A nickel-molybdenum-based electrolytic water catalyst, a high-temperature molten salt preparation method thereof and application thereof

Abstract

This invention belongs to the field of electrocatalyst preparation technology, specifically relating to a nickel-molybdenum-based water electrolysis catalyst and its high-temperature molten salt preparation method and application. This invention can prepare two high-performance electrocatalysts for hydrogen evolution at the cathode and oxygen evolution at the anode in water electrolysis. The specific methods are as follows: 1) In the cathode hydrogen evolution catalyst, molybdate is used as the molybdenum source and cerium acetylacetone is used as the cerium source. After uniform mixing, they are first subjected to a high-temperature melting and solidification reaction, and then annealed and reduced in a hydrogen-argon mixture to obtain the hydrogen evolution catalyst at the cathode of the electrolyzer; 2) In the anode oxygen evolution catalyst, molybdate is used as the molybdenum source, cerium acetylacetone as the cerium source, and iron acetylacetone as the iron source. After uniform mixing, they are first subjected to a high-temperature melting and solidification reaction, and then annealed and reduced in a hydrogen-argon mixture to obtain the oxygen evolution catalyst at the anode of the electrolyzer. The catalysts prepared by this invention exhibit excellent performance in both hydrogen evolution and oxygen evolution catalysis, and can achieve long-term stable operation at ampere-level current densities in electrolyzer devices.

Description

Technical Field

[0001] This invention relates to the field of electrocatalyst preparation technology, specifically to a nickel-molybdenum-based water electrolysis catalyst and its high-temperature molten salt preparation method and application. Background Technology

[0002] Hydrogen production through water electrolysis involves using electricity to decompose water into hydrogen and oxygen, and is an important technological approach for obtaining "green hydrogen." Currently, low-temperature water electrolysis technologies mainly include proton exchange membrane electrolysis (PEMWE), alkaline water electrolysis (ALK), and anion exchange membrane electrolysis (AEMWE). Among these, PEMWE produces hydrogen with high purity and efficiency, but it heavily relies on precious metal catalysts, leading to high costs. Alkaline water electrolysis (ALK) and anion exchange membrane electrolysis (AEMWE), on the other hand, can use non-precious metal-based catalysts and are considered ideal technological routes for achieving low-cost, large-scale production of green hydrogen.

[0003] However, alkaline water electrolysis (ALK) and anion exchange membrane water electrolysis (AEMWE) technologies operating in alkaline media face dual constraints. In alkaline electrolytes, not only is the kinetics of the oxygen evolution reaction (OER) at the anolyte slow, but the hydrogen evolution reaction (HER) at the cathode is also limited by a sluggish interfacial water dissociation step, requiring both the anode and cathode to overcome extremely high overpotentials. This significantly increases the overall energy consumption of hydrogen production and limits the improvement of electrolysis efficiency. Furthermore, most existing methods for preparing non-precious metal catalysts only optimize the performance of a single catalytic reaction (OER or HER), and the processes are complex. There is a lack of a simple, low-cost, universally applicable, and scalable integrated solution that can also prepare high-performance bifunctional catalysts for both hydrogen evolution and oxygen evolution. Therefore, developing a simple and universal non-precious metal-based catalyst preparation technology to address the high energy consumption and catalytic performance bottlenecks faced by alkaline water electrolysis in hydrogen production remains a critical technical challenge that urgently needs to be solved. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a nickel-molybdenum-based water electrolysis catalyst with simple process, low cost, universality and potential for large-scale preparation, which can be compatible with the preparation of high-performance hydrogen evolution and oxygen evolution bifunctional catalysts, as well as its high-temperature molten salt preparation method and application.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing high-temperature molten salt of a nickel-molybdenum-based water electrolysis catalyst, comprising the following steps: 1) Cathode hydrogen evolution catalyst: Molybdate and acetylacetone rare earth salt are mixed and ground evenly. The evenly ground powder is then uniformly covered by the cleaned porous metal substrate. Next, it is annealed in air, cooled, cleaned with 1.0 mol / L KOH solution and deionized water, and dried. Finally, it is annealed in H2 / Ar mixed gas to obtain the hydrogen evolution catalyst at the cathode of the electrolyzer. 2) Anode oxygen evolution catalyst: Molybdate, acetylacetone salt, and acetylacetone rare earth salt are mixed and ground evenly. The acetylacetone salt is iron acetylacetone or cobalt acetylacetone. The evenly ground powder is uniformly covered by the cleaned porous metal substrate. Then, it is annealed in air, cooled, cleaned with 1.0 mol / L KOH solution and deionized water, and dried. Finally, it is annealed in H2 / Ar mixed gas to obtain the oxygen evolution catalyst at the anode of the electrolytic cell.

[0006] Further, in step 1), the molybdate is at least one of ammonium molybdate, sodium molybdate, and lithium molybdate, and the molybdate content is 1.0–5.0 g; the acetylacetone rare earth salt is at least one of cerium acetylacetone, lanthanum acetylacetone, praseodymium acetylacetone, neodymium acetylacetone, samarium acetylacetone, europium acetylacetone, gadolinium acetylacetone, terbium acetylacetone, dysprosium acetylacetone, holmium acetylacetone, erbium acetylacetone, thulium acetylacetone, ytterbium acetylacetone, lutetium acetylacetone, scandium acetylacetone, and yttrium acetylacetone, and the acetylacetone rare earth salt content is 0.05–0.5 g. The content of molybdate and acetylacetone rare earth salt is based on a porous metal substrate with a single sheet area of ​​6.0 cm². 2 calculate.

[0007] Furthermore, in step 1), the annealing temperature under air is 400–800℃, and the holding time is 30–300 min; the annealing temperature under H2 / Ar mixed gas is 300–700℃, and the holding time is 30–300 min.

[0008] Furthermore, in step 1), the molybdate content is 1.0–5.0 g, and the acetylacetone rare earth salt content is 0.05–0.3 g; the annealing temperature under air is 700 °C, and the holding time is 120 min; the annealing temperature under H2 / Ar mixed gas is 500 °C, and the holding time is 120 min.

[0009] Further, in step 2), the molybdate is at least one of ammonium molybdate, sodium molybdate, and lithium molybdate, and the molybdate content is 1.0–5.0 g; the acetylacetone rare earth salt is at least one of cerium acetylacetone, lanthanum acetylacetone, praseodymium acetylacetone, neodymium acetylacetone, samarium acetylacetone, europium acetylacetone, gadolinium acetylacetone, terbium acetylacetone, dysprosium acetylacetone, holmium acetylacetone, erbium acetylacetone, thulium acetylacetone, ytterbium acetylacetone, lutetium acetylacetone, scandium acetylacetone, and yttrium acetylacetone, and the acetylacetone rare earth salt content is 0.05–0.5 g, the acetylacetone salt content is 0.05–0.5 g, and the molybdate, acetylacetone salt, and acetylacetone rare earth salt content are based on a porous metal substrate with a single sheet area of ​​6.0 cm². 2 calculate.

[0010] Furthermore, in step 2), the annealing temperature under air is 400–800℃, and the holding time is 30–300 min; the annealing temperature under H2 / Ar mixed gas is 300–700℃, and the holding time is 30–300 min.

[0011] Furthermore, in step 2), the molybdate content is 2.0g, the acetylacetone rare earth salt content is 0.2g, the acetylacetone salt content is 0.2g, the air annealing temperature is 700℃, and the holding time is 120min; the H2 / Ar mixed gas annealing temperature is 500~700℃, and the holding time is 120min.

[0012] Furthermore, the porous metal substrate in steps 1) and 2) includes nickel foam, nickel mesh, nickel felt, cobalt foam, cobalt mesh, or cobalt felt.

[0013] A high-performance nickel-molybdenum non-precious metal-based water electrolysis catalyst prepared by the above-described method.

[0014] Application of a high-performance nickel-molybdenum non-precious metal-based water electrolysis catalyst prepared by the above-mentioned method in catalytic reactions in anion exchange membrane electrolyzers and alkaline electrolyzers.

[0015] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention employs a high-temperature molten salt method to grow a catalytic layer in situ on a porous metal substrate, achieving homogeneous doping of rare earth elements and transition metal elements and the preparation of an integrated self-supporting catalyst. In the catalyst prepared by high-temperature molten salt, the catalytic layer uniformly coats the substrate, a structure that greatly enhances the bonding force between the catalyst and the conductive substrate; it ensures charge transport and structural integrity under high current density, laying the foundation for ultra-long-term stable operation of the catalyst at industrial-grade current densities; and it effectively solves the problems of easy detachment and poor durability of traditional powder-coated catalysts. The method of this invention requires only two steps of solid-state annealing, effectively overcoming the difficulty of large-scale scaling up of traditional hydrothermal or solvothermal methods.

[0016] 2. Significantly enhanced alkaline hydrogen evolution catalytic activity and industrial-grade durability, surpassing the performance of commercial precious metal catalysts. This invention effectively accelerates the slow Volmer water dissociation step in alkaline hydrogen evolution through the synergistic effect of rare earth doping and the MoO2 / MoNi4 heterostructure. Taking Ce doping, the most preferred rare earth doping, as an example: the resulting catalyst only requires 60mV and 165mV overpotentials in a three-electrode system to reach -100mA / cm. 2 and -500mA / cm 2 The high current density of this catalyst significantly outperforms commercial Pt / C catalysts (136 and 381 mV) and undoped rare-earth MoO2 / MoNi4 (146 and 318 mV). The hydrogen evolution catalyst prepared by this invention effectively overcomes the limitation of traditional MoO2 / MoNi4 catalysts exhibiting low alkaline hydrogen evolution activity due to their single hydrolysis site. In an AEM electrolyzer device, this catalyst, combined with a non-precious metal anode, achieves 1.0 A / cm² activity with only 1.86 V. 2 With an industrial-grade current density and the ability to operate stably for over 1200 hours, this technology demonstrates excellent prospects for practical applications and is expected to further promote the development of AEMWE hydrogen production technology.

[0017] 3. The preparation method has good universality and can be extended to the preparation of non-precious metal-based oxygen evolution catalysts. The rare earth doping strategy of this invention has broad applicability, extending the doping elements to all lanthanide rare earths (except radioactive promethium), and can prepare alkaline hydrogen evolution performance significantly better than undoped MoO2 / MoNi4 catalysts. Furthermore, by controlling the type of doping element (e.g., simultaneous doping with Fe and Ce), anodic oxygen evolution catalysts with significantly better performance than commercial RuO2 can also be prepared. This provides a general and efficient strategy for the design and construction of low-cost, all-non-precious metal-based water electrolysis catalysts. Attached Figure Description

[0018] Figure 1 The XRD patterns are of the products of the present invention (corresponding to Embodiment 1 and Comparative Example 1); Figure 2 These are the SEM images, SEM-EDS images, and HR-TEM images of the product of the present invention (corresponding to Embodiment 1); Figure 3 The figures show the LSV polarization curves and overpotential comparisons of the products of this invention (corresponding to Example 1, Comparative Example 1, Comparative Example 2, and a commercial Pt / C catalyst) in 1.0 mol / L KOH solution, as well as the figures for Example 1 and Comparative Example 1 at -100 / -1000 mA / cm². 2 The following is an Et test plot; Figure 4 The Vi curve test diagram of the product of the present invention (corresponding to Example 1 and Comparative Example 1) on the AEM electrolytic cell device; Figure 5 This is a test image showing the long-term Vt durability of the product of the present invention (corresponding to the catalyst in Example 1) in an AEM electrolyzer device; Figure 6 The LSV polarization curves and overpotential comparison diagrams of the products of the present invention (corresponding to Examples 1, 2 and 3) in 1.0 mol / L KOH solution are shown. Figure 7 This is a comparison graph of the overpotential of the product of the present invention (corresponding to Embodiment 1 and Embodiments 4-16) under different current densities; Figure 8 The XRD patterns are of the products of the present invention (corresponding to Embodiment 17 and Comparative Examples 3-5); Figure 9 The LSV polarization curves and overpotential comparison diagrams of the products of this invention (corresponding to Example 13, Comparative Examples 3-5 and commercial RuO2 catalyst) in 1.0 mol / L KOH solution are shown. Figure 10 The product of this invention (corresponding to Example 17 and Comparative Example 3) at 100 mA / cm 2 The following is an Et test plot; Figure 11 The LSV polarization curves of the product of the present invention (corresponding to Examples 17-19) in 1.0 mol / L KOH solution are shown. Figure 12 The LSV polarization curves of the product of this invention (corresponding to Example 20 and the commercial RuO2 catalyst) in 1.0 mol / L KOH solution are shown. Figure 13 Digital photographs of the catalysts prepared for scale-up of the products of the present invention (corresponding to Examples 21 and 22); Figure 14 The LSV polarization curves of the product of the present invention (corresponding to the catalysts of Example 23 and Comparative Example 6) in 1.0 mol / L KOH solution and the overpotential comparison diagram at different current densities are shown. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of the invention.

[0020] Example 1: Preparation of rare earth Ce-doped cathode hydrogen evolution catalyst (1) Mix 2.0g of ammonium molybdate tetrahydrate and 0.2g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (6.0cm) 2 Then, the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-cerium-oxygen precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum-cerium-oxygen precursor was placed in a tube furnace and annealed at 500°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated hydrogen evolution catalyst for the cathode of the electrolytic cell with Ce-doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0021] Comparative Example 1 Without adding cerium acetylacetone hydrate, the other conditions were the same as those in Example 1.

[0022] Comparative Example 2 Ammonium molybdate tetrahydrate and cerium acetylacetone hydrate were not added, and the remaining conditions were the same as those in Example 1.

[0023] The porous nickel foam substrate was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere. After cooling, it was cleaned with a 1.0 mol / L KOH solution, rinsed with deionized water, dried, and placed in a tube furnace. It was then annealed at 500°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, the nickel foam substrate was obtained.

[0024] The XRD test results of Example 1 and Comparative Example 1 are as follows: Figure 1 As shown, by Figure 1 It can be seen that both are ultimately catalysts for the coexistence of two phases of MoO2 and MoNi4 alloy. Although rare earth cerium was added in Example 1, no diffraction peak of CeO2 was found in the XRD, indicating that Ce may be uniformly doped in MoO2 / MoNi4. Figure 2 The SEM image of af clearly shows that the Ce-doped MoO2 / MoNi4 catalyst layer uniformly coats the nickel foam substrate, and Ni, Mo, O and Ce elements are uniformly dispersed in the catalyst, which further proves that the catalyst of Example 1 was successfully prepared. Figure 2g and h show that the catalyst surface in Example 1 has a thin catalytic layer, and the MoO2 and MoNi4 crystal planes correspond to (-111) and (330) respectively, and there is a very obvious heterogeneous interface between them. The LSV curves of Example 1, Comparative Example 1, Comparative Example 2, and the commercial Pt / C catalyst were tested in 1.0 mol / L KOH solution. See [link to relevant documentation]. Figure 3 a; The catalysts prepared in Example 1 require only 60 and 165 mV overpotentials to reach -100 and -500 mA / cm, respectively. 2 The current density is significantly better than that of Comparative Examples 1 and 2, and also better than the 136 and 381 mV of commercial Pt / C catalysts. Figure 3 b) Compared with Comparative Example 1, the addition of Ce significantly improved the basic hydrogen evolution catalytic activity of the catalyst, mainly due to Ce promoting the slow Volmer step; the catalysts of Example 1 and Comparative Example 1 at current densities of -100 / -1000 mA / cm² 2 Stability tests were conducted, and the catalyst in Example 1 operated stably for 1000 hours continuously, while the catalyst in Comparative Example 1 showed significant performance degradation after only 250 hours of operation (see [link]). Figure 3 c) indicates that rare earth Ce can not only promote the dissociation of interfacial water, but also significantly improve the long-term durability of the catalyst. The above three-electrode results show that the catalyst prepared in Example 1 of this invention has high catalyst activity and long-term stability in the alkaline hydrogen evolution reaction. In order to further verify the performance of the catalyst in the AEM electrolyzer, it was subsequently assembled with a NiFe-based anode to form an AEM electrolyzer device. Figure 4 The results showed that Example 1 achieved 1.0 A / cm² in an AEM electrolytic cell at 60°C with only 1.86 V. 2 The industrial-grade current density is significantly better than the 2.03V of the catalyst in Comparative Example 1, further demonstrating that the catalyst prepared in Example 1 still has excellent catalytic performance under actual working conditions. Figure 5 Further verification shows that Example 1 also has good long-term durability under actual working conditions. The device can also operate stably for more than 1200 hours at industrial-grade current density, showing good application prospects. Example 1 shows that the Ce-doped MoO2 / MoNi4 integrated catalyst supported on a nickel foam substrate prepared by the high-temperature molten salt method exhibits good catalytic activity and excellent long-term durability for HER in alkaline three-electrode and AEM electrolyzer devices. Its activity and durability are superior to those of current commercial Pt / C catalysts. This invention is expected to prepare non-noble metal-based catalysts with better overall performance and lower cost. In particular, the all-non-noble-based electrolyzer has the application potential to have long-term stable operation at ampere-level current densities.

[0025] Example 2: Preparation of rare earth Ce-doped cathode hydrogen evolution catalyst (1) Mix 2.0g of ammonium molybdate tetrahydrate and 0.05g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (6.0cm) 2 Then, the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-cerium-oxygen precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum-cerium-oxygen precursor was placed in a tube furnace and annealed at 500°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated hydrogen evolution catalyst for the cathode of the electrolytic cell with Ce-doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0026] Example 3

[0027] To investigate the effect of rare earth cerium content on the hydrogen evolution performance of the catalyst, 0.3 g of cerium acetylacetone hydrate was added in Example 3, and the other conditions were the same as those in Example 2.

[0028] As can be seen from the above examples, the addition of rare earth element Ce is one of the important factors affecting the high-performance hydrogen evolution activity of the catalyst. Therefore, a series of catalysts with different Ce doping contents were further prepared to clarify the trend of the effect of Ce content on performance. The LSV curves of the catalysts in Examples 1-3 were tested in a 1.0 mol / L KOH solution, see [link to relevant documentation]. Figure 6 Examples 1-3 demonstrate that even by varying the amount of cerium acetylacetone hydrate added, hydrogen evolution catalysts with superior performance compared to current commercial Pt / C catalysts can still be prepared. Figure 3 and Figure 6 This indicates that, within a certain range, changing the preparation conditions can also produce high-performance hydrogen evolution catalysts, while further clarifying the key role of rare earth Ce in this process.

[0029] Example 4: Preparation of Rare Earth La-Doped Cathode Hydrogen Evolution Catalyst (1) Mix 2.0g of ammonium molybdate tetrahydrate and 0.2g of lanthanum acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate and lanthanum acetylacetone hydrate; (2) Clean the porous nickel foam substrate (6.0cm) 2 Then, the ammonium molybdate tetrahydrate-lanthanum acetylacetonate hydrate mixed powder is uniformly coated on the porous nickel foam substrate to obtain a porous nickel foam substrate coated with the ammonium molybdate tetrahydrate-lanthanum acetylacetonate hydrate mixed powder. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate and lanthanum acetylacetonate hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-lanthanum oxide precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum lanthanum oxygen precursor was placed in a tube furnace and annealed at 500°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated hydrogen evolution catalyst for the cathode of the electrolyzer with La doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0030] Example 5: Preparation of Rare Earth Pr-Doped Cathode Hydrogen Evolution Catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of praseodymium acetylacetonate was added in Example 5, and the other conditions were the same as those in Example 4.

[0031] Example 6: Preparation of Rare Earth Nd-Doped Cathode Hydrogen Evolution Catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of neodymium acetylacetonate was added in Example 6, and the other conditions were the same as those in Example 4.

[0032] Example 7: Preparation of Rare Earth Sm-Doped Cathode Hydrogen Evolution Catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of samarium acetylacetonate salt was added in Example 7, and the other conditions were the same as those in Example 4.

[0033] Example 8: Preparation of Rare Earth Eu-Doped Cathode Hydrogen Evolution Catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of europium acetylacetone hydrate was added in Example 8, and the other conditions were the same as those in Example 4.

[0034] Example 9: Preparation of Rare Earth Gd-Doped Cathode Hydrogen Evolution Catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of gadolinium acetylacetonate was added in Example 9, and the other conditions were the same as those in Example 4.

[0035] Example 10: Preparation of Rare Earth Tb-Doped Cathode Hydrogen Evolution Catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of terbium acetylacetonate was added in Example 10, and the other conditions were the same as those in Example 4.

[0036] Example 11 Preparation of rare earth Dy-doped cathode hydrogen evolution catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of dysprosium acetylacetonate hydrate was added in Example 11, and the other conditions were the same as those in Example 4.

[0037] Example 12 Preparation of rare earth Ho-doped cathode hydrogen evolution catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of holmium acetylacetonate was added in Example 12, and the other conditions were the same as those in Example 4.

[0038] Example 13 Preparation of rare earth Er-doped cathode hydrogen evolution catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of erbium acetylacetonate was added in Example 13, and the other conditions were the same as those in Example 4.

[0039] Example 14 Preparation of rare earth Tm-doped cathode hydrogen evolution catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of thulium acetylacetonate was added in Example 14, and the other conditions were the same as those in Example 4.

[0040] Example 15 Preparation of rare earth Yb-doped cathode hydrogen evolution catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of ytterbium acetylacetonate hydrate was added in Example 15, and the other conditions were the same as those in Example 4.

[0041] Example 16 Preparation of rare earth Lu-doped cathode hydrogen evolution catalyst To investigate the effect of rare earth elements on the hydrogen evolution performance of the catalyst, 0.2 g of lutetium acetylacetonate was added in Example 16, and the other conditions were the same as those in Example 4.

[0042] Examples 4-16 expanded the doping elements to include all lanthanide rare earth elements, except for radioactive promethium. The catalysts from Examples 1 and 4-16 were placed in a 1.0 mol / L KOH solution to test LSV curves, and overpotential statistics were performed at different current densities (see [link to documentation]). Figure 7 );from Figure 7It is evident that the alkaline hydrogen evolution catalytic performance of all lanthanide rare earth-doped catalysts is significantly improved compared to MoO2 / MoNi4 (Comparative Example 1), indicating that the method of the present invention has good universality. Under certain conditions, doping with appropriate amounts of rare earth elements or other elements that can accelerate interfacial water dissociation can prepare high-performance non-noble metal-based alkaline hydrogen evolution catalysts.

[0043] Example 17 Preparation of Fe / Ce co-doped anodic oxygen evolution catalyst (1) Mix 2.0g of ammonium molybdate tetrahydrate, 0.2g of iron acetylacetone and 0.2g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (6.0cm) 2 Then, the mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-iron-cerium-oxygen precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum-iron-cerium-oxygen precursor was placed in a tube furnace and annealed at 600°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated oxygen evolution catalyst for the anode of the electrolytic cell with Fe / Ce co-doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0044] Comparative Example 3 Without adding cerium acetylacetone hydrate, the other conditions were the same as those in Example 17.

[0045] Comparative Example 4 Without adding acetylacetone iron, the other conditions were the same as those in Example 17.

[0046] Comparative Example 5 Without adding acetylacetone iron and acetylacetone cerium hydrate, the other conditions were the same as those in Example 17.

[0047] The XRD test results from Examples 17 and Comparative Examples 3-5 show that all catalysts eventually form two phases of MoO2 and MoNi4 alloy. Figure 8However, diffraction peaks of metallic Mo appeared in the catalysts of Example 17 and Comparative Example 3 with added iron, which may be because the presence of iron promotes the reduction of Mo. In addition, no diffraction peaks of CeO2 appeared in the XRD of the four catalysts, indicating that Ce is uniformly doped in the catalyst. The LSV curves of Examples 17, Comparative Examples 3-5, and the commercial RuO2 catalyst were tested in 1.0 mol / L KOH solution. See [link to relevant documentation]. Figure 9 a; The catalysts prepared in Example 1 require only 195 and 237 mV overpotentials to reach 10 and 100 mA / cm, respectively. 2 The current density was significantly better than that of Comparative Examples 3, 4, and 5, and also better than the 241 and 330 mV of commercial RuO2 catalysts. Figure 9 (b) Compared with Comparative Examples 3-5, the simultaneous addition of Fe and Ce significantly improved the alkaline oxygen evolution catalytic activity of the catalyst; the catalysts of Example 17 and Comparative Example 3 at a current density of 100 mA / cm² 2 Stability tests were conducted. In Example 17, the catalyst showed no significant potential fluctuations after 300 hours of continuous operation, while in Comparative Example 3, a significant increase in potential was observed (see...). Figure 10 This indicates that rare earth element Ce can not only enhance the oxygen evolution activity of catalysts but also significantly improve their long-term durability.

[0048] Example 18 Preparation of Fe / Ce co-doped anodic oxygen evolution catalyst (1) Mix 2.0g of ammonium molybdate tetrahydrate, 0.2g of iron acetylacetone and 0.2g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (6.0cm) 2 Then, the mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-iron-cerium-oxygen precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum-iron-cerium-oxygen precursor was placed in a tube furnace and annealed at 500°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated oxygen evolution catalyst for the anode of the electrolytic cell with Fe / Ce co-doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0049] Example 19 Preparation of Fe / Ce co-doped anodic oxygen evolution catalyst To investigate the effect of annealing temperature on the oxygen evolution performance of the catalyst, in Example 19, the annealing temperature was 700°C in a 10% H2 / Ar mixed gas, and the other conditions were the same as those in Example 18. Besides the significant impact of doping elements on catalytic performance, annealing temperature is also a crucial factor affecting catalyst performance. Therefore, a series of catalysts with different annealing temperatures were prepared. The LSV curves of the catalysts from Examples 17-19 were tested in a 1.0 mol / L KOH solution. (See attached image.) Figure 11 Examples 17-19 demonstrate that, within a certain range, even by changing the annealing temperature, oxygen evolution catalysts with performance superior to currently available commercial RuO2 catalysts can still be prepared. Figure 9 and Figure 11 This indicates that, within a certain range of conditions, changing the preparation conditions can also produce oxygen evolution catalysts with excellent performance.

[0050] Example 20 Preparation of Co / Ce co-doped anodic oxygen evolution catalyst (1) Mix 2.0g of ammonium molybdate tetrahydrate, 0.2g of cobalt acetylacetone and 0.2g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate-cobalt acetylacetone-cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (6.0cm) 2 Then, the mixed powder of ammonium molybdate tetrahydrate-cobalt acetylacetone-cerium acetylacetone hydrate is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the mixed powder of ammonium molybdate tetrahydrate-cobalt acetylacetone-cerium acetylacetone hydrate. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate-cobalt acetylacetone-cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-cobalt-cerium-oxygen precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum-cobalt-cerium-oxygen precursor was placed in a tube furnace and annealed at 500°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated oxygen evolution catalyst for the anode of the electrolytic cell with Co / Ce co-doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0051] This embodiment expands the doping element by replacing iron with cobalt; the LSV curves of Example 20 and the commercial RuO2 catalyst were tested in 1.0 M KOH solution (see Example 20). Figure 12 );from Figure 12 It is evident that the alkaline oxygen evolution catalytic performance of the cobalt-doped catalyst is significantly better than that of current commercial RuO2 catalysts. However, the oxygen evolution activity of cobalt-doped catalysts is not as good as that of iron-doped catalysts, indicating that the method of this invention has a certain degree of universality. Under certain conditions, doping with appropriate amounts of rare earth elements and other transition metal elements can prepare high-performance non-precious metal-based alkaline oxygen evolution catalysts.

[0052] Example 21 Preparation of rare earth Ce-doped cathode hydrogen evolution catalyst (1) Mix 59.0g of ammonium molybdate tetrahydrate and 5.9g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (13.3cm × 13.3cm, area approximately 176.89cm²). 2 Then, the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-cerium-oxygen precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum-cerium-oxygen precursor was placed in a tube furnace and annealed at 500°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated hydrogen evolution catalyst for the cathode of the electrolytic cell with Ce-doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0053] Example 22 Preparation of Fe / Ce co-doped anodic oxygen evolution catalyst (1) Mix 59.0g of ammonium molybdate tetrahydrate, 5.9g of iron acetylacetone and 5.9g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (13.3cm × 13.3cm, area approximately 176.89cm²). 2 Then, the mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the mixed powder of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate-iron acetylacetone-cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere; after cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-iron-cerium-oxygen precursor supported on porous nickel foam. (4) The porous nickel foam supported nickel-molybdenum-iron-cerium-oxygen precursor was placed in a tube furnace and annealed at 600°C for 120 min in a 10% H2 / Ar mixed gas atmosphere (volume fraction of 10%). After cooling, an integrated oxygen evolution catalyst for the anode of the electrolytic cell with Fe / Ce co-doped MoO2 / MoNi4 supported on a nickel foam substrate was obtained.

[0054] Examples 21 and 22 scaled up the catalyst preparation area to 176.89 cm². 2 (See) Figure 13 This indicates that the method of the present invention has certain prospects for large-scale preparation and provides technical support for the development of low-cost, large-area catalysts.

[0055] Example 23 Preparation of a porous nickel foam-supported nickel-molybdenum-cerium-oxygen cathode hydrogen evolution catalyst (1) Mix 2.0g of ammonium molybdate tetrahydrate and 0.2g of cerium acetylacetone hydrate and grind them evenly to obtain a mixed powder of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate; (2) Clean the porous nickel foam substrate (6.0cm) 2 Then, the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder is uniformly covered on the porous nickel foam substrate to obtain a porous nickel foam substrate covered with the ammonium molybdate tetrahydrate-cerium acetylacetone hydrate mixed powder. (3) The porous nickel foam substrate covered with a mixture of ammonium molybdate tetrahydrate and cerium acetylacetone hydrate powder was placed in a muffle furnace and annealed at 700°C for 120 min in air atmosphere. After cooling, it was washed with KOH solution with a concentration of 1.0 mol / L, rinsed with deionized water, and dried to obtain a nickel-molybdenum-cerium-oxygen cathode hydrogen evolution catalyst supported on porous nickel foam. Comparative Example 6 Without adding cerium acetylacetone hydrate, the other conditions were the same as those in Example 23.

[0056] from Figure 14 Electrochemical tests showed that when only air annealing was performed, the alkaline hydrogen evolution activities of Example 23 and Comparative Example 6 were basically equivalent. The hydrogen-argon mixed gas annealing of Example 1 was crucial for improving the hydrogen evolution activity of the catalyst.

[0057] The above results indicate that the catalyst prepared by this invention not only has excellent catalytic performance at the cathode hydrogen evolution end, but also can produce a high-performance anode oxygen evolution catalyst by controlling element doping. The method of this invention provides a promising preparation strategy for preparing high-performance non-precious metal-based electrolytic water catalysts.

[0058] The above-described embodiments 1 and 17 are the best embodiments.

[0059] The above embodiments are only the preferred embodiments of the present invention and do not limit any modifications to the present invention. Any modifications, changes and optimizations made according to the embodiments of the present invention shall fall within the scope of protection of the present invention.

Claims

1. A method for preparing high-temperature molten salt of a nickel-molybdenum-based water electrolysis catalyst, characterized by the following steps: for: 1) Cathode hydrogen evolution catalyst: Molybdate and acetylacetone rare earth salt are mixed and ground evenly. The evenly ground powder is then uniformly covered by the cleaned porous metal substrate. Next, it is annealed in air, cooled, cleaned with 1.0 mol / L KOH solution and deionized water, and dried. Finally, it is annealed in H2 / Ar mixed gas to obtain the hydrogen evolution catalyst at the cathode of the electrolyzer. 2) Anode oxygen evolution catalyst: Molybdate, acetylacetone salt, and acetylacetone rare earth salt are mixed and ground evenly. The acetylacetone salt is iron acetylacetone or cobalt acetylacetone. The evenly ground powder is uniformly covered by the cleaned porous metal substrate. Then, it is annealed in air, cooled, cleaned with 1.0 mol / L KOH solution and deionized water, and dried. Finally, it is annealed in H2 / Ar mixed gas to obtain the oxygen evolution catalyst at the anode of the electrolytic cell.

2. The method for preparing high-temperature molten salt of nickel-molybdenum based water electrolysis catalyst according to claim 1, characterized in that: In step 1), the molybdate is at least one of ammonium molybdate, sodium molybdate, and lithium molybdate, and the molybdate content is 1.0–5.0 g; the acetylacetone rare earth salt is at least one of cerium acetylacetone, lanthanum acetylacetone, praseodymium acetylacetone, neodymium acetylacetone, samarium acetylacetone, europium acetylacetone, gadolinium acetylacetone, terbium acetylacetone, dysprosium acetylacetone, holmium acetylacetone, erbium acetylacetone, thulium acetylacetone, ytterbium acetylacetone, lutetium acetylacetone, scandium acetylacetone, and yttrium acetylacetone, and the acetylacetone rare earth salt content is 0.05–0.5 g. The content of molybdate and acetylacetone rare earth salt is based on a porous metal substrate with a single sheet area of ​​6.0 cm². 2 calculate.

3. The method for preparing high-temperature molten salt of nickel-molybdenum based water electrolysis catalyst according to claim 1, characterized in that: In step 1), the annealing temperature under air is 400-800℃ and the holding time is 30-300min; the annealing temperature under H2 / Ar mixed gas is 300-700℃ and the holding time is 30-300min.

4. The method for preparing high-temperature molten salt of nickel-molybdenum based water electrolysis catalyst according to claim 1, characterized in that: In step 1), the molybdate content is 1.0–5.0 g, and the acetylacetone rare earth salt content is 0.05–0.3 g; the annealing temperature under air is 700℃, and the holding time is 120 min; the annealing temperature under H2 / Ar mixed gas is 500℃, and the holding time is 120 min.

5. The method for preparing high-temperature molten salt of nickel-molybdenum based electrolytic water catalyst according to claim 1, characterized in that: In step 2), the molybdate is at least one of ammonium molybdate, sodium molybdate, and lithium molybdate, and the molybdate content is 1.0–5.0 g; the acetylacetone rare earth salt is at least one of cerium acetylacetone, lanthanum acetylacetone, praseodymium acetylacetone, neodymium acetylacetone, samarium acetylacetone, europium acetylacetone, gadolinium acetylacetone, terbium acetylacetone, dysprosium acetylacetone, holmium acetylacetone, erbium acetylacetone, thulium acetylacetone, ytterbium acetylacetone, lutetium acetylacetone, scandium acetylacetone, and yttrium acetylacetone, and the acetylacetone rare earth salt content is 0.05–0.5 g, the acetylacetone salt content is 0.05–0.5 g, and the molybdate, acetylacetone salt, and acetylacetone rare earth salt content are based on a porous metal substrate with a single sheet area of ​​6.0 cm². 2 calculate.

6. The method for preparing high-temperature molten salt of the nickel-molybdenum-based electrolytic water catalyst according to claim 1, characterized in that: In step 2), the annealing temperature under air is 400–800℃ and the holding time is 30–300 min; the annealing temperature under H2 / Ar mixed gas is 300–700℃ and the holding time is 30–300 min.

7. The method for preparing high-temperature molten salt of the nickel-molybdenum-based electrolytic water catalyst according to claim 1, characterized in that: In step 2), the molybdate content is 2.0g, the acetylacetone rare earth salt content is 0.2g, the acetylacetone salt content is 0.2g, the air annealing temperature is 700℃, and the holding time is 120min; the H2 / Ar mixed gas annealing temperature is 500~700℃, and the holding time is 120min.

8. The method for preparing high-temperature molten salt of nickel-molybdenum based water electrolysis catalyst according to claim 1, characterized in that: The porous metal substrates in steps 1) and 2) include nickel foam, nickel mesh, nickel felt, cobalt foam, cobalt mesh, or cobalt felt.

9. The high-performance nickel-molybdenum non-precious metal-based water electrolysis catalyst prepared by the method according to claim 1.

10. The application of a high-performance nickel-molybdenum non-precious metal-based water electrolysis catalyst prepared by the method described in claim 1 in catalytic reactions in anion exchange membrane electrolyzers and alkaline electrolyzers.

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