Carbonization and aromaticity-driven electron transfer in hydrochars from tropical woods as electrochemical cell electrode for energy conversion and storage

This research examines tropical woods hydrochar as sustainable energy conversion and storage materials. Hydrothermal carbonization produces hydrochar, which is characterized by its physical, chemical, and electrochemical properties. Results show that biomass type affects hydrochar shape, functional groups, crystallinity, and carbonization. Eucalyptus hydrochar has a dense porous network, whereas mango and longan hydrochars maintain more of their lignocellulosic structure, balancing structural integrity and reactivity. The irregular, amorphous Gliricidia hydrochar is moderate aromatic and amorphous. The greatest electron transfer rate constants were found in gliricidia wood (5.55 ± 0.11 s⁻¹), followed by mango (5.44 ± 0.91 s⁻¹), eucalyptus (3.77 ± 1.06 s⁻¹), and longan (3.61 ± 0.08 s⁻¹), depending on carbonization and aromatic content. At 100 mV/s, mango wood hydrochar has the greatest specific capacitance (4.3 F/g), followed by longan (3.5 F/g), eucalyptus (3.1 F/g), and gliricidia (2.9 F/g). These findings emphasize the necessity of choosing hydrochar based on functional qualities for energy conversion and storage applications.