A critical review of the production, activation, and morphological characteristic study on functionalized biochar

Biomass is a widely accepted renewable energy source currently generated from various sources like agricultural wastes, forest residue, microorganisms, and solid wastes. It can be converted into various sources of energy materials based on the type of conversion and application. Thermochemical conversion methods like pyrolysis, carbonization, hydrothermal conversion, etc., are generally used in the conversion process, producing solid, liquid, and gas products with various proportions based on conversion parameters. Biochar, a product/by-product from thermochemical conversion post modification can be used in energy storage materials like batteries and supercapacitors as electrodes, advanced applications like carbon dots, nanotubes, and graphene, etc., with significantly higher surface area, porosity, and lower cost than traditional activated carbon. Post-modification of biochar involves either physical or chemical activation methods to improve porosity and surface area, this improves the functionality of the biochar as electrochemical energy storage and application. This review summarizes some of the thermochemical conversion methods, activation, and techniques to improve the functionality of the biochar produced. This review also discusses the morphological diversification of biochar after activation and its significance in electrochemical energy applications.