A cobalt silicate modified BiVO4 photoanode for efficient solar water oxidation

Abstract

BiVO4 is one of the most promising photoanode materials for photoelectrochemical (PEC) water splitting, but it usually suffers from severe charge recombination. In this work, cobalt silicate (Co-Sil) was decorated on a nanoporous BiVO4 photoanode as a novel cocatalyst by photoelectrophoretic deposition that integrated photoelectrochemical oxidation and electrophoretic deposition. The resultant BiVO4/Co-Sil photoanode reached a photocurrent density of 5.0 mA/cm2 at 1.23 VRHE, around 3-fold enhancement compared with the pristine BiVO4 photoanode. Detailed PEC measurements combined with density functional theory calculations revealed that the excellent performance of the Co-Sil cocatalyst could be attributed to the electron transfer from Co-Sil to BiVO4, the reduced overpotential of the OOH* formation, and the photoelectrochemical oxidation of Co(II). Furthermore, a high photostability was achieved for the BiVO4/Co-Sil photoanode by dissolving NaVO3 in the electrolyte. This work may provide new insights on the rational design and effective fabrication of promising cocatalysts for solar water splitting.