Co-thermal in-situ reduction of inorganic carbonates to reduce carbon-dioxide emission

Thermal decomposition of inorganic metal carbonates is the main path to prepare metal oxides; nonetheless, it is always accompanied by the emission of large amounts of CO 2 as one of the gas products. This study reports a concept of co-thermal in-situ reduction of inorganic carbonates by using the energy released by carbonate decomposition under pure hydrogen atmosphere, which reduces the decarboxylation temperature and significantly inhibits the CO 2 emissions. A combination of hydrogen—deuterium exchange, isotope experiment, and density functional theory calculations demonstrates that the CO results from the selective cleavage of Ca-O bonds at the surface of CaCO 3 via the direct hydrogenation mechanism at relatively low temperature. However, it undergoes the reverse water—gas shift reaction path at high temperature, i.e. , CO being produced by the reduction of CO 2 released by the decomposition of carbonates. This study sheds light on the potential of green hydrogen technology for inorganic carbonate valorization toward high value-added products, which can facilitate the large-scale industrial applications.