Preparation Of Nickel-Based Electrode Materials And Its Electrocatalytic Performance For Overall Water Splitting

Hydrogen production from water electrolysis is an important approach to obtain clean hydrogen energy and solve the global energy shortage problem.However,the slow kinetics of the four-electron oxygen evolution reaction（OER）at the anode is the main bottleneck of this process,thus the required electric potential is usually much higher than the theoretical potential.In order to overcome this energy barrier,designing and developing earth-abundant non-precious metal based electrocatalysts has always been a major challenge in this technology.In this study,we choose advantageous nickel-based materials as the research object to explore the heterogeneous interface engineering and surface oxygen defect strategies as well as their synergistic effect on the performance enhancement of the sulfur-phosphorus doped Ni（OH）₂ nanosheets.It is expected to obtain inexpensive electrocatalysts with high activity and the stability closer to industrial applications.Through a controllable two-step cyclic voltammetry electrodeposition method,a unique"raisins on bread"structured Ni-S-P electrocatalyst with NiS and Ni₂P nanoparticles embedded in amorphous Ni（OH）₂ nanosheets is prepared on nickel foam.In 1 M KOH solution,only a HER overpotential of 120 mV and an OER overpotential of 219 mV are needed to achieve a current density of 10 mA cm^-2.Meanwhile,it shows extraordinary overall water splitting activity in alkaline media(the cell voltage of only1.58 V@10 mA cm^–2)and ultra-long stability(160 h@10 mA cm^–2and 120 h@50mA cm^–2).The results show that the interaction of electrons,the synergy of heterogeneous interfaces and the acceleration of charge transfer promote the HER and OER processes.Combined with a PV solar cell,the Ni-S-P dual-functional catalyst also exihbits advantageous solar-driven water splitting performance,enabling the solar-hydrogen energy conversion efficiency to reach 12.5%.Based on the above part,after one-step cyclic voltammetry electrodeposition,a simple reduction method is adopted to form oxygen vacancy riched NiS/Ni（OH）₂nanosheets（Ni-S-x）,and the methods of XPS,Raman,XAFS analysis are conducted to explore the effect of the formed oxygen vacancies on the structure of the catalyst.The introduction of oxygen vacancies further enhances the OER performance of the Ni-S-x catalyst.At a high current density of 300 mA cm^-2,only an overpotential of 227.9 mV is required,and the Tafel slope is reduced to 38.3 mV/dec.Also,the catalyst has great electrochemical stability（40 h）and regeneration performance of oxygen vacancy active sites.After 3 times of deactivation-regeneration long-term cycle stability assessment（168 h）,the catalyst still shows excellent oxygen evolution activity.