Hydrothermal-Dependent Oxygen Vacancy-Rich NiFe Layered Double Hydroxide/BiVO₄ Photoanodes for Stable Solar Water Splitting

Developing a facile but effective approach to fabricatestablephotoelectrocatalytic enhancing photoanodes is crucial for solar watersplitting. Herein, a facile hydrothermal-controlled strategy is adoptedto synthesize NiFe layered double hydroxide (LDH)/BiVO4 photoanodes with well-controlled oxygen vacancies (O-vac's) by regulating the pH of the precursor solution and hydrothermaltime as demonstrated by results of high-resolution transmission electronmicroscopy, X-ray photoelectron spectroscopy, and electron paramagneticresonance assays. In optimal experimental conditions (pH = 3.0; hydrothermaltime = 20 h), the obtained v-NiFe-LDH/BiVO4 photoanodeaccelerates the transportation of the photogenerated holes from BiVO4 to the active sites on the surface of NiFe-LDH with Ni andFe species in the LDH acting as hole-shuttling mediators to facilitatethe oxygen evolution reaction. Moreover, loading of NiFe-LDH on BiVO4 significantly enhances the charge separation/injection efficiencyof photoanodes. As a consequence, the optimized v-NiFe-LDH/BiVO4 photoanode demonstrates a photocurrent density of 5.81 mAcm(-2) at 1.23 V-RHE as well as outstandingstability over 80 h in the borate buffer with saturated V5+ ion electrolyte, which advances in long-term stable PEC performanceusing NiFe-based oxygen evolution cocatalysts on BiVO4.