Photochemical Deposition of Co-Ac Catalyst on ZnO for Solar Water Oxidation

Photo assisted electrochemical splitting of water is a promising method for solar energy storage as hydrogen fuel. However, the overall solar to fuel conversion efficiency is limited by the rapid recombination of photogenerated charge carriers and sluggish kinetics of water oxidation at the photoanode. Hence, the design of an efficient and cost effective co-catalyst for water oxidation is a challenging task. In the present study, a novel Co-based catalyst (Co-Ac) is prepared photochemically and used for photoelectrochemical water oxidation reaction in a neutral medium. Arrays of ZnO nanorods are deposited on a conducting glass substrate by an electrochemical method. By exposing ZnO in a neutral acetate solution containing Co(NO₃)₂ to UV radiation, Co-Ac is deposited on the surface of ZnO. Co-Ac acts as a co-catalyst to enhance the water oxidation kinetics and to reduce the charge carrier recombination at the semiconductor electrode. The on-set potential for oxygen evolution reaction is lower at the Co-Ac-ZnO photoanode in relation to the bare ZnO. There is a three to four fold increase in the photooxidation current due to the presence of Co-Ac on ZnO, indicating a high activity of the catalyst. This material is remarkable owing to its ease of formation, high catalytic activity and stability under operating conditions. Results of these studies will be presented.