Zinc oxide nanoflake/reduced graphene oxide nanocomposite-based dual-acting electrodes for solar-assisted supercapacitor applications†

There is an ever-growing requirement for systems that enable both conversion and storage of solar energy in the same device, thereby reducing the need for grid electricity and fossil fuels. Although photo-supercapacitors (PSCs) potentially meet this requirement, it is essential to develop high-performance devices in which conversion and storage can be achieved on the same electrode. This study investigated two-electrode PSC systems based on three-dimensional (3D) zinc oxide (ZnO) nanoflakes/reduced graphene oxide (rGO) nanocomposites to meet the need for in situ solar energy conversion/storage. To better understand the effect of rGO and 3D ZnO nanoflakes separately, three different compositions have been studied, in which the weight percent of rGO changes from 8 to 32%. The energy density increases as the amount of rGO increases, but the composite material loses its light sensitivity above a critical value. Therefore, the electrodes containing 16% rGO exhibited higher performance than those containing 32% and 8% rGO. As a result, the (16%) rGO/ZnO-based PSC exhibited superior performance compared to the other samples, with its ability to maintain 100% of its performance at 40 000 cycles, its areal capacitance of 40 mF cm⁻² and energy density values of 22 μW h cm⁻², which were 170% higher than under dark condition measurements.