Biomass-Derived Microporous Carbon Materials with an Open Structure of Cross-Linked Sub-microfibers with Enhanced Adsorption Characteristics

Abstract

Moringa oleifera seed shells exhibit a unique structure of cross-linked sub-microfibers (0.5–1.5 μm diameter) with a well-connected macroporous network. Controlled pyrolysis (500–800 °C) and cyclic activation of the precursor provided a porous carbon material with a structure that minimizes mass-transfer constraints. Under both slow (10 °C/min–1) and flash pyrolysis, the structure was preserved, while a significant microporosity was developed. By flash pyrolysis (700–800 °C), a material with enhanced characteristics for potential application as a molecular sieve (SDA = 450–470 m2 g–1, and SBET = 5 m2 g–1) was obtained. Cyclic activation of carbonized shells, consisting of an oxygen chemisorption stage (180 °C) followed by a desorption stage in an inert atmosphere (450–900 °C), resulted in a controlled development of microporosity upon successive activation cycles. After 10 activation cycles, respective SDA and SBET values of 1172 and 761 m2 g–1 were obtained. Higher development of the surface area and a w...