Preparation of vertically aligned WO3 nanoplate array films based on peroxotungstate reduction reaction and their excellent photoelectrocatalytic performance

Abstract Here, we developed a novel, facile, controllable and scalable method based on peroxotungstate reduction reaction to prepare vertically aligned WO3 nanoplate array (NPA) films with preferentially exposed highly reactive (002) facets used in efficient photoelectrocatalytic (PEC) applications. In this method, a slow and controllable reduction of peroxotungstates by ethanol was used, which was the critical step to ensure the uniform and ordered synthesis of orthorhombic WO3 H2O NPA films which assembled directly on F-doped tin oxide substrates under the capping effect of oxalate, and subsequently WO3 H2O NPA films were converted into monoclinic WO3 NPA films by calcination. The effects of synthetic temperature and time, and the concentration of oxalate on the crystalline phase and morphology of the WO3 H2O films were studied systematically. The WO3 NPA film annealed at an optimized temperature of 500 °C exhibited the highest water splitting current density of ∼1.42 mA/cm2 at 1.23 V vs RHE in 0.1 M Na2SO4 under AM 1.5 G illumination. It was further improved by decorating with a Co–Pi co-catalyst, which achieved a more stable current density of ∼1.95 mA/cm2 with an incident photon-to-current conversion efficiency of ∼51% at 400 nm. The WO3 NPA film also showed excellent stability and efficiency (rate constant ∼0.8127 h−1) for PEC degradation of methylene blue.