Controllable Preparation And Electrocatalytic Hydrogen Evolution Performance Of Doped Molybdenum Disulfide Loaded Graphene Hybrids

The development and utilization of clean energy has become an important direction for the development of countries around the world,with increasing emphasis on energy and environmental issues.Among them,hydrogen energy is considered to be the most ideal“future energy”,it is a kind of high efficient,clean energy source and can be recycled.Electrocatalytic technology has become one of the best ways to produce hydrogen from electrolyzed water,as it is a hydrogen production technology with high efficiency,energy saving,safety,reliability and pollution.Three-dimensional graphene has a large specific surface area,high porosity and electrical conductivity but has substantially no catalytic activity,while transition metal sulfide has a high electrocatalytic active site,small specific surface area and low electrical conductivity.The two are combined to carry the doped transition metal sulfide nanoparticles onto the graphene three-dimensional network skeleton,so that the respective advantages and synergies can be fully utilized to obtain a high-performance electrocatalytic hydrogen evolution material.In this paper,one step hydrothermal method is used to synthesize ultra-thin molybdenum disulfide nanoparticles/three-dimensional graphene（UT-MoS₂/rGO）and ultra-thin element A-doped molybdenum disulfide nanoparticles/three-dimensional graphene（A-MoS₂/rGO）.The structure and composition of the material were characterized by XRD,Raman,TEM and XPS etal.The electrochemical performance of the electrode was evaluated by cyclic voltammetry curve,polarization curve,Tafel curve slope,cycle stability and AC impedance spectrum.The structure and composition of the chemical properties were analyzed.The results show that a series of reaction conditions are explored in the undoped system:different molybdenum sources,reaction temperature,reaction time,and different MoS₂:rGO mass ratios.Phosphomolybdic acid is used as precursor of molybdenum source,graphene oxide is used as carrier,and L-cysteine is used as reducing agent dopant.The best electrochemical performance of UT-MoS₂/rGO hybrid material is generated by one-step hydrothermal method at 160°C for 6 h.The microscopic morphology is graphene-like,and MoS₂ is grown on the graphene surface in a vertical,ultra-thin,low-stacking manner,it is similar to graphene wrinkles.It can work under a low HER overpotential（-66 mV）,the current density is-10 mA·cm^-2,the overvoltage is-145 mV,the AC impedance is 0.76Ωand a lower Tafel slope(42.9 mV?dec^-1)with a higher durability up to 98%upon conducting CV test at 0.1⁰.2 V for 1000 cirlces.In the doping system,whether it is doped at the A site or B site,it exhibits high catalytic activity.Fe-MoS₂ and MoS_2-xB_x in Fe-MoS₂/rGO and MoS_2-xB_x/rGO exposed more active sites and are grown on the rGO surface in an ultra-thin dendritic vertical.They can work under a low HER overpotential（-58 mV and-62 mV）,when the current density is-10 mA·cm^-2,the overvoltages are-144.8 mV and-153.8 mV,the AC impedance is 0.76Ωand 4.8Ω,and a lower Tafel slope(39 mV?dec^-1 and 45.2mV?dec^-1)with a higher durability up to 94%amd 95%upon conducting CV test at 0.1⁰.2V for 1000 cirlces.This shows its excellent electrochemical stability.