Study On Photoelectric Catalyst For Hydrogen Production By Water Decomposition And Carbon Dioxide Reduction

The excessive use of fossil fuels has caused the greenhouse effect,and the sustainable development has been seriously challenged.The development of clean and renewable energy and the conversion of carbon dioxide into high value-added chemicals are effective ways to deal with this problem.This dissertation aims at solving the scientific and technical problems,such as the high recombination rate of the photo-generated charges and poor CO₂RR selectivity stability,in the photocatalytic H₂ evolution from water splitting and CO₂ electroreduction reaction（CO₂RR）,a systematic research was then made from the perspectives of catalyst band regulation and surface regulation.The structure-activity relationship of the Zn_xCd_1-xS/Co P quantum dot for H₂ evolution from water splitting under visible light and N,O co-regulated Ni based catalyst for CO₂RR were studied.The main research contents and results are as follows:（1）Zn_xCd_1-xS with sulfur vacancies/Co P quantum dots（ZCS_v/Co P QDs）heterojunction was constructed via a one-step phosphating process.The experiment results combined with theoretical study show that the phosphating process transforms Co O_x QDs to Co P QDs with P-Zn,P-Cd and S-Co bonds in situ formed at the interface,and generated considerable amount of sulfur vacancies in ZCS_v.The generated S vacancies decrease the band gap of ZCS via forming new defect energy,a type II heterojunction was then obtained what’s more,the formed interface bond enhances the interface compatibility of the heterojunction.The combined strategy of the vacancy engineering and quantum effect facilitated the separation and transfer of photo-generated charges,and resulted in a high activity towards H₂ evolution under visible light(17.53 mmol g^-1 h^-1).The performance of the as-prepared ZCS_v/Co P QDs is at the top of the currently reported Zn_xCd_1-xS based catalysts.（2）A N,O co-regulated Ni nanoparticles（N,O-Ni/N-CMK3）on the mesoporous carbon CMK-3 was prepared to solve the serious hydrogen evolution during CO₂RR and the poor selectivity of Ni catalyst for CO₂RR.The experimental shows that N and O co-regulated Ni surface has a significantly lower adsorption strength for*CO and*H,compared with the metal Ni surface.As a result,N,O-Ni/N-CMK3 exhibits enhanced performance for CO₂RR.The Fararic efficiency of CO is about 97%,and a high J_CO(13.01 m A cm^-2)and TOF(4.25 s^-1)are obtained.This work provides a new strategy to design highly active and selective transition metal catalysts for CO₂RR via adjusting the surface chemical environment.（3）We designed and prepared a bamboo porous carbon nanotubes（N,O-Ni/CNTs）with abundant N,O co-regulated Ni to solve the problem of poor stability of N,O co-regulated Ni particle for CO₂RR.The comprehensive study shows that the N,O co-regulated sigle-atom Ni confined in porous carbon nanotubes has high activity,CO selectivity and electrochemical stability for CO₂reduction.The Faraday efficiency of CO at-0.56～-0.96 V is over 90%,especially,the Faraday efficiency is close to 100%at-0.66 V,and the j _CO for N,O-Ni/CNTs-1000 is as high as 27 m A cm^-2 at-0.96 V.In particular,the catalyst has long durability,and the FEco was still close to 100%after the stability test.This work provides a new idea for the design of high-activity and high-stability CO₂RR catalysts from the atomic level.