Synthesis of BiVO4 nanoflake array films for photoelectrochemical water oxidation

Abstract

Because of the potential for application in photoelectrochemical cells for water splitting, the synthesis of nanostructured BiVO₄ is receiving increasing attention. Here we report a simple new drop-casting method for the first time to synthesize un-doped and doped bismuth vanadate (BiVO₄) nanoflake array films. Synthesis parameters such as the amount of polyethylene glycol 600 (PEG-600) and the precursor solution drying time are investigated to optimize the films for photoelectrochemical water oxidation. The BiVO₄ films consisting of nanoflakes with an average thickness of 20 nm and length of 2 μm were synthesized from a precursor solution containing Bi³⁺, V³⁺ and PEG-600 with a Bi : V: PEG-600 volume ratio of 2 : 2 : 1, dried at 135 °C for 55 min. Photoelectrochemical measurements show that the BiVO₄ nanoflake array films have higher photoelectrochemical activity than the BiVO₄ nanoparticle films. Additionally, the nanoflake arrays were tested after incorporating W and Mo to enhance the photoelectrochemical activity. The 2% W, 6% Mo co-doped BiVO₄ nanoflake array films demonstrate the best photoelectrochemical activity with photocurrent densities about 2 times higher than the un-doped BiVO₄ nanoflake films and greater than the photocurrents of individually Mo doped or W doped BiVO₄ films. The origin of enhanced photoelectrochemical activity for the co-doped film may be due to the improved conductivity through the BiVO₄ or slightly enhanced water oxidation kinetics.