A single-atom la-doped composite hydrogen evolution electrocatalytic material and a preparation method thereof

Abstract

The application relates to the field of hydrogen production by electrolysis of water, in particular to a single-atom La-doped composite hydrogen evolution electrocatalytic material and a preparation method thereof. The preparation method of the single-atom La-doped composite hydrogen evolution electrocatalytic material comprises the following steps: preparing silkworm sand porous carbon; preparing Zn3In2S6 / C; preparing a precursor; and preparing the composite hydrogen evolution electrocatalytic material La-Zn3In2S6 / C. The unique flower-spherical layered structure and the narrow band gap characteristics of the Zn3In2S6 carrier provide abundant anchoring sites, and the 4f orbit electron regulation of La is combined, so that the hydrogen evolution overpotential of the catalyst is only 62 mV under a current density of 10 mA / cm2, the Tafel slope is as low as 45 mV / dec, the catalytic activity is close to the level of a commercial Pt / C, and by introducing the porous biological carbon substrate derived from calcined silkworm sand, the high specific surface area and excellent electrical conductivity are utilized, La atom agglomeration can be effectively prevented, and the charge transmission efficiency can be greatly improved.

Description

Technical Field

[0001] This invention relates to the field of hydrogen production by water electrolysis, specifically to a single-atom La-doped composite hydrogen evolution electrocatalytic material and its preparation method. Background Technology

[0002] Hydrogen, due to its high energy density and the fact that its combustion product is only water, is considered an ideal clean energy carrier for the future. Currently, water electrolysis is the most important green hydrogen production method, but its large-scale application still faces challenges. Traditional Pt-based catalysts, while highly efficient, are expensive and have limited reserves, resulting in high hydrogen production costs. Furthermore, existing catalysts have limited active sites, leading to slow hydrogen evolution reaction (HER) kinetics, necessitating the development of low-cost, highly active non-precious metal catalysts. Therefore, exploring novel electrocatalytic materials, such as single-atom catalysts, has become a key direction for overcoming these technological bottlenecks.

[0003] Single-atom catalysts (SACs) can significantly reduce the amount of precious metals used and improve catalytic activity by isolating and dispersing metal atoms on a support. As a rare earth metal, La has unique advantages in regulating electronic structure due to its unoccupied 4f orbitals and variable valence states, which can optimize the hydrogen adsorption free energy and improve HER performance. However, the preparation of La single-atom catalysts still faces many challenges: (1) Atom aggregation problem: During high-temperature treatment, La atoms are prone to migrate and aggregate to form nanoparticles, resulting in a reduction of active sites; (2) Insufficient stability: In acidic or alkaline electrolytes, La single atoms may detach from the support, affecting long-term catalytic stability; (3) Support dependence: The catalytic performance of La is highly dependent on the conductivity and anchoring ability of the support material, and a suitable support needs to be designed to inhibit its dissolution.

[0004] The support material has a decisive influence on the performance of single-atom catalysts. An ideal support needs to have a high specific surface area, abundant anchoring sites, and good conductivity. The ternary sulfide Zn3In2S6 has shown significant advantages in the field of catalysis due to its unique flower-shaped layered structure and narrow band gap: (1) High exposure of active sites: The layered porous structure provides a large number of surface active sites; (2) Excellent stability: The weak electronegativity of S²⁻ can enhance stability; (3) Synergistic effect: The Zn / In bimetallic sites can regulate the electronic state of La and optimize the H* adsorption kinetics. In addition, bio-carbon, due to its low cost, high porosity, and excellent conductivity, is further used as a substrate for single-atom La-doped Zn3In2S6 to increase the specific surface area and promote performance improvement.

[0005] Therefore, it is necessary to propose a single-atom La-doped composite hydrogen evolution electrocatalyst material with high specific surface area, abundant anchoring sites and good conductivity support, and its preparation method, so as to improve its performance in electrocatalyzing hydrogen evolution. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a single-atom La-doped composite hydrogen evolution electrocatalyst material and its preparation method.

[0007] This invention provides a method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material, comprising the following steps: S1: Preparation of porous carbon from silkworm excrement Silkworm excrement is placed in a tube furnace and calcined at a high temperature of 500-600℃ for 2-3 hours to obtain porous carbon from silkworm excrement. The preferred calcination temperature is 500℃ and the preferred calcination time is 2 hours. S2: Preparation of Zn3In2S6 / C Zinc sulfate heptahydrate, indium trichloride tetrahydrate, porous carbon from silkworm excrement, and thioacetamide were added to deionized water and stirred for 30 min. The mixture was then transferred to a reaction vessel and subjected to hydrothermal reaction for 12-13 h. After cooling, the mixture was centrifuged at 6500 rpm for 5 min and then washed three times alternately with deionized water and ethanol. After vacuum drying at 60 °C, Zn3In2S6 / C was obtained. The preferred hydrothermal reaction time was 12 h. S3: Preparation of precursors Lanthanum chloride was added to anhydrous ethanol and stirred thoroughly to dissolve. Then, Zn3In2S6 / C was added and stirred for 30 min. The mixture was then poured into a centrifuge tube and centrifuged at 6500-7000 rpm for 5 min. The precursor was then vacuum dried at 60-80℃ for 4-6 h. The preferred centrifugation rate was 6500 rpm, the preferred vacuum drying temperature was 80℃, and the preferred vacuum drying time was 4 h. S4: Preparation of composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C The above precursor was placed in a tube furnace and heated to 300-400℃ under an argon atmosphere, and held at that temperature for 1-2 hours. After cooling, it was washed and dried to obtain the composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C. The preferred heating temperature of the tube furnace was 300℃, and the preferred holding time was 1 hour.

[0008] Furthermore, the mass ratio of zinc sulfate heptahydrate, indium trichloride tetrahydrate, porous carbon from silkworm excrement, and thioacetamide is (1.73-1.75):(2.35-2.36):1:(3.6-3.62), preferably 1.73:2.35:1:3.6.

[0009] Furthermore, the solid-liquid ratio of the porous carbon from silkworm excrement to deionized water is 1g:(140-145)mL, preferably 1g:140mL.

[0010] Furthermore, the solid-liquid ratio of lanthanum chloride to anhydrous ethanol is 1 g: (25-30) mL, preferably 1 g: 25 mL.

[0011] Furthermore, the amount of Zn3In2S6 / C added is 50% of the mass of lanthanum chloride.

[0012] Furthermore, the hydrothermal reaction temperature is 160-170℃, preferably 160℃.

[0013] Furthermore, the heating rate of the tube furnace is 5℃ / min.

[0014] A single-atom La-doped composite hydrogen evolution electrocatalyst material, which is prepared by the preparation method of the single-atom La-doped composite hydrogen evolution electrocatalyst material described in any one of the above claims.

[0015] The present invention has the following advantages: 1. In this invention, single-atom La is used to replace traditional Pt-based catalysts. With nearly 100% atomic utilization, the amount of precious metals used is reduced by more than 90%, and the material cost is reduced to 20% of that of Pt / C catalysts. Furthermore, by combining the unique 4f orbital electronic structure and variable valence state of La, the amount of precious metals used is significantly reduced while optimizing the hydrogen adsorption free energy.

[0016] 2. In this invention, the unique flower-shaped layered structure and narrow band gap of the Zn3In2S6 support provide abundant anchoring sites. The Zn / In bimetallic synergistic regulation of the electronic structure, combined with the electronic regulation of the 4f orbital of La, enables the catalyst to have a hydrogen evolution overpotential of only 62mV at a current density of 10mA / cm², a Tafel slope as low as 45mV / dec, and catalytic activity close to that of commercial Pt / C.

[0017] 3. In this invention, by introducing a porous bio-carbon substrate derived from calcined silkworm excrement, its high specific surface area and excellent conductivity can not only effectively prevent the aggregation of La atoms, but also significantly improve the charge transport efficiency. Attached Figure Description

[0018] Figure 1 The images are scanning electron microscope (SEM) images of porous carbon from silkworm excrement, La-Zn3In2S6 / C, Zn3In2S6 in Comparative Example 2, and Zn3In2S6 / C in Comparative Example 3, as described in the embodiments of the present invention.

[0019] Figure 2 The elemental distribution diagram of the composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C in the embodiments of the present invention is shown.

[0020] Figure 3 The images show X-ray powder diffraction test results of La-Zn3In2S6 / C in the embodiments of the present invention and Zn3In2S6 / C in Comparative Example 3.

[0021] Figure 4This is an electron microscope image of La-Zn3In2S6 / C with spherical aberration correction in an embodiment of the present invention.

[0022] Figure 5 The images show the BET test results for La-Zn3In2S6 / C in the embodiments of the present invention and La-Zn3In2S6 in Comparative Example 4.

[0023] Figure 6 The images show the HER test results and Tafel slope diagrams of the catalytic materials in 0.5 M H2SO4 in the embodiments and comparative examples 1-3 of this invention. Detailed Implementation

[0024] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of this invention.

[0025] An example of a method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material includes the following steps: S1: Preparation of porous carbon from silkworm excrement Silkworm excrement was placed in a tube furnace and calcined at 500°C for 2 hours to obtain porous carbon from silkworm excrement. S2: Preparation of Zn3In2S6 / C Zinc sulfate heptahydrate, indium trichloride tetrahydrate, porous carbon from silkworm excrement, and thioacetamide were added to deionized water and stirred for 30 min. The mixture was then transferred to a reaction vessel and heated at 160 °C for 12 h. After cooling, the mixture was centrifuged at 6500 rpm for 5 min and washed three times alternately with deionized water and ethanol. After vacuum drying at 60 °C, Zn3In2S6 / C was obtained. The mass ratio of zinc sulfate heptahydrate, indium trichloride tetrahydrate, porous carbon from silkworm excrement, and thioacetamide was 1.73:2.35:1:3.6, and the solid-liquid ratio of porous carbon from silkworm excrement to deionized water was 1 g:140 mL. S3: Preparation of precursors Lanthanum chloride was added to anhydrous ethanol at a solid-liquid ratio of 1 g: 25 mL and stirred thoroughly to dissolve. Then, the Zn3In2S6 / C mixture was added, and the mixture was stirred for 30 min. The solution was then poured into a centrifuge tube, centrifuged at 6500 rpm for 5 min, and then dried under vacuum at 60 °C for 4 h to obtain the precursor. The amount of Zn3In2S6 / C added was 50% of the mass of lanthanum chloride. S4: Preparation of composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C The above precursor was placed in a tube furnace and heated to 300°C at 5°C / min under an argon atmosphere, and held at that temperature for 1 hour. After cooling, it was washed and dried to obtain the composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C.

[0026] Comparative Example 1 The difference between Comparative Example 1 and the Example is that the La-Zn3In2S6 / C in the Example is replaced with Pt / C catalyst.

[0027] Comparative Example 2 The difference between Comparative Example 2 and the Example is that the porous carbon from silkworm excrement in step S2 is removed, and step S3 is also removed to obtain Zn3In2S6 catalyst material.

[0028] Comparative Example 3 The difference between Comparative Example 3 and the Example is that step S3 is removed to obtain the Zn3In2S6 / C catalyst material.

[0029] Comparative Example 4 The difference between Comparative Example 4 and the Example is that the porous carbon in the silkworm excrement in step S2 is removed to obtain the La-Zn3In2S6 catalytic material.

[0030] Characterization analysis Figures 1-6 The figures represent the morphological characterization, elemental distribution, X-ray powder diffraction test pattern, aberration-corrected electron microscopy test pattern, BET test pattern, HER test pattern, and Tafel slope diagram of the embodiments.

[0031] Figure 1 The scanning electron microscope (SEM) images (a), (b), (c), and (d) show the morphological characteristics of porous carbon from silkworm excrement in the examples, Zn3In2S6 in Comparative Example 2, Zn3In2S6 / C in Comparative Example 3, and La-Zn3In2S6 / C in the examples, respectively. Figure 1 (a) It can be seen that the silkworm excrement forms a porous structure through pyrolysis and carbonization at high temperature. The porous structure can increase the specific surface area and conductivity of Zn3In2S6. Figure 1 (b) It can be seen that Zn3In2S6 has a flower-shaped structure, which indicates that Zn3In2S6 was successfully synthesized by hydrothermal method; Figure 1 (c) shows the Zn3In2S6 / C structure synthesized by hydrothermal synthesis. As can be clearly seen from the figure, the flower-shaped Zn3In2S6 can be uniformly loaded on the surface of the porous silkworm excrement derivative, thereby increasing the specific surface area of ​​Zn3In2S6, which can enhance the catalytic active sites. Figure 1 (d) shows the doped La-Zn3In2S6 / C structure, whose morphology is similar to... Figure 1 (c) Similarly, a porous carbon framework is supported on a flower-shaped Zn3In2S6.

[0032] Figure 2 The elemental distribution of the composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C prepared in the examples is shown. Figure 2 As can be seen from (a), (b), (c), and (d), the distribution of C, S, In, Zn, and La elements shows that the entire material structure is mainly composed of porous carbon from silkworm excrement and Zn3In2S6. Figure 2 (e) It can be seen that the La element is uniformly distributed in Zn3In2S6 / C.

[0033] Figure 3 The X-ray diffraction characteristics of La-Zn3In2S6 / C prepared in Example 1 and Zn3In2S6 / C prepared in Comparative Example 3 are shown in the figure. As can be seen from the figure, the Zn3In2S6 / C synthesized via hydrothermal method in Comparative Example 3 exhibits diffraction peaks at 2θ = 27.5°, 47.5°, and 56.5°, indicating that the Zn3In2S6 / C material was successfully prepared in this experiment. No other diffraction peaks were observed in the X-ray spectrum, indicating that the synthesized sample was relatively pure. In contrast, the diffraction peaks of Zn3In2S6 / C after doping with La atoms in Example 1 are essentially consistent with the diffraction peaks before doping, indicating that doping with La atoms does not change the overall structural composition of the material.

[0034] Figure 4 The image shows an aberration-corrected electron microscope image of La-Zn3In2S6 / C prepared for the example. Figure 4 As can be seen, La atoms appear as isolated bright spots in the Z-contrast image, with no clustering observed. La atoms are uniformly distributed on the material surface in a single-atom state, and the size of the bright spots is close to the theoretical atomic diameter. This suggests that the uniform distribution of La atoms is due to doping.

[0035] Figure 5 The BET test curve of La-Zn3In2S6 / C prepared in the example is shown. Based on the Brunauer-Emmet-Teller (BET) spectrum, the specific surface area of ​​La-Zn3In2S6 / C is calculated to be 1643 m². 2 / g, greater than that of La-Zn3In2S6 without silkworm excrement as a substrate in Comparative Example 4 (286 m). 2 The presence of / g suggests that the addition of porous silkworm excrement increased the specific surface area of ​​the material, giving it more active sites in the electrocatalytic hydrogen evolution process.

[0036] Figure 6 (a) and (b) are the HER test results and Tafel slope diagrams of the catalysts in 0.5 M H2SO4 in Examples and Comparative Examples 1-3. Figure 6 (a) It can be seen that when the current density reaches 10 mA·cm -2At the same current density, the overpotential of La-doped Zn3In2S6 / C is 63 mV. The overpotentials of Pt / C are 72 mV, Zn3In2S6 / C is 132 mV, and Zn3In2S6 is 154 mV, with La-Zn3In2S6 / C exhibiting the lowest overpotential. The Tafel slope, derived from the LSV curve, is an important indicator of catalyst kinetics; a smaller Tafel slope indicates a smaller overpotential and a faster hydrogen evolution rate. Figure 6 In (b), the slope of La-Zn3In2S6 / C is 16mV dec. -1 Under the same conditions, the Tafel slope of Pt / C is 26 mV dec. -1 The Tafel slope of Zn3In2S6 / C is 48mV dec. -1 The Tafel slope of Zn3In2S6 is 53mV dec. -1 This clearly shows that doping with La atoms reduces the overpotential and Tafel slope of the entire material, indicating that the catalytic activity and hydrogen evolution efficiency of the doped material are both improved.

[0037] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims. Parts not described in detail in this specification are prior art known to those skilled in the art.

Claims

1. A method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst, characterized in that, Includes the following steps: S1: Preparation of porous carbon from silkworm excrement Silkworm excrement is placed in a tube furnace and calcined at a high temperature of 500-600℃ for 2-3 hours to obtain porous carbon from silkworm excrement. The preferred calcination temperature is 500℃ and the preferred calcination time is 2 hours. S2: Preparation of Zn3In2S6 / C Zinc sulfate heptahydrate, indium trichloride tetrahydrate, porous carbon from silkworm excrement, and thioacetamide were added to deionized water and stirred for 30 min. The mixture was then transferred to a reaction vessel and subjected to hydrothermal reaction for 12-13 h. After cooling, the mixture was centrifuged at 6500 rpm for 5 min and then washed three times alternately with deionized water and ethanol. After vacuum drying at 60 °C, Zn3In2S6 / C was obtained. The preferred hydrothermal reaction time was 12 h. S3: Preparation of precursors Lanthanum chloride was added to anhydrous ethanol and stirred thoroughly to dissolve. Then, Zn3In2S6 / C was added and stirred for 30 min. The mixture was then poured into a centrifuge tube and centrifuged at 6500-7000 rpm for 5 min. The precursor was then vacuum dried at 60-80℃ for 4-6 h. The preferred centrifugation rate was 6500 rpm, the preferred vacuum drying temperature was 80℃, and the preferred vacuum drying time was 4 h. S4: Preparation of composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C The above precursor was placed in a tube furnace and heated to 300-400℃ under an argon atmosphere, and held at that temperature for 1-2 hours. After cooling, it was washed and dried to obtain the composite hydrogen evolution electrocatalyst material La-Zn3In2S6 / C. The preferred heating temperature of the tube furnace was 300℃, and the preferred holding time was 1 hour.

2. The method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material according to claim 1, characterized in that, The mass ratio of zinc sulfate heptahydrate, indium trichloride tetrahydrate, porous carbon from silkworm excrement, and thioacetamide is (1.73-1.75):(2.35-2.36):1:(3.6-3.62), wherein the preferred mass ratio is 1.73:2.35:1:3.

6.

3. The method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material according to claim 1, characterized in that, The solid-liquid ratio of porous carbon from silkworm excrement to deionized water is 1g:(140-145)mL, wherein the preferred solid-liquid ratio of porous carbon from silkworm excrement to deionized water is 1g:140mL.

4. The method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material according to claim 1, characterized in that, The solid-liquid ratio of lanthanum chloride to anhydrous ethanol is 1 g: (25-30) mL, wherein the preferred solid-liquid ratio of lanthanum chloride to anhydrous ethanol is 1 g: 25 mL.

5. The method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material according to claim 1, characterized in that, The amount of Zn3In2S6 / C added is 50% of the mass of lanthanum chloride.

6. The method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material according to claim 1, characterized in that, The hydrothermal reaction temperature is 160-170℃, with 160℃ being the preferred temperature.

7. The method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material according to claim 1, characterized in that, The heating rate of the tube furnace is 5℃ / min.

8. A single-atom La-doped composite hydrogen evolution electrocatalyst material, characterized in that, It is prepared by the method for preparing a single-atom La-doped composite hydrogen evolution electrocatalyst material according to any one of claims 1-7.

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