Preparation Of Modified Copper Foam Loaded Nickel Based Catalysts And The Study Of Their Catalytic Urea Electrooxidation Behavior

Urea electrooxidation reaction（UOR）has been widely studied as an anodic reaction for new energy fields,such as direct urea fuel cells and urea electrolysis for hydrogen production.However,its application is limited by its high starting oxidation potential and poor catalyst activity.In this paper,a multicomponent complex with excellent performance was prepared for catalytic urea electrooxidation by regulating and controlling the structure and composition of the catalyst using copper foam（CF）as the support,and its electrocatalytic behavior was investigated.The details of the study are as follows:（1）CF_melectrodes were obtained by modifying CF through a"chemical oxidation and reduction"process,and then CF_m@Ni electrodes were prepared by electrochemical deposition of nickel（Ni）nanoparticles on their surfaces,and the behavior of the as-prepared electrodes in catalytic UOR in alkaline environments was studied.The surface of CF_melectrode has nanowire structure,and after loading Ni nanomaterials on it,the surface of nanowire appears rough and uneven film-like structure.Comparing the electrocatalytic performance in CF,CF@Ni and CF_m@Ni electrodes in 1.0 mol·dm^-3KOH and 0.1 mol·dm^-3urea solution,it was proved that CF_m@Ni possessed the best catalytic activity.The oxidation current density reached 332.1 mA·cm^-2at 0.8 V potential in 3.0 mol·dm^-3KOH and 0.3 mol·dm^-3urea solution with good stability,the electrochemically active area（EASA）of the electrode was 2730 cm²,the activation energy（E_a）of the UOR was 8.041 kJ·mol^-1,and the diffusion coefficient(D_urea)was 2.19×10^-3cm²·s^-1.（2）Ni-P complexes were loaded on CF_melectrodes by electrodeposition for catalytic urea electrooxidation.Compared with CF_m@Ni,the nanowire structure was still exhibited on the CF_m@Ni-P electrode after the doping of P.The results of electrochemical studies showed that the oxidation current density reached 658.9 mA·cm^-2at 0.8 V for UOR catalyzed by CF_m@Ni-P in the reaction solutions of 3.0 mol·dm^-3and 0.3 mol·dm^-3for KOH and urea solutions,respectively.The current density fluctuation of this electrode in the stability test was small,with an EASA of 3442.2 cm²,the E_aand D_ureaof UOR were 4.664kJ·mol^-1and 4.05×10^-3cm²·s^-1,respectively.（3）The CF_mloaded Ni_xFe_y-P electrode（CF_m@Ni_xFe_y-P）was prepared by the further addition of iron salt（Fe SO₄7H₂O）during the electrodeposition process for catalytic urea electrooxidation.The Ni_xFe_y-P material is and adheres to Cu nanowires in the form of spheres,and this structure can provide the reaction solution with sufficient transport channels and reaction sites to improve the reaction rate.The results showed that the oxidation current density reached 840.8 mA·cm^-2at a potential of 0.8 V in a mixed solution of 4.0 mol·dm^-3KOH and 0.3 mol·dm^-3urea,and exhibited good catalytic stability.The EASA of the electrode was 3861.8 cm²,the E_aof UOR was 4.87 kJ·mol^-1,and the D_ureawas9.32×10^-3cm²·s^-1.Due to the special structure of CF_m@Ni_xFe_y-P electrode and the synergistic effect between the three elements of Nickel,Iron and Phosphorus,it has superior electrocatalytic performance.In addition,the effects of chemical oxidation time and reduction time during the modification of CF supports,electrodeposition time and potential during the preparation of CF_m@Ni,and the contents of P and Fe in CF_m@Ni-P and CF_m@Ni_xFe_y-P electrodeposition solutions on the electrocatalytic properties of the as-prepared electrodes were investigated in the paper.The effects of reaction solution composition,temperature and scan rate on the properties of CF_m@Ni,CF_m@Ni-P and CF_m@Ni_xFe_y-P during the catalytic UOR were investigated.