Preparations And Electrocatalytic Hydrogen Evolution Reaction Of MoS₂-based Core-shell Structures

Electrochemical water splitting is one of the effective methods for hydrogen production.The high cost and storage scarcity severely limited their practical applications,although traditional noble-metal electrocatalysts have exhibited excellent catalytic activities.Studies revealed that the cheap and efficient transition metal sulfides?such as MoS₂?have been widely applied in the field of electrocatalytic hydrogen evolution reaction?HER?.However,the serious aggregation and poor conductivity for pure MoS₂ have greatly affected the final HER performance.To improve the dispersibility and conductivity of MoS₂,the MOFs derivatives@MoS₂composites with core-shell structure have been prepared through the hydrothermal or solvothermal methods,by using MOFs derivatives as substrates to react with MoS₂.In the composite structure,MoS₂ nanosheets were uniformly coated on the surface of MOFs derivatives.The application of such composite system in the HER field was carried out in detail.The research content was as follows:?1?The dodecahedral Zn-MOF nanoparticles were firstly prepared by a co-precipitation method,and the nitrogen-doped carbon?NC?was further obtained by the high-temperature calcination of MOF precursors.Then the NC@MoS₂ composites were constructed by the hydrothermal method.The resulting composites have a typical core-shell structure,in which MoS₂ nanosheets were uniformly and densely grown on the NC surface.The coating degree of MoS₂ nanosheets could be effectively adjusted by changing the NC content in the composite.Notably,the composite?NC2@MoS₂?with a moderate NC content has the smallest overpotential(200 mV,10 mA cm^-2)and Tafel slope(53 mV dec^-1)as well as high stability and durability.The excellent HER properties of composites can be attributed to the unique core-shell structure and the synergistic interaction of various components.?2?The dodecahedral ZnCo-MOF nanoparticles were prepared by a co-precipitation method,and the metal/nitrogen co-doped carbon?ZnCo/NC?was obtained by a high temperature calcination of MOF precursors.Then the ZnCo/NC@MoS₂ composites were constructed by a hydrothermal reaction.The particle size of internal ZnCo-MOF and the thickness of outer MoS₂ nanosheets could be effectively controlled by changing the Zn/Co molar ratio.Among them,the composite?ZnCo/NC-0.33@MoS₂?with an appropriate Zn/Co ratio exhibited the smallest overpotential(130 mV,10 mA cm^-2)and Tafel slope(60.2 mV dec^-1)together with high cycle stability and durability.The excellent HER properties of composites can be attributed to the appropriate Zn/Co ratio,unique core-shell structure and the synergistic effect of different components.?3?The NiCo-PBA nanocubes were prepared by a co-precipitation method,and the NiCo-P/NC concave nanocubes were obtained by a high-temperature phosphatizing.Then the NiCo-P/NC@MoS₂ composite with core-shell structure were assembled by a solvothermal method.The composites exhibited much better HER performances than both pure components,and the phosphating temperature has a significant effect on the HER properties of composites.Among them,the composite?NiCo-P/NC-350@MoS₂?prepared by a suitable phosphating temperature showed the smallest overpotential(138 mV,10 mA cm^-2)and Tafel slope(78.1 mv dec^-1),as well as high cycle stability and durability.This can be attributed to the intrinsic catalytic activity of hollow NiCo-P/NC,unique core-shell structure,and the synergistic interaction between different components.