Preparation Of Efficient Molybdenum Disulphide-Based Catalysts And Their Catalytic Interfacial Chemistry Study For Lithium-oxygen Batteries

In order to achieve conversion of old and new energy and carbon neutrality and carbon peaking,a great deal of researches are currently focused on electrochemical energy storage and conversion technologies to meet the need for efficient energy utilization.Currently,conventional lithium-ion batteries are limited by energy density and cannot meet the requirements for applications in future energy systems.Since the lithium-oxygen batteries were first proposed in 1996,they have attracted a lot of attention worldwide due to their high theoretical energy density(～3500Wh kg-1).Even though lithium-oxygen batteries have such obvious advantages,their practical application is still at an early stage of development,with problems such as low actual energy density,poor rate capability and limited cycle performance.To address these issues,a great deal of researches have been carried out in recent years to construct high performance cathode catalysts,explore stable electrolytes,modify anode and select suitable separator.Among these,the development of high performance catalysts is a key strategy in improving lithium-oxygen batteries performance by promoting the reaction kinetics of the oxygen reduction reaction(ORR)and oxygen precipitation reaction(OER).The cathode catalyst determines the electrochemical performance in lithiumoxygen batteries.Notably,molybdenum disulphide(MoS2)has been widely used in water splitting,supercapacitors,hydrogen evolution reaction and energy storage batteries due to its low cost,high physical/chemical stability,tunable electronic structure and excellent electrocatalytic activity.Mo edges are considered as the most catalytically active sites in MoS2,and these metal edge sites tend to be rapidly deactivated by oxidation or covered by discharge products during ORR in lithiumoxygen batteries systems.Furthermore,due to strong π-π bonding interactions and high surface energy,MoS2 nanosheets are inclined to stacking and agglomeration,and this hinders the full utilization of surface area and impedes ion diffusion pathways,thus leading to slow reaction kinetics and poor cycling stability.To this end,MoS2-based catalysts with a variety of structures have been prepared by different strategies.MoS2based catalysts with various structures have been prepared by different methods,and they all exhibit certain catalytic activity in lithium-oxygen batteries,but the catalytic performance still remain to be improved.In this project,the core-shell MoS2-x@CNTs composites were synthesized by hydrothermal,annealing and subsequent treatment with NaBH4 reduction,and MoS2 nanosheets with sulphur vacancy defects were uniformly coated on the CNTs surfaces.In addition,we also successfully prepared MoS2/CoS2 composites with heterostructure by hydrothermal and chemical vapor deposition for sulphidation.The synthesized materials were used as cathode catalysts for lithium-oxygen batteries to inquire their bifunctional ORR/OER catalytic activity,and reaction products at different stages were characterized to investigate the enhancement factors induced by vacancy and heterostructure engineering on the catalytic performance.This work provides effective strategies to construct efficient and robust cathode catalysts towards advanced lithiumoxygen batteries and other energy-related devices.