Synthesis Of Two Dimensional Materials Supported Molybdenum Sulfide Catalysts And Their Performance In Electrochemical Hydrogen Evolution

Hydrogen is regarded as an important energy carrier for the new century,and water electrolysis is one of the most important ways to product hydrogen efficiently.Molybdenum sulfide is a promising candidate to replace noble metals as a cheap and high efficient electrocatalyst for hydrogen evolution reaction（HER）.However,the limited active sites and the unsatisfactory electrical conductivity prevent its application in HER.Many studies have shown that the combination with support materials with high conductivity and large specific surface area could improve the performance of molybdenum sulfide in HER.In this thesis,we try to develop the methods to prepare the porous nitrogen-doped graphene and MXenes supported molybdenum sulfide catalysts and systematically investigate their catalytic performance in HER.The main contents and results are summarized as follows:（1）The porous nitrogen-doped graphene was firstly prepared by one pot method,and the non-stoichiometric molybdenum sulfide（Mo S_x）with abundant active sulfur sites on its basic plane was grown on the porous nitrogen-doped graphene via the pyrolysis method.Therefore,a new composite material（Mo S_x@CN）with a special structure and morphology was obtained.Experiments demonstrate that the introduction of the porous N-doped graphene facilitates the fast transfer of charge and the efficient infiltration of electrolyte,and the N dopants could be as the nucleation sites for Mo S_x,which effectively inhibits the agglomeration of Mo S_x to expose more active bridging S₂^2-sites.In 0.5 M H₂SO₄,the Mo S_x@CN catalyst shows an outstanding HER activity,which the overpotential is only 256 m V at 100m A cm^-2 with a low Tafel slope of 49 m V dec^-1.In addition,Mo S_x@CN also has a good electrochemical stability.（2）The Ti₃C₂T_x nanosheet was prepared by etching Ti₃Al C₂ with LiF and HCl,and Ti₃C₂T_x was used as a substrate to grow non-stoichiometric Mo S_x via the rapid pyrolysis of（NH₄）₂Mo S₄.For the obtained Mo S_x-Ti₃C₂T_x composite,we found that the introduction of Ti₃C₂T_x could expose more catalytically active sites of Mo S_x and accelerate the charge transfer rate,which significantly improves the HER activity of Mo S_x-Ti₃C₂T_x in 0.5 M H₂SO₄.The Mo S_x-Ti₃C₂T_x only requires an overpotential of240 m V to achieve the current density of 10 m A cm^-2,and the corresponding Tafel slope is 88 m V dec^-1.Meanwhile,Ti₃C₂T_x effectively reduces the agglomeration of Mo S_x in the catalytic process,and further improves the stability of the catalyst.