Preparation And Electrocatalytic Performance Of Metal Chalcogenides

As an ideal energy carrier,H2 has the highest energy density per unit mass.When it is burned in engines or converted into electricity in fuel cells,it only produces H2O.The clean and renewable H2 production method is to electrolyze water using renewable energy(especially solar energy).Electrochemical water splitting is divided into two half reactions:hydrogen evolution reaction(HER)and oxygen evolution reaction(OER).They both require catalysts to reduce the electrochemical overpotential.Noble metal-based catalysts,such as Pt,Ir and Ru,are the most efficient catalysts for HER and OER.However,the low reserves and high prices of these precious metals limit their large-scale application.Metal chalcogenides possess the advantages of adjustable electronic structure,abundant active sites,low cost,environmental friendliness and excellent electrochemical performance.Metal ions can be in single,double or polymetallic forms,and anions associated with metal cations include oxygen,sulfur,selenium,and tellurium ions.In order to make full use of metal chalcogenides,it is necessary to develop low-cost and efficient methods to control their composition and electronic structure.Common regulation strategies include the construction of Schottky structures,heterostructures,metal doping and defect control.This paper focuses on the control strategies of two metal chalcogenides,which are applied to electrochemical HER,OER and Zn-air batteries.The main research contents are as follows:First,CoO/CoP heterostructure catalyst was synthesized through a simple oxidation-phosphation strategy and the HER catalytic performance was investigated.In 1 M KOH electrolyte,CoO/CoP heterostructure catalyst only needs a low overpotential of 236 mV to achieve a current density of 400 mA·cm-2,which is 249 mV lower than that of unphosphated Co3O4 and exceeds most reported non-noble metal-based HER electrocatalysts.Experimental results show that the strong electron transfer on the CoO/CoP interface promotes the occurrence of HER.The relatively high solar-to-hydrogen efficiency of 10.5%and excellent stability prove its potential in solar-driven water splitting.Then,Fe-doping CoSe catalyst(Fe-Co-Se)was synthesized by a hydrothermal method and used as an efficient OER catalyst.In 1 M KOH electrolyte,Fe-Co-Se exhibits a low overpotential of 211 mV at a current density of 10 mA·cm-2,which is 61 mV lower than that of pure CoSe.In addition,the catalyst achieves a high current density of 1200 mA·cm-2 at a low overpotential of 346 mV.In-situ and ex-situ spectra clarified the formation of the iron/cobalt oxyhydroxide/hydroxyl(Fe/CoOOH),which are real active species.In addition,using Fe-Co-Se as the air electrode,the maximum power density of Quasi-solid-state Zn-air battery is 91 mW·cm’2.Furthermore,the galvanostatic discharge curve of portable Zn-air battery at current density of 10 mA·cm-2 stays stable up to 60 h,which is better than precious Ir/C catalyst under the same conditions.