Improving the photoelectrochemical stability of a bismuth vanadate photoanode for solar water oxidation

Bismuth vanadate (BiVO4) has attracted significant attention as a photoanode material in photoelectrochemical water-splitting devices. However, its photoelectrochemical performance is limited by rapid photogenerated charge recombination and photocorrosion. Herein, we report a simple post-synthetic treatment for BiVO4 that overcomes its surface and bulk limitations and deposits a thin polyaniline layer to improve photostability. To further improve the water oxidation kinetics, a nickel- and iron-containing cocatalyst is deposited on the outermost layer of the photoanode. Comprehensive electrochemical, photoelectrochemical, and surface photovoltage characterizations reveal that the polyaniline layer effectively preserves the surface composition of photocharged BiVO4 and prevents its photocorrosion, whereas the cocatalyst offers an additional driving force for water oxidation. The photocharged BiVO4/polyaniline/cocatalyst photoanode exhibits a photocurrent density of 5.2 mA/cm2 at 1.23 V (vs. the reversible hydrogen electrode) with long-term photostability over 18 h. This work provides a simple strategy for improving the photoelectrochemical stability of photocharged BiVO4 photoanodes.