Heteroatoms-doped hierarchical porous carbons: Multifunctional materials for effective methylene blue removal and cryogenic hydrogen storage

Abstract

Activated carbons (ACs) have been widely used for dye removal and for H2 storage but often demonstrate limited performance due to their low porosity and lacking beneficial surface functional groups. Herein, we have designed a series of urea/thiourea and K2CO3 modified ACs from “sucrose – a biomass-derived carbohydrate” via two-step pyrolysis/activation method. As-prepared ACs demonstrate excellent textural features (e.g., specific surface area (SSA) = 2842 m2/g; pore volume = 1.35 cm3/g) and optimal heteroatom content (N = 4.1 at%; S = 2.1 at% content). Moreover, these ACs exhibit an outstanding methylene blue (MB) adsorption capacity ~398.09 mg/g at an initial concentration of 200 mg/L surpassing most biomass derived ACs reported previously. The π–π stacking, hydrogen bonding and acid-base interaction is the key mechanism behind excellent MB adsorption from aqueous solution. Moreover, an efficient H2 adsorption capacity up to 2.21 wt% was observed at 77 K/1 bar with predominant role governed by narrow micropores (~0.68 nm). Therefore, the current study proposes a straightforward synthetic protocol for developing a multifunctional material (ACs) which not only act for wastewater remediation but also as energy sorbents. Moreover, our study clearly demonstrates the role of porosity and heteroatom content on both MB adsorption and H2 storage performance.