Boosting Carbonate Hydrogenation through In Situ Formation of the CaO/CaCO3 Interface

High-temperature calcination of carbonate minerals in energy-intensive industrial sectors is one of the greatest contributors to global carbon dioxide (CO2) emissions. The hydrogenation of the most abundant carbonate minerals could potentially mitigate unavoidable CO2 emissions by converting them into value-added products, but progress has been hindered by a limited understanding of this process. Here, we aim to elucidate the underlying mechanism of self-induced direct hydrogenation of carbonates (DHC) to produce metal oxides and syngas at relatively lower temperature without using any catalysts. Various in situ technologies corroboratively illustrate H2 molecules can penetrate into CaCO3 to form multiple CaO/CaCO3 interfaces, resulting in porous CaO. The density functional theory calculations reveal the neighboring O and C sites at the active CaO/CaCO3 interface are responsible for the heterolytic dissociation of H2, leading to the progressively self-induced DHC. An intrinsic microkinetic analysis by tracing the formation rate of the intermediate further verifies its self-induced catalytic characteristics. This subverts the consensus regarding the infeasible self-catalysis of stable ionic crystals. By lowering the temperature to 650 °C, 100% CaCO3 conversion is achieved with a CO selectivity of 91.8% in a packed bed reactor. Inspired by extensive applications of DHC to various carbonates, this innovative idea of treating carbonates as a White Carbon resource may pave a breakthrough pathway toward Carbon Neutrality in the industry.