Improvement of photoelectrochemical HClO production under visible light irradiation by loading cobalt oxide onto a BiVO4 photoanode

Simultaneous photoelectrochemical production of H2 and hypochlorous acid (HClO) as a value-added oxidation reagent compared with O2 on a semiconductor electrode by using visible light is one of the breakthrough technologies for a sustainable and economical energy conversion process. However, the selectivity and HClO production performance on the photoelectrode in the electrolyte with a dilute chloride ion concentration close to that of seawater are still low, and the effect of co-catalyst loading on the reaction has not been clarified. Here, we showed that loading cobalt oxide via facile spin-coating onto a BiVO4/WO3 photoelectrode effectively improved the HClO production. Controlling the loading amount of CoOx and the calcination temperature enabled us to prepare the photoelectrode for producing HClO with almost 100% selectivity, along with maintaining the photoelectrochemical performance under visible light irradiation. Achieving efficient HClO production by simple co-catalyst loading processes is an important step toward the construction of a solar energy conversion system.