Preparation Of Non-precious Metal-based(Ni Co Mo)Hierarchical Structure And Study On Its Performance Of Electrocatalytic Hydrazine Oxidation Reaction

With the depletion of energy and the deterioration of environmental degradation,hydrogen energy,as a green and environmentally friendly secondary energy source,has gradually used by people.Among them,hydrogen produced by electrolyzed water is gradually widely used due to its simple,non-polluting process and high-purity of hydrogen production.However,the actual cell voltage for water electrolysis is high,and the power consumption is higher.In the emergency hydrogen production scenario,it is a meaningful challenge to reduce the electrical energy consumption of hydrogen produced electrochemically to reduce the heavy dependence on power resources.Electrolytic hydrogen generation based on the hydrazine oxidation reaction(HzOR)and hydrogen evolution reaction(HER)is a promising method of electrolytic hydrogen production,which has the advantages of environmental protection and no carbon-containing by-product emissions.Moreover,the required cell voltage(400 to 600 mV)for electrolysis of hydrazine(N2H4)is much lower than that for electrolysis of H2O.At present,the most commonly used high performance non-precious metal electrocatalysts,the overpotential of HzOR is still as high as 300 to 500 mV at 10 mA cm-2,and the current density is only several milliamperes per square centimeter at a potential of 0 V(vs.RHE).Therefore,design and preparation of low-overpotential,high-efficiency HzOR electrocatalysts have become the main research purpose of this paper.The main research contents of this article are as follows:(1)Design and preparation of CuxO@NiCoP/NF hierarchical structure electrode and research on HzOR performance:by hydrothermal-phosphating method,NiCoP nanowires were grown in-situ on the 3D foam nickel(NF),and then Cu nanoparticles were grown on the NiCoP nanowires via facile electrodeposition,and finally the surface copper was incompletely oxidized prepared CuxO@NiCoP/NF electrode.By changing the deposition current and time in the electrodeposition step,and the oxidation temperature and time in the oxidation step,it was confirmed that the best preparation conditions.In the end,CuxO@NiCoP/NF showed better HzOR performance,with a low onset potential of-78 mV,and a large current density 156.8 mA cm-2@0 V.However,during the electrocatalytic HzOR process,the CuxO@NiCoP/NF is easily oxidized,and has poor electrochemical stability.Therefore,how to improve the electrocatalytic activity and stability of the material HzOR is a key issue.(2)NiCo(OH)x@NiCoP/NF hierarchical structure electrode and its HzOR&HER bifunction performance study:using the highly conductive NiCoP prepared in the previous chapter as the intermediate conductive matrix,ultrathin NiCo(OH)x nanosheets are in-situ grown on NiCoP to construct a hierarchical self-supported NiCo(OH)x@NiCoP/NF electrode.The NiCo(OH)x@NiCoP/NF exhibits excellent performance for both HzOR and HER:display a low onset potential of-91 mV for HzOR,and the current density at 0 V is as high as 223 mA cm-2;the overpotential for HER is only 164 mV at a current density of 100 mA cm-2.When used as the bifunctional electrode for both HzOR and HER,an extremely low cell voltage of 0.03 V is rquired at a current density of 10 mA cm-2 during electrolysis of N2H4,which is less than 2%that for the traditional process of water electrolysis.This work opens a promising way for electrolytic hydrogen generation at an extremely low cell voltage.(3)Design and preparation of sea urchin-like NiMo4N5/NF electrode and its bifunction performance of HzOR&HER:the hydrothermally synthesized NiMoO4 sea urchin micron column,subjected to high temperature carbon coating treatment,to synthesize N-doped and C-coated hierarchical micro-nano structure NiMo4N5/NF electrode.NiMo4N5/NF electrode exhibits excellent performance for both HzOR and HER:display an onset potential of-13 mV for HzOR,and the current density at 0 V is as high as 139 mA cm-2;the overpotential for HER is only 91 mV at a current density of 100 mA cm-2,and show a high current density 199 mA cm-2@-0.15 V.When used as the bifunctional electrode for both HzOR and HER for electrolyzing N2H4,only required an extremely low cell voltage of 0.2 V at a large current density of 100 mA m-2.After the electrolysis,the NiMo4N5/NF electrode still has high electrocatalytic activity for HzOR and HER,and the morphological structure and crystal structure have not changed greatly,showing excellent electrocatalytic stability.This work provides a promising method for stabilizing electrolyzed hydrogen for a long period of time under low cell voltage.