Insight into the key factors governing the catalytic activity and stability of Ni/ZnO catalysts in CO2 hydrogenation†

The requirements for industrial catalysts are not only high efficiency but also excellent stability. Therefore, understanding the crucial factors governing the catalytic performance and long-term stability is fundamental yet challenging due to the structural complexity of heterogeneous catalysts. Herein, ZnO-supported Ni catalysts with different ZnO morphologies were used for CO₂ hydrogenation. The results revealed that catalytic activity and stability were strongly related to weak basic sites and Ni–ZnO interactions, respectively. The Ni/r-ZnO (nanorod) catalyst, which possessed a higher amount of weak basic sites responsible for the adsorption and activation of CO₂, exhibited better catalytic activity. Nonetheless, r-ZnO, predominantly exposing nonpolar facets, was not conducive to Ni–r-ZnO interactions, which led to the agglomeration of supported Ni species during CO₂ hydrogenation and was the primary cause of the deactivation of the Ni/r-ZnO catalyst. Meanwhile, carbon deposition could be another minor factor affecting catalytic stability. Kinetic and in situ DRIFTS spectroscopy results demonstrated that the reaction proceeded through an H₂-assisted associated mechanism, with the adsorption and activation of CO₂ as the rate-determining step. These results not only deepen the fundamental understanding of Ni-/ZnO-catalyzed CO₂ hydrogenation but also provide potential insights for developing highly active and stable catalysts for CO₂ hydrogenation.