N-type semiconducting WO3 is widely investigated as a photoanode operating in water and seawater splitting devices. Because of the propensity of WO3 to favor photo-oxidation of acidic electrolyte anions and, in parallel, the formation on the electrode surface of the peroxo species, the choice of the appropriate electrolyte to allow stable operation of the photoanode is of critical importance. Our results from structural and photoelectrochemical tests performed using mesoporous WO3 photoanodes exposed to 80 h long photoelectrolysis in a 1 M aq. methanesulfonic acid supporting electrolyte demonstrate the photostability of both the WO3 photomaterial and the CH3SO3H electrolyte. The reasons for the stability of aqueous solutions of CH3SO3H are discussed on the basis of earlier literature reports.
© 2022 The Authors. Published by American Chemical Society.