Preparation Of Molybdenum-based Composite Material And Its Application In Hydrogen Evolution Of Electrolyzed Water

The hydrogen evolution reaction（HER）of electrolyzed water is a stable and convenient way to obtain a large amount of hydrogen.The overpotential of HER requires an excellent electrocatalyst to adjust.Molybdenum-based materials have received extensive attention due to their superior hydrogen adsorption energy and platinum-like d-band state.However,the high-temperature preparation conditions of molybdenum-based compounds are likely to cause the product particles to sinter and collapse,which will significantly reduce the number of active sites in the catalyst.The introduction of carbon support,heteroatom doping,formation of composite structure and other means can improve the activity of the catalyst.Carbon is a commonly used conductive structure material.When the carbon source is mixed with the precursor and sintered,the resulting carbon layer can play a role in space confinement,increase the material’s conductivity and reduce the interface resistance.In this paper,two different molybdenum-based catalysts are generated by phosphating and direct phosphating of the precursor after in-situ sulfurization,and the relationship between the physical structure and chemical composition of the material and the electrochemical performance are explored.The specific research is as follows:（1）MoS₂ nanomaterials produced after high-temperature vulcanization of MoO₃/DDA and sulfur powder are used as precursors,and NH₄H₂PO₂ is used as a source of phosphorus and nitrogen,and Mo S₂ is subjected to high-temperature phosphating to prepare Mo S₂/Mo P composite materials.The in-situ coating of carbon,the combination of Mo S₂/Mo P materials and the double doping of nitrogen atoms ensure the continuity of electrons and mass transfer.The Mo S₂/Mo P composite has significant catalytic performance:the overpotential is 128 m V at an exchange current density of 10 m A·cm^-2,the Tafel slope is 87 m V·dec^-1,and the durability exceeds 10 h.Compared with the precursor Mo S₂,the Mo S₂/Mo P composite has a smaller impedance and a larger electrochemically active surface area.（2）Using MoO₃/DDA as the precursor and Na H₂PO₂ as the phosphorus source,the two are directly phosphated at high temperature.The ultra-thin carbon layer generated by the carbonization of dodecylamine can well wrap the molybdenum phosphide nanosheets and maintain the precursor.The flaky morphology and the formation of many nanoparticles on the surface increase the active area.The Mo P/C nanocomposite produced by phosphating at 800℃has the best HER performance.In 0.5 mol·L^-1 H₂SO₄,the overpotential of Mo P-800 is 111 m V at an exchange current density of 10 m A·cm^-2.The Phil slope is 68 m V·dec^-1,the electric double layer capacitance is 47 m F cm^-2,and the stability is 27 h.