Preparation Of Hexagonal Nickel-based Catalyst For Hydrogen Production Performance

As a clean and sustainable secondary energy source,hydrogen plays a crucial role in addressing the global climate crisis and achieving the goal of carbon neutrality.Due to its high flammability and inconvenient transportation,the use of solid hydrogen storage sources to release hydrogen under certain conditions is an effective strategy to develop hydrogen energy.Ammonia borane is considered one of the most attractive carriers due to its high hydrogen content（19.6 wt%）,good stability and ease of transportation.In addition,providing environmentally friendly and renewable hydrogen generation technology is also the key to achieving the"double carbon"goal.Hydrogen production by electrolysis of water is an immediate way to produce hydrogen,which is of great interest because of mild conditions,high purity and non-pollution.The oxygen precipitation reaction is the key to the electrolytic water reaction,and the study of the oxygen precipitation process has an important impact on the electrolytic water hydrogen production.For the research of key catalysts,the main research of the paper is as follows:（1）Ultrasmall hexagonal nickel nanoparticles（hcp-Ni NPs）and cubic phase nickel nanoparticles（fcc-Ni NPs）were synthesized by simple high-temperature colloid method and loaded onto In₂O₃ carrier by dipping method.Methane（CH₄）plasma surface treatment was applied for hydrogen production from ammonia-borane hydrolysis under ultrasonic assistance.The TOF value of hcp-Ni/In₂O₃ NPs at room temperature was 7.5 mol _H2·mol_Ni^-1·min^-1,which was 1.7 times higher than that of fcc-Ni/In₂O₃ NPs,demonstrating the superiority of metastable phase nickel-based catalysts for hydrogen production of ammonia borane.DFT calculations showed that the hcp-Ni/In₂O₃ had higher hydrophilicity and lower activation energy for water dissociation than the fcc-Ni/In₂O₃,which modulated the surface electronic state of the catalyst and promotes the hydrogen production rate of ammonia borane hydrolysis.（2）The Ni₃Fe-LDH nanosheet precursors were first synthesized by a solvothermal method.The low-temperature methane（CH₄）plasma technique was used to control the time and power,and the resulting reducing components and the micro-carbon environment generated by the in situ catalytic CH_x of nickel elements topologically transformed the nickel-containing layered precursors in situ,resulting in porous Ni₃Fe NPs modified with carbon layers of different thicknesses.Electrocatalytic tests showed that the catalysts with medium carbon layer thickness（400 W 20 min-CH₄）obtained by reduction under CH₄ atmosphere had superior catalytic performance with only 331 m V at 100 m A cm^-2.The effect of modification of carbon species on the performance of electrochemical alkaline oxygen precipitation was investigated based on metastable phase nickel-based catalysts.A carbon layer with relatively medium thickness can help the faster desorption of oxygen species in the OER reaction,adjust the electronic structure of the catalyst and significantly enhance the OER activity.This thesis provides a general method for the preparation of metastable phase nickel-based metal nanomaterials.Through the rational design of the metastable phase nickel-based catalyst structure,it provides a novel perspective for the design of next-generation high-performance and low-cost catalysts,and hopefully can be further applied to various catalytic and clean energy fields.