Effect of Catalytically Silent Cerium Hydroxide in Cobalt–Cerium Mixed Double Hydroxide for Enhanced Water Oxidation Kinetics in a BiVO₄ Photoanode

Coupling of the BiVO₄ photoanode and a mixed metal hydroxide having cobalt and cerium yielded a photo current density of 3.74 mA/cm² with an onset cathodic shift of ∼370 mV, resulting in an impressive solar-to-hydrogen efficacy of 4.3%. The addition of catalytically silent cerium to Co­(OH)_x not only enhanced the stability but also improved charge injection and surface oxidation kinetics. The water oxidation performance of BiVO₄-CoCe­(OH)_x could be attributed to the synergistic effect of both cobalt and cerium, where cerium incorporation enhanced the surface passivation, aiding the stability of the photoanode and formation of Co­(II)/(III) active sites to fasten the surface kinetics of BiVO₄. An average Faradaic yield of ∼94% suggests that majority of the holes have been utilized for water oxidation. We believe that the present design of the BiVO₄ photoanode with mixed metal hydroxide provides a promising and efficient strategy for modification of a photoanode with stable and highly active oxygen evolution cocatalysts.