Preparation Of Dual-function Nickel-Cobalt Based Self-supported Electrode And Its Performance In Hydrogen Production By Electrocatalytic Electrolysis Of Urea

Nature has abundant water resources,and hydrogen production from water electrolysis is one of the main sources of hydrogen for green and sustainable development in the future.However,the slow kinetic process of water electrolysis process limits the overall efficiency of the reaction,so the development and design of catalysts with excellent performance is the key to realize the commercial application of catalysts.Nickel-and cobalt-based catalysts are widely used in electrocatalytic hydrogen production due to their abundant reserves,low price and excellent catalytic performance.Morphology design,structural control,defect engineering,electronic control,doping technology,heterostructure construction and other strategies were used to optimize the performance of the catalysts.In this paper,the morphology design and hetero-atom doping of composite materials were studied.The prepared composite materials were used in the electrolysis of aquatic hydrogen and electrolysis of urea for hydrogen production.The main contents are as follows:(1)Al doped Co2Fe(CN)6 nanocube were grown in situ on nickel foam(NF)substrate.The morphology is composed of many closely bonded and uniformly distributed nanocubes.The reaction path of Urea oxidation reaction(UOR)is different from that of most other nickel-based catalysts,which use NiOOH derivatives as catalytic active site to significantly improve the catalytic performance of the catalyst for UOR.In addition,the synergistic effect of Co2Fe(CN)6 and the doping of Al is attbibuted to the catalytic activity.UOR overpotential is 80 mV(vs.RHE)to achieve a current density of 100 mA/cm2.The Tafel slope is 100 mV/dec.The hydrogen evolution reaction(HER)requires an overpotential of 167 mV(vs.RHE)at the current density of 10 mA/cm2 and the Tafel slope is 129 mV/dec.In addition,the catalyst material can remained its electrocatalytic acvitiy steadly for 24 h,indicating that it has excellent electrocatalytic activity and stability.(2)Cl-NiCo(PO4)(OH)nanosheets were in situ grown on nickel foam by a simple one-step electrochemical deposition method.The porous nano-flake morphology provides a large specific surface area,and also provides a way for the bubbles generated in the process of water decomposition to dissipate quickly,thus improving the HER performance.In addition,the doping of chloride ions could increase the active sites of the composite,which improved the electrocatalytic performance of the composite.The electrocatalyst requires an overpotential of 61 mV(vs.RHE)at the current density of 10 mA/cm2 and the slope of Tafel is 113 mV/dec.The current density of the material was stable for 24 h,indicating its excellent electrocatalytic activity and stability.Using self-supporting electrode Cl-NiCo(PO4)(OH)/NF as the cathode and Al-Co2Fe(CN)6/NF as the anode,a two-electrode cell was constructed for "water(1.0 M KOH as the electrolyte)and Urea electrolysis(1.0 M KOH+0.5 M Urea as the electrolyte),respectively.The full-cell needs voltages of 1.68 V and 1.60 V at current density of 100 mA/cm2 for water and urea electrolysis,respectively,which are superior to the traditional precious metals Pt/C‖IrO2 electrolytic cell.