Graphitized Biocarbon Derived from Hydrothermally Liquefied Low-Ash Corn Stover

Graphitized biocarbon can be utilized for energy-storage applications such as supercapacitors. The scientific community has geared its attention to obtain such value-added products from abundantly available and low-cost biomass feedstock agricultural residues such as corn stover. Lignocellulosic components embedded within the cell wall of biomass substrates can provide a fine template for enhanced ion storage, transport, and rate capabilities, desirable for electrochemical storage. Presented is the utilization of homogenized low-ash content corn stover milled and sieved to desired specifications, which underwent hydrothermal liquefaction in the presence of Ni-based catalytic salts at 275 °C. The hydrochar obtained using the solid residue extracted from the reaction slurry was washed to acid neutral. The materials were subjected to catalytic activation using ZnCl2 followed by thermal annealing at 400 °C for morphological and pore size enhancement of the resulting biochar. Carbonization was performed on acid-neutralized hydrochar at 850 °C to further enhance pore structures and increase graphitization for improved conductivity. Catalytic materials exhibited a specific capacitance of 316 F g–1 and held a 100% retention beyond 10,000 cycles. The Brunauer–Emmett–Teller method, Raman spectroscopy, X-ray diffraction, cyclic voltammetry, chronopotentiometry, and electrochemical impedance spectroscopy are discussed herein.