Oxygen Vacancies Enhanced WO₃/BiVO₄ Photoanodes Modified by Cobalt Phosphate for Efficient Photoelectrochemical Water Splitting

Efficient charge separation is critical for improving the photoconversion efficiency in photoelectrochemical (PEC) water splitting. Herein, we develop an oxygen vacancy (OV)-enriched WO3/BiVO4 photoanode modified by cobalt phosphate (CoPi) cocatalysts for significant enhancement in PEC performances. Experimental results and theoretical calculations based on density functional theory demonstrate that the OV that penetrated from WO3 to the BiVO4 layer will act as a highway for the charge transfer between semiconductor interfaces. Specifically, the existence of oxygen vacancies can not only tune the electronic structure and decrease the energy barrier for the stepped hole transfer but also improve the hydrophilic ability of the electrode. Meanwhile, CoPi as oxygen evolution cocatalysts can further accelerate transport of holes to the electrode surface for the oxidation of water. Benefitted from this, the (WO3/BiVO4)-OV/CoPi photoanode yields a photocurrent of 2.3 mA cm–2 at 1.23 V vs RHE with long-time stability. This work will provide a universal strategy for rational designing and fabricating highly efficient PEC water splitting systems.