Modification Of The Active Sites Of Molybdenum-based Electrocatalysts And Their Performance Research For Hydrogen Evolution Reaction

The molybdenum-based materials,for its low price,good conductivity and excellent stability,have recived tremendous interest in the application of hydrogen evolution reaction(HER),oxygen reduction reaction(ORR),supercapacitors and Lithium-ion batteries.Recently,although a variety of control methods have been achieved for regulating the molybdenum-based catalyst active sites and the intrinsic electronic structure and achieved an in-depth understanding of the catalytic mechanisms and improving catalytic activity.However,the electrocatalytic properties of molybdenum-based materials still need to be improved further,and the reaction mechanism is still unknown.Therefore,it’s high time for us to explore new control methods and construct accurate models to study the relationship among conductivity,active sites and catalytic properties.The purpose of this paper is to analyze the limiting factors of the catalytic performance of the electrode materials during the electrochemical process of hydrogen production from electrolyzed water.Therefore,this paper will mainly introduce the molybdenum-based compounds as cheap and efficient hydrogen production catalyst,a series of design composites were developed based on performance-oriented,including through the combination to achieve conductivity control,the use of defective engineering to achieve more active sites of exposure,through the doping to achieve the regulation of the electronic structure of the hydrogen evolution catalyst.The initial potential decreases,the current density increases,that is,to achieve efficient hydrogen evolution.Based on the above understanding,three methods are adopted to control the conductivity and active sites of molybdenum-based catalysts,and the hydrogen evolution properties of the catalysts obtained by different methods are investigated.The main contents are as follows:(1)MoS2/MoO2 composite catalyst was synthesized by hydrothermal sulfuration treatment based on porous and highly conductive MoO2 substrate.The results show that MoS2/MoO2 are effective HER catalyst in 0.5 mol L-1 H2SO4,with a onset potential of-104 mV vs.RHE,a Tafel slope of 76.1 mV dec-1,a overpotential(240 mV at 10 mA cm-2)and an electrochemical durability.A series of structure characterization and electrochemical tests were applied to study the mechanism of MoS2/MoO2 for HER.The results show that the high hydrogen production activity of MoS2/MoO2 is mainly attributed to the high electrical conductivity and porous structure of MoO2.The one-dimensional pore structure ensures rapid electron transport and ion diffusion.(2)The carbon-molybdenum disulfide(C-MoS2)hierarchical spheres were prepared by simple microemulsion.The results show that the C-MoS2 hierarchical spheres with high electrochemical area and rich defects in MoS2 nanosheets exhibit high electrocatalytic activity for HER,and in the 0.5 mol L-1 H2SO4,an extremely low onset potential(-103 mV),a overpotential(159 mV at 10 mA cm-2)and a small Tafel slope(56.1 mV dec-1).The long-term Cyclic Voltammetry test and i-t test showed that the catalyst has excellent stability.The excellent HER shows that the inverted molybdenum reaction method provides a new method for regulating the molybdenum catalytic sites on the MoS2 electrocatalyst surface.(3)Cobalt and Nitrogen codoped MoO2 Nanowires(Co-N-Mo O2 NWs)were prepared by Co and N co-doping template and substrate MoO2 nanowires.In fact,Co-N-MoO2 exhibits high catalytic activity in both HER and ORR in basic electrolyte.The results indicate that there is an electron transfer progress between MoO2 nanowires and dopant atoms in Co-N-MoO2.The synergistic manipulation of N and Co doping with the opposite electron density states leaded to the relatively moderate bonding energy of Mo-H/O,and caused the enhanced catalytic activity with more catalytically active sites.