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CN-122006820-A - Fct phase NiAg nanoparticle catalyst and preparation method and application thereof

CN122006820ACN 122006820 ACN122006820 ACN 122006820ACN-122006820-A

Abstract

The invention discloses an fct phase NiAg nanoparticle catalyst and a preparation method and application thereof. The fct-phase NiAg nanoparticle catalyst has a core-shell structure and comprises a bimetallic core containing Ni and Ag and a nitrogen-doped carbon layer coated on the surface of the bimetallic core, wherein the crystal phase of the fct-phase NiAg nanoparticle is a metastable fct phase. The catalyst provided by the invention overcomes the synthetic bottleneck of a NiAg insoluble system, realizes anti-sintering and structure locking at high temperature, can construct an efficient transmission network of electrons and hydrogen when being applied to the field of magnesium hydride, and establishes a double channel of electron conduction and hydrogen rapid permeation on the surface of the magnesium hydride so as to realize unification of rapid kinetics and long-cycle stability.

Inventors

  • LI WENFENG
  • LIU HU
  • TIAN JIE

Assignees

  • 中国科学院青海盐湖研究所

Dates

Publication Date
20260512
Application Date
20260408

Claims (10)

  1. 1. The fct-phase NiAg nanoparticle catalyst is characterized by having a core-shell structure and comprising a bimetallic core containing Ni and Ag and a nitrogen-doped carbon layer coated on the surface of the bimetallic core, wherein the crystal phase of the fct-phase NiAg nanoparticle catalyst is metastable fct phase.
  2. 2. The fct-phase NiAg nanoparticle catalyst of claim 1, wherein the nitrogen-doped carbon layer has an electron transport channel, and the pore diameter of the channel is 0.5-5 nm; and/or the diameter of the fct phase NiAg nano particle catalyst is 10-30 nm; And/or the diameter of the bimetal core is 5-20 nm; And/or the thickness of the nitrogen-doped carbon layer is 1-5 nm; And/or the nitrogen-doped carbon layer comprises 75-99 wt% of C and 1-25 wt% of N; And/or the fct phase NiAg nanoparticle catalyst comprises 10-30wt% of Ni, 10-30wt% of Ag, 30-70wt% of C and 1-10wt% of N.
  3. 3. A method for preparing fct phase NiAg nanoparticle catalyst, comprising: uniformly mixing a silver source, a nickel source, a reducing agent, a dispersing agent, a carbon source and a nitrogen source, and carrying out heating reaction, ageing treatment and anti-solvent precipitation separation to prepare a catalyst precursor; Carrying the catalyst precursor on the surface of a carbon carrier through electrostatic adsorption to obtain a supported precursor; calcining the supported precursor in an inert reducing atmosphere, carbonizing in situ to form a nitrogen-doped carbon layer, reducing Ni and Ag, and assembling into a bimetallic core to prepare the fct-phase NiAg nano-particle catalyst.
  4. 4. The preparation method of the catalyst precursor is characterized by comprising the steps of dissolving a silver source, a nickel source, a reducing agent and a dispersing agent in a carbon source and a nitrogen source, uniformly mixing, preheating for 5-15 min at 75-85 ℃, heating to 190-210 ℃ for reaction for 8-12 h, cooling to 20-30 ℃ for aging for 1-12 h, adding the antisolvent, and carrying out precipitation separation for 5-10 min at a centrifugal speed of 8000-11000 r/min to obtain the catalyst precursor; Preferably, the mass ratio of the silver source to the nickel source to the reducing agent to the dispersing agent is 30-40:45-55:75-85:80-90; preferably, the carbon source and the nitrogen source are the same substance, and oleylamine is used as the carbon source and the nitrogen source; Particularly preferably, the usage amount of the oleylamine is 1100-1700 parts by mass of the oleylamine corresponding to the sum of 230-270 parts by mass of silver source, nickel source, reducing agent and dispersing agent; Particularly preferably, the volume ratio of the antisolvent to the oleylamine is 4:1-5:1; Preferably, the silver source comprises silver nitrate; Preferably, the nickel source comprises nickel acetylacetonate; Preferably, the reducing agent comprises ascorbic acid; preferably, the dispersant comprises cetyltrimethylammonium chloride; preferably, the antisolvent comprises a mixture of cyclohexane and ethanol; particularly preferably, the volume ratio of the cyclohexane to the ethanol is 1:3-4; And/or dispersing the carbon carrier in a solvent for 2-4 hours by ultrasonic treatment, adding the catalyst precursor, carrying out ultrasonic treatment at 0-5 ℃ for 2-4 hours, and carrying the catalyst precursor on the surface of the carbon carrier by utilizing electrostatic adsorption to prepare the supported precursor; preferably, the carbon support comprises ketjen black; Preferably, the solvent comprises cyclohexane; Preferably, the mass ratio of the carbon carrier to the catalyst precursor is 1-5:1-2; Preferably, the mass ratio of the carbon carrier to the solvent is 1:100-1:500; And/or the preparation method specifically comprises the steps of heating to 700-800 ℃ at a heating rate of 2-3 ℃ per minute, and calcining the supported precursor at a high temperature for 1-6 hours in a reducing atmosphere; preferably, the reducing atmosphere comprises a mixture of argon and hydrogen; Particularly preferably, the volume ratio of the argon to the hydrogen is 90-95:10-5.
  5. 5. A method for preparing fct phase NiAg nanoparticle catalyst, comprising: uniformly mixing a silver source, a nickel source, a reducing agent, a dispersing agent, a carbon source, a nitrogen source, an auxiliary dispersing agent and a solvent to form a homogeneous mixed solution, and performing a polymerization reaction on the carbon source and the nitrogen source by aid of microwaves to obtain a nitrogen-containing carbon precursor layer on the surface of the NiAg precursor; In-situ carbon pyrolysis reaction is carried out on the precursor in a reducing atmosphere, the nitrogen-containing carbon precursor layer is converted into a nitrogen-doped carbon layer, and the NiAg is alloyed to form an fct phase, so that an fct phase NiAg nanoparticle catalyst is prepared; Preferably, the mass ratio of the silver source, the nickel source, the reducing agent, the dispersing agent, the carbon source, the nitrogen source, the auxiliary dispersing agent and the solvent is 30-40:45-55:75-85:80-90:200-400:100-300:10-50:5000-10000; Preferably, the silver source comprises silver nitrate; Preferably, the nickel source comprises nickel acetylacetonate; Preferably, the reducing agent comprises ascorbic acid; preferably, the dispersant comprises cetyltrimethylammonium chloride; preferably, the carbon source comprises sucrose; Preferably, the nitrogen source comprises melamine; preferably, the auxiliary dispersing agent comprises polyethylene glycol; Preferably, the solvent comprises diethylene glycol; Preferably, the technological parameters of the microwaves are 150-200 ℃ and 400-800W microwave power for heat preservation reaction for 0.5-2 hours; preferably, the reducing atmosphere comprises a mixture of argon and hydrogen; particularly preferably, the volume ratio of the argon to the hydrogen is 9-19:1; Preferably, the temperature of the in-situ carbon pyrolysis reaction is 600-800 ℃ and the time is 2-4 hours; Preferably, the preparation method comprises the steps of centrifuging a product of the nitrogen-carbon-containing precursor layer at a rotating speed of 8000-11000 r/min for 5-10 min, washing, and vacuum drying at 60-80 ℃ for 12-24 h to obtain the precursor.
  6. 6. A method for preparing fct phase NiAg nanoparticle catalyst, comprising: uniformly mixing a silver source, a nickel source, a silicon source, a reducing agent, a nitrogen source, a template agent, a carbon source and water, forming gel in an acidic environment, and then carrying out pyrolysis reduction reaction in a reducing atmosphere to prepare an fct phase NiAg nano-particle catalyst; Preferably, the reducing agent and the nitrogen source are the same substance; Particularly preferably, the mass ratio of the silver source, the nickel source, the silicon source, the reducing agent, the template agent, the carbon source and the water is 30-40:40-50:100-300:50-150:10-50:100-200:1000-3000; Particularly preferably, the reducing agent and nitrogen source comprise urea; Preferably, the silver source comprises silver nitrate; preferably, the nickel source comprises nickel nitrate; Preferably, the silicon source comprises ethyl orthosilicate; Preferably, the template agent comprises polyethylene glycol; preferably, the carbon source comprises sucrose; Preferably, the preparation method specifically comprises the steps of uniformly mixing the materials in an acidic environment with a pH value of 3-4 at 20-60 ℃ to form sol, and then preserving heat for 6-24 hours to form gel; preferably, the preparation method specifically comprises the steps of drying the gel at 60-100 ℃ for 12-24 hours, then heating to 600-800 ℃ at a heating rate of 2-5 ℃ per minute under the reducing atmosphere, and carrying out pyrolysis reduction reaction for 2-6 hours to form a NiAg alloy and carbon-nitrogen doped silicon dioxide composite shell layer, so as to obtain the fct phase NiAg nanoparticle catalyst.
  7. 7. A method for preparing fct phase NiAg nanoparticle catalyst, comprising: Taking a bimetal organic framework material as a precursor, carrying out pyrolysis reduction on the bimetal organic framework material in a reducing atmosphere, and carrying out pyrolysis on the organic framework to form a nitrogen-doped carbon layer, wherein bimetal ions are reduced and alloyed to prepare fct-phase NiAg nanoparticle catalyst; preferably, the bimetal organic framework material comprises a Ni-Ag-ZIF-8 bimetal MOF material; preferably, the reducing atmosphere comprises a mixture of argon and hydrogen; particularly preferably, the volume ratio of the argon to the hydrogen is 9-19:1; Preferably, the high-temperature pyrolysis is performed at a temperature of 700-900 ℃ for 2-6 hours.
  8. 8. The preparation method of the nitrogen-doped carbon-coated fct-phase NiAg/MgH 2 composite hydrogen storage material is characterized by comprising the following steps of: providing the fct phase NiAg nanoparticle catalyst of claim 1 or 2; mixing and ball-milling the fct phase NiAg nano particle catalyst and magnesium hydride to prepare a nitrogen-doped carbon-coated fct phase NiAg/MgH 2 composite hydrogen storage material; Preferably, the mass ratio of the fct phase NiAg nano particle catalyst to the magnesium hydride is 1-2:8-18; preferably, the ball milling adopts a forward rotation-reverse rotation-intermittent circulation mode, and the total ball milling time is 4-12 hours; Particularly preferably, the ball milling adopts a circulation mode of forward rotation for 3-10 min, reverse rotation for 3-10 min and intermittent rotation for 3-10 min.
  9. 9. The nitrogen-doped carbon-coated fct-phase NiAg/MgH 2 composite hydrogen storage material prepared by the preparation method of claim 8 is characterized in that the hydrogen storage capacity of the nitrogen-doped carbon-coated fct-phase NiAg/MgH 2 composite hydrogen storage material at 300 ℃ is more than 5 wt%.
  10. 10. A solid hydrogen storage medium comprising the nitrogen-doped carbon-coated fct phase NiAg/MgH 2 composite hydrogen storage material of claim 9.

Description

Fct phase NiAg nanoparticle catalyst and preparation method and application thereof Technical Field The invention belongs to the technical field of rare earth permanent magnet material production, and particularly relates to an fct phase NiAg nanoparticle catalyst and a preparation method and application thereof. Background The hydrogen energy is used as clean secondary energy with high energy density, and the core bottleneck of large-scale popularization and application is that a high-efficiency and safe storage and transportation technology system is not mature. Compared with the potential safety hazard and the energy efficiency short plate of the traditional gas and liquid hydrogen storage modes, the solid hydrogen storage technology has the dual advantages of high safety and high volume energy density. Among many solid hydrogen storage media, magnesium hydride (MgH 2) has outstanding characteristics of high theoretical hydrogen storage capacity of 7.6 wt%, abundant resource storage, environmental friendliness and the like, but MgH 2 has high thermodynamic stability, the hydrogen release temperature is usually higher than 300 ℃, and the kinetics of hydrogen absorption and release is delayed, so that the practical application is restricted. To improve the hydrogen storage performance of MgH 2, the introduction of transition metal catalysts is currently the dominant approach. Pd as a noble metal, the scarcity and high cost constitute an industrial barrier that is difficult to surmount. Therefore, the construction of a nickel silver (Ni-Ag) bimetallic catalyst by using silver (Ag) which has the same period as Pd but is low in price instead of Pd has become a strategic direction for reducing the cost. Theoretical calculations indicate that if a face-centered tetragonal (fct) phase NiAg intermetallic compound with an ordered atomic arrangement can be synthesized, its specific lattice parameters and electronic structures will confer catalytic performance that is comparable to or even superior to noble metals. However, ni and Ag are typically immiscible systems in macroscopic thermodynamics, have a very large positive enthalpy of mixing, and there is a large solid solution gap (Miscibility Gap) and a very strong tendency to phase separate, which makes it difficult for Ni and Ag atoms to spontaneously form an ordered lattice structure. The traditional alloy synthesis process often relies on high-temperature annealing to drive atomic diffusion to induce ordered transformation, but has contradiction that huge immiscible energy barriers are overcome and strict high-temperature conditions are generally needed for constructing ordered fct, on one hand, nano particles which are in a naked state and lack of strong physical confinement protection are extremely easy to generate serious macroscopic phase separation (layering of Ni and Ag) and severe Ostwald (particle coarsening) curing under the high-temperature driving, so that the catalyst is deactivated in the preparation stage or is rapidly deactivated in the subsequent high-temperature hydrogen storage cycle. In order to solve the problems of Ni and Ag that are easily phase-separated and coarsened in grains at high temperature, the prior art attempts to coat nanoparticles with carbon shells, thereby confining them in a fixed space. However, with the conventional coating process, if the coating layer is not dense enough, active metal atoms cannot be limited at high temperature, so that Ni and Ag still escape outwards and delaminate or aggregate into a large block, resulting in catalyst failure. On the contrary, if the thickness of the carbon layer is increased to forcibly wrap the metal atoms, the excessively thick coating layer forms a serious physical barrier at the catalyst interface, which keeps out the hydrogen molecules needed to participate in the reaction, thereby greatly retarding the permeation and diffusion rates of the hydrogen. Therefore, how to overcome the thermodynamic immiscible resistance under the high-temperature environment and construct a protective layer for the NiAg alloy, which can dead and dead lock metal atoms, not separate the metal atoms and enable hydrogen to freely penetrate, so as to synchronously realize the synthesis and anti-sintering protection of the metastable fct phase NiAg core is a key technical problem to be solved in the field. Disclosure of Invention The invention mainly aims to provide an fct phase NiAg nano particle catalyst and a preparation method and application thereof, so as to overcome the defects of the prior art. In order to achieve the purpose of the invention, the technical scheme adopted by the invention comprises the following steps: The first aspect of the invention provides an fct-phase NiAg nanoparticle catalyst, which has a core-shell structure and comprises a bimetallic core containing Ni and Ag and a nitrogen-doped carbon layer coated on the surface of the bimetallic core, wherein the crystal phase of the