Evaluation of pyrochar and hydrochar derived activated carbons for biosorbent and supercapacitor materials

This study investigated effects of different thermal processes on characteristics of activated carbon to produce efficient biosorbents or supercapacitors using biomass resources. Pyrolysis char and hydrochar obtained from woody biomass were used as precursors for activated carbon under different atmospheric conditions (N₂ and air). In order to provide functional groups on the carbon surface, activated carbon under N₂ condition was subsequently acidified by HNO₃ and the other was simultaneously acidified under air condition. Additionally, potential for application as Pb²⁺ adsorbent and supercapacitor was evaluated. Thermochemical behaviors such as bonding cleavage and dehydration during activation processes were observed by TG and Py-GCMS analysis. Elemental analysis, FT-IR, Raman spectroscopy, and XPS analysis were carried out to confirm changes in structures of each carbon products. New plausible reaction mechanism for this observation was suggested with respect to the formation of a key intermediate in the presence of excess air. As for performance in applications, air activated carbon using hydrochar exhibited high versatility to function as both Pb²⁺ adsorbent (~41.1 mg/g) and energy storage material (~185.9 F/g) with high specific surface area, mesopore ratio, surface functional groups.