A method for improving the hydrogen evolution performance of platinum-based catalysts in the full pH range

Abstract

The application discloses a method for improving the hydrogen evolution performance of a platinum-based catalyst in a full pH range, which is to use dimethylamine borane as a reducing agent and a boron source, to carry out boron doping on a noble metal platinum atom through a low-temperature liquid phase method, and to prepare a nano-sized boron-doped platinum-based catalyst by adjusting the pH of a solution and adding boric acid in the reaction. Compared with nonmetal elements H, C, N and P with larger electronegativity, the electronegativity of B is smaller than that of Pt, which is more conducive to the adsorption of positively charged protons on the metal site and improves the HER reaction kinetics; meanwhile, B is the smallest nonmetal element in the group IIIA, and the atomic size is smaller than that of C, N and P, so B is easier to be doped into the lattice gap of platinum, which causes the lattice of platinum to be in tensile strain, thereby accelerating the efficiency of water dissociation to produce hydrogen intermediates and enhancing the adsorption energy of the hydrogen intermediates, and effectively improving the HER catalytic activity of the catalyst in the full pH range.

Description

Technical Field

[0001] This invention belongs to the field of new energy materials technology, specifically relating to a method for improving the catalytic activity of platinum-based noble metal catalysts in the hydrogen evolution reaction of water electrolysis across the entire pH range. Background Technology

[0002] In the pursuit of sustainable global energy development, hydrogen energy is considered one of the most promising energy carriers due to its clean, renewable, and abundant properties. Among the various existing hydrogen production methods, the hydrogen evolution reaction (HER) in electrochemical water splitting has attracted significant attention due to its high efficiency, sustainability, and environmental friendliness. To date, Pt group noble metal catalysts have reached the peak of the HER volcano curve, due to the near-zero Gibbs free energy of adsorption of free hydrogen (H*) in acidic solutions. Unfortunately, in alkaline and neutral media, the slow reaction kinetics of water splitting (Volmer step, H2O + e⁻) hinder further progress. – →H*+OH – Platinum's reactivity is two to three orders of magnitude lower than that of acidic media, which greatly limits its large-scale commercial application.

[0003] To improve the hydrogen desorption efficiency of Pt group noble metal catalysts, numerous methods have been employed, such as alloying Pt group metals (PGMs) with transition metals, forming heterojunctions, and doping light elements (C, P, N, Si, B) into the Pt lattice. Among these strategies, the design of interstitial doping of light elements in Pt group metal catalysts has attracted significant attention. Unlike traditional bimetallic alloys, appropriate concentrations of light nonmetallic or metalloid elements tend to serve as interstitial dopants rather than substitutional dopants in the primary metal lattice of the PGM, as they occupy the largest available interstitial sites. Interstitial dopants are relatively stable, and under partial leaching conditions, interstitial alloys largely maintain the lattice structure of the primary Pt group metals compared to substitutional alloys. In such interstitial-doped PGM catalysts, the strong hybridization of the sp orbitals of the interstitial dopant and the d orbitals of the PGM can tune the electronic structure of the catalyst. Compared to N and P, which are highly electronegative nonmetals in Group VA, B is the lightest metalloid in Group IIIA, with lower electronegativity than all PGMs. This makes it easier for the metal sites to exert an electron-withdrawing effect, carrying a negative charge to capture positively charged protons and activate HER catalytic activity. Therefore, interstitial boron doping in PGMs can promote hydrolysis efficiency through inter-electron coupling, which is beneficial for the large-scale commercial application of PGM catalysts. Summary of the Invention

[0004] The purpose of this invention is to provide a method for improving the catalytic activity of platinum-based noble metal catalysts in the hydrogen evolution reaction (HER) under all pH conditions. This method involves incorporating a certain proportion of boron while reducing platinum atoms, ensuring that the boron atoms exist within the interstitial spaces of the platinum lattice. This enhances the adsorption and desorption capacity of the active sites of the platinum-based metal catalyst for hydrogen intermediates, promotes the HER reaction kinetics of the noble metal active sites, and ultimately improves the HER catalytic activity of the platinum catalyst.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: One method to improve the hydrogen evolution performance of platinum-based catalysts across the entire pH range involves using dimethylaminoborane (DMAB, C2H) 10 Using boron (BN) as a reducing agent and boron source, boron is doped into the interstitial spaces of platinum atoms while reducing platinum to obtain a boron-doped platinum-based catalyst, thereby exhibiting highly efficient hydrogen evolution performance across the entire pH range; the operation includes the following steps: (1) Prepare dimethylaminoborane solution and platinum precursor solution respectively; (2) Add boric acid and ammonium fluoride to the platinum precursor solution to obtain a mixed solution of platinum precursor; (3) Under ice bath conditions, dimethylaminoborane solution is added at a constant rate to the mixed solution of platinum precursor in step 2) for reduction to obtain nano-sized boron-doped platinum-based catalyst.

[0006] Furthermore, the platinum-based catalyst is a supported catalyst, and its support is at least one of active porous carbon, graphene oxide, and ZIF-8, preferably active porous carbon.

[0007] Furthermore, the platinum precursor used in step (1) is at least one of chloroplatinic acid, platinum chloride, and platinum sulfide.

[0008] Furthermore, in step (2), the amounts of boric acid and ammonium fluoride added are 2-10 times and 0.5-1.5 times the mass of the platinum precursor, respectively. Ammonium fluoride can further adjust the pH of the mixed solution during the reaction by inhibiting the dissociation of ammonia, while boric acid can inhibit the aggregation of platinum atoms at low temperatures. Therefore, the addition of both boric acid and ammonium fluoride can reduce the size of the formed platinum particles.

[0009] Furthermore, the volume ratio of the dimethylaminoborane solution to the platinum precursor mixture used in step (3) is 0.01-0.1.

[0010] Furthermore, the pH of the mixed solution of dimethylaminoborane and platinum precursor used in step (3) should be adjusted to 8-12 before the reaction.

[0011] Furthermore, the dimethylaminoborane solution used in step (3) should be pre-cooled to 1-5°C before the reaction.

[0012] Furthermore, the restoration time described in step (3) is 2-4 hours.

[0013] Furthermore, the mass percentage of platinum atoms in the obtained catalyst is 1-50%, and the doping amount of boron atoms is 1%-30% of the molar amount of platinum atoms.

[0014] The beneficial effects of this invention are as follows: (1) This invention incorporates boron, which has a lower electronegativity than non-metallic elements such as H, C, N, and P, into the lattice of platinum. This facilitates electron transfer between platinum and boron atoms in the lattice, thereby improving charge transport efficiency. At the same time, since boron has a lower electronegativity than platinum, the metal sites are more likely to exert an electron-withdrawing effect, capturing positively charged protons, thereby promoting the adsorption of proton hydrogen at platinum active sites and improving the HER reaction kinetics.

[0015] (2) The present invention causes tensile strain in the platinum lattice by boron doping, and some platinum atoms are in a defect state, exposing active sites, thereby accelerating the efficiency of water dissociation to generate hydrogen intermediates and enhancing the adsorption energy of hydrogen intermediates, effectively improving the HER catalytic activity of the catalyst in the full pH environment.

[0016] (3) This invention can be widely applied to various platinum-based precious metals, including iridium, palladium, ruthenium, osmium, rhodium, etc., and has broad application prospects. Attached Figure Description

[0017] Figure 1 The X-ray diffraction patterns are those of the products obtained in Example 1 and Comparative Examples 1 and 2.

[0018] Figure 2 The image shows the product obtained in Example 1 under a transmission electron microscope.

[0019] Figure 3 The HER polarization curves of the products obtained in the examples and comparative examples are shown in an acidic environment.

[0020] Figure 4 The HER polarization curves of the products obtained in the examples and comparative examples are shown in an alkaline environment. Detailed Implementation

[0021] A method for improving the hydrogen evolution performance of platinum-based catalysts across the entire pH range includes the following steps: (1) Prepare dimethylaminoborane solution and platinum precursor solution respectively; (2) Add boric acid and ammonium fluoride to the platinum precursor solution to obtain a mixed solution of platinum precursor; wherein the amount of boric acid and ammonium fluoride added is 2-10 times and 0.5-1.5 times the mass of platinum precursor, respectively; (3) Adjust the pH of the mixed solution of dimethylaminoborane and platinum precursor to 8-12 respectively; then pre-cool the dimethylaminoborane solution to 1-5℃, and then add the dimethylaminoborane solution to the mixed solution of platinum precursor at a volume ratio of 0.01-0.1 under ice bath conditions to reduce for 2-4 hours, so as to obtain nano-sized boron-doped platinum-based catalyst.

[0022] The precursor of platinum is at least one of chloroplatinic acid, platinum chloride, and platinum(II) chloride.

[0023] The mass percentage of platinum atoms in the obtained catalyst is 1-50%, and the doping amount of boron atoms is 1%-30% of the molar amount of platinum atoms.

[0024] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.

[0025] Example 1: Synthesis of boron-doped platinum (Pt-B / C) nanoparticles (1) Dissolve 50 mg ammonium fluoride (NH4F) and 100 mg boric acid (H3BO3) in 20 mL of ultrapure water, then add 9.96 mL of 4 mg / mL H2PtCl4 aqueous solution, and add an appropriate amount of ammonia (NH3·H2O) to adjust the pH to 10.

[0026] (2) Add an appropriate amount of ammonia (NH3·H2O) to 120 ml of ultrapure water to adjust the pH to 10, then add 60 mg of activated porous carbon, sonicate for 1 hour, and then mix with the solution obtained in step (1), sonicate at room temperature for 4 hours to make the solution evenly dispersed.

[0027] (3) 10 mL of 0.5 mol / L dimethylaminoborane solution (pH=10) was added dropwise to 150 mL of the slurry obtained in step (2). The mixture was stirred and reduced in an ice-water bath for 2 hours, and then heated to 45 °C and stirred for 2 hours to separate the solution from the catalyst. The slurry was then filtered and dried overnight in a vacuum oven at 70 °C. Finally, the dried sample was ground for half an hour to obtain a uniform powder, which is the Pt-B / C catalyst with a platinum loading of 15% and a platinum-boron atomic ratio of 4:1.

[0028] Comparative Example 1: (1) Add 39.82 mg of H2PtCl4 to ultrapure water and add an appropriate amount of ammonia (NH3·H2O) to adjust the pH to 10.

[0029] (2) Continue stirring the mixed solution obtained in step (1) overnight at room temperature, then add 60 mg of activated porous carbon and sonicate for 1 hour.

[0030] (3) At 60 °C, add 0.5 mol L to the mixed solution obtained in step (2) at a uniform rate. -1 20 ml of hydrazine hydrate (H4N2·H2O) solution was reacted for 8 hours and then cooled to room temperature. The slurry was then filtered and dried overnight at 70°C in a vacuum oven. Finally, the dried sample was ground for half an hour to obtain a uniform powder, which is the Pt-H / C catalyst with a platinum loading of 15% and a platinum-hydrogen atomic ratio of 4:1.

[0031] Comparative Example 2: (1) At room temperature, 39.82 mg of H2PtCl4 and 60 mg of active porous carbon were added to ultrapure water and ultrasonically treated for 1 hour. Then, the mixture was heated in a water bath at 75°C until the water evaporated completely to obtain carbon-supported chloroplatinic acid powder.

[0032] (2) The carbon-supported chloroplatinic acid powder obtained in step (1) was placed in a tube furnace and heated to 400°C at a rate of 5°C / min in a 10% H2 / 90% Ar atmosphere, and held at that temperature for 2 hours. After naturally cooling to room temperature, it was washed with ultrapure water to obtain Pt / C powder.

[0033] (3) Place 40 mg of sulfur powder and the Pt / C powder obtained in step (2) at the upstream and center of a tube furnace, respectively, and heat to 500°C at a rate of 5 °C / min in an Ar atmosphere, and hold for one hour. After naturally cooling to room temperature, wash with ultrapure water to obtain a Pt-S / C catalyst with a platinum loading of 15% and a platinum-sulfur atomic ratio of 4:1.

[0034] Comparative Example 3: The purchased Pt / C had a platinum loading of 20% wt.

[0035] Example 2: Synthesis of boron-doped platinum nanoparticles on graphene (1) Dissolve 50 mg ammonium fluoride (NH4F) and 100 mg boric acid (H3BO3) in 20 mL of ultrapure water, then add 9.96 mL of H2PtCl4 aqueous solution at 4 mg / mL, and add an appropriate amount of ammonia (NH3·H2O) to adjust the pH to 10.

[0036] (2) Add an appropriate amount of ammonia (NH3·H2O) to 120 ml of ultrapure water to adjust the pH to 10, then add 60 mg of graphene oxide (rGO), sonicate for 1 hour, and then mix with the solution obtained in step (1), sonicate at room temperature for 4 hours to make the solution evenly dispersed.

[0037] (3) 10 mL of 0.5 mol / L dimethylaminoborane solution (pH=10) was added dropwise to 150 mL of the slurry obtained in step (2). The mixture was stirred and reduced in an ice-water bath for 2 hours, and then heated to 45 °C and stirred for 2 hours to separate the solution from the catalyst. The slurry was then filtered and dried overnight in a vacuum oven at 70 °C. Finally, the dried sample was ground for half an hour to obtain a uniform powder, which is the Pt-B / rGO catalyst with a platinum loading of 15% and a platinum-boron atomic ratio of 4:1.

[0038] Example 3: Synthesis of ZIF-8 boron-doped platinum nanoparticles (1) Dissolve 50 mg ammonium fluoride (NH4F) and 100 mg boric acid (H3BO3) in 20 mL of ultrapure water, then add 9.96 mL of 4 mg / mL H2PtCl4 aqueous solution, and add an appropriate amount of ammonia (NH3·H2O) to adjust the pH to 10.

[0039] (2) Add an appropriate amount of ammonia (NH3·H2O) to 120 ml of ultrapure water to adjust the pH to 10, then add 60 mg of ZIF-8, sonicate for 1 hour, and then mix with the solution obtained in step (1). Sonicate at room temperature for 4 hours to make the solution evenly dispersed.

[0040] (3) 10 mL of 0.5 mol / L dimethylaminoborane solution (pH=10) was added dropwise to 150 mL of the slurry obtained in step (2). The mixture was stirred and reduced in an ice-water bath for 2 hours, and then heated to 45 °C and stirred for 2 hours to separate the solution from the catalyst. The slurry was then filtered and dried overnight in a vacuum oven at 70 °C. Finally, the dried sample was ground for half an hour to obtain a uniform powder, which is the Pt-B / ZIF-8 catalyst with a platinum loading of 15% and a platinum-boron atomic ratio of 4:1.

[0041] Example 4: Synthesis of boron-doped platinum (Pt-B / C) nanoparticles (1) Dissolve 40 mg ammonium fluoride (NH4F) and 80 mg boric acid (H3BO3) in 20 mL of ultrapure water, then add 9.96 mL of H2PtCl4 aqueous solution at 4 mg / mL, and add an appropriate amount of ammonia (NH3·H2O) to adjust the pH to 10.

[0042] (2) Add an appropriate amount of ammonia (NH3·H2O) to 120 ml of ultrapure water to adjust the pH to 10, then add 60 mg of activated porous carbon, sonicate for 1 hour, and then mix with the solution obtained in step (1), sonicate at room temperature for 4 hours to make the solution evenly dispersed.

[0043] (3) Add 8 mL of 0.5 mol / L dimethylaminoborane solution (pH=10) dropwise to 150 mL of the slurry obtained in step (2), stir and reduce in an ice-water bath for 2 hours, then heat to 45 °C and stir for 2 hours to separate the solution from the catalyst. After that, filter the slurry and dry it overnight in a vacuum oven at 70 °C. Finally, grind the dried sample for half an hour to obtain a uniform powder, which is the Pt-B / C catalyst with a platinum loading of 15% and a platinum-boron atomic ratio of 9:1.

[0044] Example 5: Synthesis of boron-doped platinum (Pt-B / C) nanoparticles (1) Dissolve 60 mg ammonium fluoride (NH4F) and 120 mg boric acid (H3BO3) in 20 mL of ultrapure water, then add 9.96 mL of H2PtCl4 aqueous solution at 4 mg / mL, and add an appropriate amount of ammonia (NH3·H2O) to adjust the pH to 10.

[0045] (2) Add an appropriate amount of ammonia (NH3·H2O) to 120 ml of ultrapure water to adjust the pH to 10, then add 60 mg of activated porous carbon, sonicate for 1 hour, and then mix with the solution obtained in step (1), sonicate at room temperature for 4 hours to make the solution evenly dispersed.

[0046] (3) 15 mL of 0.5 mol / L dimethylaminoborane solution (pH=10) was added dropwise to 150 mL of the slurry obtained in step (2). The mixture was stirred and reduced in an ice-water bath for 2 hours, and then heated to 45 °C and stirred for 2 hours to separate the solution from the catalyst. The slurry was then filtered and dried overnight in a vacuum oven at 70 °C. Finally, the dried sample was ground for half an hour to obtain a uniform powder, which is the Pt-B / C catalyst with a platinum loading of 15% and a platinum-boron atomic ratio of 7:3.

[0047] Figure 1 The figures show the XRD patterns of the products obtained in Example 1 and Comparative Examples 1 and 2. As can be seen from the figures, the platinum catalysts with different heteroatom doping all shifted to a lower angle, indicating that the heteroatoms are incorporated into the interstitial spaces of the platinum lattice, which is beneficial for exposing more active sites.

[0048] Figure 2 This is a TEM image of the boron-doped platinum-based catalyst prepared in Example 1. As can be seen from the image, the obtained boron-doped platinum metal nanoparticles have a particle size of about 3 nm, exhibiting good dispersibility. The lattice spacing is 0.23 nm, which, compared to the 0.227 nm of metallic platinum, shows a certain degree of lattice expansion, indicating that boron is doped into the interstitial spaces of platinum without forming a compound.

[0049] Figure 3The figures show the acidic HER performance test results of the catalysts prepared in the examples and comparative examples. As can be seen from the figures, the heteroatom-doped catalysts all exhibited significantly better acidic HER activity than commercial Pt / C catalysts. This indicates that interstitial atom doping can significantly improve the HER activity of Pt catalysts. Among them, the boron-doped catalyst obtained in Example 1 showed the best performance, with a performance of [missing data - likely a value] at 10 mA / cm². -2 The overpotential at the point is 7 mV, indicating that boron doping is more beneficial to improving the acidic HER performance of platinum-based catalysts, but excessive boron doping will cause a decrease in catalyst performance. Meanwhile, a comparison of Examples 1-3 shows that different supports do not significantly affect the excellent performance of boron-doped platinum catalysts in acidic electrolytes.

[0050] Figure 4 The figures show the alkaline HER performance test results of the catalysts prepared in the examples and comparative examples. As can be seen from the figures, the heteroatom-doped catalysts all exhibited significantly better alkaline HER activity than commercial Pt / C catalysts. Among them, Example 1 showed the best overpotential at 10 mA cm⁻¹. -2 The overpotential was only 36 mV, which is better than that of Comparative Example 1 (46 mV) and Comparative Example 2 (49 mV). Examples 2 and 3 show that boron-doped platinum catalysts with different supports still maintain excellent HER performance under alkaline conditions, and Examples 4 and 5 further demonstrate that appropriate boron doping is beneficial to improving the alkaline HER performance of the catalyst.

[0051] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.

Claims

1. The application of a boron-doped platinum-based catalyst in hydrogen evolution reaction under all pH conditions, characterized in that: The boron-doped platinum-based catalyst is obtained by using dimethylaminoborane as a reducing agent and boron source, and by doping boron into the interstitial spaces of platinum atoms while reducing platinum. Its preparation includes the following steps: (1) Prepare dimethylaminoborane solution and platinum precursor solution respectively; (2) Add boric acid and ammonium fluoride to the platinum precursor solution to obtain a mixed solution of platinum precursor; (3) Under ice bath conditions, dimethylaminoborane solution is added at a constant rate to the mixed solution of platinum precursor in step 2) and reduced for 2-4 hours to obtain nano-sized boron-doped platinum-based catalyst.

2. The application according to claim 1, characterized in that: The platinum precursor used in step (1) is at least one of chloroplatinic acid, platinum chloride, and platinum chloride.

3. The application according to claim 1, characterized in that: In step (2), the amounts of boric acid and ammonium fluoride added are 2-10 times and 0.5-1.5 times the mass of the platinum precursor, respectively.

4. The application according to claim 1, characterized in that: The volume ratio of the dimethylaminoborane solution to the platinum precursor mixture used in step (3) is 0.01-0.

1.

5. The application according to claim 1, characterized in that: The pH of the dimethylaminoborane solution and the platinum precursor mixture used in step (3) should be adjusted to 8-12 before the reaction.

6. The application according to claim 1, characterized in that: The dimethylaminoborane solution used in step (3) should be pre-cooled to 1-5°C before the reaction.

7. The application according to claim 1, characterized in that: The mass percentage of platinum atoms in the obtained catalyst is 1-50%, and the doping amount of boron atoms is 1%-30% of the molar amount of platinum atoms.

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