Modulation Of The Electronic Structure Of Nickel-based Catalysts As Wells As Urea Electro-oxidation Performance

Developing sustainable energy production and storage technologies applied to mitigate the energy crisis and environmental pollution has become very important due to the continuous depletion of traditional fossil fuels and energy sources.In recent years,the preparation of new energy sources and the realization of energy conversion by electrochemical methods are hot research topics.Among them,urea oxidation reaction（UOR）has received a lot of attention.On the one hand,UOR can be applied as an anode reaction in the fields of hydrogen production by water electrolysis and rechargeable metal-air batteries;on the other hand,UOR can change the environmental problems such as water pollution and air pollution brought by traditional urea-containing wastewater.Among them,efficient and inexpensive electrocatalysts are the key.Based on this,two cost-effective catalyst materials were synthesized and used in urea electrocatalytic oxidation reaction in the paper.The relative work and contents are as follows:1.In this experiment,a series of Ni Co alloy catalysts with different ratios were synthesized by a hydrothermal synthesis method by modulating the doping amount of Co.The doping of Co elements can modulate the electronic structure but the excessive increase of its amount can further decrease the activity of the catalyst.In this case,there is an optimum value of Co doping.The catalytic activity was effectively improved compared to the pure Ni monolithic catalyst when the Ni/Co ratio was 4:1,with onset potential(E_onset)of 0.23 V vs.Ag/Ag Cl,Tafel slope of 63.9 m V dec^-1and peak current density（j_p）of 51.5 m A cm^-2,superior to metal Ni and other Ni Co alloys.Subsequently,the Ni4Co1 catalyst was applied to DUHPFC with a power density of 6.41 m W cm^-2.2.A series of Co single-doped NSH,Mo single-doped NSH and Co/Mo co-doped NSH catalysts with different ratios were synthesized.Co and Mo elements can effectively modulate the pure Ni S/Ni₃S₄electronic structure,while Co can reduce the overpotential of the reaction and Mo can effectively improve the CO₂poisoning phenomenon during the urea reaction.Subsequently,a series of single-and double-ion doped NSHs were analyzed for their electrochemical performance,and the best catalytic performance was obtained when their Co content was 10%and Mo content was 5%.The optimized assemblies showed advanced UOR performance compared to pure Ni S/Ni₃S₄and Ni S/Ni₃S₄doped with single Co/Mo elements,providing 147.1 m A cm^-2at 1.6 V and operating for more than 18 hours without degradation.The assembly of Mo_0.05,Co-NSH catalyst into DUHPFC showed good performance with open-circuit voltage and power density of 0.86 V and 5.96 m W cm^-2,respectively.This work prepared efficient electrocatalysts with multi-metal doping and heterogeneous phase structure providing an excellent avenue for electrochemical energy conversion and wastewater treatment applications.