Study On Electrocatalytic Properties Of Anionic/Cationic Regulated Transition Metal(Hydr) Oxides

With the growing energy crisis and environmental problems,the development of clean energy is critical to the sustainable development of society.As a promising clean energy,hydrogen energy has been widely concerned because of its high energy density and environmental friendliness.Among various hydrogen production technologies,electrocatalytic water splitting is considered to be one of the cleanest,environmentally friendly and sustainable hydrogen production methods.Electrocatalytic water splitting involves two important half-reactions:oxygen evolution reaction?OER?and hydrogen evolution reaction?HER?.Currently,noble metal oxides?RuO₂ and IrO₂?and Pt/C are the superior electrocatalysts for OER and HER,respectively,but their high cost and limited resource greatly hindered their wide application.Therefore,current research focuses on the development of low-cost,abundant and highly-efficient OER and HER electrocatalysts.Studies have shown that anionic/cationic regulation is an effective way to adjust the electronic and catalytic properties of the catalyst.In this thesis,the electrocatalytic performances of the transition metal?hydr?oxides are mainly modified by anionic/cationic regulation.The main contents are as follows:?1?Using the layered double hydroxides?LDHs?as model,CoAl LDHs was treated with dielectric barrier discharge plasma containing S^2-aqueous solution?modified water DBD plasma?to rapidly achieve anionic regulation and cationic defects.The obtained samples were characterized by SEM,TEM,AFM,XRD and XPS.The results showed that the modified water DBD plasma technology could induce the formation of amorphous and porous structures to effectively increase the flexibility of the structure and the number of active sites.In addition,the etching effect of the plasma induced the formation of Al³⁺vacancies,which could expose more active sites and regulate the electronic structure of the adjacent active sites of Co.S^2-regulation could increase conductivity of CoAl LDHs and regulate chemical adsorption for promoting interaction with reactants.The electrochemical results showed that the modified CoAl LDHs had superior OER catalytic performance.The current study provides a simple,rapid and effective way for cationic defect and anionic regulation to design new catalysts for electrochemistry.?2?Using the spinels-structured oxides as a model,zirconium?Zr?regulation of CoFe₂O₄?CoFe oxides?nanosheets were grown on nickel foam?NF?as highly-efficient electrocatalysts toward both OER and HER via a one-step solvothermal method.The unique nanosheets structure on 3D NF provided a larger active surface area,more reaction sites and fast electron transportation.The experimental results demonstrated that the incorporation of Zr into CoFe oxides could tune the nanosheet morphology and electronic structure around Co and Fe sites to effectively enhance the intrinsic activity of active sites.Electrochemical impedance spectroscopy?EIS?and density functional theory?DFT?calculation further demonstrated that Zr regulated CoFe oxides had higher electrical conductivity and faster electron transfer rate than pure CoFe oxides.Therefore,the as-synthesized Zr regulated CoFe oxides nanosheets had superior OER and HER performance.This study opens up opportunities to rational design and optimizes the electronic structure of electrocatalysts for practical water splitting.