Advances in bio-waste derived activated carbon for supercapacitors: Trends, challenges and prospective

The ever-increasing demand for green and clean energy urge the development of cheap and efficient electrode materials for supercapacitors (SCs). In this context, several naturally abundant bio-wastes have been explored to develop porous carbons for SCs due to their easy availability, high performances, and simple processing methods. Although various BDCs are utilized for SC, the relation between the bio-waste precursor and resultant carbon materials are not very well understood. Here, we highlight how the different bio-waste precursors affect the surface characteristics of the carbon nanostructures and outlined their subsequent effect on electrochemical performances. Moreover, the surface modification of carbon materials using pre-processing, carbonization and activation methods is provided. The supercapacitive properties of activated carbons (AC) with their unique surface features derived from the different feedstock are systematically summarized. Finally, the challenges and future directions for the development of AC from bio-waste are discussed. Overall, this review provides a guide to understand how best to refine and carbonize this biomass to achieve optimum supercapacitive performance.