Synthesis Of Ni/Nio Heterogeneous Nanosheets For Photo-Assisted Water Electrolysis

Electrocatalytic water splitting is environmentally friendly method of generating renewable hydrogen energy.However,this process of decomposing water is usually accompanied by high overpotential.A simple and universal strategy is developed to enhance hydrogen evolution?HER?and oxygen evolution?OER?of electrocatalysts are of great significance in practical applications.Recently,the surface plasmon resonance?SPR?effect on gold was demonstrated to enhance the electrocatalytic HER or OER activity.As abundant and low-cost alternatives,semiconductors can also efficiently harvest and convert solar energy.However,the exploration of semiconductor photo-assisted enhancement of the activity of electrocatalyst has not attracted the attention of scholars.Herein,we chose Ni/NiO as the model system and synthesized Ni/NiO heterostructured ultrathin nanosheet array,in which Ni serves as HER-active species,while NiO acts as harvesting-light semiconductor and OER-active site origin.It is found that the HER and OER activities of Ni/NiO-NF can be significantly improved?10-and 2.6-fold enhancement of mass activity for HER and OER,respectively?after exposure to light irradiation.After achieving equilibrium,the electrocatalytic performance exhibits high stability even after 12 h.We demonstrate that the greatly enhanced HER and OER activities could be attributed to the photogenerated electrons transferring from excited NiO to HER-active Ni and the photogenerated holes greatly facilitating the oxidation of inactive Ni^II to active Ni^III/IV,respectively.Additionally,the Ni/NiO can also be directly implemented as both anode and cathode in the two electrode system for overall water splitting.When the two electrodes of Ni/NiO are simultaneously illuminated,the current density of 20 mA cm^-2 only requires 1.67 V.This work may open new avenues to fabricate highly efficient water-electrolysis bifunctional electrocatalysts and other renewable energy conversion systems?e.g.,CO₂ reduction and biomass conversion?.