Biomass-derived nanostructures and hydrothermal carbon spheres: A review of electrochemical applications in redox flow battery

Carbon nanostructures can be derived from bioresources such as agricultural wastes, wood residues, and algal derivatives through renewable pathways. These nanostructures are produced using methods like pyrolysis, carbonization, and chemical activation, resulting in materials with large surface area, porosity, and electrical conductivity. These properties are crucial for RFB as they enhance the efficient movement of ions and electrons, leading to improved performance. Hydrothermal carbon spheres are produced through hydrothermal synthesis, where biomass or other carbon precursors are subjected to high temperature and pressure in an aqueous environment. This method yields carbon spheres with uniform distribution, excellent purity, and favorable electrochemical properties. These spheres contribute to the performance of RFB by maintaining solid structure while conducting electrodes, thereby increasing battery energy density. This review compares biomass-derived carbon nanostructures and hydrothermally produced carbon spheres, highlighting the strengths and weaknesses of each. Biomass products are economical and environmentally friendly, though their quality may vary. Hydrothermal carbon spheres offer superior electrochemical properties and uniformity but involve complex, energy-intensive production processes. The sustainability of biomass resources is influenced by the availability and processing of raw materials, emphasizing economic and environmental considerations.