Boosting charge transport in the BiVO₄ photoanode interface modified with an aluminum hydroxide layer for solar water oxidation

Solar light-driven photoelectrochemical (PEC) water splitting into hydrogen (H-2) and oxygen (O-2) is a promising technology for the conversion of light energy to clean chemical energy. However, practical applications are currently limited by the slow rate of its oxygen evolution reaction. In this study, n-type monoclinic BiVO4 photoelectrodes fabricated by a non-vacuum deposition method was developed for an effective PEC system of water oxidation into O-2. Doping Mo ions inside the BiVO4 bulk and modifying the surface with redox-inert aluminum hydroxide, Al(OH)(3) successfully improved the anodic photocurrent density. The resulting Al-modified Mo:BiVO4 exhibited a highly efficient anodic photocurrent density of 2.48 mA cm(-2) at +1.23 V vs. RHE, and an applied bias photon-to-current efficiency (ABPE) of 0.65% at +0.8 V vs. RHE was achieved. Thus, this work is unprecedented in finding that modifying the surface of BiVO4 with an Al species improves its PEC properties and yields high photocurrent density. In fact, surface modification of BiVO4 with Al(OH)(3) layers significantly increased surface wettability, indicating the strong interaction of H2O with the BiVO4 surface. Moreover, Al(OH)(3) as the passivation layers were found to play a significant role in efficient charge carrier transportation on the BiVO4 interface.