Enhancing CO2 Hydrogenation to Methanol at Mixed-Phase Interfaces on ZnZrOx Solid Solution Catalysts

Zinc–zirconium oxides (ZnZrOx) 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 ZnZrOx crystalline phase on performance is not yet fully elucidated. Here, we report a mixed-phase ZnZrOx, comprising coexisting tetragonal and monoclinic domains, and correlate this biphasic architecture with the catalytic performance. At 320 °C, the mixed-phase ZnZrOx 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 ZnZrOx catalysts for CO2 hydrogenation to CH3OH, offering strategic insights for the design of advanced oxide-based hydrogenation systems.