Preparation Of Self-Supported Co And Mo Metal Catalysts And Electrocatalytic Performance For Hydrogen Evolution Reaction

Transition metal sulfides,nitrides,and carbon-based materials are widely used in the field of electrolytic water splitting due to their various properties such as high electrical conductivity,low valence band,abundant resources,and controllable structure.However,these materials are often accompanied by volume shrinkage during catalysis,leading to reduced stability and electrochemical performance.Therefore,constructing electrode materials with abundant active sites is essential for enhancing electrochemical performance.Additionally,porous or fibrous network structures within the material can effectively mitigate volume expansion caused by hydrogen generation during the reaction process,thus improving cycling stability.This thesis focuses on electrode materials and structures,optimizing material structures and substrate materials,and controlling sample morphology to synthesize materials of different dimensions.The electrocatalytic hydrogen evolution performance of these materials was explored in detail:（1）A novel electrocatalyst,the hollow oxygen-rich multi-metallic nitride Co₂Ni Mo-N,was synthesized using a rhombic cobalt-nickel precursor as a template via a one-step hydrothermal method.The template was dissolved by the proton produced from the hydrolysis of molybdic acid ions in the solvent.The Co,Ni,and Mo elements worked synergistically to activate the activity of Mo and enhance the material’s electrical conductivity.The porous hollow structure exposed sufficient active sites,promoting electron and mass transfer.Abundant oxygen vacancies loweredΔG_H*of H*adsorption,facilitating the Volmer step and ultimately improving the electrocatalytic hydrogen precipitation performance of the material.The Co₂Ni Mo-N catalyst exhibited outstanding HER activity,with a low overpotential of 69 m V and a low Tafel slope of 73.90 m V·dec^-1 in 1 M KOH.（2）Self-supported Co Mo S（Co Mo S@CNF）catalysts on carbon nanofibers were prepared by a one-step hydrothermal method using carbonized,electrospun polyacrylonitrile-dopamine（DMH）polymer fibers.The-OH group on dopamine immobilized 1,2,3,4-butanetetracarboxylic acid on the fiber surface,trapping Co and Mo ions.Co Mo S nanosheets and nanospheres grew on the CNF surface,creating a stacked structure of core-shell and laminar nanosheets that provided abundant active sites,convenient ion diffusion pathways,and channels for the released H₂.Density functional theory calculations showed that the heterojunctions formed by Co S₂ and Mo₂S₃ had low free energy for hydrogen adsorption.The Co Mo S@CNF electrode required only 105.20 m V of overpotential to achieve 10 m V·cm^-2 in 1 M KOH,and the electrochemical performance remained stable even after 20 hours of continuous operation at an overpotential of 10 m V·cm^-2.（3）A one-step hydrothermal method was used to create a ZIF-8 molecular cage containing Co and Mo metal salts.This was followed by an electrostatic spinning technique and heat treatment to produce a nitrogen-doped carbon network coated Co Mo metal cluster catalyst（Co Mo/CN@CNFs/MEL）.By pyrolyzing melamine,the 1D fibers were transformed into 3D networks to cover the nitrogen-doped carbon networks on the fiber surface.The unique structural features,including uniform and dispersed Co and Mo metal clusters,porous nitrogen-doped carbon networks,and continuous conductive carbon nanofibers,make it ideal for the HER reaction.The catalyst exhibited excellent catalytic performance at 1 M KOH due to the synergistic effect of these structures,with a low overpotential(η₁₀=148 m V)and low Tafel slope(98.85 m V·dec^-1).At high current densities,the electrocatalytic performance of the catalyst was comparable to that of commercial Pt/C.