Herein we report the oxidation of Ce3+ to Ce4+ using a porous WO3 photoanode and a Pt cathode with excellent Faradaic efficiency (FE (Ce4+)) of up to 98% under solar simulated light in an aqueous electrolyte solution containing a high concentration of SO42- anions. The competing side oxidative reactions such as S2O82- and O-2 production were found to be suppressed in the presence of Ce3+. The Ce4+ yield (YI (Ce4+)) from Ce3+ reached up to 95%. Also, a noble-metal-free biomass-derived inexpensive electrode was found to be an efficient replacement of the Pt cathode. (C) 2019 Elsevier Ltd. All rights reserved.