Computational screening of single-atom doped In₂O₃ catalysts for the reverse water gas shift reaction

The reverse water gas shift (RWGS) reaction is an important method for converting carbon dioxide (CO₂) into valuable chemicals and fuels by hydrogenation. In this paper, the catalytic activity of single-atom metal-doped (M = Pt, Ir, Pd, Rh, Cu, Ni) indium oxide (c-In₂O₃) catalysts in the cubic phase for the RWGS reaction was investigated using density functional theory (DFT) calculations. This was achieved by identifying metal sites, screening oxygen vacancies, followed by further calculating the energy barriers for the direct and indirect dissociation pathways of the RWGS reaction. Our results show that the single-atom dopant in the indium oxide lattice promotes the creation of oxygen vacancies on the In₂O₃ surface, thereby facilitating the adsorption and activation of CO₂ by the oxide surface and initiating the subsequent RWGS reaction. Furthermore, we find that the oxygen vacancy (O_V) formation energy on the surface of the single-atom metal doped c-In₂O₃(111) surface can be used as a descriptor for CO₂ adsorption, and the higher the O_V formation energy, the more stable the CO₂ adsorption structure is. The Cu/In₂O₃ structure has relatively high energy barriers for both direct (1.92 eV) and indirect dissociation (2.09 eV) in the RWGS reaction, indicating its low RWGS reactivity. In contrast, the Ir/In₂O₃ and Rh/In₂O₃ structures are more conducive to the direct dissociation of CO₂ into CO, which may serve as more efficient RWGS catalysts. Furthermore, microkinetic simulations show that single atom metal doping to In₂O₃ enhances CO₂ conversion, especially under high reaction temperatures, where the formation of oxygen vacancies is the limiting factor for CO₂ reactivity on the M/In₂O₃ (M = Cu, Ir, Rh) models. Among these three single-atom catalysts, the Ir/In₂O₃ model was predicted to have the best CO₂ reactivity at reaction temperatures above 573 K.