A sustainable carbon-consuming cycle based on sequential activation of CO2 and CH4 using metal oxides

Abstract

Naturally abundant metal oxides can be used as reusable CO2-philic absorbents, and the resulting CO2-bound metal carbonates are disposed in nature; although common, this carbon capture and sequestration process is unsustainable. Herein, we revisit the use of metal carbonates as pre-activated CO2 reservoir containing reactive carbonate species that can combine with CH4 to produce CH3COOH. The direct stoichiometric coupling of CH4 with CO2 to form CH3COOH is thermodynamically non-spontaneous. However, theoretical calculations identified metal carbonates that spontaneously react with CH4 to form CH3COOH and the corresponding metal oxides. We designed new metal oxide-assisted carbon-consuming cycle involving sequential CO2/CH4 activation to form CH3COOH with nearly 100% selectivity, which can be generalized to various metal oxides. Particularly, Co3O4 nanoparticles encapsulated by mesoporous silica shell produced the best CH3COOH productivity of 0.7 μmolCH3COOH gCo3O4–1 at 250 °C, which enables the sustainable incremental production of CH3COOH without decrease in productivity over 15 repeated cycles.