A systematic preparation mechanism for directional regulation of pore structure in activated carbon including specific surface area and pore hierarchy

Abstract

Currently, the simultaneous and directional regulation of specific surface area (SBET) and pore hierarchy (the percentage of mesoporous and macroporous volume to total pore volume, Vmes+mac/Vt) of activated carbon (AC) lacks a systematic preparation mechanism. In this study, AC samples were prepared from coconut husks, and the effect of carbonization methods, activation methods, and process parameters on the development of the pore structure were explored. N2 adsorption–desorption results indicated that AC samples prepared via conventional carbonization were microporous. Hierarchical AC samples were obtained by the combination of hydrothermal carbonization at 240 °C and physical activation. CaCl2 impregnation was found to be beneficial to the preparation of meso-/macroporous AC samples. Based on these results, a series of AC samples with typically varied pore hierarchies (18.05–76.73 %) with similar specific surface areas (∼450.0 m2 g−1) were obtained. AC samples with similar pore hierarchies and different specific surface areas were also prepared, including microporous AC (SBET: 330.5–761.4 m2 g−1; Vmes+mac/Vt: 12.21–14.06 %), hierarchical AC (SBET: 445.9–780.7 m2 g−1; Vmes+mac/Vt: 51.04–54.89 %), and meso-/macroporous AC samples (SBET: 371.1–516.0 m2 g−1; Vmes+mac/Vt: 67.39–75.25 %). A systematic preparation mechanism for the directional regulation of the pore structure of AC is proposed, which is significant for the preparation of high-efficiency AC for different applications.