Synthesis of Co3O4 nanospheres for enhanced photo-assisted supercapacitor

The design of the novel photo-assisted supercapacitor electrodes is considered an effective way to store abundant solar energy and improve energy storage performance. However, the mechanism of photo-induced charge transfer undergoing semiconductor energy band levels is still unclear. Herein, we have synthesized Co3O4 nanospheres (p-type semiconductor) for photo-assisted supercapacitors, and proposed its mechanism of enhanced photo-assisted energy storage by supported experiments and density functional theory (DFT) investigations. Results show the photo-generated charge produced by Co3O4 with semiconductor characteristics will promote the charging reaction under continuous light. After the charging process, the semiconductor characteristics gradually disappear, and the generated Co2+−OH is not sensitive to light response. On the basis of this result, we further propose a new type of light-assisted strategy in tandem with a n-type semiconductor (TiO2) additional electrode, which can provide photo-generated electrons and holes in the charge/discharge processes. The specific capacitance (523 F g−1) under light with TiO2 assisting is increased by 16.7% when compared with that without TiO2-assisted under dark (450 F g−1) at 1 A g−1. This work may provide a theoretical basis and new strategy for improving the energy storage capacity of supercapacitors.