Preparation Of Three-dimensional Nickel-based Sulfide And Its Catalytic Performance For Electro-oxidation Of Urea

Urea electro-oxidation has broad application prospects in urea electrolytic hydrogen production and direct urea fuel（DUFC）batteries.Because urea has a wide range of sources and the electro-oxidation products are non-toxic N₂,CO₂,H₂O,it is an ideal clean alternative energy source.Electrolysis of urea-containing wastewater can produce hydrogen and degrade urea,which not only produces energy but also reduces pollution.DUFC is a new energy conversion device that converts chemical energy in fuel into electrical energy.It has high conversion efficiency,low pollution,and a wide range of fuel sources.It effectively saves fossil energy consumption and improves environmental pollution.However,the poor catalytic activity of the urea electro-oxidation catalyst and the excessively high initial oxidation potential limit its progress.Therefore,in this paper,by changing the preparation conditions of the catalyst and combining the performance of the electrode test,the highly efficient catalytically active anode for efficient hydrogen production by urea electrolysis is optimized.The details are as follows:1.Use the control variable method to explore the optimal reactant ratio,temperature and time,and use a simple one-step hydrothermal method to grow a three-dimensional porous Ni₃S₂@Ni foam electrode on a nickel foam substrate.The surface of the Ni₃S₂@Ni foam electrode is composed of loose mesh connections,which provides a large specific surface area and exposes more active sites.The structure-rich reaction site and electrolyte transmission channel can accelerate the interface reaction.The Ni₃S₂@Ni foam electrode has excellent electrocatalytic oxidation performance of urea.The peak current density reaches 752 m A cm^-2at 0.6 V in 5 M KOH+0.33 M urea solution.The reactant diffusion coefficient of the urea electrooxidation process is 5.87×10^-5 cm² s^-1,activation energy is 5.71 KJ mol^-1,Ni₃S₂@Ni foam electrode catalyzes the urea electro-oxidation reaction mechanism is E-C mechanism,the initial oxidation potential of urea is the same as the generation potential of Ni OOH,the higher Direct electro-oxidation of urea can occur.2.After SEM test,the Co-Mo F electrode was optimized,then it was raised to 350°C at2°C/min in a muffle furnace,and calcined for 2 h.using SEM,TEM test optimized the best Co₃O₄,showing a loose sheet-like cross structure,which provided for the compounding of Ni₃S₂ With the excellent template,the performance of different Co₃O₄@Ni foam electrodes was compared by cyclic voltammetry,and further optimization was performed,but the test found that the performance of a single Co₃O₄@Ni foam electrode is not good,and the performance of Co₃O₄@Ni₃S₂@Ni foam electrode is compared to Ni₃S₂ The@Ni foam electrode has been greatly improved.The peak current density at 5 V KOH+0.33 M urea at0.6 V reaches 954 m A cm^-2.From the comparison of the Nyquist curve of the Co₃O₄@Ni₃S₂@Ni foam electrode and the Ni₃S₂@Ni foam electrode,it is found that the former has a smaller arc in the low frequency region of the Nyquist curve in 5 M KOH+0.33M urea solution,and the impedance is smaller,which is more conducive to reaction get on.