A bimetallic hydrogen evolution catalyst, methods of making and uses

Abstract

The application belongs to the technical field of hydrogen evolution catalysts, and particularly relates to a bimetallic hydrogen evolution catalyst, a preparation method and an application. A mixed aqueous solution containing RhCl3 and HAuCl4 is added into a hydride carrier solution containing PVP, and is uniformly mixed to obtain a bimetallic hydrogen evolution catalyst. The hydride carrier is a cobaltocenium derivative. In the cobaltocenium derivative, H on one cyclopentadiene ring of cobaltocenium is replaced by 5 methyl groups. The application 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 H NMR spectrum. DETAILED DESCRIPTION

[0028] Example 1

[0029] A preparation method of a bimetallic hydrogen evolution catalyst, comprising the following steps:

[0030] 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 hydride carrier solution.

[0031] The hydride carrier is a cobaltocenium derivative, and the cobaltocenium derivative is that the H on one cyclopentadiene in cobaltocenium is replaced by 5 methyl groups. The structural formula is: There are 5 H on one cyclopentadiene, and each of the 5 H is replaced by a methyl group.

[0032] 2) Preparation of bimetallic catalyst:

[0033] ① Take 1 ml of RhCl3 and HAuCl4 solution mixture (i.e. 0.5 ml of RhCl3 and 0.5 ml of HAuCl4 solution mixture), stir for 10 min for standby;

[0034] 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;

[0035] 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 bimetallic hydrogen evolution catalyst.

[0036] The reaction formula is:

[0037]

[0038] M is Au, Rh, and X is Cl.

[0039] 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.

[0040] Example 2

[0041] An aqueous solution of 1 mmol / ml of ammonia borane (NH3BH3) 10 ml was prepared, and 1 ml of the ammonia borane aqueous solution was added to the bimetallic hydrogen evolution catalyst solution 11 ml in Example 1, and it was observed that 3 mmol H2 was generated. The reaction formula is:

[0042] .

[0043] Example 3

[0044] In order to compare the catalytic effects of the bimetallic hydrogen evolution catalyst of Example 1 and Au monometallic catalyst and 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 effects were compared.

[0045] The preparation method of the Au monometallic catalyst is as follows:

[0046] 1) Preparation of precursor solution: ① 0.001 mmol / mL of HAuCl4 solution 10 ml was prepared, ② 0.01 g / ml of PVP (polyvinylpyrrolidone) 10 ml was prepared, and ③ the freshly prepared hydride carrier (0.03 mmol) was dissolved in 5 ml of THF solution to obtain a hydride carrier solution.

[0047] 2) Preparation of monometallic catalyst:

[0048] ① 1 ml of HAuCl4 solution was taken and stirred for 10 min for standby;

[0049] ② 5 ml of PVP solution was taken and added to 5 ml of hydride carrier solution under nitrogen atmosphere, and stirred for 10 min for standby;

[0050] ③ Under the condition of nitrogen protection, 1 ml of HAuCl4 solution was added dropwise into 10 ml of hydride carrier containing PVP, and stirred for 30 min to obtain a monometallic hydrogen evolution catalyst.

[0051] The preparation method of the Rh monometallic catalyst is as follows:

[0052] 1) Preparation of precursor solution: ① 0.001 mmol / mL of RhCl3 solution 10 ml was prepared, ② 0.01 g / ml of PVP (polyvinylpyrrolidone) 10 ml was prepared, and ③ the freshly prepared hydride carrier (0.03 mmol) was dissolved in 5 ml of THF solution to obtain a hydride carrier solution.

[0053] 2) Preparation of monometallic catalyst:

[0054] ① 1 ml of RhCl3 solution was taken and stirred for 10 min for standby;

[0055] 2. Take 5ml PVP solution into 5ml hydride carrier solution under nitrogen atmosphere, stir for 10min for standby;

[0056] 3. Under the condition of nitrogen protection, add 1ml RhCl3 solution into 10ml PVP-containing hydride carrier, stir for 30min, to obtain single metal hydrogen evolution catalyst.

[0057] The experimental results are shown in Table 1. Figure 3 It can be seen that the catalytic effect of AuRh is obviously better than that of single metal AuNPs and RhNPs, and exhibits a synergistic effect between the bimetallic catalysts.

[0058] Example 4

[0059] 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.

[0060] The hydrogen evolution reaction was carried out by the method of Example 2, and the hydrogen evolution reactions of different bimetallic catalysts were compared. The results are shown in Table 2. Figure 4 It can be seen from Table 2 that the bimetallic catalyst of Au and Rh has the best catalytic effect, which is obviously better than that of other bimetallic catalysts. Figure 4

[0061] Example 5

[0062] The hydride carrier of the application, i.e. the cobaltocenium 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:

[0063] 1. Pentamethylated cobaltocenium 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.

[0064] ​2, The unique thermodynamic stability and hydrogen donor ability of metallocene 2 make it have incomparable advantages in the hydrogenation reaction of olefins and recyclability. The present application utilizes the chemical properties of metallocene 2 as an excellent hydrogen storage and hydrogen release 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, completing the hydrogen release process, and the hydrogen release process can be realized on the time scale of seconds; through equation-3, metallocene 3 can generate precipitate metallocene 1 by adding HPF6 solution, and more than 90% of the recovery can be realized.

[0065] The preparation method of pentamethylated cobaltocene hexafluorophosphate is:

[0066] 1, 1, 2, 3, 4, 5-pentamethylcyclopentadiene (15.2g, 78mmol) is added to THF (200ml) solution.

[0067] 2, n-butyllithium (48.8ml, 1.6M) is added to the solution of step 1 at-78℃, and then stirred at-30℃ for 30min.

[0068] 3, CoCl2(10.1g, 78mmol) is dissolved in THF (100ml) and added dropwise to the solution in step 2, stirred at room temperature for 30min, and then cooled to-10℃.

[0069] 4, THF solution of CpNa (18.1g, 78mmol) is added to the solution in step 3, and stirred at room temperature for 6h. The reaction is completed. Cp is the abbreviation of cyclopentadienyl.

[0070] 5, the solution is pumped by vacuum pump, the solid residue is dissolved in water, and washed with diethyl ether for 3 times, extracted, and the water phase is left.

[0071] 6, excess HPF6 is added to the water phase solution, and solid precipitate is generated, which is dried to remove water and washed with diethyl ether to obtain pure pentamethylated cobaltocene hexafluorophosphate.

[0072] The specific equation-1, equation-2, equation-3 reaction is as shown in Figure 5 The schematic diagram of activated methanol hydrogen production and recyclability of cobaltocene derivative is as shown in Figure 6 .

[0073] The 1 HNMR, 13 C NMR, MS spectrum of metallocene 2 is as shown in Figures 7-9 The 1 HNMR of recovered metallocene 1 is as shown in Figure 10The NaBD4 in equation-1 was replaced by deuterated NaBD4 to obtain deuterated metallocene 2, and the peaks of metallocene 2 were finally determined by comparison Figure 7 ): the 1.55 ppm signal of deuterium D disappeared, indicating that the signal can be attributed to the exo -H (H4) of metallocene 2. Subsequently, 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 13 The C NMR shows peaks at 80.49 ppm, 49.88 ppm, 17.47 ppm, 14.13 ppm, 11.98 ppm, corresponding to -CH3, -C5Me5 and three C signals in the cyclopentadiene. Figure 9 The mass spectrum shows a weak molecular peak at m / e 260.1 and a base peak at m / e 259.1, the former corresponding to compound metallocene 2, and the latter attributed to the loss of hydride of metallocene 2 and the formation of stable pentamethyl cobalt cation. Figure 10 The peaks integrated for 5 and 15 in the correspond to the Cp and groups in metallocene 1, respectively.

[0074] Example 6

[0075] If the metallocene 1 with the molecular formula is replaced by a material with the molecular formula (CoCpCp) + (PF6) - (that is, the H on the two cyclopentadienes is not substituted) or (that is, 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, the corresponding hydride sandwich structure is easy to collapse, and the material is not recyclable; the latter two groups, the molecular structure is too stable, the corresponding hydride material has insufficient hydrogen supply capacity, and cannot achieve 100% activation of methanol.

[0076] Effect of three compounds on hydrogen evolution:

[0077] Three sealed containers (sealed containers connected to hydrogen absorption device) respectively contain 1 mmol of hydride of three metallocenes. 1.1 mmol of methanol solution is injected into the three sealed containers by syringe, and the generation and amount of hydrogen can be observed by hydrogen absorption device.

[0078] (CoCpCp) + (PF6) - , hydrogenation of 1 mmol of methanol was observed. For hydrogenation of 1 mmol of methanol was observed. For

[0079] hydrogenation of 1 mmol of methanol was observed. For + hydrogenation of 1 mmol of methanol was observed. For - hydrogenation of 1 mmol of methanol was observed. For hydrogenation of 1 mmol of methanol was observed. For hydrogenation of 1 mmol of methanol was observed. For

[0080] Metallocene 2 can be recovered by HPF6 and NaBH4, and methanol can also be recovered by HPF6 with a recovery rate of more than 90%. Due to the difference in solubility of metallocene 2 and methanol, they can be separated by extraction.

[0081] It should be understood by those of ordinary skill in the art that the above discussion of any of the embodiments is merely exemplary and is not intended to suggest that the scope of protection of the present application is limited to these examples; 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 as described above. In order to be brief, they are not provided in detail.

[0082] One or more embodiments of the present application are intended to cover all such alternatives, modifications and variations falling within the broad scope of the present application. Therefore, any omission, modification, equivalent replacement, improvement, etc. made in the spirit and principles of one or more embodiments of the present application should be included in the scope of protection of the present application.

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.

Images