Tuning CO2 hydrogenation selectivity via metal-oxide interfacial sites

Abstract CO2 hydrogenation over ZrO2-supported NiFe catalysts is investigated to illustrate the role of Fe in controlling the activity and selectivity, and to reveal the structure-function relationship between metal-oxide interfaces and catalytic selectivities. The Ni-ZrO2 interfaces and Ni-FeOx interfaces are identified as the most likely active sites for the methanation reaction and the reverse water-gas shift reaction, respectively, using combined in-situ and ex-situ characterization techniques. The reaction mechanisms of CO2 hydrogenation to CH4 on the Ni-ZrO2 interfacial sites and to CO on the Ni-FeOx interfacial sites are further revealed by combined in-situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations. Both experimental and theoretical results demonstrate that the binding energy of absorbed CO (*CO) is a key descriptor to predict CO2 hydrogenation selectivity: weak interaction (e.g., Ni-FeOx interfaces) promotes *CO desorption to increase CO selectivity, while moderate interaction (e.g., Ni-ZrO2 interfaces) facilitates further hydrogenation of *CO to produce CH4.