CO₂ Hydrogenation to Methanol and Ethanol on In₂O₃-Based Single-Atom Catalysts and a New Scaling Relation

Conversion of CO2 into high-value chemicals is a hot issue both industrially and scientifically, and the development of suitable catalysts is the key problem. Using density functional theory (DFT) calculations and microkinetic simulations, we investigated the mechanisms for reduction of CO2 to methanol and ethanol on the iridium-doped In2O3 single-atom catalyst, which exhibits high selectivity to ethanol. The favorable pathways and two key steps controlling the formation and selectivity of methanol and ethanol were identified. Further calculations of the energy barriers for the two key steps on the other nine single-metal-atom-doped In2O3 show that Mn-doped In2O3 may possess higher selectivity to ethanol than Ir-doped In2O3, while Ru-, Fe-, and Rh-doped In2O3 might be good catalysts for methanol. Furthermore, we found that there exists a linear relation (ADTS relation) between the CO2 separate adsorption energies and the adsorption energies of transition states. It is demonstrated that for a bimolecular (A + B) surface reaction, the ADTS relation holds true when the sum of the interactions of B with A and B with the surface are constant. The present work also outlines a methodology to identify reaction descriptors to screen catalysts on the basis of reaction mechanisms and microkinetic analysis.