A novel synergy of Co/La co-doped porous BiVO4 photoanodes with enhanced photoelectrochemical solar water splitting performance

Abstract

This work discussed a straightforward approach to manufacture Co-, La-, and Co/La-doped BiVO4 nanoporous films. The effect of doping in the photoelectrochemical (PEC) water splitting performance was evaluated through PEC test and the strong electronic correlation of the framework in the density functional theory (DFT) calculation was taken into account. It was shown that replacing Bi atoms with Co would decrease the bandgap of BiVO4, but doping with La shifted the bandgap from indirect to direct and resulted in the negative shift of onset potential. Furthermore, doping Co and La ions into BiVO4 also introduced deep levels into the BiVO4 bandgap. After the optimization of the mole ration of Co to La, the (0.7/0.3)Co/La:BiVO4 photoanode achieved a high photocurrent density of 3.65 mA cm−2 under the simulated solar irradiation with a bias of 1.23 VRHE, resulting in an H2/O2 production rate of 57.6/25.8 μmol cm−2 h−1. More importantly, without any co-catalysts and hole scavengers, the photoanode presented a favorable stability during 16 h test. The enhanced PEC performance was mainly due to improved visible light absorption and carrier separation ability. Both the experimental and theoretical demonstrations proved that the dual-element doping strategy shed light on designing efficient and stable photoelectrodes for solar energy conversion.