Enhancement of charge separation and hole utilization in a Ni2P2O7-Nd-BiVO4 photoanode for efficient photoelectrochemical water oxidation

Abstract

It is necessary for photoelectrochemical (PEC) water splitting to reduce the electron-hole recombination rate and enhance the water oxidation reaction kinetics. Here, we prepared Ni2P2O7-Nd-BiVO4 composite photoanodes by coupling Ni2P2O7 co-catalysts to neodymium (Nd)-doped BiVO4 surfaces through photo-assisted electrodeposition. The Ni2P2O7-Nd-BiVO4 photoanode exhibits a high photocurrent density of 3.6 mA cm−2 at 1.23 V vs reversible hydrogen electrode (RHE), which is three times higher than that of the bare BiVO4 (1.2 mA cm−2). Detailed characterizations demonstrate that Nd doping reduces the band gap, significantly increases the carrier density and effectively reduces the charge transfer resistance. More importantly, the Ni2P2O7 co-catalyst has multiple roles. Specifically, it can act as a hole extraction layer to accelerate hole migration and inhibit hole-electron recombination. At the same time, it significantly improves the water oxidation reaction kinetics. In addition, it also provides more water oxidation active sites. This work provides ideas for the design and study of efficient BiVO4-based photoanodes.