A new electrochemical synthesis route for a BiOI electrode and its conversion to a highly efficient porous BiVO4 photoanode for solar water oxidation

Abstract

A new electrodeposition condition utilizing p-benzoquinone reduction was developed to produce BiOI electrodes composed of extremely thin 2D BiOI crystals. These electrodes served as precursors to form porous BiVO₄ electrodes via mild chemical and thermal treatments. The resulting porous BiVO₄ electrodes showed outstanding photoelectrochemical performance for sulfite oxidation reaching 1.25 mA cm⁻² at 0.5 V vs. RHE in 0.1 M potassium phosphate buffer (pH 7) containing 0.1 M sodium sulfite. When a ca. 100 nm thick FeOOH layer was deposited on the surface of BiVO₄ as an oxygen evolution catalyst, the kinetics of water oxidation was improved to the level of sulfite oxidation and the maximum power point for solar water oxidation was achieved at a bias as low as 0.55 V vs. RHE with a photocurrent density of 1.17 mA cm⁻². The remarkable solar water oxidation performance achieved by the porous BiVO₄–FeOOH system strongly encourages further morphological and compositional optimizations of the BiVO₄-based photoanode systems to realize highly efficient and practical solar water oxidation.