Bimetal hydrogen evolution catalyst, preparation method and application

Abstract

The invention belongs to the technical field of hydrogen evolution catalysts, and particularly relates to a bimetallic hydrogen evolution catalyst and a preparation method and application thereof.The bimetallic hydrogen evolution catalyst is obtained by adding a mixed aqueous solution containing RhCl3 and HAuCl4 into a hydride carrier solution containing PVP and evenly mixing the mixture, the hydride carrier is a cobaltocene derivative, and the preparation method comprises the following steps that 1, the bimetallic hydrogen evolution catalyst is obtained; according to the cobaltocene derivative, H on one cyclopentadiene in cobaltocene is substituted by five methyl groups; the method has higher hydrogen production efficiency.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of hydrogen evolution catalysts, and particularly relates to a bimetallic hydrogen evolution catalyst, a preparation method and use. BACKGROUND

[0002] The hydrogen evolution reaction (HER) is the core process of water electrolysis for hydrogen production, and the core material is a hydrogen evolution catalyst. Research progress of carbon-supported noble metal-based electrocatalysts in hydrogen evolution reaction, Liu Xue, Yang Yun, Chemical Technology and Development, Vol. 54, No. 6, discloses that noble metal nanomaterials (Pt, Rh, Ru, Ir) have excellent hydrogen binding energy, outstanding stability and adjustable electronic properties, and are considered to be the most effective hydrogen evolution reaction (HER) electrocatalysts. The free energy of the surface of the noble metal is relatively high, so the noble metal usually needs to be supported on a carrier to prevent it from aggregating during synthesis and reaction. Carbon-based materials are considered to be an excellent catalyst carrier, and the advantages include: 1) carbon materials have high electrical conductivity, which helps the transfer of electrical charges from the carrier to the catalyst surface; 2) carbon-based materials have large specific surface area and porosity, which is beneficial to the exposure of active sites, thus promoting the transportation of reactants and products; 3) carbon-based materials exhibit excellent electrochemical stability in a wide potential window.

[0003] Bimetallic catalysts are important hydrogen evolution catalysts, and preparation of RuNi bimetallic catalyst and research on its alkaline water electrolysis hydrogen evolution performance, Chen Yan, Shanxi Datong University, Master's Degree Thesis, discloses that the synergistic catalysis of bimetallic catalysts plays an important role in replacing noble metals, improving catalytic activity and selectivity, etc. There are various interactions between the transition metal M and the noble metal Ru in the Ru-M (Ni, Fe, Co, Cu, etc.) alloy, which can make the d-band center of the Ru atom deviate from the Fermi level, modify the electronic structure of Ru, and regulate the catalytic activity of Ru. SUMMARY

[0004] The technical problem to be solved by the application is to provide a bimetallic hydrogen evolution catalyst, a preparation method and use, which have higher hydrogen production efficiency.

[0005] The embodiment of the application provides a preparation method of a bimetallic hydrogen evolution catalyst, which comprises the following steps: adding a mixed aqueous solution containing RhCl3 and HAuCl4 into a hydride carrier solution containing PVP, and uniformly mixing to obtain a bimetallic hydrogen evolution catalyst, wherein the hydride carrier is a cobaltocenium derivative, and the cobaltocenium derivative is a derivative in which the H on one cyclopentadiene in cobaltocenium is replaced by 5 methyl groups.

[0006] Preferably, the molar ratio of RhCl3 and HAuCl4 is 0.8-1.2:1, more preferably, the molar ratio of RhCl3 and HAuCl4 is 1:1, and the concentration of RhCl3 and HAuCl4 in the mixed aqueous solution containing RhCl3 and HAuCl4 is 0.0005-0.01 mol / L respectively.

[0007] Preferably, the solvent of the hydride carrier solution containing PVP is tetrahydrofuran.

[0008] Preferably, in the hydride carrier solution containing PVP, the concentration of the hydride carrier is 0.001-0.01 mol / L (preferably 0.003 mol / L), and the concentration of PVP is 0.001-0.01 g / mL (preferably 0.005 mol / L).

[0009] The volume ratio of the mixed aqueous solution containing RhCl3 and HAuCl4 and the hydride carrier solution containing PVP is 1:8-20 (preferably 1:10).

[0010] Preferably, the mixed aqueous solution containing RhCl3 and HAuCl4 is added to the hydride carrier solution containing PVP, and the mixture is uniformly mixed, all in a protective atmosphere. Preferably, the protective atmosphere is nitrogen.

[0011] The embodiment of the present application provides a bimetallic hydrogen evolution catalyst prepared by the preparation method.

[0012] The embodiment of the present application provides the use of the bimetallic hydrogen evolution catalyst, and the bimetallic hydrogen evolution catalyst is used for catalyzing hydrogen evolution.

[0013] The embodiment of the present application has the beneficial effect that the bimetallic catalyst RhAu is prepared by selecting Rh and Au, and has obviously higher hydrogen production efficiency compared with single metal catalyst or the combination of Au and other common hydrogen evolution metals, so that the hydrogen production speed can be greatly improved.

[0014] The hydride carrier is dissolved in a THF solution and mixed with PVP to prepare the bimetallic catalyst, and PVP is a surfactant and can be used as an auxiliary stabilizer of the catalyst.

[0015] The bimetallic nanoparticles of the present application are embedded on the hydride carrier, the bimetallic nanoparticles are in an alloy form, and are stabilized by the coordination of the cobaltocene derivative, so that the catalytic effect is effectively exerted.

[0016] The present application selects a cobaltocene derivative, that is, a derivative in which the H on one cyclopentadiene in cobaltocene is replaced by 5 methyl groups, as a carrier, and the combination of the bimetallic catalyst and the carrier can obviously improve the catalytic efficiency of the bimetallic catalyst.

[0017] This invention uses a cobalt cyclopentadiene derivative, specifically, a cobalt cyclopentadiene in which one hydrogen atom is replaced by five methyl groups. AuRh catalysts prepared using metallocene derivatives as supports exhibit bimetallic synergistic effects. In this process, the metallocene acts as both a reducing agent for the catalyst precursor and a catalyst support. Regarding the steric effect... Much larger than Cp; in terms of electronic effects, It has a stronger electron-donating ability, which makes the catalyst more stable. The electronic structure and spatial configuration of the catalyst can be adjusted, enabling AuRh to exhibit a bimetallic synergistic effect. This synergistic effect not only improves the catalytic efficiency of the catalyst but also reduces the amount of precious metals used. Attached Figure Description

[0018] Figure 1 These are TEM and EDS images of the bimetallic hydrogen evolution catalyst of Example 1 of the present invention. A and E are two TEM images, B~D and F~H are the EDS images corresponding to the two TEM images, B and F are the combined EDS images of Au and Rh, C and G are the EDS images of Au, and D and H are the EDS images of Rh.

[0019] Figure 2 The above are XPS spectra of the bimetallic hydrogen evolution catalyst of Example 1 of the present invention, where (a) is the XPS spectrum of Rh and (b) is the XPS spectrum of Au.

[0020] Figure 3 The curves show the hydrogen evolution reaction of ammonia borane catalyzed by AuRhNPs, AuNPs, and RhNPs.

[0021] Figure 4 The curves of hydrogen evolution reaction of ammonia borane catalyzed by different bimetallic catalysts are shown.

[0022] Figure 5 The reactions are those represented by equations -1, -2, and -3.

[0023] Figure 6 A schematic diagram illustrating the activation of methanol to produce hydrogen using cobalt diacetic derivatives and its recyclability.

[0024] Figure 7 For metallocene 2 1 H NMR spectrum.

[0025] Figure 8 For metallocene 2 13 C NMR spectrum.

[0026] Figure 9 The MS spectrum of metallocene 2.

[0027] Figure 10 The recovered metallocene 1 1 HNMR spectrum. DETAILED DESCRIPTION

[0028] Example 1 A preparation method of a bimetallic hydrogen evolution catalyst, comprising the following steps: 1) Preparation of precursor solution: ① Preparation of 0.001 mmol / mL RhCl3 and 0.001 mmol / mL HAuCl4 solution, each 10 ml, ② Preparation of 0.01 g / ml PVP (polyvinylpyrrolidone) 10 ml, ③ Dissolution of freshly prepared hydride carrier (0.03 mmol) in 5 ml THF solution to obtain a hydride carrier solution.

[0029] The hydride carrier is a cobaltocenium derivative, in which the H on one of the cyclopentadiene rings in cobaltocenium is replaced by 5 methyl groups. The structural formula is: There are 5 H on one of the cyclopentadiene rings, and each of the 5 H is replaced by a methyl group.

[0030] 2) Preparation of bimetallic catalyst: ① Take 1 ml of RhCl3 and HAuCl4 solution (i.e. mix 0.5 ml of RhCl3 and 0.5 ml of HAuCl4 solution), stir for 10 min for standby; ② Take 5 ml of PVP solution and add it to 5 ml of hydride carrier solution under nitrogen atmosphere, stir for 10 min for standby; ③ Under the condition of nitrogen protection, drop 1 ml of RhCl3 and HAuCl4 mixed solution into 10 ml of hydride carrier containing PVP, stir for 30 min to obtain a bimetallic hydrogen evolution catalyst.

[0031] The reaction formula is:

[0032] M is Au, Rh, and X is Cl.

[0033] Figure 1 TEM in the above-mentioned formula confirms the formation of bimetallic nanoparticles. Figure 2 It is shown that Au and Rh are reduced to 0-valent noble metal catalysts.

[0034] Example 2 Prepare 10 ml of 1 mmol / ml aqueous solution of ammonia borane (NH3BH3), take 1 ml of ammonia borane aqueous solution and add it to 11 ml of bimetallic hydrogen evolution catalyst solution in Example 1, and it can be observed that 3 mmol of H2 is generated. The reaction formula is: .

[0035] Example 3 To compare the catalytic effect of the bimetallic hydrogen evolution catalyst of Example 1 and the Au monometallic catalyst, Rh monometallic catalyst. The Au monometallic catalyst and Rh monometallic catalyst were prepared according to the method of Example 1, and the hydrogen evolution reaction was carried out according to the method of Example 2, and the catalytic effect was compared.

[0036] The preparation method of the Au monometallic catalyst is: 1) Preparation of precursor solution: ①Prepare 0.001 mmol / mL of HAuCl4 solution 10 ml, ②Prepare 0.01 g / ml of PVP (polyvinylpyrrolidone) 10 ml, ③Dissolve the freshly prepared hydride carrier (0.03 mmol) in 5 ml THF solution to obtain a hydride carrier solution.

[0037] 2) Preparation of monometallic catalyst: ①Take 1 ml of HAuCl4 solution, stir for 10 min for standby; ②Take 5 ml of PVP solution and add it to 5 ml of hydride carrier solution under nitrogen atmosphere, stir for 10 min for standby; ③Under the condition of nitrogen protection, add 1 ml of HAuCl4 solution to 10 ml of hydride carrier containing PVP, stir for 30 min to obtain a monometallic hydrogen evolution catalyst.

[0038] The preparation method of the Rh monometallic catalyst is: 1) Preparation of precursor solution: ①Prepare 0.001 mmol / mL of RhCl3 solution 10 ml, ②Prepare 0.01 g / ml of PVP (polyvinylpyrrolidone) 10 ml, ③Dissolve the freshly prepared hydride carrier (0.03 mmol) in 5 ml THF solution to obtain a hydride carrier solution.

[0039] 2) Preparation of monometallic catalyst: ①Take 1 ml of RhCl3 solution, stir for 10 min for standby; ②Take 5 ml of PVP solution and add it to 5 ml of hydride carrier solution under nitrogen atmosphere, stir for 10 min for standby; ③Under the condition of nitrogen protection, add 1 ml of RhCl3 solution to 10 ml of hydride carrier containing PVP, stir for 30 min to obtain a monometallic hydrogen evolution catalyst.

[0040] The experimental results are shown in Figure 3 It can be seen that the catalytic effect of AuRh is obviously better than that of monometallic AuNPs and RhNPs, and the synergistic effect between the bimetallic catalysts is exhibited.

[0041] Example 4 The bimetallic catalysts of Au and Co, Ni, Rh, Pd and other metals were prepared by the method similar to Example 1. Taking AuCo catalyst as an example, the difference between its preparation method and Example 1 is that CoCl2 is used instead of RhCl3. The other steps are the same as Example 1. Other bimetallic catalysts are similar to AuCo catalyst.

[0042] The hydrogen evolution reaction was carried out by the method of Example 2, and the hydrogen evolution reactions of different bimetallic catalysts were compared, and the results are shown in Figure 4 From Figure 4 It can be seen that the bimetallic catalyst of Au and Rh has the best catalytic effect, which is obviously superior to other bimetallic catalysts.

[0043] Example 5 The hydride carrier of the present application, i.e. the cobaltocene derivative, is convenient to recycle and can realize hydrogen storage, hydrogen evolution and recycling. The hydrogen storage, hydrogen evolution and recycling process is as follows: 1. Pentamethylated cobaltocene hexafluorophosphate The molecular formula is shown in equation-1 (hereinafter referred to as metallocene 1). In metallocene 1, one cyclopentadiene (Cp) is replaced by five methyl groups to form a five-methylcyclopentadiene (Cp*) with stronger electron-donating ability and larger steric hindrance, which makes the 18-electron metallocene 1 sandwich structure more stable. Metallocene 1 is reduced to the corresponding hydride metallocene 2 (equation-1) under the action of a reducing agent (such as NaBH4). Metallocene 2 also has a stable 18-electron structure, so it shows good thermodynamic stability and hydrogen donor ability.

[0044] 2. The unique thermodynamic stability and hydrogen donor ability of metallocene 2 make it have unparalleled advantages in the hydrogenation reaction of olefins and recyclability. The present application takes advantage of this chemical property of metallocene 2, making it an excellent hydrogen storage and hydrogen evolution material. Through equation-1, metallocene 2 completes the hydrogen storage process; through equation-2, metallocene 2 reacts with methanol to generate metallocene 3 and release hydrogen gas, completing the hydrogen evolution process, and this hydrogen evolution process can be realized on a time scale of seconds; through equation-3, metallocene 3 can generate precipitate metallocene 1 by adding HPF6 solution, and more than 90% of the metallocene 3 can be recycled.

[0045] The preparation method of pentamethylated cobaltocene hexafluorophosphate is as follows: 1. 1,2,3,4,5-pentamethylcyclopentadiene (15.2 g, 78 mmol) was added to a THF (200 ml) solution.

[0046] 2. n-BuLi (48.8 ml, 1.6 M) was added to the solution of step 1 at -78 °C, then stirred at -30 °C for 30 min.

[0047] 3. CoCl2(10.1 g, 78 mmol) was dissolved in THF (100 ml) and added dropwise to the solution of step 2, stirred at room temperature for 30 min, then cooled to -10 °C.

[0048] 4. A THF solution of CpNa (18.1 g, 78 mmol) was added to the solution of step 3, stirred at room temperature for 6 h. The reaction was completed. Cp is the abbreviation of cyclopentadienyl.

[0049] 5. The solution was pumped by vacuum, the solid residue was dissolved in water and washed with diethyl ether for 3 times, extracted, and the aqueous phase was retained.

[0050] 6. Excess HPF6 was added to the aqueous solution, and a solid precipitate was generated. After drying and removing water, and washing with diethyl ether, the pure pentamethylated cobaltocene hexafluorophosphate was obtained.

[0051] The specific equation-1, equation-2, equation-3 reactions are shown in Figure 5 . The schematic diagram of the activation of methanol by cobaltocene derivative to produce hydrogen and recyclability is shown in Figure 6 .

[0052] The 1 HNMR, 13 C NMR, MS spectra of metallocene 2 are shown in Figures 7-9 , and the 1 HNMR of the recovered metallocene 1 is shown in Figure 10 . Replace NaBH4 in equation-1 with deuterated NaBD4 to obtain deuterated metallocene 2, and compare them to determine the peak of metallocene 2 ( Figure 7 ): the signal of deuterium D at 1.55 ppm disappears, indicating that the signal can be attributed to the exo -H (H4) of metallocene 2. Then, the peaks at 4.33 ppm, 2.01 ppm, 1.53 ppm and 0.83 ppm are attributed to H2, H1, H5 and H3. The signal at 1.74 ppm is assigned as an impurity. Figure 8 The 13 C NMR in Figure 9The mass spectrum shows a weak molecular ion peak at m / e 260.1 and a base peak at m / e 259.1, the former corresponding to the compound metallocene 2, and the latter attributed to the loss of a hydride from metallocene 2 and the formation of a stable pentamethyl cobalt cation. Figure 10 The peaks at 5 and 15 correspond to the Cp and groups in metallocene 1, respectively.

[0053] Example 6 If the metallocene 1 with the formula is replaced by a material with the formula (CoCpCp) + (PF6) - (i.e. the H on the two cyclopentadienes is not substituted) or (i.e. the H on the two cyclopentadienes is substituted by 5 methyl groups), the activation of methanol can also be achieved, but the former is too active and the corresponding hydride sandwich structure collapses easily, so the material is not recyclable; the latter has two groups and the molecular structure is too stable, so the corresponding hydride material has insufficient hydrogen supply capacity and cannot achieve 100% activation of methanol.

[0054] Effect of the three compounds on hydrogen evolution: Three sealed containers (connected to a hydrogen absorption device) each contain 1 mmol of hydride of the three metallocenes. 1.1 mmol of methanol solution is injected into each sealed container using a syringe, and the generation and amount of hydrogen can be observed through the hydrogen absorption device.

[0055] The hydride of (CoCpCp) + (PF6) - , can be observed to generate hydrogen immediately after the injection of methanol, and the yield is 1 mmol. The hydride of does not generate hydrogen after the injection of methanol, and even if Pt / C is added to catalyze the hydrogen evolution reaction, no hydrogen can be generated.

[0056] The hydride of (CoCpCp) + (PF6) - does not produce a precipitate after the addition of HPF6, indicating that this compound cannot be recycled. The hydride of produces a yellow precipitate after the addition of HPF6, and the yield is 0.9 mmol.

[0057] Metallocene 2 can be recycled by HPF6 and NaBH4, and methanol can also be recycled by HPF6, with a recovery rate of over 90%. Due to the difference in solubility of metallocene 2 and methanol, they can be separated by extraction.

[0058] Those skilled in the art should understand that the above discussion of any embodiment is only intended to be illustrative and is not intended to be limiting to the scope of the present application; the above embodiments or technical features among different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes such as the different aspects of one or more embodiments of the present application as described above, which are not provided in details for the sake of brevity.

[0059] One or more embodiments of the present application are intended to cover all such alternatives, modifications, and variations as fall within the broad scope of the present application. Accordingly, any one of the above-cited examples, or any other unrecited example, can be prepared without departing from the spirit and principles of one or more embodiments of the present application, and the present application is not limited to any one of the examples.

Claims

1. A method for preparing a bimetallic hydrogen evolution catalyst, characterized by, A mixed aqueous solution containing RhCl3 and HAuCl4 is added to a hydride carrier solution containing PVP, mixed uniformly to obtain a bimetallic hydrogen evolution catalyst, wherein the hydride carrier is a cobaltocenium derivative, and the H on one of the cyclopentadiene rings in the cobaltocenium derivative is replaced by 5 methyl groups.

2. The production method according to claim 1, wherein The molar ratio of RhCl3 to HAuCl4 is 0.8-1.2:

1.

3. The production method according to claim 2, wherein The molar ratio of RhCl3 to HAuCl4 is 1:

1.

4. The production method according to claim 1, wherein The solvent of the hydride carrier solution containing PVP is tetrahydrofuran.

5. The preparation method according to claim 4, characterized in that, In the hydride carrier solution containing PVP, the concentration of the hydride carrier is 0.001-0.01 mol / L, and the concentration of PVP is 0.001-0.01 g / mL.

6. The production method according to claim 5, wherein The volume ratio of the mixed aqueous solution containing RhCl3 and HAuCl4 to the hydride carrier solution containing PVP is 1:8-20.

7. The production method according to any one of claims 1 to 6, wherein The mixed aqueous solution containing RhCl3 and HAuCl4 is added to the hydride carrier solution containing PVP, and the mixing is carried out in a protective atmosphere.

8. The production method according to claim 7, wherein The protective atmosphere is nitrogen.

9. A bimetallic hydrogen evolution catalyst characterized by, The bimetallic hydrogen evolution catalyst is prepared by the preparation method of any one of claims 1-8.

10. Use of a bimetallic hydrogen-evolving catalyst as claimed in claim 9, characterized in that, The bimetallic hydrogen evolution catalyst is used for catalyzing hydrogen evolution.

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