A Ni / NiO@RE 2 O 3 / C nanocatalysts, their 100-gram-scale preparation methods, and applications

Abstract

This invention belongs to the field of AEMWE catalysis applications, specifically relating to a Ni / NiO@RE catalyst. 2 O 3 / C nanocatalysts, their 100-gram-scale preparation methods, and applications. This invention provides Ni / NiO@RE... 2 O 3 A method for preparing Ni / NiO@RE nanocatalysts at the gram scale involves ultrasonically dispersing nickel acetylacetonate, rare earth acetate, and a carbon support in a solvent until uniform dispersion. The resulting dispersion is then heated and stirred until dry, followed by grinding. The ground material is then calcined in a hydrogen-containing gas to convert nickel acetylacetonate into Ni and NiO, and rare earth acetate into rare earth oxides. This method can achieve Ni / NiO@RE nanocatalysts. 2 O 3 The Ni / NiO@RE nanocatalyst was prepared on a gram-scale basis. 2 O 3 / C nanocatalysts can significantly improve the hydrogen production efficiency of alkaline HER and exhibit excellent electrocatalytic performance on AEMWE's MEA.

Description

A Ni / NiO@RE2O3 / C nanocatalyst, its preparation method at the 100-gram scale, and its application. Technical Field

[0001] This invention belongs to the field of catalytic applications in anion exchange membrane electrolysis (AEMWE), particularly in the fields of hydrogen evolution reaction (HER) and membrane electrode assembly (MEA) in AEMWE. Specifically, it relates to a Ni / NiO@RE2O3 / C nanocatalyst and its 100-gram-scale preparation method and application. Background Technology

[0002] Hydrogen energy boasts advantages such as high energy density, wide availability, cleanliness, environmental friendliness, and renewability, making it an ideal energy carrier for addressing global fossil fuel shortages and environmental pollution. From the perspective of hydrogen energy sources, the production of green hydrogen using water electrolysis technology has significant fundamental research value and practical application implications. Among various water electrolysis hydrogen production technologies, anion exchange membrane electrolysis (AEMWE) is a promising green hydrogen production technology that combines low cost, high efficiency, mild operating conditions, safety, environmental friendliness, and high flexibility. This is because AEMWE technology has the following outstanding advantages: (1) It can use relatively inexpensive non-precious metal catalysts, which greatly reduces the cost of catalysts; (2) It can operate at lower temperatures and pressures, which reduces the requirements for high temperature and high pressure resistance of equipment, and reduces equipment investment costs and operating risks; (3) Anion exchange membranes (AEM) have good selective permeability to anions such as hydroxide ions, which can achieve rapid ion transport, improve the electrolysis reaction rate, and thus improve hydrogen production efficiency; (4) It has good gas isolation effect, which can effectively prevent hydrogen and oxygen from mixing, and has high safety; (5) It is environmentally friendly, which reduces wastewater discharge and product purification steps.

[0003] To achieve high performance in AEMWE devices, it is first necessary to significantly improve the alkaline HER catalytic performance of the catalyst. From the perspective of the catalytic mechanism of alkaline HER, using highly active and stable catalysts is beneficial for improving the Vollmer step kinetics and HER hydrogen production efficiency under alkaline conditions. Noble metal-based nanomaterials and non-noble metal-based nanomaterials are two commonly used types of alkaline HER catalysts. However, noble metals are expensive and scarce, while non-noble metal-based catalysts often exhibit lower activity and stability, severely hindering the sustainable hydrogen production and practical application of AEMWE. How to significantly improve the alkaline HER performance of non-noble metal-based nanomaterials, and subsequently develop highly active and stable non-noble metal-based catalysts, thereby achieving a substantial improvement in the performance of their AEMWE devices, is crucial for the large-scale commercialization of AEMWE technology as a third-generation water electrolysis technology in the current and future stages.

[0004] In recent years, significant efforts have been made in developing various non-precious metal-based HER catalysts. Numerous studies have shown that Ni-based materials possess excellent corrosion resistance, high conductivity, low cost, and abundant reserves, effectively promoting the adsorption and dissociation of H2O. They hold promise as highly efficient and practical non-precious metal-based HER catalysts, and may even replace platinum group metal catalysts. However, Ni-based materials have limitations in their ability to effectively promote the adsorption and dissociation of OH- produced by water splitting. * Ni-based materials exhibit strong affinity, hindering subsequent H2O adsorption and resulting in slow alkaline Vollmer step kinetics, thus inhibiting the water electrolysis reaction. Therefore, further effective control and optimization of the nanostructure and electronic structure of Ni-based materials are needed. In recent years, various modification methods for Ni-based HER materials have been successfully reported, such as doping with non-metallic elements like N, P, and S, crystal phase control, construction of core-shell or heterojunction structures, regulation of the interaction between the metal and the support, and introduction of oxygen vacancy defects. However, most of these Ni-based materials employ a combination of Ni with 3d orbitals and metals or non-metals with only d-orbital energy levels or shielded f-orbital energy levels. However, the concentrated distribution of d-orbital electrons may lead to low electron transfer efficiency, resulting in H2O dissociation. * Difficulty in desorption reduces the HER reaction rate, thus its HER hydrogen production performance and corresponding MEA catalytic performance still have room for improvement. The current research hotspot and challenge lies in rationally screening effective elements with higher orbital energy levels and combining them with Ni to form a novel class of Ni-based non-noble metal catalysts to significantly improve the hydrogen production efficiency of alkaline HER. Summary of the Invention

[0005] The primary objective of this invention is to overcome the problem that existing nickel-based catalysts cannot significantly improve the hydrogen production efficiency of alkaline HER, and to provide a novel method for preparing Ni / NiO@RE2O3 / C nanocatalysts at the gram scale. The Ni / NiO@RE2O3 / C nanocatalysts obtained by this method can significantly improve the hydrogen production efficiency of alkaline HER.

[0006] A second objective of this invention is to provide a Ni / NiO@RE2O3 / C nanocatalyst prepared by the above method.

[0007] A third objective of this invention is to provide the application of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst in the cathodic hydrogen evolution reaction (HER) or membrane electrode assembly (MEA) of anion exchange membrane electrolysis of water (AEMWE).

[0008] The key to this invention lies in using nickel acetylacetone as the nickel source and rare earth acetate as the rare earth oxide (RE) source. A mixture of nickel acetylacetone and rare earth acetate is calcined in a hydrogen-containing gas to convert nickel acetylacetone into Ni and NiO, and rare earth acetate into rare earth oxides. Simultaneously, an alcoholamine mixed solvent is used as a dispersant. The resulting nanocatalyst, as a cathode catalyst, exhibits highly efficient catalytic performance in AEMWE. The reason for this is speculated to be: firstly, the alcoholamine mixed solvent can play a dual role in dissolving and uniformly dispersing, enabling thorough integration of the components; secondly, besides scandium ([Ar]3d... 1 4s 2 ) and yttrium ([Kr]4d 1 5s 2 In addition to [Xe]4f, rare earth metals (RE) often possess special properties. n-1 5d 0-1 6s 2 (n = 1-15) The unique advantages of nickel acetylacetonate (RE) such as its electronic structure, crystal structure, and low electronegativity allow it to combine with Ni. Because RE has lower electronegativity and a stronger ability to donate electrons, it provides electrons and modulates the electronic environment around Ni atoms, lowering the activation energy of the electrocatalytic reaction and thus increasing the reaction rate. Furthermore, using nickel acetylacetonate as the nickel source and rare earth acetate as the RE source, rare earth ions (RE... 3+ It has a high charge density and a large ionic radius, and tends to form stable high-coordination-number complexes with the carboxyl oxygen in acetate. 3+ It readily binds to acetate ions via bidentate coordination, forming a complex with high surface activity. This strong coordination makes RE... 3+ Rare earth acetates tend to accumulate on the surface of catalyst precursors, and due to their high surface energy, they tend to migrate to the surface of catalyst particles during high-temperature calcination to reduce the total energy of the system; Ni 2+ Nickel acetylacetonate has a low charge density and forms a relatively stable chelate ring with acetylacetone ligands (β-diketones). It exists as a neutral molecule in solution, exhibits good solubility, and is not prone to excessive accumulation on the catalyst surface. During high-temperature calcination, Ni… 2+It may diffuse into the interior of the particles and form a core-shell structure with rare earth acetate. At the same time, the rare earth acetate decomposes into RE oxide (RE2O3) after high-temperature calcination, while nickel acetylacetonate decomposes into NiO and Ni after high-temperature calcination. This results in a specific structure in which the catalyst has Ni, NiO and RE2O3 from the inside out. This specific structure can improve the efficiency of the cathode hydrogen evolution reaction through multiple dimensions such as surface active site optimization, electronic structure regulation and synergistic catalytic effect. Specifically, the key bottleneck of alkaline HER lies in the fact that under alkaline conditions, HER requires the generation of H* intermediates through water dissociation. This process is kinetically slow due to the high polarization energy barrier of water molecules. RE2O3 surfaces exhibit strong oxyphilicity, enabling stable adsorption of OH intermediates and promoting water dissociation to generate H. The Ni core ensures rapid electron transfer from the external circuitry to the surface active sites, reducing ohmic polarization losses. Simultaneously, Ni forms a strong interaction with the surface REs, promoting electron transfer from Ni to REs and enhancing the surface RE active sites. The surface RE2O3 sites specifically adsorb OH and promote water dissociation to generate H, while the internal Ni and NiO sites efficiently adsorb H. + It also promotes H2 desorption; AEMWE needs to adapt to the volatility of renewable energy, requiring the catalyst to have rapid start-up and shutdown capabilities. The RE2O3 on the surface can rapidly activate water dissociation at low overpotentials through strong OH* adsorption, while the internal Ni and NiO ensure the stability of electron conduction and avoid performance degradation under dynamic loading. Based on this, the present invention was completed.

[0009] The method for preparing Ni / NiO@RE2O3 / C nanocatalysts by the present invention includes ultrasonically dispersing nickel acetylacetonate, rare earth acetate, and carbon support in an alcohol amine mixed solvent, heating and stirring the resulting dispersion until it evaporates to dryness, grinding it, and then calcining the ground material in a hydrogen-containing gas to convert nickel acetylacetonate into Ni and NiO and rare earth acetate into rare earth oxides, thereby obtaining the Ni / NiO@RE2O3 / C nanocatalyst.

[0010] The beneficial effects of this invention are as follows:

[0011] (1) The metal elements in the Ni / NiO@RE2O3 / C nanocatalyst provided by the present invention include nickel and a variety of rare earth elements, and its element coverage is wide;

[0012] (2) The method provided by the present invention can grow Ni / NiO@RE2O3 nanoparticles in situ on a carbon support. The Ni / NiO@RE2O3 nanocatalyst has a special three-layer structure and has distinctive features in terms of nanostructure. It is quite different from the nanostructure of common nickel-based catalysts. The Ni / NiO@RE2O3 / C nanocatalyst particles have small particle size and uniform size, and the nanoparticles can be uniformly dispersed on the carbon support.

[0013] (3) The Ni / NiO@RE2O3 / C nanocatalyst provided by this invention exhibits high catalytic performance as a cathode catalyst in AEMWE, enabling efficient expression of alkaline HER and MEA catalytic performance. In particular, the Ni / NiO@La2O3 / C nanocatalyst demonstrates the best catalytic performance. In alkaline HER, the Ni / NiO@La2O3 / C nanocatalyst requires only 32 mV to achieve 10 mAcm⁻¹. -2 The current density exceeds that of commercial platinum-carbon catalysts (59 mV @ 10 mA cm⁻¹). -2 ), and far surpasses rare-earth-free Ni / NiO / C catalysts (216 mV @ 10 mA cm⁻¹). -2 Furthermore, the Ni / NiO@La2O3 / C nanocatalyst requires only 1.8V on an AEMWE MEA to achieve 2 A cm⁻¹. -2 The current density is superior to that of commercial platinum-carbon catalysts (1.9 V @ 2 A cm⁻¹). -2 This demonstrates the good application potential of AEMWE devices and has a broad prospect for practical application.

[0014] (4) The method provided by the present invention can achieve the preparation of 500g of catalyst under laboratory conditions, and is expected to further expand the preparation scale, and has great practical development potential in batch preparation.

[0015] (5) The method provided by the present invention is simple, efficient and easy to operate. It only requires ultrasonic dispersion, evaporation and grinding and high temperature calcination to obtain Ni / NiO@RE2O3 / C nanocatalyst. Attached Figure Description

[0016] Figure 1 shows transmission electron microscopy (TEM) images of Ni / NiO@RE2O3 / C nanocatalysts and rare-earth-free Ni / NiO / C nanocatalysts.

[0017] Figure 2 shows the X-ray diffraction patterns of Ni / NiO@RE2O3 / C nanocatalyst and rare earth-free Ni / NiO / C nanocatalyst.

[0018] Figure 3 shows the aberration-corrected transmission electron microscope (TEM) image of the Ni / NiO@La2O3 / C nanocatalyst; Figure 3a is the aberration-corrected TEM image; Figure 3b is the Fast Fourier Transform (FFT) image; Figures 3c, 3e, and 3g are magnified aberration-corrected high-resolution TEM images of the region shown in Figure 3a. Figures 3d, 3f, and 3h correspond to the atomic arrangement models of the body-centered cubic La2O3, face-centered cubic NiO, and face-centered cubic Ni regions in Figures 3c, 3e, and 3g, respectively.

[0019] Figure 4 shows the linear sweep voltammetry curves of samples 1-20, commercial Raney nickel, and commercial platinum-carbon catalysts in a three-electrode system; Figure 4a is the HER polarization curve; Figure 4b is the corresponding overpotential trend graph.

[0020] Figure 5 shows the Tafel slope of samples 1-20 and commercial Raney nickel and commercial platinum carbon catalysts in HER.

[0021] Figure 6 shows the cyclic voltammetry and impedance curves of Ni / NiO@La2O3 / C, Ni / NiO@Sm2O3 / C, Ni / NiO / C nanocatalysts, commercial Raney nickel, commercial platinum-carbon catalysts, and Raney nickel in a three-electrode system; Figure 6a shows the cyclic voltammetry curve of Ni / NiO@La2O3 / C; Figure 6b shows the cyclic voltammetry curve of Ni / NiO@Sm2O3 / C; Figure 6c shows the cyclic voltammetry curve of Ni / NiO / C; Figure 6d shows the cyclic voltammetry curve of the commercial platinum-carbon catalyst; Figure 6e shows the cyclic voltammetry curve of the commercial Raney nickel; Figure 6f shows the cyclic voltammetry curve of Ni / NiO@La2O3 / C-NiCl2; Figure 6g shows the cyclic voltammetry curve of Ni / NiO@La2O3 / C-KOH; Figure 6h shows the cyclic voltammetry curve of Ni / NiO@La2O3 / C-Ar; Figure 6i shows the cyclic voltammetry curve of the sample Ni. Capacitance current plots of Ni / NiO@La2O3 / C, Ni / NiO@Sm2O3 / C, Ni / NiO / C nanocatalysts, commercial platinum-carbon catalysts, commercial Raney nickel, Ni / NiO@La2O3 / C-NiCl2, Ni / NiO@La2O3 / C-KOH, and Ni / NiO@La2O3 / C-Ar based on different scan rates; Figure 6j shows the impedance plots of Ni / NiO@La2O3 / C, Ni / NiO@Sm2O3 / C, Ni / NiO / C nanocatalysts, commercial platinum-carbon catalysts, commercial Raney nickel, Ni / NiO@La2O3 / C-NiCl2, Ni / NiO@La2O3 / C-KOH, and Ni / NiO@La2O3 / C-Ar.

[0022] Figure 7 shows the MEA test results of Ni / NiO@La2O3 / C, Ni / NiO@Sm2O3 / C, Ni / NiO / C nanocatalysts and commercial platinum-carbon catalysts on the AEMWE device.

[0023] Figure 8 shows the linear sweep curves and MEA polarization curves of Ni / NiO@La2O3 / C, Ni / NiO@Sm2O3 / C, Ni / NiO / C nanocatalysts, Raney nickel, and commercial platinum-carbon catalysts on a three-electrode system. Detailed Implementation

[0024] The method for preparing Ni / NiO@RE2O3 / C nanocatalysts at the gram scale provided by this invention includes the preparation of nickel acetylacetone (C 10 H 14 NiO4, rare earth acetate, and carbon support are ultrasonically dispersed in an alcohol amine mixed solvent. The resulting dispersion is then heated and stirred until it evaporates to dryness and then ground. The ground material is then calcined in a hydrogen-containing gas to convert nickel acetylacetone into Ni and NiO and rare earth acetate into rare earth oxides, thus obtaining the Ni / NiO@RE2O3 / C nanocatalyst.

[0025] In the 100-gram-scale preparation process of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst, the preferred molar ratio of nickel acetylacetone to rare earth acetate is (20~40):1, such as 20:1, 22:1, 24:1, 26:1, 28:1, 30:1, 32:1, 34:1, 36:1, 38:1, 40:1, etc. To obtain 2 g of Ni / NiO@RE2O3 / C nanocatalyst, the amount of nickel acetylacetone can be 30 mmol; to obtain 500 g of Ni / NiO@RE2O3 / C nanocatalyst, the amount of nickel acetylacetone can be 7.5 mol.

[0026] In the 100-gram-scale preparation process of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst, the preferred ratio of rare earth acetate to carbon support is 1 mmol:(0.1~1) g. Specifically, based on 1 mmol of rare earth acetate, the preferred amount of carbon support is 0.1~1 g, such as 0.1 g, 0.2 g, 0.3 g, 0.4 g, 0.5 g, 0.6 g, 0.7 g, 0.8 g, 0.9 g, 1 g, etc.

[0027] In the 100-gram-scale preparation process of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst, the preferred ratio of solvent to carbon support is (100~600) mL:0.5 g. Specifically, based on the amount of carbon support being 0.5 g, the preferred amount of solvent is 100~600 mL, such as 100 mL, 120 mL, 140 mL, 160 mL, 180 mL, 200 mL, 220 mL, 240 mL, 260 mL, 280 mL, 300 mL, 320 mL, 340 mL, 360 mL, 380 mL, 400 mL, 420 mL, 440 mL, 460 mL, 480 mL, 500 mL, 520 mL, 540 mL, 560 mL, 580 mL, 600 mL, etc.

[0028] In the 100-gram-scale preparation process of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst, the rare earth acetate may include at least one of scandium acetate, yttrium acetate, lanthanum acetate, cerium acetate, praseodymium acetate, neodymium acetate, samarium acetate, europium acetate, gadolinium acetate, terbium acetate, dysprosium acetate, holmium acetate, erbium acetate, thulium acetate, ytterbium acetate, and lutetium acetate.

[0029] In the preparation of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst at the gram scale, there is no special limitation on the type of carbon support. For example, it can be commercial Cabot conductive carbon black (Vulcan XC-72R type).

[0030] In the 100-gram-scale preparation process of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst, the alkanolamine mixed solvent is particularly preferably a mixture of ethanol, water, and ammonia. This alkanolamine mixed solvent can play a dual role in dissolving and uniformly dispersing, uniformly mixing the nickel, rare earth element precursors, and carbon support. Furthermore, the strong reducing property of hydrogen at high temperatures is used to reduce the metal precursors, thereby preparing Ni / NiO@RE2O3 / C nanocatalysts with uniform size, uniform particle size distribution, and tunable composition. The volume ratio of ethanol, water, and ammonia in the alkanolamine mixed solvent is preferably 5:5:1 to 5:5:10, specifically 5:5:1, 5:5:2, 5:5:4, 5:5:6, 5:5:8, 5:5:10, etc.

[0031] In the preparation of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst at the 100-gram scale, the ultrasonic dispersion time is preferably 0.5 h to 10 h, such as 0.5 h, 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, etc.

[0032] In the preparation of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst at the gram scale, the heating conditions preferably include a temperature of 30 ℃ to 200 ℃, such as 30 ℃, 40 ℃, 60 ℃, 80 ℃, 100 ℃, 120 ℃, 140 ℃, 160 ℃, 180 ℃, 200 ℃, etc.; and a time of 1 h to 10 h, such as 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, etc.

[0033] In the preparation of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst at the gram scale, the preferred calcination conditions include a calcination temperature of 400 ℃ to 700 ℃, such as 400 ℃, 420 ℃, 440 ℃, 460 ℃, 480 ℃, 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃, 700 ℃, etc.; and a calcination time of 1 h to 10 h, such as 1 h, 2 h, 4 h, 6 h, 8 h, 10 h, etc.

[0034] In the 100-gram-scale preparation process of the above-mentioned Ni / NiO@RE2O3 / C nanocatalyst, the hydrogen-containing gas is preferably a mixture of hydrogen and an inert gas. The volume ratio of hydrogen to inert gas in the hydrogen-containing gas is preferably (2%~10%):(98%~90%), such as 2%:98%, 4%:96%, 6%:94%, 8%:92%, 10%:90%, etc. The inert gas can be nitrogen, argon, or helium, preferably argon.

[0035] The present invention also provides a Ni / NiO@RE2O3 / C nanocatalyst prepared by the above method.

[0036] The present invention also provides the application of the Ni / NiO@RE2O3 / C nanocatalyst in the cathodic hydrogen evolution reaction (HER) or membrane electrode assembly (MEA) of anion exchange membrane water electrolysis.

[0037] The present invention will be described in detail below through specific embodiments. These embodiments are intended to explain the invention and should not be construed as limiting it. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0038] Example 1

[0039] Taking a single batch of 2 g as an example, the preparation method of Ni / NiO@Sc2O3 / C nanocatalyst includes the following steps:

[0040] 30 mmol of nickel acetylacetone, 1 mmol of scandium acetate, and 0.5 g of Vulcan XC-72R carbon support were placed in a beaker, and 150 mL of ethanol, 150 mL of pure water, and 150 mL of ammonia were added. The beaker containing the materials was then placed in an ultrasonicator and ultrasonically dispersed for 5 h until homogeneous. The beaker was then placed open on a magnetic stirrer and heated and stirred at 60 °C for 10 h to evaporate the solvent. The evaporated product was scraped off with a spatula and further transferred to a mortar for grinding. The finely ground mixture was calcined in a tube furnace at 600 °C in a 5% H2 / 95% Ar atmosphere for 5 h. After the reaction was completed and the temperature was lowered, Ni / NiO@Sc2O3 / C nanocatalyst was obtained. The contents of nickel (Ni) and scandium (Sc) in the obtained Ni / NiO@Sc2O3 / C nanocatalyst were determined by scanning electron microscopy-X-ray energy distribution spectroscopy.

[0041] Example 2

[0042] Taking a single batch of 500 g as an example, the preparation method of Ni / NiO@Y2O3 / C nanocatalyst includes the following steps:

[0043] 7.5 mol of nickel acetylacetone, 0.25 mol of yttrium acetate, and 125 g of Vulcan XC-72R carbon support were placed in a beaker, and 7.5 L of ethanol, 7.5 L of pure water, and 7.5 L of ammonia were added. The beaker containing the materials was then placed in an ultrasonicator and ultrasonically dispersed for 10 h until homogeneous. The beaker was then placed open on a magnetic stirrer and heated and stirred at 200 °C for 1 h to evaporate the solvent. The evaporated product was scraped off with a spatula and further transferred to a mortar for grinding. The finely ground mixture was calcined in a tube furnace at 400 °C in an atmosphere of 10% H2 / 90% Ar for 10 h. After the reaction was completed and the temperature was lowered, Ni / NiO@Y2O3 / C nanocatalyst was obtained. The contents of nickel (Ni) and yttrium (Y) in the obtained Ni / NiO@Y2O3 / C nanocatalyst were determined by scanning electron microscopy-X-ray energy distribution spectroscopy.

[0044] Example 3

[0045] Taking a single batch of 2 g as an example, the preparation method of Ni / NiO@La2O3 / C nanocatalyst includes the following steps:

[0046] 30 mmol of nickel acetylacetone, 1 mmol of lanthanum acetate, and 0.5 g of Vulcan XC-72R carbon support were placed in a beaker, and 150 mL of ethanol, 150 mL of pure water, and 300 mL of ammonia were added. The beaker containing the materials was then placed in an ultrasonicator and ultrasonically dispersed for 0.5 h until homogeneous. The beaker was then placed open on a magnetic stirrer and heated and stirred at 100 °C for 5 h to evaporate the solvent. The evaporated product was scraped off with a spatula and further transferred to a mortar for grinding. The finely ground mixture was calcined in a tube furnace at 700 °C in an atmosphere of 8% H2 / 92% Ar for 1 h. After the reaction was completed and the temperature was lowered, Ni / NiO@La2O3 / C nanocatalyst was obtained. The contents of nickel (Ni) and lanthanum (La) in the obtained Ni / NiO@La2O3 / C nanocatalyst were determined by scanning electron microscopy-X-ray energy distribution spectroscopy.

[0047] Example 4-16

[0048] The nanocatalyst was prepared according to the method of Example 1, except that scandium acetate was replaced with other rare earth acetates in the same molar amount. The types of rare earth acetates are shown in Table 1. The other conditions were the same as in Example 1, and Ni / NiO@RE2O3 / C nanocatalysts were obtained. The contents of nickel (Ni) and rare earth elements (RE) in the obtained Ni / NiO@RE2O3 / C nanocatalysts were determined by scanning electron microscopy-X-ray energy distribution spectroscopy.

[0049] Comparative Example 1

[0050] The nanocatalyst was prepared according to the method of Example 1, except that scandium acetate was not added, and the other conditions were the same as in Example 1, to obtain the reference nanocatalyst.

[0051] Comparative Example 2

[0052] The nanocatalyst was prepared according to the method of Example 1, except that the solvent was replaced by a 0.1 mol / L KOH aqueous solution with the same total volume instead of 150 mL ethanol, 150 mL pure water and 150 mL ammonia. The other conditions were the same as in Example 1, and Ni / NiO@RE2O3 / C nanocatalyst was obtained.

[0053] Comparative Example 3

[0054] The nanocatalyst was prepared according to the method of Example 1, except that nickel acetylacetone was replaced with the same molar amount of nickel chloride hexahydrate, and the other conditions were the same as in Example 1, to obtain the reference nanocatalyst.

[0055] Comparative Example 4

[0056] The nanocatalyst was prepared according to the method of Example 1, except that the 5% H2 / 95% Ar atmosphere used in the calcination process was replaced with a 5% O2 / 95% Ar atmosphere, while the other conditions were the same as in Example 1, and a reference nanocatalyst was obtained.

[0057] Table 1

[0058]

[0059] As can be seen from the results in Table 1, the method provided by this invention can achieve the controllable preparation of different Ni / NiO@RE2O3 / C nanocatalysts, and the atomic percentage of rare earth elements in these Ni / NiO@RE2O3 / C nanocatalysts is in the range of 6.2% to 7.2%.

[0060] Table 2

[0061]

[0062] As can be seen from the results in Table 2, the overpotentials of the Ni / NiO@RE2O3 / C catalysts (Examples 1-16) obtained using the method provided by this invention are all less than or equal to 163 mV, which is much lower than the values ​​of comparative samples 17-20, indicating that this type of Ni / NiO@RE2O3 / C catalyst has superior alkaline HER catalytic performance. Furthermore, the Tafel slope of the Ni / NiO@RE2O3 / C catalysts obtained using the method provided by this invention is no higher than 157.0 mV dec. -1 This indicates that its electrochemical reaction kinetics are relatively fast.

[0063] The Ni / NiO@RE2O3 / C nanocatalyst provided by this invention has a simple, efficient, and easy-to-operate preparation process. It only requires a few steps, namely ultrasonic dispersion, evaporation and grinding, and high-temperature calcination, to prepare Ni / NiO@RE2O3 / C nanocatalysts with clean surfaces and rare earth-free Ni / NiO / C nanocatalysts. Moreover, the single batch preparation scale can reach 500 g, indicating that this preparation technology has great potential for practical development and application.

[0064] Figure 1 shows transmission electron microscopy (TEM) images of samples 1-17 and a commercial platinum-carbon catalyst. Each figure includes a corresponding average particle size distribution chart. As can be seen from the figures, the vast majority of nanoparticles in samples 1-17 are uniformly dispersed on the carbon support, with an average particle size between 8.0 and 15.0 nm, which is relatively small.

[0065] Figure 2 shows the powder X-ray diffraction patterns of samples 1-17. The horizontal axis represents the diffraction angle (2θ / degree), and the vertical axis represents the diffraction intensity. The standard cards are the face-centered cubic (fcc) phase card of Ni (JCPDS, No. 04-0850) and the hexagonal phase card of Ni (JCPDS No. 45-1027). From the positions of the diffraction peaks on each crystal plane, except for samples 2, 9, 11, 12, and 14 which correspond to the hexagonal phase card of Ni, the X-ray diffraction peaks of the other samples correspond well to the face-centered cubic phase card of Ni (JCPDS No. 04-0850). This demonstrates that rare earth doping did not cause a change in the crystal phase of the nickel-based catalyst, and also signifies the successful synthesis of the Ni / NiO@RE2O3 / C catalyst.

[0066] Figure 3 shows an aberration-corrected transmission electron microscope (TEM) image of the Ni / NiO@La2O3 / C nanocatalyst obtained in Example 3. The image reveals varying degrees of crystallinity and distinct grain boundaries on the surface of individual nanoparticles. In particular, the crystal orientation at the edges differs significantly from that in the central region (Figure 3a). Fast Fourier Transform (FFT) analysis clearly distinguishes three sets of crystal planes representing different crystal phases, and no diffraction rings of polycrystalline materials are observed, further indicating that Ni / NiO@La2O3 / C possesses a single-crystal-dominated heterostructure (Figure 3b). To further verify the different compositions of this heterostructure, atomic-level structural analysis was performed on the marked areas in Figure 3a. At the edge regions of the nanoparticles, a clear atomic arrangement with a lattice spacing of 0.226 nm is observed, corresponding to the body-centered cubic (bcc) phase La2O3. <001> The crystal orientation family standard arrangement is consistent (Fig. 3c and Fig. 3d). Meanwhile, in adjacent regions at the edges and interior, atomic arrangements of the (200) crystal plane in the fcc phase NiO with a lattice spacing of 0.208 nm can also be found (Fig. 3e and Fig. 3f). Furthermore, the situation of the fcc phase Ni is consistent with that along the… <100> The region axis is similar to the fcc phase NiO with space group Fm-3m (225), except for the lattice spacing (0.176 nm) in the (200) plane (Fig. 3g and Fig. 3h). These crystal plane and atomic arrangement analysis results are highly consistent with the aforementioned structural analysis results (Fig. 1b-i and Fig. 2a-h). Based on the above test results, it is proved that the Ni / NiO@La2O3 / C sample has a three-layer structure: the surface layer is bcc-La2O3, the subsurface layer is fcc-NiO, and the interior is fcc-Ni.

[0067] Figure 4 shows the linear sweep voltammetry curves for samples 1-20, commercial Raney nickel, and commercial platinum-carbon catalysts. In the alkaline HER performance test, the test conditions were: 1 M KOH solution as the electrolyte, and a scan rate of 1 mV / s. -1According to the linear sweep voltammetry curves, each catalyst can reach a current-voltage ratio of 10 mA cm⁻¹. -2 The overpotential values ​​are shown in Table 2. Among them, Sample 3 (Ni / NiO@LaO3 / C catalyst) has the lowest overpotential, requiring only 32 mV, which is significantly better than the commercial platinum-carbon catalyst (59 mV).

[0068] Figure 5 shows the Tafel slopes for samples 1–20, commercial Raney nickel, and commercial platinum-carbon catalysts. The Tafel slope represents the electrochemical reaction kinetics, with sample 3 exhibiting the lowest Tafel slope (29.2 mV dec). -1 This indicates that its electrochemical reaction kinetics are the fastest, significantly superior to commercial platinum-carbon catalysts (67.3 mV dec). -1 ).

[0069] Figure 6 shows the cyclic voltammetry and impedance spectroscopy curves of Sample 3, Sample 7, Samples 17-20, and commercial Raney nickel catalyst and commercial platinum-carbon catalyst between 0.2 V and 0.4 V. It is clear from these figures that Sample 3 (Ni / NiO@La2O3 / C catalyst) has the most active sites, with an electrochemical active surface area of ​​50.1 mF cm⁻¹. -2 It far exceeds that of commercial platinum-carbon catalysts (1.7 mF cm⁻¹). -2 Meanwhile, Sample 3 has the lowest impedance value, indicating that its charge conduction efficiency has been significantly improved.

[0070] Figure 7 compares the MEA performance of Sample 1, Sample 3, Sample 7, and a commercial platinum-carbon catalyst in AEMWE. The catalysts were uniformly sprayed onto the AEM surface; the amounts of Ni / NiO@La2O3 / C, Ni / NiO@La2O3 / C, and Ni / NiO / C catalysts were 10 mg / cm³. -2 The amount of commercial platinum-carbon catalyst used is 1 mg cm⁻¹. -2 The polarization curves of each catalyst were tested under standard test conditions (1M KOH electrolyte, 60 °C, atmospheric pressure) using constant current mode. As shown in Figure 7, Ni / NiO@La2O3 / C exhibited a polarization of 1 A cm⁻¹ at 1.6 V and 1.8 V, respectively. -2 and 2 A cm -2 The current density output is superior to that of commercial platinum-carbon catalysts (1.7 V @ 1 A cm⁻¹). -2 1.9 V @ 2 A cm -2 Furthermore, the operating voltage of Ni / NiO@La2O3 / C is 2.0 V @ 2 Acm. -2It has reached the U.S. Department of Energy's (DOE) 2025 target (1.8 V @ 2 A cm). - ²), demonstrating significant potential for industrial applications.

[0071] Figure 8 shows the linear sweep curves and MEA polarization curves of Sample 1, Sample 3, Sample 7, commercial platinum-carbon catalyst, and commercial Raney nickel in a three-electrode system, as well as on an AEMWE device. Specifically, in the three-electrode system, the overpotential corresponding to Ni / NiO@La2O3 / C is only 32 mV@10 mA cm⁻¹. -2 Its performance is far superior to that of commercial platinum-carbon catalysts (59mV@10 mA cm⁻¹). -2 ) and the performance of Raney Ni (99 mV@10 mA cm⁻¹) -2 It is significantly superior to all other Ni / NiO@RE2O3 / C (45~163 mV@10 mA cm⁻¹). -2 A comprehensive comparison of Figures 7 and 8 shows that the Ni / NiO@La2O3 / C catalyst exhibits the highest alkaline HER catalytic performance in both the semi-reaction system and the MEA application scenario, fully demonstrating that the catalyst has significant advantages in nanostructure and excellent HER and MEA catalytic performance.

[0072] In summary, the Ni / NiO@RE2O3 / C nanocatalyst provided by this invention can be used as a highly efficient cathode catalyst for HER in AEMWE, exhibiting excellent catalytic performance that is significantly superior to commercial platinum-carbon catalysts and commercial Raney nickel catalysts. It can be used as a highly efficient cathode catalyst in HER and corresponding MEA in AEMWE, and shows outstanding advantages and broad prospects in the mass production of nickel-based nanocatalysts and their application in energy devices.

[0073] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for preparing Ni / NiO@RE2O3 / C nanocatalysts at the gram scale, characterized in that, The method involves ultrasonically dispersing nickel acetylacetonate, rare earth acetate, and a carbon support in a mixed solvent, wherein the mixed solvent is a mixture of ethanol, water, and ammonia. The resulting dispersion is then heated and stirred until it evaporates to dryness, followed by grinding. The ground material is then calcined in a hydrogen-containing gas to convert nickel acetylacetonate into Ni and NiO, and rare earth acetate into rare earth oxides. The hydrogen-containing gas is a mixture of hydrogen and an inert gas, wherein the volume ratio of hydrogen to inert gas in the hydrogen-containing gas is (2%~10%):(98%~90%), thus obtaining the Ni / NiO@RE2O3 / C nanocatalyst.

2. The method for preparing Ni / NiO@RE2O3 / C nanocatalyst at the gram scale according to claim 1, characterized in that, The molar ratio of nickel acetylacetone to rare earth acetate is (20~40):1; the ratio of rare earth acetate to carbon support is 1 mmol:(0.1~1) g; and the ratio of mixed solvent to carbon support is (100~600) mL:0.5 g.

3. The method for preparing Ni / NiO@RE2O3 / C nanocatalyst at the gram scale according to claim 1, characterized in that, The rare earth acetate is selected from at least one of scandium acetate, yttrium acetate, lanthanum acetate, cerium acetate, praseodymium acetate, neodymium acetate, samarium acetate, europium acetate, gadolinium acetate, terbium acetate, dysprosium acetate, holmium acetate, erbium acetate, thulium acetate, ytterbium acetate, and lutetium acetate.

4. The method for preparing Ni / NiO@RE2O3 / C nanocatalysts on a gram-scale scale according to any one of claims 1 to 3, characterized in that, The ultrasonic dispersion time is 0.5 h to 10 h.

5. The method for preparing Ni / NiO@RE2O3 / C nanocatalysts on a gram-scale scale according to any one of claims 1 to 3, characterized in that, The heating conditions include a temperature of 30 ℃ to 200 ℃ and a time of 1 h to 10 h.

6. The method for preparing Ni / NiO@RE2O3 / C nanocatalysts on a gram-scale scale according to any one of claims 1 to 3, characterized in that, The calcination conditions include a calcination temperature of 400 ℃ to 700 ℃ and a calcination time of 1 h to 10 h.

7. The Ni / NiO@RE2O3 / C nanocatalyst prepared by the method described in any one of claims 1 to 6.

8. The application of the Ni / NiO@RE2O3 / C nanocatalyst according to claim 7 in the cathodic hydrogen evolution reaction of anion exchange membrane water electrolysis.

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