Photo‐Rechargeable Organic Supercapacitor via Light‐Activated Electrolytes

Abstract Light‐mediated energy storage is key in diverse applications, including photonic devices, solar energy harvest, and others. Here, we demonstrate the construction of a photo‐rechargeable supercapacitor, in which light‐induced recharging is based, for the first time, on photoactive labile electrolytes. Specifically, the supercapacitor dielectric medium consisted of 2‐nitrobenzaldehyde as the electrolyte. In the dark, 2‐nitrobenzaldehyde is not ionized and the device displayed low capacitance. However, upon light irradiation, 2‐nitrobenzaldehyde undergoes chemical transformation and forms labile benzoic acid derivatives. These photoacids further ionize upon illumination, with the redox‐active photoinduced ionic species giving rise to significantly enhanced capacitance. Importantly, the generation of photoinduced electrolytes is reversible, facilitating multiple charge–discharge cycles. The photo‐rechargeable device exhibited extended discharge times, high specific capacitance, capacitance retention, and cyclic stability. The use of the photo‐rechargeable supercapacitor is demonstrated for practical charging and powering an external load. Light‐induced energy storage mediated by photoactive electrolytes is a new and powerful concept and may open new avenues for photo‐charged devices, solar energy harvesting, and storage.