Reduced graphene oxide -MnO2 nanocomposite for CO2 capture from flue gases at elevated temperatures

Abstract

The newly prepared reduced graphene oxide-MnO2 (rGO-MnO2) nanocomposite has exhibited highly selective CO2 adsorption from gaseous mixtures at elevated temperatures. The Mn2+ basic sites are scattered over the rGO-MnO2 nanocomposite which produce an effective BET surface area of 710 m2 g−1 for selective CO2 capture. The selective adsorption of CO2 (5.87 mmol g−1) over N2 (0.36 mmol g−1) and CH4 (0.41 mmol g−1) at 298 K/1 bar was achieved by the nanocomposite. The heat of adsorption followed a unique correlation with the quantity of CO2 adsorbed and fits well to the Fowler-Guggenheim equation. The mechanism of CO2 adsorption on the nanocomposite was complemented with molecular modelling and simulations. The rGO-MnO2 have shown better CO2 adsorption capacity of 28.5 mmol g−1 at 323 K/20 bar as compared to zeolite derivatives, MOFs, and carbons as reported in the literature. The formation of inert frameworks with 3–6 nm porous structure in the nanocomposite thermally stabilizes to capture CO2 repeatedly. The nanocomposite with adsorption capacity of 3.69 mmol g−1 at 373 K/1 bar is quite close to real-life conditions for flue gas treatment.