W:BiVO4-WO3-V2O5 heterostructures increase light absorption and charge transport in photoanodes for water splitting

Efficient light absorption and charge separation and transfer are the main obstacles that still need to be addressed to increase the performance of photoanodes for the water oxidation reaction. Here, we show that the combi-nation of W:BiVO4, WO3, and V2O5 can simultaneously improve light absorption and the separation and transport of electrons and holes in the photoanode and consequently its photoelectrochemical performance for the water oxidation reaction. The high photoelectrochemical activity of the photoanode is due to the different bandgap energies of W:BiVO4 (2.44 eV), WO3 (2.90 eV), and V2O5 (2.27 eV), which provide higher absorption of visible light and improved charge transport in the heterojunction: V2O5 facilitates the transport of holes while WO3 increases electron mobility. As a result, the W:BiVO4-WO3-V2O5 photoanode produces a photocurrent density as high as 8.2 mA cm(-2) at 1.23 V vs. RHE in sodium sulfate electrolyte (pH 6.96). By modifying the surface of the W:BiVO4-WO3-V2O5 photoanode with an electrocatalyst for water oxidation, the photocurrent can reach 12.1 mA cm-2. Thus, the multiple ternary heterojunctions of W:BiVO4-WO3-V2O5 proved an efficient strategy for producing high-performance photoanodes for photoelectrochemical applications.