uniformly dropped onto the surface of a glassy carbon electrode or a carbon paper electrode and allowed to dry naturally in air to serve as the working electrode. The GaN loading on the working electrode was 0.2-0.5 mg / cm³. 2 ; (2) Preparation of electrolyte: Dissolve the Pt source precursor in a 0.3-0.7M sulfuric acid solution to obtain an electrolyte. The concentration of the Pt source precursor in the electrolyte is 100-300 μmol / L. Inert gas is introduced into the electrolyte to remove the air and the inert gas atmosphere is maintained by continuous gas flow. (3) Electrodeposition reaction: The Ag / AgCl reference electrode, graphite rod counter electrode and working electrode prepared in step (1) are placed in the electrolyte obtained in step (2), and cyclic voltammetric electrochemical scanning is performed at a scanning rate of 5-20 mV / s between -0.1V and -0.6V, with 100-200 cycles. (4) Rinse the electrolyte on the surface of the glassy carbon electrode or carbon paper electrode with ethanol, then put the glassy carbon electrode or carbon paper electrode into ethanol and sonicate it. Collect the sample multiple times, and finally dry the collected sample to obtain the Pt / GaN catalyst.

2. The method for preparing the electrocatalyst Pt / GaN for hydrogen evolution as described in claim 1, characterized in that: In step (1), the raw material ratio is GaN nanoparticles: ethanol = (1-3) mg: (200-500) μL.

3. The method for preparing the electrocatalyst Pt / GaN for hydrogen evolution as described in claim 1 or 2, characterized in that: In step (1), the volume concentration of the ethanol is ≥95%.

4. The method for preparing the electrocatalyst Pt / GaN for hydrogen evolution as described in claim 1, characterized in that: The Pt source precursor is H2PtCl6·6H2O.

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