Modeling thermocatalytic systems for CO₂ hydrogenation to methanol

The hydrogenation of CO₂ to CH₃OH over Cu-based catalysts holds significant potential for advancing carbon sequestration and sustainable chemical processes. While numerous studies have focused on catalyst development, the environmental effects on underlying reaction mechanisms have yet to be fully understood. In this work, we develop a grand potential theory for a comprehensive analysis of CO₂ hydrogenation to CH₃OH over Cu (111) and Cu (211) surfaces. By integrating electronic and classical density functional calculations to bridge the "pressure gap", the theoretical results revealed that the HCOO* formation rate may vary by several orders of magnitude depending on reaction conditions. The grand potential theory enables us to elucidate the molecular mechanisms underlying the need for high H₂ pressure, the prevalence of saturated CO₂ adsorption, and the important roles of CO and H₂O in hydrogenation. Moreover, this study addressed and clarified controversies over CO₂ versus CO adsorption and hydrogenation, the formate versus carboxy pathways, and the difference in HCOO* hydrogenation activity between Cu (111) and Cu (211) surfaces. The theoretical analysis offers a new perspective for optimizing reaction conditions and catalyst performance in methanol synthesis and can be generalized to enhance our understanding of heterogeneous catalysis under industrially relevant conditions.