Modulating Electronic Interaction over Zr–ZnO Catalysts to Enhance CO₂ Hydrogenation to Methanol

Abstract

ZnZrOx catalysts have been widely used to catalyze CO2 hydrogenation to methanol, the catalytic characteristics of active sites being closely related to the electronic interaction between components. However, the electronic interaction between Zn and Zr sites for ZnZrOx catalysts is not clear. Herein, we investigate the impact of electronic interaction between Zn and Zr on the catalytic behavior of ZnZrOx catalysts. XPS results and DFT calculations demonstrate that there is an electronic interaction between Zr and Zn with the electron transfer from Zr to Zn, resulting in the formation of electron-rich Zn sites. Combined with H2-TPD, propylene hydrogenation reaction, H2–D2 exchange experiments, in situ DRIFTS, and solid-state 1H NMR results, it is evident that more electron transfer from Zr to Zn is conductive to accelerate H2 dissociation to form more hydride species, likely due to the formation of electron-rich Zn sites. Meanwhile, such electron transfers can promote CO2 adsorption to form more bidentate bicarbonate and bidentate carbonate species and also boost their hydrogenation to formate and methoxy species with the assistance of hydride species. The experimental results show that more electron transfer from Zr to Zn is favorable to enhance the CH3OH selectivity and yield, indicating that such an electronic interaction is more dominant in enhancing the CO2 hydrogenation to CH3OH. This work reveals the pivotal role of the electronic interaction of active sites of catalysts for CO2 hydrogenation, which is beneficial to rationally design and optimize the required catalysts.