Molybdenum-Based Nanomaterials:Preparation And Their Electrocatalytic Properties For Water Splitting

Hydrogen energy as a promising clean energy has attracted much attention recently,and the technology of hydrogen production by electrolysis is one of the green methods of hydrogen production.The key of its research is to develop low cost and high activity catalyst to promote the process of hydrogen production by electrolysis.Molybdenum-based catalyst is of great research value due to its low price and d orbital electronic properties.This paper mainly focused on molybdenum carbide catalyst and nickel-molybdenum based catalyst,through different structural design and electronic structure regulation to improve the performance and stability of the catalyst,studied the surface valence state and atomic coordination law of the catalyst,revealed the catalytic process of the speed step and active site composition.The main research contents are as follows:(1)The Co/Mo2C/Co6Mo6C2@C catalyst was prepared by wet chemical method and sintering method with the metal organic framework material ZIF-67 as cobalt source and ammonium molybdate as molybdenum source.Through the testing and characterization of the phase,morphology,valence state and electrochemical properties of the product,it was found that the product particles formed a hollow structure on the ZIF-67 skeleton.The catalyst required 106 mV and 80 mV to reach an overpotential of 10 mA/cm2 under alkaline and acidic conditions,with a Tafel slope of 78 mV/dec.In addition,Co6Mo6C2 is stable for 60 h and 50 h at current densities of lOmA/cm2 under acidic and alkaline conditions,respectively.Electrochemical activity surface area tests and electrochemical impedance spectroscopy demonstrate that Co6Mo6C2 provides a larger catalytic area and a smaller resistance.Studies have shown that the formation of Co6Mo6C2 strengthens the strong electron coupling between CoMo-C structures and the synergistic effect between Co and Mo can regulate the electronic structure and the D-band center,thus optimizing the adsorption and desorption energy,and finally optimizing the intrinsic activity of the catalyst,and its hollow structure exposes more active sites.Finally,the catalyst showed good hydrogen evolution performance.(2)NiMo oxide array was synthesized on foam substrate by hydrothermal method,and then Ni/NiO/CeO2@MoO3-x catalyst was obtained by high-temperature heat treatment in argon-hydrogen atmosphere.Physical characterization,hydrogen evolution,oxygen evolution and complete hydroelectricity chemical tests were performed on the catalyst.The results show that the oveipotential of hydrogen evolution and oxygen evolution reaction reaching 1000 mA/cm2 are 141 mV and 370 mV,respectively,at 1.0M KOH for Ni/NiO/CeO2@MoO3-x.It takes 1.67 V to reach the current density of 1000 mA/cm2,and the current density has been stable for 600 h.The excellent performance is attributed to the regulatory effects of CeO2 and MoO3-X.On the one hand,they change the electronic structure of Ni and Mo,optimize the hydrogen binding energy,and improve the intrinsic activity of the catalyst.On the other hand,they increase the overall charge transfer rate and the number of catalytic sites,and further improve the catalytic activity.In addition,nanorods covered with particles significantly improve the catalyst’s hydrophilic and gas-phobic properties,accelerate bubble evacuation,and ensure the catalyst’s high current performance.