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

Developing a facile but effective approach to fabricate stable photoelectrocatalytic enhancing photoanodes is crucial for solar water splitting. Herein, a facile hydrothermal-controlled strategy is adopted to synthesize NiFe layered double hydroxide (LDH)/BiVO4 photoanodes with well-controlled oxygen vacancies (Ovac's) by regulating the pH of the precursor solution and hydrothermal time as demonstrated by results of high-resolution transmission electron microscopy, X-ray photoelectron spectroscopy, and electron paramagnetic resonance assays. In optimal experimental conditions (pH = 3.0; hydrothermal time = 20 h), the obtained v-NiFe-LDH/BiVO4 photoanode accelerates the transportation of the photogenerated holes from BiVO4 to the active sites on the surface of NiFe-LDH with Ni and Fe species in the LDH acting as hole-shuttling mediators to facilitate the oxygen evolution reaction. Moreover, loading of NiFe-LDH on BiVO4 significantly enhances the charge separation/injection efficiency of photoanodes. As a consequence, the optimized v-NiFe-LDH/BiVO4 photoanode demonstrates a photocurrent density of 5.81 mA cm–2 at 1.23 VRHE as well as outstanding stability over 80 h in the borate buffer with saturated V5+ ion electrolyte, which advances in long-term stable PEC performance using NiFe-based oxygen evolution cocatalysts on BiVO4.