Photo-assisted supercapacitors: Working principles, electrode materials and prospects

Unlike traditional supercapacitors, photo-assisted supercapacitors integrate photoactive materials into conventional supercapacitor structures, enabling the direct combination of renewable solar energy with energy storage devices. This integration effectively addresses the challenge of intermittency inherent in renewable energy sources. While considerable reviews have been devoted to photo-assisted rechargeable batteries and related photochemical energy storage systems, a comprehensive overview focusing specifically on the energy storage mechanisms and tailored electrode material design for photo-assisted supercapacitors remains scarce. In light of the growing importance of photo-assisted supercapacitors in modern industrial applications, this review systematically summarizes the development process, working principles, categorization, key components of photo-assisted supercapacitors, and research progess of photoactive electrode materials. The operational principles, including photo-charging and energy storage mechanisms, are introduced first, followed by a summary of the classification and constituent components of such devices. Given the critical role of electrode materials, existing photoactive electrode materials are categorized into three groups: metal oxides and oxide-based composites, metal sulfides and sulfide-based composites, and g-C 3 N 4 -based composites. The recent advance in these photoactive materials is emphasized, covering aspects of material design, performance enhancement, and the underlying light-enhanced mechanisms. Finally, current challenges and future prospects in the field of photo-assisted supercapacitors are outlined. It is expected that this review will provide valuable context, theoretical guidance, and practical design strategies for the development of novel photo-assisted supercapacitors.