Cobalt Oxide-Coated Single Crystalline Bismuth Vanadate Photoanodes for Efficient Photoelectrochemical Chlorine Generation.

Bismuth vanadate (BiVO) is an outstanding photoanode material for photoelectrochemical water splitting. In this work, a series of single crystalline BiVO photoanodes are synthesized by pulsed laser deposition (PLD). Once coated with a thin layer of cobalt oxide (CoO) cocatalyst, also by PLD, the photoanodes support efficient photoelectrochemical generation of chlorine (Cl) from brine under simulated solar light. The activity of the chlorine generation reaction (ClER) is optimized when the thickness of CoO is about 3 nm, with the faradic efficiency of ClER exceeding 60%. Detailed studies show that the CoO cocatalyst layer is amorphous, uniform in thickness, and chemically robust. As such, the cocatalyst also effectively protects the underlying BiVO photoanodes against chlorine corrosion. This work provides insights into using artificial photosynthesis for byproducts that carry significant economic value while avoiding the energetically expensive oxygen evolution reactions.