Biomass-derived Electrode Materials and Sustainable Processes for Supercapacitors

Abstract

Biomass is one of the most abundant natural resources and has been used as a source of energy for thousands of years. Biomass as a precursor for energy storage materials is still relatively novel and faces several obstacles before becoming commonly used in today’s electrical devices. Currently, energy storage devices, such as batteries, capacitors, and supercapacitors, utilize petroleum-derived graphitic carbons for anodes, generating a need for more sustainable materials. Biomass, as a carbon-rich source for electrode materials, presents a viable and economically feasible alternative due to the prevalent lignocellulosic compounds: lignin, cellulose, and hemicellulose. Preliminary studies on the solid residues from the enzymatic hydrolysis of corn stover were conducted, where biocarbon synthesized via a two-step thermal activation at 375 °C followed by high temperature carbonization at 850 °C, underwent physical and electrochemical characterizations.Using the preliminary results on solid residues from the enzymatic hydrolysis of corn stover, next level optimization studies were conducted by varying hydrothermal liquefaction (HTL) parameters and converting subsequent solid residues into biocarbon for electrodes. Another exciting opportunity is in the valorization of biomass that comes out of phytoremediation of nickel containing soils, as the biomass inherently contains nickel catalyst. Enhanced catalytic methods were demonstrated through the utilization of phytoremediation techniques where hyperaccumulator species (water hyacinth) was cultivated in Ni2+ doped water and converted into electrode grade biocarbon through thermochemical/catalytic methods. Electrochemical results demonstrated a high specific capacitance of 541 F g-1 for activated carbons. Physical characterizations, such as BET and Raman spectroscopy, denoted surface areas in excess of 3000 m2 g-1, pore volumes reaching 2.13 cm3 g-1, and enhanced C=C formation contributing to the high specific capacitance. Process scale-up analysis was performed on corn stover-derived biocarbon production. Aspen Plus simulations and technoeconomic analyses (TEA) were conducted on the scaled methods with results indicating achievable production goals and an economically favorable process. Areas of research presented here encompass sustainable engineering, process intensification, energy storage, catalysis, phytoremediation, economics, statistical modeling, and computer simulation.