Boosting charge transport in the BiVO 4 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 BiVO 4 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 BiVO 4 bulk and modifying the surface with redox-inert aluminum hydroxide, Al(OH) 3 successfully improved the anodic photocurrent density. The resulting Al-modified Mo:BiVO 4 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 BiVO 4 with an Al species improves its PEC properties and yields high photocurrent density. In fact, surface modification of BiVO 4 with Al(OH) 3 layers significantly increased surface wettability, indicating the strong interaction of H 2 O with the BiVO 4 surface. Moreover, Al(OH) 3 as the passivation layers were found to play a significant role in efficient charge carrier transportation on the BiVO 4 interface.