Enhancing CO₂ Hydrogenation to Methanolat Mixed-Phase Interfaces on ZnZrO_x SolidSolution Catalysts

Abstract

Zinc–zirconium oxides (ZnZrO_x) are highly selective and stable catalysts for the hydrogenation of CO₂ to CH₃OH. However, their catalytic activity has remained relatively moderate, and the influence of the ZnZrO_x crystalline phase on performance is not yet fully elucidated. Here, we report a mixed-phase ZnZrO_x, comprising coexisting tetragonal and monoclinic domains, and correlate this biphasic architecture with the catalytic performance. At 320 °C, the mixed-phase ZnZrO_x catalyst delivers a CO₂ conversion of 9.2% coupled with an impressive CH₃OH selectivity of 87%, representing a 1.4-fold increase in conversion compared to its purely tetragonal counterpart while maintaining equivalent selectivity. In-depth characterizations attribute this improved performance primarily to the emergence of a two-phase interface, which enhances the dissociation and activation of H₂. Density functional theory calculations further reveal that this interfacial region plays a vital role in promoting heterolytic H₂ dissociation, boosting the formation of HCOO* and lowering the energy barriers of the rate-determining step for CH₃OH formation. This work highlights the effectiveness of the crystal-phase architecture in optimizing ZnZrO_x catalysts for CO₂ hydrogenation to CH₃OH, offering strategic insights for the design of advanced oxide-based hydrogenation systems.