Preparation Of Fe Doped Molybdenum Disulfide/Graphene Composite And Research On Their Electrochemical Hydrogen Evolution Reaction

With the depletion of petroleum fuel and the serious pollution caused by the irregular use of petroleum fuel,it is imperative to develop new clean energy（hydrogen energy）.Making high-purity hydrogen from a large number of water resources on earth is becoming more and more interested,such as the hydrogen evolution reaction（HER）in electrochemical water splitting is a remarkable technique.However,the hydrogen-production process usually demands the assistance of electrocatalysts due to the existence of electrochemical overpotential.Therefore,it is the key to develop the novel and low cost-efficient electrocatalysts with high catalytic activity for a prerequisite for the application of the H₂ economy.Recently,two-dimensional（2D）layered transition-metal dichalcogenide（especially Mo S₂）has been widely studied as promising hydrogen evolution catalysts for replacing platinum group metals.Due to the good conductivity and rich catalytic sites,the 1T Mo S₂（metallic）has received much attention.However,1T-Mo S₂ exhibits fatal defects:metastable and extremely harsh synthesis conditions,which strictly limit its application.The purpose of the work is to improve the electrocatalytic hydrogen evolution performance of Mo S₂.Combined with its own strength and weakness,Mo S₂was modified by doping with heteroatoms,phase engineering（improving 1T phase from 2H Mo S₂）,coupling conductive substrates.The relationship between the crystal structure,microstructure and HER activity of Mo S₂ was investigated.The main research contents and conclusions are as follows:（1）High 1T content of Fe-MoS₂ nanomaterials was prepared through hydrothermal method.Fe atoms were successfully doped into the crystal lattice of Mo S₂,inducing the partial phase transition from 2H semiconductor phase to 1T metallic phases of Mo S₂,and the existence of 1T metallic phase greatly improves the conductivity of the nanomaterials.Based on the optimized reaction temperature（200℃）and molar ratio of Fe:Mo:S（0.03:1:3.5）,the Fe-Mo S₂ nanomaterials exhibits the best HER performance.The Fe-Mo S₂ has a small overpotential of 248m V at 10 m A?cm^-2 cathodic current density,Tafel slope as small as 56.4 m V?dec^-1 and maintain outstanding stability after 2000 CV cycles simultaneously.（2）Fe-MoS₂/r GO composite were synthesized through hydrothermal method,in which the well-dispersed vertically aligned petaloid-like 1T-Fe-Mo S₂ nanostructures were cleverly integrated into the two-dimensional structure of reduced graphene oxide（r GO）.The r GO provided nucleating sites and Fe-Mo S₂ nanosheets would be induced to vertically grow on the surface of r GO,avoiding aggregation and collapse.Furthermore,the addition of highly conductive graphene further improves the conductivity and stability of the composite.Under optimized graphene content of 25mg,the sample exhibits the best HER performance.The sample has a lower overpotential of 197 m V at 10 m A?cm^-2 cathode current density,the Tafel slope as small as 53 m V?dec^-1 and maintain outstanding stability after 3000 CV cycles simultaneously.