Light-assisted melanin-based electrochemical energy storage: physicochemical aspects

The integration of solar energy conversion and electrochemical energy storage functions is critical for limiting the anthropogenic effects on climate change and preventing possible energy shortages related to the increase of the world population. Electrochemical technologies (batteries and supercapacitors) have been investigated to store the energy generated from intermittent sources, like the Sun. Abundant, low-cost, non-toxic, potentially biodegradable, organic molecular materials, extracted from natural sources, are ideal candidates for applications in sustainable electrochemical energy storage technologies (as opposed to those currently used in high performance devices, often costly, toxic and scarce, thus potentially triggering geopolitical issues). Among natural materials, eumelanin, a ubiquitous bio-pigment in flora and fauna, stands out for its redox-activity, UV-Vis absorption, chemical and thermal stability. This topical review suggests melanin as promising sustainable multifunctional material to enhance the electrochemical energy storage properties of organic materials by solar light. The vision behind this research is to pave a way towards the discovery of organic materials and devices that can seamlessly integrate solar energy conversion and storage within the same multifunctional material.