Carbon-supported entropy catalysts, their preparation, and their application in hydrogen production from borohydrides.

Abstract

This invention discloses a carbon-supported medium-entropy catalyst, its preparation method, and its application in the catalytic alcoholysis of ammonia and borane to produce hydrogen. The catalyst comprises a carbon support and CuCoNiRE medium-entropy alloy nanoparticles supported on the carbon support; in the CuCoNiRE medium-entropy alloy nanoparticles, RE represents La, Ce, Pr, or Nd, and the molar ratio of Cu, Co, Ni, and RE is 1:1:1:X, where 0 < X ​​≤ 1. The preparation method includes: using anhydrous ethanol as a solvent to prepare Cu... 2+ Co 2+ Ni 2+ RE 3+ Each metal salt precursor solution is prepared; carbon dioxide activated carbon powder (CAC) and metal salt precursor solution are mixed to form a slurry and coated onto carbon cloth, which is then dried to obtain precursor carbon cloth; the precursor carbon cloth is heated and cooled in an inert atmosphere under the action of an electric pulse using a carbothermal shock reduction method, during which the metal salt disperses, decomposes and agglomerates to form CuCoNiRE medium entropy alloy nanoparticles, and the powder on the carbon cloth is collected to obtain the catalyst.

Description

Technical Field

[0001] This invention relates to the field of catalytic hydrogen production, specifically to a carbon-supported medium-entropy alloy catalyst containing rare earth elements, its preparation method, and its application in catalytic borohydride hydrogen production. Background Technology

[0002] The continued consumption of fossil fuels has triggered a severe energy crisis and environmental problems. Developing secondary clean energy sources is essential to achieving a low-carbon economic model and environmentally sustainable development. Hydrogen energy, with its abundant reserves, high calorific value, and clean byproducts, is considered an ideal energy carrier.

[0003] The key technologies in the hydrogen energy industry chain lie in hydrogen production and storage. Among them, ammonia borane (NH3BH3, abbreviated as AB), as the simplest BN compound, possesses an ultra-high hydrogen storage capacity of 19.6 wt%, and is considered one of the most promising hydrogen storage materials. Under the action of a suitable catalyst, AB aqueous solution or methanol solution can rapidly release hydrogen under environmental conditions. The alcoholysis method also has advantages such as greater stability at low temperatures and the ability to reconstitute reaction byproducts into AB. For the AB alcoholysis hydrogen production reaction, the preparation of high-performance catalysts is a key technology for meeting the requirements of mobile hydrogen storage. Currently, highly active noble metal-based catalysts such as Ru, Rh, Pt, and Pd have been developed; however, the high cost of noble metals greatly limits their commercial application. Designing low-cost, high-activity non-noble metal catalysts has become a research hotspot, and how to effectively improve the catalytic activity and stability of non-noble metal catalysts for the AB alcoholysis hydrogen production reaction is a current research challenge. Alloying, reducing metal particle size, and increasing specific surface area have been proven to be effective methods to improve the activity of metal catalysts.

[0004] Medium-entropy alloys (MEAs) represent a novel alloy design concept. Based on the definition of mixed configuration entropy (S), a MEA is defined as an alloy where 1R ≤ S ≤ 1.5R, where R is the ideal gas constant. For bimetallic alloys, due to the different functions of the metals, the surface charge is redistributed, and their electronic properties directly control the adsorption and activation of reactants and intermediates, thus determining catalytic performance. Changing the elemental composition can easily adjust their electronic properties. However, binary alloys often have large immiscibility gaps, making them prone to phase separation or the formation of intermetallic compounds. According to the principle of maximum entropy generation, increasing the mixed configuration entropy helps improve the compatibility between the main components, forming a stable single-phase solid solution structure rather than intermetallic compounds. Simultaneously, the large differences in atomic size among the constituent elements in MEAs lead to severe lattice distortion due to the random occupancy of metal atoms in the crystal lattice, significantly impacting macroscopic properties such as material hardness, electrical conductivity, and thermal conductivity. This lattice distortion places MEAs in a state of thermodynamic non-equilibrium, resulting in higher potential energy and a lower energy barrier during catalysis. The severe lattice distortion in medium-entropy alloys raises the energy barrier for atomic diffusion, and the slow atomic diffusion significantly improves the thermal stability of medium-entropy alloys, resulting in good durability under reaction conditions such as high temperature, air, and acids and bases, which is beneficial to improving catalytic stability. Furthermore, the generation of lattice distortion provides more active sites for catalytic reactions, which is conducive to improving catalytic activity.

[0005] Carbothermal shock reduction (CTS) is a novel method for the rapid preparation of medium-entropy alloys, enabling the rapid, large-scale production of multi-component nano-metal catalysts. Compared to traditional catalyst preparation processes, it offers advantages such as high efficiency, environmental friendliness, and stable multi-component fusion. CTS primarily involves adding various metal precursor salts to a conductive carbon support and then thermally shocking the metal salt precursors using the high temperatures generated by the instantaneous discharge of a power source. The extremely high heating and cooling rates achieve rapid decomposition of the metal salts and rapid fusion cooling of the metal elements, resulting in single-phase, uniformly dispersed nano-alloy particles that maintain extremely small particle sizes even at the high temperatures inducing grain growth. This method can reduce the size of high-entropy and medium-entropy alloys to the nanoscale and achieve the mutual solubility of complex elements. By adjusting the electrical pulse parameters, the alloy composition, particle size, and phase can be controlled.

[0006] Catalyst supports typically employ microporous, mesoporous, or oxide materials to highly disperse metal nanoparticles while simultaneously limiting particle aggregation and growth, thereby increasing the catalyst's specific surface area. Carbon nanospheres possess high specific surface area and pore volume. By treating carbon powder in a high-temperature carbon dioxide atmosphere, the surface can be etched through the reaction of carbon and carbon dioxide, effectively increasing the specific surface area and pore volume of the carbon support, thus ensuring stable adhesion of metal particles. Summary of the Invention

[0007] This invention provides a carbon-supported medium-entropy alloy catalyst, which has advantages such as simple preparation, controllable size, stable performance, and low cost. By adding large-sized rare earth elements, this invention increases the interplanar spacing of the alloy, resulting in drastic lattice distortion and providing more catalytic active sites, thereby enhancing its activity in catalyzing the hydrogen production from the alcoholysis of ammonia and borane. Furthermore, it utilizes the adsorption characteristics of rare earth elements for OH* substances, improving the adsorption and activation of methanol (CH3OH) by the medium-entropy alloy catalyst.

[0008] A carbon-supported medium-entropy alloy catalyst, comprising a carbon support and CuCoNiRE medium-entropy alloy nanoparticles supported on the carbon support;

[0009] In the CuCoNiRE medium-entropy alloy nanoparticles, RE represents La, Ce, Pr or Nd, and the molar ratio of Cu, Co, Ni and RE is 1:1:1:X, where 0 < X ​​≤ 1, preferably 0.15 ≤ X ≤ 1, further preferably 0.15 ≤ X ≤ 0.6, and even more preferably 0.15 ≤ X ≤ 0.3. Under these preferred conditions, the catalyst can exhibit better conversion frequency (TOF) and cycle stability.

[0010] Rare earth elements such as La exhibit good affinity for OH* substances. This invention has found that medium-entropy alloy catalysts obtained by miscibly dissolving Cu, Co, and Ni transition metal atoms with large-sized La, Ce, Pr, or Nd rare earth atoms are beneficial for the adsorption and activation of methanol (CH3OH) in the ammonia boron alcoholysis catalytic reaction, thereby improving catalytic efficiency. Furthermore, by adding a specific proportion of rare earth atoms such as La, the mixing entropy of the medium-entropy alloy system can be controlled, significantly improving the catalyst's cycle stability.

[0011] The CuCoNiRE medium-entropy alloy nanoparticles have a chemical composition expressed in molar ratio, preferably CuCoNiLa. 0.3 With this composition, the catalyst exhibits both good catalytic activity and cycle stability, with a TOF value reaching 147.89 mol. H2 mol cat - 1 min -1 Furthermore, after five cycles of catalytic hydrogen release, the TOF remains at 66.7% of that of the first cycle, and its activation energy can be as low as 31.3 kJ / mol. -1 .

[0012] The carbon-supported medium-entropy alloy catalyst described herein can be formed by the aggregation of carbon nanospheres. Rare-earth medium-entropy alloy nanoparticles are uniformly distributed on the surface of the carbon nanosphere support, resulting in a very large specific surface area. Furthermore, the diameter of the carbon nanospheres can be 20–25 nm.

[0013] The carbon-supported entropy alloy catalyst described herein has an average particle size of 10–40 nm for the CuCoNiRE entropy alloy nanoparticles.

[0014] The molar ratio of the CuCoNiRE medium-entropy alloy nanoparticles to the carbon support in the carbon-supported medium-entropy alloy catalyst can be 1:10 to 150.

[0015] This invention also provides a method for preparing the aforementioned carbon-supported entropy alloy catalyst, comprising:

[0016] Under a flowing carbon dioxide atmosphere, the nano-carbon powder is heated to 880-920℃ and held for 1-2 hours, and then cooled to room temperature to obtain carbon dioxide activated carbon powder (CAC).

[0017] Cu was prepared using anhydrous ethanol as a solvent. 2+ Co 2+ Ni 2+ RE 3+ Each metal salt precursor solution;

[0018] CAC and metal salt precursor solution are mixed to form a slurry and coated onto carbon cloth, then dried to obtain precursor carbon cloth.

[0019] The carbon thermal shock reduction method is used to heat and cool the precursor carbon cloth in an inert atmosphere under the action of an electric pulse. During this process, the metal salt disperses, decomposes and agglomerates to form CuCoNiRE medium-entropy alloy nanoparticles. The powder on the carbon cloth is collected to obtain the carbon-supported medium-entropy alloy catalyst.

[0020] This invention synthesizes a single-phase quaternary medium-entropy alloy catalyst with highly miscible Cu, Co, Ni transition metal atoms and La, Ce, Pr, or Nd rare earth metal atoms via carbothermal shock reduction. Compared to pure transition metal alloys, the introduction of rare earth elements into the catalyst of this invention has the following effects: 1) The dissolution of large-sized rare earth atoms expands the interplanar spacing of the alloy, generating more lattice distortion, thereby increasing the number of catalytic active sites; 2) Utilizing the unique OH* affinity of rare earth elements in the alloy, the catalyst effectively enhances the adsorption of methanol as a reactant, thereby improving the efficiency of hydrogen production; 3) The addition of rare earth elements to the CuCoNi ternary alloy expands the mixing entropy of the alloy system, resulting in a more stable FCC single-phase structure, thereby improving the catalyst's cycle life. In summary, this strategy of simultaneously improving the catalytic activity and cycle stability of medium-entropy alloys through the introduction of unique rare earth elements is of great significance for promoting the development of high-density ammonia boron alcoholysis hydrogen production technology.

[0021] In the preparation method of the carbon-supported entropy alloy catalyst, the carbon dioxide flow rate can be 30–40 mL / min. -1 .

[0022] In the preparation method of the carbon-supported entropy alloy catalyst, the nano-carbon powder can be BP-2000.

[0023] The method for preparing the carbon-supported entropy alloy catalyst described above allows for a heating rate of 5–15 °C / min for the nano-carbon powder. -1 .

[0024] In the preparation method of the carbon-supported entropy alloy catalyst, the ratio of the amount of metal ions in each metal salt precursor solution to the volume of anhydrous ethanol can be independently 1-1.5 mmol:50 mL.

[0025] In the preparation method of the carbon-supported entropy alloy catalyst, the ratio of CAC mass to the volume of each metal salt precursor solution can be independently 72 mg: Y mL, where 0 < Y ≤ 2.5.

[0026] In the preparation method of the carbon-supported entropy alloy catalyst, the drying temperature can be 45-55℃ and the time can be 0.5-1.5h.

[0027] The method for preparing the carbon-supported entropy alloy catalyst, wherein the inert atmosphere refers to an atmosphere that will not participate in the reaction, such as a rare gas atmosphere like argon.

[0028] The preparation method of the carbon-supported entropy alloy catalyst may include the following electrical pulse parameters: DC power supply, pulse voltage 12-20V, preferably 16V, and current 3.6A.

[0029] The present invention also provides the application of the carbon-supported entropy alloy catalyst in the catalytic hydrogen production from ammonia boron alcoholysis.

[0030] As a general inventive concept, the present invention also provides a method for catalytic hydrogen production from ammonia borane alcoholysis, using the aforementioned carbon-supported medium-entropy alloy catalyst for catalytic hydrogen production from ammonia borane alcoholysis.

[0031] Compared with the prior art, the beneficial effects of this invention are as follows:

[0032] 1. This invention enables the simple preparation of carbon-supported rare-earth medium-entropy alloy nanoparticle catalysts with uniform alloy composition and an average particle size of only 10–40 nm by adjusting CTS parameters. Stable single-phase structure and extremely fine size of the medium-entropy alloy can be achieved at a relatively low carbon thermal shock temperature (690°C) provided by a 16V voltage.

[0033] 2. This invention marks the first application of rare-earth medium-entropy alloy nanoparticles in the catalytic hydrogen production from ammonia borane. By adding large-sized rare-earth atoms such as La to the CuCoNi ternary alloy, the interplanar spacing of the alloy is increased, resulting in drastic lattice distortion and providing more catalytic active sites, thereby enhancing its activity in catalyzing the alcoholysis of ammonia borane to produce hydrogen. Furthermore, the adsorption characteristics of rare-earth elements such as La for OH* substances are utilized to improve the adsorption and activation of methanol (CH3OH) by the medium-entropy alloy catalyst. In addition, by adding a specific proportion of rare-earth atoms such as La, the mixing entropy of the medium-entropy alloy system is controlled, significantly improving the catalyst's cycle stability. CuCoNiLa 0.3 The high activity and stability of / CAC originate from the inherent electronic structure of the medium-entropy alloy, the synergistic promoting effect of rare earth metals, and the interaction between the metal support. At 30℃, this catalyst system achieves a catalytic activity of 147.89 mol / L in the catalytic alcoholysis of AB to produce hydrogen. H2 mol cat -1 min -1 After 5 cycles of hydrogen desorption, its catalytic efficiency still reached 66.7% of its initial activity, with an activation energy as low as 31.3 kJ / mol. -1 . Attached Figure Description

[0034] Figure 1 The graph shows the BET test results for activated toner CAC and nano toner BP-2000.

[0035] Figure 2 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of activated carbon powder (CAC).

[0036] Figure 3 The temperature change curves of the CuCoNiLa / CAC series rare earth medium entropy alloy catalysts prepared in Examples 1-3 of this invention during the CTS process are shown.

[0037] Figure 4 The images show the XRD patterns of the CuCoNiLa / CAC series rare earth medium entropy alloy catalysts prepared in Examples 1-3 of this invention.

[0038] Figure 5 The images shown are scanning transmission electron microscope (STEM) images and CuCoNiLa alloy particle size distribution diagrams of the CuCoNiLa rare earth medium entropy alloy catalyst prepared in Example 1 of this invention.

[0039] Figure 6The images shown are scanning transmission electron microscope (STEM) images and CuCoNiLa alloy particle size distribution diagrams of the CuCoNiLa rare earth medium entropy alloy catalyst prepared in Example 2 of this invention.

[0040] Figure 7 The images shown are scanning transmission electron microscope (STEM) images and CuCoNiLa alloy particle size distribution diagrams of the CuCoNiLa rare earth medium entropy alloy catalyst prepared in Example 3 of this invention.

[0041] Figure 8 The CuCoNiLa prepared in Example 4 of this invention 0.3 Scanning transmission electron microscopy (STEM) images and particle size distribution diagrams of the CAC-16V rare earth medium entropy alloy catalyst.

[0042] Figure 9 CuCoNiLa prepared in Example 4 of this invention 0.3 High-resolution transmission electron microscopy images of the / CAC-16V rare earth medium entropy alloy catalyst and CuCoNi / CAC-16V prepared in Comparative Example 1, along with their interplanar spacing measurements.

[0043] Figure 10 The graphs show the performance of the CuCoNiLa / CAC series catalysts prepared in Examples 1-3 of this invention in catalyzing the hydrogen production from the alcoholysis of ammonia borane at 30°C.

[0044] Figure 11 CuCoNiLa prepared in Examples 2 and 4 of this invention, and Comparative Examples 1, 7, and 8 of this invention. x Performance test chart and conversion frequency bar chart of the CAC-16V (x=0,0.15,0.3,0.6,1) series catalysts at 30℃ for hydrogen production via ammonia borosilicate alcoholysis.

[0045] Figure 12 CuCoNiLa prepared in Examples 2 and 4 of this invention, and Comparative Examples 1, 7, and 8 of this invention. x The conversion frequency graph and the relationship between La doping amount, mixing entropy, and remaining activity of the / CAC-16V (x=0,0.15,0.3,0.6,1) series catalysts during the catalytic hydrogen production cycle of ammonia borane alcoholysis at 30℃ for 5 cycles are shown in the figure.

[0046] Figure 13 The graphs show the performance of the catalysts prepared in Examples 4, 1, and 9-11 of this invention in catalytic hydrogen production via ammonia boron alcoholysis at 30°C, and the bar graphs show the conversion frequency before and after 5 catalytic cycles for hydrogen release.

[0047] Figure 14CuCoNiLa prepared in Example 4 of this invention 0.3 Performance test diagrams of the / CAC-16V catalyst at 20℃, 25℃, 30℃, and 35℃ for hydrogen production via ammonia boron alcoholysis, and the calculated Arrhenius activation energy diagram.

[0048] Figure 15 For comparison with CuCoNi / CAC-16V prepared in Comparative Example 1 and CuCoNiLa prepared in Example 4 of this invention 0.3 A bar chart of methanol adsorption energy data obtained from simulation calculations using / CAC-16V. Detailed Implementation

[0049] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0050] The preparation methods of activated carbon powder CAC involved in the following embodiments and comparative examples include: under a flowing carbon dioxide atmosphere, BP-2000 nano-carbon powder is heated at a rate of 10°C / min. -1 The temperature was raised to 900℃ and held for 1 hour, then cooled to room temperature to obtain carbon dioxide activated toner (CAC); the carbon dioxide gas flow rate was 30–40 mL / min. -1 . Figure 1 The BET test results shown demonstrate that, compared to the raw material BP-2000, the specific surface area of ​​CAC after carbon dioxide activation treatment increased from 1308.1 m². 2 g -1 Increased to 1469.1m 2 g -1 Scanning electron microscope (SEM) and transmission electron microscope (TEM) images of activated carbon powder (CAC) are shown below. Figure 2 As shown. Subsequent embodiments and comparative examples all use this activated carbon powder (CAC) as a carrier.

[0051] Example 1

[0052] Preparation of CuCoNiLa / C-12V rare earth medium entropy alloy catalyst:

[0053] (1) Weigh 213.2 mg CuCl2·2H2O, 297.4 mg CoCl2·6H2O, 297.1 mg NiCl2·6H2O, and 464.3 mg LaCl3·7H2O and add them to 20 mL of anhydrous ethanol respectively. Stir magnetically for 2 h to completely dissolve the metal salts. Then, prepare a fixed concentration metal precursor solution 1 (0.025 M CuCl2·6H2O) in a 50 mL volumetric flask. 2+ ), Metal precursor solution 2 (0.025M Co 2+), Metal precursor solution 3 (0.025M Ni) 2+ ) and metal precursor solution 4 (0.025M La 3+ ).

[0054] (2) Take 2 mL of metal precursor solutions 1, 2, 3, and 4 respectively, mix them with 72 mg of activated carbon powder (CAC), and ultrasonically disperse for 1 h to obtain a uniform slurry. Coat the slurry evenly on a carbon cloth with an area of ​​4 cm × 6 cm, cut it into 12 equal parts, and dry it at 50 °C for 1 h. Take a piece of carbon cloth and fix it to an aluminum clamp. The two ends of the clamp are connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current is set to 3.6 A and the charging voltage is 12 V. After the clamp is placed in a quartz hood for gas purging and filled with argon, the circuit is turned on, the electric pulse generator discharges instantaneously, and the carbon cloth heats up rapidly. The metal salts loaded on the carbon cloth disperse and decompose, and then agglomerate to form a medium-entropy alloy. After the power is turned on, remove the quartz hood, collect the powder on the carbon cloth, and obtain the CuCoNiLa / CAC-12V medium-entropy alloy catalyst.

[0055] The temperature-time curve of the CuCoNiLa / CAC-12V catalyst prepared in this embodiment during the CTS process is shown below. Figure 3 As shown in the figure, the 12V label corresponds to the catalyst in this embodiment, the 16V label corresponds to the catalyst in Example 2, and the 20V label corresponds to the catalyst in Example 3. The temperature change curves show that the peak temperature for preparing the CuCoNiLa medium-entropy alloy catalyst at 12V is 505℃, the peak temperature at 16V is 690℃, and the peak temperature at 20V is 810℃.

[0056] The XRD pattern of the CuCoNiLa / CAC-12V catalyst prepared in this embodiment is as follows: Figure 4 As shown in the figure. The 12V label corresponds to the catalyst in this example, the 16V label corresponds to the catalyst in Example 2, and the 20V label corresponds to the catalyst in Example 3. XRD results show that the catalyst prepared at 12V voltage has no obvious alloy diffraction peaks. Figure 3 This is because the metal ion precursor is not completely converted into an alloy at lower voltages, resulting in fewer metal particles and thus less obvious crystal diffraction peaks in the XRD pattern. Obvious alloy peaks are observed at both 16V and 20V, indicating the formation of a stable single-phase CuCoNiLa medium-entropy alloy.

[0057] The scanning transmission electron microscope (STEM) image of the CuCoNiLa / CAC-12V catalyst prepared in this embodiment is shown below. Figure 5As shown, STEM reveals that CuCoNiLa alloy particles are uniformly dispersed on the surface of the carbon support, with an average particle size of 11.6 nm.

[0058] Example 2

[0059] Preparation of CuCoNiLa / CAC-16V rare earth medium entropy alloy catalyst:

[0060] Two mL of each of the metal precursor solutions 1, 2, 3, and 4 prepared in Example 1 were mixed with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry was obtained. This slurry was then uniformly coated onto a carbon cloth measuring 4 cm × 6 cm, cut into 12 equal portions, and dried at 50 °C for 1 h. One piece of carbon cloth was fixed to an aluminum clamp, the two ends of which were connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current was set to 3.6 A, and the charging voltage to 16 V. After the clamp was placed in a quartz shroud for gas purging and filled with argon, the circuit was turned on. The electric pulse generator discharged instantaneously, and the carbon cloth rapidly heated up. The metal salts loaded on the carbon cloth dispersed, decomposed, and then agglomerated to form a medium-entropy alloy. After the energizing was completed, the quartz shroud was removed, and the powder on the carbon cloth was collected to obtain the CuCoNiLa / CAC-16V medium-entropy alloy catalyst.

[0061] The scanning transmission electron microscope (STEM) image of the CuCoNiLa / CAC-16V catalyst prepared in this embodiment is shown below. Figure 6 As shown, STEM revealed that CuCoNiLa alloy particles were uniformly dispersed on the surface of the carbon support, with an average particle size of approximately 18.9 nm. Compared to the CuCoNiLa / CAC-12V catalyst prepared in Example 1, its average particle size is increased.

[0062] Example 3

[0063] Preparation of CuCoNiLa / CAC-20V ​​rare earth medium entropy alloy catalyst:

[0064] Two mL of each of the metal precursor solutions 1, 2, 3, and 4 prepared in Example 1 were mixed with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry was obtained and uniformly coated onto a carbon cloth measuring 4 cm × 6 cm. The slurry was cut into 12 equal portions and dried at 50 °C for 1 h. One piece of carbon cloth was fixed to an aluminum fixture, the two ends of which were connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current was set to 3.6 A and the charging voltage to 20 V. After the fixture was placed in a quartz shroud for gas purging and filled with argon gas, the circuit was turned on, the electric pulse generator discharged instantaneously, and the carbon cloth heated rapidly. The metal salts loaded on the carbon cloth dispersed, decomposed, and then agglomerated to form a medium-entropy alloy. After the energizing was completed, the quartz shroud was removed, and the powder on the carbon cloth was collected to obtain the CuCoNiLa / CAC-20V ​​medium-entropy alloy catalyst.

[0065] The scanning transmission electron microscope (STEM) image of the CuCoNiLa / CAC-20V ​​catalyst prepared in this embodiment is shown below. Figure 7 As shown, STEM revealed that CuCoNiLa alloy particles were uniformly dispersed on the surface of the carbon support, with an average particle size of approximately 31.1 nm.

[0066] Example 4

[0067] CuCoNiLa 0.3 Preparation of CAC-16V rare earth medium entropy alloy catalyst:

[0068] Take 2 mL of each of the metal precursor solutions 1, 2, and 3 prepared in Example 1, and 0.6 mL of metal precursor solution 4, and mix them with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry is obtained. This slurry is then uniformly coated onto a carbon cloth measuring 4 cm × 6 cm, cut into 12 equal portions, and dried at 50 °C for 1 h. One piece of carbon cloth is fixed to an aluminum clamp, with both ends of the clamp connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current is set to 3.6 A, and the charging voltage to 16 V. After the clamp is placed in a quartz shroud for gas purification and filled with argon, the circuit is turned on. The electric pulse generator discharges instantaneously, and the carbon cloth rapidly heats up. The metal salts loaded on the carbon cloth disperse, decompose, and then agglomerate to form a medium-entropy alloy. After the energizing process is complete, the quartz shroud is removed, and the powder on the carbon cloth is collected to obtain CuCoNiLa. 0.3 / CAC-16V medium entropy alloy catalyst.

[0069] The CuCoNiLa prepared in this embodiment 0.3 Scanning transmission electron microscopy (STEM) image of the CAC-16V catalyst is shown below. Figure 8 As shown, CuCoNiLa can be observed using STEM. 0.3The alloy particles are uniformly dispersed on the surface of the carbon nanosphere carrier, with an average particle size of 18.2 nm.

[0070] Figure 9 CuCoNiLa prepared in this embodiment 0.3 High-resolution TEM images of the CuCoNi / CAC-16V catalyst and the CuCoNi / CAC-16V catalyst prepared in Comparative Example 1. Measurements of their lattice fringes confirmed that both are single-phase alloys. Fourier and inverse Fourier transforms of the lattice fringes revealed a significant increase in the interplanar spacing of the La-added quaternary rare-earth medium-entropy alloy nanoparticles. This demonstrates that the incorporation of large-sized La atoms generates more lattice distortion within the crystal, providing more active sites for the catalytic alcoholysis of ammonia borane, and that the presence of lattice distortion enhances the stability of the medium-entropy alloy catalyst.

[0071] Example 5

[0072] Hydrogen production experiment by alcoholysis of ammonia borane under catalytic conditions:

[0073] To investigate the catalytic effect of the catalyst on hydrogen production from ammonia borane alcoholysis, this invention conducted experiments on hydrogen production from ammonia borane alcoholysis under catalytic conditions. The experimental procedure is as follows:

[0074] The catalytic experiment was conducted in a 50 mL single-necked round-bottom flask. 25 mg of catalyst was added to 4 mL of methanol and ultrasonically dispersed. After homogeneous mixing, the flask was transferred to an oil bath at 30 °C and heated at 600 rpm. -1 The flask was magnetically stirred at a high speed. The neck of the flask was connected to a condenser, which was then connected to a 500mL glass bottle with a rubber stopper filled with water via a rubber tube. 30mg of ammonia borane was dissolved in 0.5mL of methanol and added to the round-bottom flask using a syringe. When hydrogen gas was generated, the gas displaced an equal volume of water from the bottle. The mass of the displaced water was read using an electronic balance and converted into volume, which was recorded as the amount of H2 produced. The mass of the displaced water was recorded every second until the mass of the water no longer changed, at which point the reaction was considered complete. After the first reaction, the ammonia borane methanol solution was added four times, and the volume was counted to test the catalyst's cycle performance.

[0075] The performance graphs and corresponding conversion frequency bar charts of the CuCoNiLa / CAC series catalysts prepared at different voltages in Examples 1-3 of this invention for catalytic hydrogen production from ammonia borosilicate alcoholysis are shown below. Figure 10 As shown in the figure, the CuCoNiLa / CAC-16V obtained in Example 2 exhibits the highest catalytic activity, with a TOF value of 102.36 min. -1 .

[0076] CuCoNiLa prepared at 16V voltage as obtained in Examples 2 and 4 of this invention, and Comparative Examples 1, 7, and 8 of this invention x The performance graphs and corresponding conversion frequency histograms of the / CAC (x=0,0.15,0.3,0.6,1) series catalysts for catalytic hydrogen production from ammonia borane alcoholysis are shown below. Figure 11 As shown in the figure. The CuCoNiLa obtained in Example 4 can be seen from the figure. 0.3 / CAC-16V exhibits the highest catalytic activity, with a TOF value of 147.89 min. -1 .

[0077] CuCoNiLa prepared at 16V voltage as obtained in Examples 2 and 4 of this invention, and Comparative Examples 1, 7, and 8 of this invention x The TOF value changes and the percentage of remaining catalytic activity after 5 cycles during the 5-cycle catalytic dehydrogenation process of the / CAC(x=0,0.15,0.3,0.6,1) series catalysts are shown in the figure. Figure 12 As shown in the figure, the cycling stability of the medium-entropy alloy catalysts improved after the addition of La. The sample with the best cycling performance was CuCoNiLa / CAC-16V, whose remaining activity after 5 cycles increased significantly from 51.3% to 77.1% compared to the CuCoNi / CAC-16V catalyst prepared in Comparative Example 1. In addition, the effect of different La addition amounts on the mixing entropy of the medium-entropy alloy system is also shown in the figure. As can be seen from the figure, the addition of La to the CuCoNi ternary medium-entropy alloy effectively improved the cycling stability of the medium-entropy alloy catalyst, and the increase was positively correlated with the increase in mixing entropy.

[0078] CuCoNiRE prepared at 16V voltage as obtained in Examples 4, 9-11 and Comparative Example 1 of this invention 0.3 Performance graphs of CAC (RE = La, Ce, Pr, Nd) series catalysts and CuCoNi / CAC catalysts for catalytic hydrogen production from ammonia borane alcoholysis, and bar charts showing the conversion frequency before and after 5 cycles of catalytic hydrogen release, are shown below. Figure 13 As shown in the figure, the addition of La and Ce increases both the conversion frequency and cycle stability of the CuCoNi ternary catalyst; while for Pr and Nd, although their conversion frequencies are similar to those of the ternary catalyst, their 5-cycle stability increases. This demonstrates that improving the cycle performance of medium-entropy alloy catalysts by adding rare earth elements has a certain degree of universality.

[0079] Example 6

[0080] Tests on hydrogen desorption rate and activation energy of catalysts under different temperature conditions:

[0081] At different temperatures (20, 25, 30 and 35°C), samples prepared in Example 4 were selected and hydrogen was produced by catalytic alcoholysis of ammonia borane using the test method of Example 5.

[0082] The catalyst CuCoNiLa prepared in Example 4 of this invention 0.3 The Arrhenius activation energy test results of CAC-16V for catalytic hydrogen production from ammonia borane alcoholysis at 20, 25, 30, and 35 °C are shown in the figure below. Figure 14 As shown, the results indicate a positive correlation between the hydrogen release rate and temperature; the higher the temperature, the faster the hydrogen release rate. The values ​​of CuCoNiLa were calculated using the Arrhenius equation. 0.3 The activation energy of the / CAC-16V catalytic reaction is 31.3 kJ / mol. -1 This value is relatively low among non-precious metal catalysts.

[0083] Comparative Example 1

[0084] Preparation of CuCoNi / CAC-16V medium-entropy alloy catalyst:

[0085] Two mL of each of the metal precursor solutions 1, 2, and 3 prepared in Example 1 were mixed with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry was obtained and uniformly coated onto a carbon cloth measuring 4 cm × 6 cm. The slurry was cut into 12 equal portions and dried at 50 °C for 1 h. One piece of carbon cloth was fixed to an aluminum fixture, the two ends of which were connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current was set to 3.6 A and the charging voltage to 16 V. After the fixture was placed in a quartz shroud for gas purging and filled with argon gas, the circuit was turned on. The electric pulse generator discharged instantaneously, and the carbon cloth heated rapidly. The metal salts loaded on the carbon cloth dispersed, decomposed, and then agglomerated to form a medium-entropy alloy. After the energizing was completed, the quartz shroud was removed, and the powder on the carbon cloth was collected to obtain the CuCoNi / CAC-16V medium-entropy alloy catalyst.

[0086] Example 7

[0087] CuCoNiLa 0.15 Preparation of CAC-16V rare earth medium entropy alloy catalyst:

[0088] Take 2 mL of each of the metal precursor solutions 1, 2, and 3 prepared in Example 1, and 0.3 mL of the metal precursor solution 4 prepared in Example 1, and mix them with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry is obtained. This slurry is then uniformly coated onto a carbon cloth measuring 4 cm × 6 cm, cut into 12 equal portions, and dried at 50 °C for 1 h. One piece of carbon cloth is fixed to an aluminum clamp, with both ends of the clamp connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current is set to 3.6 A, and the charging voltage to 16 V. After the clamp is placed in a quartz shroud for gas purification and filled with argon, the circuit is turned on. The electric pulse generator discharges instantaneously, and the carbon cloth rapidly heats up. The metal salts loaded on the carbon cloth disperse, decompose, and then agglomerate to form a medium-entropy alloy. After the energizing process is complete, the quartz shroud is removed, and the powder on the carbon cloth is collected to obtain CuCoNiLa. 0.15 / CAC-16V rare earth medium entropy alloy catalyst.

[0089] Example 8

[0090] CuCoNiLa 0.6 Preparation of CAC-16V rare earth medium entropy alloy catalyst:

[0091] Take 2 mL of each of the metal precursor solutions 1, 2, and 3 prepared in Example 1, and 1.2 mL of the metal precursor solution 4 prepared in Example 1, and mix them with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry is obtained. This slurry is then uniformly coated onto a carbon cloth measuring 4 cm × 6 cm, cut into 12 equal portions, and dried at 50 °C for 1 h. One piece of carbon cloth is fixed to an aluminum clamp, with both ends of the clamp connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current is set to 3.6 A, and the charging voltage to 16 V. After the clamp is placed in a quartz shroud for gas purification and filled with argon, the circuit is turned on. The electric pulse generator discharges instantaneously, and the carbon cloth rapidly heats up. The metal salts loaded on the carbon cloth disperse, decompose, and then agglomerate to form a medium-entropy alloy. After the energizing process is complete, the quartz shroud is removed, and the powder on the carbon cloth is collected to obtain CuCoNiLa. 0.6 / CAC-16V rare earth medium entropy alloy catalyst.

[0092] Example 9

[0093] CuCoNiCe 0.3 Preparation of CAC-16V rare earth medium entropy alloy catalyst:

[0094] (1) Weigh 465.7 mg CeCl3·7H2O and add it to 20 mL of anhydrous ethanol. Stir magnetically for 2 h to completely dissolve the metal salt. Then, prepare a fixed concentration metal precursor solution (0.025 M CeCl3·7H2O) in a 50 mL volumetric flask.3+ ).

[0095] (2) Take 2 mL of metal precursor solutions 1, 2, and 3 prepared in Example 1, and 0.6 mL of metal precursor solution 5, respectively, and mix them with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry is obtained. This slurry is then uniformly coated onto a carbon cloth with an area of ​​4 cm × 6 cm, cut into 12 equal parts, and dried at 50 °C for 1 h. Take a piece of carbon cloth and fix it to an aluminum clamp. The two ends of the clamp are connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current is set to 3.6 A, and the charging voltage is 16 V. After the clamp is placed in a quartz hood for gas purification and filled with argon gas, the circuit is turned on. The electric pulse generator discharges instantaneously, and the carbon cloth heats up rapidly. The metal salts loaded on the carbon cloth disperse, decompose, and then agglomerate to form a medium-entropy alloy. After the power-on is complete, remove the quartz hood, collect the powder on the carbon cloth, and obtain CuCoNiCe. 0.3 / CAC-16V medium entropy alloy catalyst.

[0096] CuCoNiRE prepared in Examples 4 and 9-11 of this invention 0.3 Performance graphs and corresponding conversion frequency histograms of the CAC-16V (RE = La, Ce, Pr, Nd) series catalysts for catalytic hydrogen production from ammonia borane alcoholysis are shown below. Figure 13 As shown in the figure. The CuCoNiLa obtained in Example 4 can be seen from the figure. 0.3 / CAC-16V exhibits the highest catalytic activity, with a TOF value of 147.89 min. -1 Secondly, CuCoNiCe 0.3 / CAC-16V, its TOF value is 128.1 min. -1 This demonstrates that adding a certain amount of rare earth elements has a universal effect on improving the activity of catalytic hydrogen production from ammonia boron alcoholysis.

[0097] Example 10

[0098] CuCoNiPr 0.3 Preparation of CAC-16V rare earth medium entropy alloy catalyst:

[0099] (1) Weigh 309.1 mg PrCl3·xH2O and add it to 20 mL of anhydrous ethanol. Stir magnetically for 2 h to completely dissolve the metal salt. Then, prepare a fixed concentration metal precursor solution (0.025 M PrCl3·xH2O) in a 50 mL volumetric flask. 3+ ).

[0100] (2) Take 2 mL of metal precursor solutions 1, 2, and 3 prepared in Example 1, and 0.6 mL of metal precursor solution 6, respectively, and mix them with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry is obtained. This slurry is then uniformly coated onto a carbon cloth with an area of ​​4 cm × 6 cm, cut into 12 equal parts, and dried at 50 °C for 1 h. Take a piece of carbon cloth and fix it to an aluminum clamp. The two ends of the clamp are connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current is set to 3.6 A, and the charging voltage is 16 V. After the clamp is placed in a quartz hood for gas purification and filled with argon, the circuit is turned on. The electric pulse generator discharges instantaneously, and the carbon cloth heats up rapidly. The metal salts loaded on the carbon cloth disperse, decompose, and then agglomerate to form a medium-entropy alloy. After the power-on is complete, remove the quartz hood, collect the powder on the carbon cloth, and obtain CuCoNiPr. 0.3 / CAC-16V medium entropy alloy catalyst.

[0101] Example 11

[0102] CuCoNiNd 0.3 Preparation of CAC-16V rare earth medium entropy alloy catalyst:

[0103] (1) Weigh 448.4 mg NdCl3·6H2O and add it to 20 mL of anhydrous ethanol. Stir magnetically for 2 h to completely dissolve the metal salt. Then, prepare a fixed concentration metal precursor solution (0.025 M NdCl3·6H2O) in a 50 mL volumetric flask. 3+ ).

[0104] (2) Take 2 mL of metal precursor solutions 1, 2, and 3 prepared in Example 1, and 0.6 mL of metal precursor solution 6, respectively, and mix them with 72 mg of activated carbon powder (CAC). After ultrasonic dispersion for 1 h, a uniform slurry is obtained. This slurry is then uniformly coated onto a carbon cloth with an area of ​​4 cm × 6 cm, cut into 12 equal parts, and dried at 50 °C for 1 h. Take a piece of carbon cloth and fix it to an aluminum clamp. The two ends of the clamp are connected to a self-built discharge platform consisting of an adjustable DC regulated power supply and an electric pulse generator (capacitor). The charging current is set to 3.6 A, and the charging voltage is 16 V. After the clamp is placed in a quartz hood for gas purification and filled with argon, the circuit is turned on. The electric pulse generator discharges instantaneously, and the carbon cloth heats up rapidly. The metal salts loaded on the carbon cloth disperse, decompose, and then agglomerate to form a medium-entropy alloy. After the power-on is complete, remove the quartz hood, collect the powder on the carbon cloth, and obtain CuCoNiNd. 0.3 / CAC-16V medium entropy alloy catalyst.

[0105] Example 12

[0106] CuCoNiLa 0.3Simulation calculations of methanol adsorption energy for / CAC-16V and CuCoNi / CAC-16V catalysts:

[0107] All density functional theory (DFT) calculations were performed using the Vienna Ab Initio Package (VASP) in the generalized gradient approximation (GGA) conforming to the PBE formula. The energy cutoff was set above 350 eV, and the force and energy convergence criteria were set as follows: and 10 -5 eV. DFT-D3 correction was used to explain long-range dispersion. The crystal plane selection for model construction was based on XRD and TEM results, choosing the (111) crystal plane with the most exposed catalyst. Methanol molecules in CuCoNi and CuCoNiLa 0.3 Adsorption energy E on the surface ads See the calculation results. Figure 15 The specific data is calculated using the following formula:

[0108] E ads =E ad / sur -E ad -E sur

[0109] Among them, E ad / sur E ad and E sur These represent the optimized adsorbate / surface structure, adsorbed molecules, and CuCoNi or CuCoNiLa, respectively. 0.3 Energy of the flat plate model. According to... Figure 15 The data shows that after adding La, the adsorption energies of methanol at Cu, Co, and Ni sites changed from -0.57 eV, -0.69 eV, and -0.72 eV to -0.85 eV, -0.91 eV, and -0.94 eV, respectively. This indicates that the introduction of La is beneficial to the adsorption and activation of the reactants. Therefore, the simulation calculation verifies the experimental results that the conversion frequency of CuCoNi ternary alloy increases significantly after adding a certain amount of La.

[0110] In summary, this invention utilizes carbothermal shock reduction to decompose the metal precursor salt, resulting in high miscibility between Cu, Co, Ni, and large-atom-sized rare earth elements, forming stable single-phase alloy nanoparticles. These nanoparticles are then successfully loaded onto an activated carbon powder support, yielding a rare earth medium-entropy alloy catalyst, CuCoNiRE / CAC, with excellent catalytic performance. The introduction of rare earth elements plays the following roles: 1) The dissolution of large-sized rare earth atoms expands the interplanar spacing of the alloy, generating more lattice distortion and thus improving catalytic activity; 2) The OH* affinity of rare earth elements enhances the adsorption and activation of the catalyst for the reactant methanol; 3) The mixed entropy of the system is increased, and the high entropy effect improves the cyclic stability of the catalyst. This series of catalysts exhibits excellent catalytic performance in the field of ammonia boron alcoholysis for hydrogen production. At 30℃, the highest activity of AB in the catalyst system reaches 147.89 mol. H2 mol cat -1 min -1 The activation energy is as low as 31.3 kJ / mol. -1 Furthermore, the addition of different rare earth elements (La, Ce, Pr, Nd) can improve the cycle stability of CuCoNi medium-entropy alloy catalysts. Compared with traditional precious metal catalysts, it has the advantages of simple preparation, low cost, and readily available raw materials, making it suitable for industrial production and a catalyst with great application prospects.

[0111] Furthermore, it should be understood that after reading the above description of the present invention, those skilled in the art can make various alterations or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. The application of a carbon-supported medium-entropy alloy catalyst in the catalytic hydrogen production from ammonia boran alcoholysis, characterized in that, The carbon-supported medium-entropy alloy catalyst comprises a carbon support and CuCoNiRE medium-entropy alloy nanoparticles supported on the carbon support. In the CuCoNiRE medium entropy alloy nanoparticles, RE represents La, Ce, Pr or Nd, and the molar ratio of Cu, Co, Ni and RE is 1:1:1:X, where 0 < X ​​≤ 1. The preparation method of the carbon-supported entropy alloy catalyst includes: Under a flowing carbon dioxide atmosphere, the nano-carbon powder is heated to 880~920℃ and held for 1~2 h, and then cooled to room temperature to obtain carbon dioxide activated carbon powder (CAC). Cu was prepared using anhydrous ethanol as a solvent. 2+ Co 2+ Ni 2+ RE 3+ Each metal salt precursor solution; CAC and metal salt precursor solution are mixed to form a slurry and coated onto carbon cloth, then dried to obtain precursor carbon cloth. The carbon thermal shock reduction method is used to heat and cool the precursor carbon cloth in an inert atmosphere under the action of an electric pulse. During this process, the metal salt disperses, decomposes and agglomerates to form CuCoNiRE medium-entropy alloy nanoparticles. The powder on the carbon cloth is collected to obtain the carbon-supported medium-entropy alloy catalyst.

2. The application according to claim 1, characterized in that, The carbon support is formed by the aggregation of carbon nanospheres; The diameter of the carbon nanospheres is 20~25 nm; The average particle size of the CuCoNiRE entropy alloy nanoparticles is 10~40 nm.

3. The application according to claim 1 or 2, characterized in that, The molar ratio of the CuCoNiRE entropy alloy nanoparticles to the carbon support is 1:10~150.

4. The application according to claim 1, characterized in that, 0.15≤X≤1。 5. The application according to claim 4, characterized in that, 0.15≤X≤0.6。 6. The application according to claim 5, characterized in that, 0.15≤X≤0.3。 7. The application according to claim 1, characterized in that, The carbon dioxide flow rate is 30–40 mL / min. -1 ; The nano-carbon powder is BP-2000.

8. The application according to claim 1, characterized in that, The ratio of the amount of metal ions to the volume of anhydrous ethanol in the solutions of each metal salt precursor was independently 1–1.5 mmol:50 mL.

9. The application according to claim 1, characterized in that, The ratio of CAC mass to the volume of each metal salt precursor solution is independently 72 mg:Y mL, where 0 < Y ≤ 2.

5.

10. The application according to claim 1, characterized in that, The parameters for the electrical pulse include: DC power supply, pulse voltage 12~20 V, and current 3.6 A.

11. The application according to claim 10, characterized in that, Pulse voltage 16 V.

Images