High performance of TiO2/CuxO photoelectrodes for regenerative solar energy storage in a vanadium photoelectrochemical cell

Photocatalysts for harvesting solar energy to either electricity or chemical fuels have attracted much attention recently, but they have big obstacles such as wide bandgaps and rapid charge recombinations to overcome for final applications. In this study, we investigates a useful method to utilize vanadium redox pairs, which are commonly applied for vanadium redox flow batteries, to diminish charge recombinations and thus to enhance photocurrent response in regenerative solar energy storage. The results reveal significant improvements in photocurrent density by forming cuprous and cupric oxides in TiO2/CuxO electrodes under solar AM 1.5 illuminations using the vanadium photoelectrochemical storage cell at 0.025M of vanadium redox species in the acid electrolytes. In addition, the stabilized photocurrent density of the copper content optimized TiO2/CuxO electrodes is almost tripled from the TiO2 only electrode because the charge recombinations can be mitigated with the content optimized TiO2/CuxO electrodes. Therefore, the optimized TiO2/CuxO electrode results in the highest charge storing performance in the catholyte chamber, and the roles of vanadium redox species are also clearly demonstrated.