Characterizations and EDLC performances of large-scale synthesized zeolite-templated carbons

We recently reported the large-scale synthesis of zeolite-templated carbon (ZTC) using biomass resources (ACS Sustainable Chem. Eng. 10 (2022) 10827–10838, Carbon Trends 9 (2022) 100228). In the synthesis, undried NaY zeolite was mixed with a biomass resource such as sugar or starch as a carbon source. The mixture was subjected to chemical vapor deposition using propylene as an additional carbon source, followed by heat treatment for graphitization and zeolite removal with hydrofluoric acid. The resulting ZTCs exhibited high structural regularity and large specific surface areas of 3750–3820 m2 g−1. This simple method eliminated the use of organic solvents and minimized the amount of the carbon sources. In this study, we analyzed these ZTCs using temperature-programmed desorption (TPD) to quantitatively and qualitatively characterize oxygen-containing functional groups and evaluated additional structural features. Finally, the electric double-layer capacitor performances of these ZTCs were evaluated using an organic electrolyte, 1 M Et4NBF4/propylene carbonate. The TPD analysis revealed that the sucrose- and xylose-derived ZTCs contained more phenol groups than the glucose- and starch-derived ZTCs. Due to the initial deprotonation of the phenol groups and the reversible redox reaction of the resulting redox-active quinone groups, the sucrose- and xylose-derived ZTCs exhibited higher capacitance than the other ZTCs through significant pseudocapacitance while maintaining high capacitance retention of 89–92% at 2 A g−1 by comparing the capacitance at 0.05 A g−1. Although the area-normalized capacitances of these ZTCs (0.036–0.039 F m−2) are lower than that of activated carbon because of their low electrical conductivity, their capacitance can be further enhanced by electrochemical oxidation.