Monolithic carbon xerogel with co-continuous hierarchical porosity via one-step, template- and catalyst-free hydrothermal reaction with resorcinol and formaldehyde

Abstract

Monolithic carbon xerogel (MCX) with co-continuous hierarchical porosity was prepared via a one-step, template- and catalyst-free hydrothermal polycondensation reaction with resorcinol (R), formaldehyde (F) and distilled water (W), followed by pyrolysis and CO₂ activation. The reaction was carried out in a pressurized Teflon mold at 100 °C for 6 h, while F/R (2.2, 2.4, 2.6, and 2.8) and R/W ratios (40 and 45) were varied to obtain a co-continuous pore structure with interconnected particles. Next, the gels were dried at 60 °C for 36 h and then at 100 °C for 12 h to produce xerogels, which were then subjected to pyrolysis at 900 °C for 2 h and CO₂ activation at 1000 °C for 2, 4 or 6 h. A co-continuous pore structure with interconnected particles was observed in gels with F/R = 2.4 and 2.6 at R/W = 40 and with F/R = 2.2 at R/W = 45, but the gel with F/R = 2.4 at R/W = 40 was the only one that showed no crack generation upon 6 h CO₂ activation. Thus, this gel was subjected to a N₂ sorption study, which resulted in a specific surface area (SSA) of 1418, 2489 and 3418 m² g⁻¹ at 2, 4 and 6 h activation, respectively. This was attributed to the introduction of micro-pores via activation, which also generated meso- and macro-pores to form hierarchical porosity.