Photo-assisted asymmetric supercapacitors based on dual photoelectrodes for enhanced photoelectric energy storage

Abstract

Photo-rechargeable energy storage devices pave a new way for directly utilizing solar energy, and therefore, the design and assembly of photo-assisted supercapacitors in order to realize the efficient storage of solar energy become increasingly important. In this study, a novel photo-assisted asymmetric supercapacitor (ASC) with dual photoelectrodes was specifically assembled. We rationally designed nanoflower-like ZnCo₂O₄ (ZCO NF) as the positive electrode, which can deliver a larger specific capacitance (563 F g⁻¹ at 1 A g⁻¹) under light illumination than that under dark conditions (456 F g⁻¹ at 1 A g⁻¹). Simultaneously, hollow sphere-structured CuCo₂S₄ (CCS HS) was prepared as the negative electrode. It exhibits a specific capacity of 305 F g⁻¹ with light, which is approximately two folds higher than that without light. More importantly, the energy density of the assembled light-sensitive ZCO NF//CCS HS ASC can reach 60.9 W h kg⁻¹ at 700 W kg⁻¹ with light, whereas it is only 46.5 W h kg⁻¹ at 700 W kg⁻¹ without light. In addition, density functional theory (DFT) approach was used to study the charge-transfer mechanism of the photo-assisted ASC with dual photoelectrodes. Thus, this study may open up a new avenue for the design of light-sensitive devices for effective solar energy storage.