Study On Molybdenum Disulfides And Nitrides For Electrocatalytic Hydrogen Evolution Reaction

Production of clean energy is an important issue in the new era to deal with the shortage of non-renewable energy.As the ideal clean energy in the 21st century,hydrogen has gradually attracted the attention of researchers.Hydrogen can be produced through efficient and environmental friendly ways,such as electrochemical methods.However,there are still some limiting factors such as high cost and poor stability of electrode catalysts to realize comparative activity.In this thesis,we report the fabrication of molybdenum disulfide and molybdenum nitrides for electrocatalytic hydrogen evolution reaction?HER?to replace noble metal.The specific content mainly includes the following aspects:Firstly,a thin layer of molybdenum disulfide?MoS₂?nanosheet is synthesized by hydrothermal method.Compared with bulk MoS₂,the as-prepared thin layer MoS₂nanosheet shows better activity under acidic conditions.Further nickel chloride is added during the preparation process to synthesize NiS_x-MoS₂ composite.Compared with pure MoS₂ and NiS_x,the as-prepared NiS_x-MoS₂ composites exhibit improved HER activity in 0.5 M H₂SO₄,only needs 218 mV to achieve the current density of 10mA cm^-2.The optimum amount of NiS_x in the composite is also investigated which we find that when adding 20%Ni of the amount of MoS₂ gives the best activity,namely NiS_x-MoS₂-20%.XRD,SEM,TEM and XPS are used to investigate the structure information of the composite.When the loading amount of NiS_x is low?NiS_x-MoS₂-10%?,the modification effect of NiS_x is insignificant.When the loading was too high?NiS_x-MoS₂-30%?,the surface of MoS₂ is almost completely covered with NiS_x which reduces the amount of active sites.Mo₂N nanoparticles uniformly dispersed on nitrogen-doped carbon substrate?Mo₂N@NC?are synthesized via thermal decomposition under Ar atmosphere and melamine and MoO₃ are used as precursors in the preparation process.HNO₃pretreatment of melamine is used to improve N/C ratio in the precursor,XRD,FT-IR and element analysis are used to analyses the effect of this pretreatment.The improved N/C ratio of precursor can effectively ensure the nitridation of MoO₃ to obtain Mo₂N.HER activity of Mo₂N@NC is tested in 1 M KOH and the composites exhibit excellent HER activity which only needs overpotential of 85 mV to achieve the current density of 10 mA cm^-2.