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

Bismuth vanadate (BiVO 4 ) is an outstanding photoanode material for photoelectrochemical water splitting. In this work, a series of single crystalline BiVO 4 photoanodes are synthesized by pulsed laser deposition (PLD). Once coated with a thin layer of cobalt oxide (CoO x ) cocatalyst, also by PLD, the photoanodes support efficient photoelectrochemical generation of chlorine (Cl 2 ) from brine under simulated solar light. The activity of the chlorine generation reaction (ClER) is optimized when the thickness of CoO x is about 3 nm, with the faradic efficiency of ClER exceeding 60%. Detailed studies show that the CoO x cocatalyst layer is amorphous, uniform in thickness, and chemically robust. As such, the cocatalyst also effectively protects the underlying BiVO 4 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.