Study On The Construction Of Nickel Sulfide Heterostructure And Its Urea Electrolysis Performance

Due to the general rise in energy demand,the depletion of fossil fuels,concerns about pollution and global warming,hydrogen and other renewable energy sources have received significant attention.Electrocatalytic water electrolysis for hydrogen production is a sustainable,clean and safe hydrogen production technology.Due to the slow kinetics of oxygen evolution reaction（OER）,the application of water electrolysis to hydrogen production is limited,and the energy-saving hydrogen production can be achieved by replacing OER with urea oxidation reaction（UOR）which has lower thermodynamic potential.Compared with noble metal catalysts,nickel-based catalysts have been extensively studied due to their low cost,easy structure adjustment,and easy formation of active phases.Ni-based catalysts for UOR can be rationally optimized by various surface engineering methods to provide more active sites,ideal crystal phases,and mass transfer channels for catalytic reactions,thereby improving the performance of Ni-based catalysts on UOR performance.Therefore,In this paper,a variety of heterostructures are constructed around nickel sulfide on a nickel foam substrate,and the performance and stability of the catalyst are jointly enhanced through the interaction between multiple components and interfaces.The main research contents are as follows:（1）Co P nanoplates dotted with porous Ni₃S₂ nanospheres for the collaborative enhancement of hydrogen production via urea-water electrolysisTwo-dimensional Co P nanowires were alternately grown on foamed nickel（NF）substrates by hydrothermal-phosphating-electrodeposition method,and then porous Ni₃S₂ nanospheres were modified to obtain a new type of NF/Co P@Ni₃S₂ heterostructure electrocatalyst.In 0.5M urea and 1M KOH solution,the HER overpotential(η_{@10 m A·cm}-2)of NF/Co P@Ni₃S₂ is 68.9 m V,and the UOR voltage is 1.371 V at 50 m A·cm^-2.In the process of electrolysis for 27 h,it showed excellent stability for HER and UOR.When it is applied to a two-electrode electrolysis system,the voltage of urea electrolysis is 1.574 V(E_{@100 m A·cm}-2),which is much lower than that of water electrolysis（E@100 m A·cm-2=1.883 V）.（2）Hetero-structured Ni Mo O₄/Mo S₂/Ni₃S₄ pompons decorated nickel foam electrode for high-efficient urea and urine electrolysisA novel Ni Mo O₄/Mo S₂/Ni₃S₄ heterostructure（NF/Ni Mo O₄-S）was prepared on NF substrate by a mild two-step hydrothermal method,which showed a highly open cashmere ball shape.Whether as the cathode of HER or the anode of UOR,the obtained NF/Ni Mo O₄-S electrode showed good activity(battery voltage 1.548 V at 50 m A·cm^-2)and stability（more than 27h）,which was significantly better than that of its precursor NF/Ni Mo O₄-pre.More importantly,even in the human urine environment,the E_{@100 m A·cm}-2=1.653V and durability of NF/Ni Mo O₄-S are still outstanding.It has a broad practical application prospect in the field of hydrogen production by water electrolysis and in the field of sewage denitrification.（3）High catalytic activity of urea and urine electrolysis initiated by adding Fe and constructing Co Fe P/Ni₃S₂ heterostructureOn the basis of preparing Co P/Ni₃S₂ catalyst,we synthesized Co Fe P/Ni₃S₂ heterostructure catalyst by hydrothermal composite electrodeposition method.The obtained Co Fe P/Ni₃S₂catalyst showed excellent activity for HER/UOR.At a current density of 100 m A·cm^-2,the overpotential of HER was only 172.9 m V,UOR and 1.374 V.In the double electrode system with Co Fe P/Ni₃S₂ as cathode and anode,the cell voltage of 100 m A·cm^-2 is only 1.504 V in1M KOH and 0.5M urea,and the stability is more than 27 h.