Preparation Of Cobalt-based Multi-Metal Nanostructured Electrocatalyst And Their Electrocatalytic Performance For Water Splitting

The huge increase in fossil fuel consumption has led to an increase in global energy demand.Driven by climate change and environmental issues,mankind is committed to research on renewable energy.Hydrogen is considered to be an ideal renewable energy source for replacing traditional fossil fuels due to its high energy density and no carbon emissions.Electrochemical water splitting can produce H₂ at the cathode and O₂ at the anode,which is of great significance for improving the energy crisis.However,due to the polarization effect caused by some mechanical side effects of the electrochemical process,a potential barrier will appear at the interface between the electrode and the electrolyte.Therefore,it is necessary to construct an effective catalyst to reduce the overpotential of each reaction in order to complete the efficient water splitting reaction.Noble metal catalysts（materials based on Pt and Ru/Ir）are the electrocatalysts that can best promote the hydrogen evolution reaction and the oxygen evolution reaction.However,these catalysts are expensive and scarce in stock,making it difficult to achieve large-scale applications.Therefore,seeking low-cost and abundant non-noble metal electrocatalysts on the earth has become the research direction for the development of high-efficiency electrocatalysts.Metal cobalt（Co）,as a non-noble-metallic element abundant in the earth,has different valences(Co^II/Co^III),and cobalt-based compounds have a variety of electronic structures.These advantages make Co-based electrocatalysts an ideal substitute for precious metal catalysts.This thesis intends to develop a series of new cobalt-based multimetal nano-arrays electrocatalysts,explore its electrocatalytic water splitting performance,and study the catalytic performance enhancement mechanism.The main exploration contents are as follows:1.Taking Ni Co LDH nanosheet array as the precursor,by introducing[Fe（CN）₆]^3-for ion exchange,further preparing Ni Co P PBA nanocubes/Ni Co LDH nanosheets precursor,and finally preparing Fe-Ni Co P/Ni Co P/NF nanocubes/nanosheets arrays by phosphating reaction.It has excellent OER performance,and only needs 201 m V to achieve a current density of 10 m A cm^-2,and has a good durability,which can be maintained for 50 hours at a current density of 10 m A cm^-2.The excellent OER performance of Fe-Ni Co P/Ni Co P/NF is mainly attributed to its rich interface structure,which is beneficial to expose more active sites and promote charge transfer,thereby enhancing the electrocatalytic OER performance.2.The Zn and F co-doped Ni Co P nanoprism arrays（Zn/F-Ni Co P/NF）were synthesized by hydrothermal method and low-temperature phosphating method with foamed nickel as the substrate.The prepared Zn/F-Ni Co P/NF nanoprism arrays have excellent HER(η₁₀=59 m V),OER(η₅₀=285 m V)performance and excellent durability.In addition,it has excellent overall hydrolysis performance,reaching a current density of 10 m A cm^-2 only needs to provide an overpotential of 1.568 V,and can perform a stability test for 40 h.Catalytic mechanism studies have shown that the high performance of Zn/F-Ni Co P/NF is due to the distortion of the crystal lattice caused by Zn/F co-doping,resulting in more defects and exposing more active sites,while the introduction of heteroatoms also helps to promote synergy and accelerate the electron transfer rate,thereby improving Catalytic activity.3.The Co₉S₈ nanoneedles grown on nickel foam were used as precursors.By the method of electrodeposition,a layer of Ni Fe-LDH nanosheets was further loaded on the precursor to prepare the Co₉S₈ nanoneedle@Ni Fe-LDH nanosheet core branch hierarchical system structure Co₉S₈@Ni Fe-LDH HAs).Co₉S₈@Ni Fe-LDH HAs/NF shows high catalytic performance for OER and HER,and the overpotentials at 10 m A cm^-2 are 190 and 145 m V,respectively.The theoretical calculation results show that the synergy between Co₉S₈ and Ni Fe-LDH can promote high catalytic performance by reducing the energy barrier of HER and OER.When Co₉S₈@Ni Fe-LDH HAs are used as anode and cathode electrocatalysts,they can provide a current density of 10 m A cm^-2 at a low battery voltage of 1.585 V and have an excellent long-term durability.