Metal oxides play a crucial role in many hydrogen-related catalytic reactions, and effective modulation of surface structure of oxide catalysts is key to enhancing the performance of these reactions.

Recently, the research team led by Professor FU Qiang and Professor MU Rentao from Dalian Institute of Chemical Physics (DICP) of the Chinese Academy of Sciences (CAS) made progress in catalysis research at oxide-oxide interfaces. They discovered that monodispersed ZnOx overlayer confined on ZnCr2O4 surface decouples the competitive activation of CO2 and H2, addressing the poisoning effect of strong CO2 adsorption on H2 activation under reaction condition to achieve efficient catalytic CO2 hydrogenation reaction.

This work was published in Angewandte Chemie International Edition April 14.

Schematic depiction of the dual-site catalytic mechanism in ZnO_x/ZnCr₂O₄ for CO₂ hydrogenation. (Image by JIA Haoran and FENG Xiaohui)

In this work, researchers developed ZnCr2O4@ZnOx catalyst by forming monodisperse ZnOx overlayer on the ZnCr2O4 surface via a vapor-phase migration process. In-situ infrared studies demonstrated that ZnCr2O4@ZnOx effectively facilitates the homolytic activation of H2 to form Zn−H species in the presence of CO2, whereas pure ZnO and ZnCr2O4 activate H2 heterolytically generating Zn−H/Cr−H and O−H species without CO2. In ZnCr2O4@ZnOx catalyst, ZnCr2O4 surface and ZnOx/ZnCr2O4 interface provide adsorption sites for CO2, while the monodispersed ZnOx provides sites for homolytic activation of H2 forming stable Zn–H species. The dual-site design of the ZnCr2O4@ZnOx catalyst successfully mitigates the poisoning effect of strong CO2 adsorption on H2 activation. At 723 K, the ZnCr2O4@ZnOx catalyst achieves a CO2 conversion of 33% with 100% CO selectivity, exhibiting stable performance for over 150 hours.

This work was supported by the National Key R&D Program of China, the National Natural Science Foundation of China, and Photon Science Center for Carbon Neutrality.