A Green Route to High-Surface Area Carbons by Chemical Activation of Biomass-Based Products with Sodium Thiosulfate

Abstract

A simple, sustainable, and affordable approach for the synthesis of highly porous carbons is presented. The procedure is based on the use of sodium thiosulfate as an activating agent and a variety of biomass-based products (glucose, sucrose, and gelatine) as carbon precursors. The synthesis scheme involves three steps: (a) mixing the reactants by grinding, (b) heat treatment at temperatures in the 800–900 °C range, and (c) extracting the carbon material from the carbonized solid by simple washing with water. The generation of the pore structure is based on the redox reaction between the carbonaceous matter and sodium thiosulfate acting as an oxidant. In this way, porous carbons with high BET surface areas in the ∼2000–2700 m2 g–1 range and large pore volumes of up to 2.4 cm3 g–1 are obtained. The porosity of these carbons consists of two pore systems made up of narrow micropores of 0.8 nm and larger pores of up to 5 nm. These porous carbons have a certain amount of sulfur (∼2–3%) that is incorporated into the carbon framework as thiophene-like and oxidized sulfur groups. Additionally, in the case of gelatine, N content up to 2–3% is preserved.