Preparation Three Kinds Of Ni-based Catalysts And Study On Their Electrocatalytic Performance For Oxygen Evolution Reaction

Hydrogen has attracted much attention due to its advantages such as high energy and green cleanliness,making it an ideal substitute for traditional fossil fuels such as coal,oil,and natural gas.Water electrolysis technology has been incorporated into the national sustainable development strategy,and has great development and application prospects.However,the anodic oxygen evolution reaction（OER）of the water electrolytic devices involves complex multi-proton coupling and multi-electron transfer,it is necessary to overcome the high thermodynamic energy barrier,which seriously restricts the development of hydrogen production-related technologies in electrolyzed water.Therefore,there is an urgent need to design and develop an efficient,stable and low-cost anode electrocatalyst that can significantly reduce the OER overpotential to improve the efficiency of electrolytic hydrogen production.At present,transition metal-based catalysts,especially nickel（Ni）based catalysts,are widely used in various energy catalysis fields due to their abundant reserves,low prices,and excellent electrocatalytic activity.This paper prepared three highly active Ni-based oxygen evolution electrocatalyst materials with different morphologies and systematically investigated their physical properties,chemical structure,and electrocatalytic oxygen evolution performance mechanism.The main research contents are as follows:（1）Preparation and OER performance of multi walled carbon nanotubes coupled with Co Ni metal-organic frameworks（Co Ni MOFs-m CNTs）composite materials:A series of different components of Co Ni MOFs and Co Ni MOFs-m CNTs were synthesized through the solvothermal method.By regulating the material structure,carbon nanotube content and other factors,the synergistic effect between Co Ni MOFs and m CNTs was studied;simultaneously optimizing the morphology,structure and electron distribution of Co Ni MOFs-m CNTs,exploring the optimization conditions for the proportion of composite carbon nanotubes and the mechanism for improving OER catalytic performance.The results show that the morphology advantage of nano-sheet and the introduction of m CNTs carrier help to increase the electrochemical active surface area and electric conductivity.In 1.0 M KOH electrolyte solution,Co Ni MOFs-m CNTs composite（6%m CNTs）show the best catalytic performance,with an overpotential of 306 m V at a current density of 10 m A cm^-2,far lower than commercial Ru O₂.At the same time,after 15 hours of durability testing,there was no significant decrease in voltage,indicating good long-term durability for Co Ni MOFs-m CNTs.（2）Preparation and OER performance study of Co Ni MOFs composite materials modified with double ligands(A_2.5B-Co Ni MOFs):A series of A_xB-Co Ni MOFs were synthesized through the solvothermal method.By changing the ratio of carboxyl and hydroxyl groups in the double ligands,the influence of chain length differences and modulation energy between ligands on the electronic structure of the catalyst was studied,and the optimal ligand ratio of A_xB-Co Ni MOFs was obtained.The experimental results show that when the ratio of carboxyl to hydroxyl groups is 2.5:1,A_2.5B-Co Ni MOFs have the best OER performance;the two-dimensional thin nanosheets provide large specific surface area and porosity,which is conducive to the local or long-range transport of protons,and also provide more Active site for alkaline adsorption,thus maximizing the catalytic performance;The mixing ratio of different ligands can change the electronic structure of the composite material,thereby affecting the overall catalytic efficiency of the composite material.At a current density of 10 m A cm^-2,A_2.5B-Co Ni MOFs have an overpotential far lower than that of commercial Ru O₂,and have a stability of more than 15 h under 1.0 M KOH alkaline conditions.（3）Preparation and bifunctional electrocatalytic performance of multi-walled carbon nanotubes,Ni O and Ni Mo O₄nanocomposites（Ni O-Ni Mo O₄/m CNTs）:A synthesized Ni O-Ni Mo O₄/m CNTs with clear Ni O-Ni Mo O₄interface,large specific surface area,and abundant oxygen vacancies were synthesized through a two-step method.The research results show that for the oxygen evolution reaction,the overpotential（277 m V）of Ni O-Ni Mo O₄/m CNTs at 10 m A cm^-2is lower than that of Ni O/m CNTs,Ni O,and commercial Ru O₂-CNPs nanocrystals.For hydrogen evolution reaction（HER）,Ni O-Ni Mo O₄/m CNTs still exhibit good HER activity,initial potential,and lower Tafel.A symmetrical double electrode electrolysis of water cells with Ni O-Ni Mo O₄/m CNTs as positive and negative electrodes was constructed.When the current density reached 10 m A cm^-2,only 1.57 V was needed.The density functional theory calculation shows that the adsorption energy of hydrogen and oxygen-containing intermediates on the surface of Ni O-Ni Mo O₄/m CNTs changes,thus reducing the energy barrier required for HER and OER.Its excellent electrocatalytic activity confirmed that multi-component coordinated regulation and defect design are effective strategies to improve the electrocatalytic activity of transition metal oxides,which can be attributed to the synergistic effect between Ni O-Ni Mo O₄interface,oxygen vacancies and m CNTs carriers.