Photo‐Rechargeable Organic Supercapacitor via Light‐Activated Electrolytes

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.