| "Energy crisis"and"environmental pollution"are major issues facing the world today.It is an urgent problem to be solved to develop new green and environmentally friendly technologies and to find new clean energy.Water electrolysis is a sustainable green energy hydrogen production technology,which is limited by the high overpotential of hydrogen evolution reaction（HER）and oxygen evolution reaction（OER）.Currently,the most effective catalysts for electrolysis of water are Pt/C and oxides of Ru and Ir,etc.,but the high cost and single catalytic activity of noble metals limit their large-scale application.Therefore,it is imminent to develop inexpensive and efficient bifunctional electrocatalysts for overall water splitting.Transition metal sulfides are widely studied alternative materials for electrocatalysts due to their diverse crystal structures and tunable electronic structures.Single-component transition metal sulfides have problems such as poor conductivity and insufficient active sites.The catalytic activity can be effectively improved by constructing heterostructure,heteroatom doping,nanostructure engineering and other surface and interface regulation methods.Based on this,this paper constructs a series of transition metal sulfide composite materials and studies their catalytic performance for electrolysis of water.The details are as follows:（1）Mo S2 has an electronic structure similar to that of noble metal Pt and is an excellent HER catalyst.However,the layered Mo S2 basal surface is inert,with only a few edge active sites.The construction of heterostructure can effectively improve its HER catalytic activity and endow the material with OER catalytic activity.In this work,we prepared Co S2/Mo S2 hollow nanomaterials using ZIF-67 as a precursor and investigated its potential as a bifunctional electrocatalyst for integral water splitting.By optimizing the ratio of Co and Mo in the composite,it was found that Mo S2 could enhance the catalytic activity for HER,Co S2 could greatly enhance the catalytic activity for OER,while Co S2/Mo S2-2 showed good catalytic activity for both HER and OER,achieving the greatest synergy,The overpotentials are 170 and270 m V,respectively.Furthermore,Co S2/Mo S2-2 can efficiently catalyze the total water splitting at a voltage of 1.66 V,which is comparable to the Pt/C and Ru O2 counterparts,demonstrating its practical application.（2）1T phase-Mo S2 has better conductivity and more active sites than 2H phase.In this work,we used nickel foam to support ZIF-67 as a precursor to synthesize 1T-Mo S2/Co3S4/Ni3S2 hybrid catalyst as a self-supporting electrode.1T-Mo S2 can improve the electron transfer in the catalytic process,the abundant interfaces and defects in the material can bring more active sites,and the self-supporting structure can ensure the effective overflow of gas.Based on the above reasons,1T-Mo S2/Co3S4/Ni3S2 exhibits small overpotentials of 50 and 240 m V for HER and OER at 10 m A cm-2,while it can achieve 100%Faradaic efficiency at a small cell voltage of 1.55 V Catalyzes water splitting.（3）Heteroatom doping is one of the effective strategies to improve the catalytic activity of catalysts.In this work,we synthesized hollow Co V LDH through a simple reaction using nanoprism-like Co2（OH）2CO3 as a precursor,and further sulfurized it into V-doped Co S2.Electrochemical tests showed that V-Co S2 has a higher catalytic performance,and its OER overpotential at 10 m A cm-2 is 277 m V,which is significantly better than that of undoped Co S2（376 m V）,demonstrating the role of heteroatom doping in transition metal sulfides.Improved feasibility. |
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