(560bn) A Computational Investigation of Catalytic Upgrading of CO2 to Methanol over Indium Oxide

Carbon dioxide (CO₂) valorization has been identified as a great challenge in the face of excess anthropogenic carbon emissions. Current industrial processes to convert CO₂ into useful platform chemicals are limited by low selectivities and middling conversions. Recent attention has been given to oxide catalysts that have demonstrated excitingly high selectivities in experiments. Specifically, indium oxide (In₂O₃) has been shown to produce methanol, an important platform chemical, at comparable conversions to industrial catalysts and at selectivities approaching 100%¹. However, our understanding of this promising catalyst is currently limited.

In this work, we investigate potential reaction mechanisms using density functional theory (DFT) calculations and microkinetic modeling (MKM). Through methodical active site selection and extensive exploration of different reaction pathways, we generate an explicitly calculated reaction mechanism through DFT energy and vibrational frequency calculations. We compare paths to methanol and CO, i.e., the reverse water gas shift reaction to reveal what controls selectivity. Using the appropriate statistical thermodynamic models, we produce a comprehensive MKM parametrized using these DFT values that enabled us to evaluate the proposed mechanism against experimental data. Comparison to other literature mechanisms will also be presented. Finally, we investigate why this oxide is so selective by performing electronic structure calculation analysis and discussing catalyst and chemistry descriptors.

1. Martin, O., A. J. Martin, et al. (2016). "Indium Oxide as a Superior Catalyst for Methanol Synthesis by CO₂ Hydrogenation." Angewandte Chemie-International Edition 55(21): 6261-6265.