Boosting CO2 hydrogenation via size-dependent metal-support interactions in cobalt/ceria-based catalysts

Metal-support interactions have a strong impact on the performance of heterogeneous catalysts. Specific sites at the metal-support interface can give rise to unusual high reactivity, and there is a growing interest in optimizing not only the properties of metal particles but also the metal-support interface. Here, we demonstrate how varying the particle size of the support (ceria-zirconia) can be used to tune the metal-support interactions, resulting in a substantially enhanced CO2 hydrogenation rate. A combination of X-ray diffraction, X-ray absorption spectroscopy, near-ambient pressure X-ray photoelectron spectroscopy, transmission electron microscopy and infrared spectroscopy provides insight into the active sites at the interface between cobalt and ceria-zirconia involved in CO2 hydrogenation to CH4. Reverse oxygen spillover from the support during treatment in hydrogen results in the generation of oxygen vacancies. Stabilization of cobalt particles by ceria-zirconia particles of intermediate size leads to oxygen spillover to the support during the CO2 and CO dissociation steps, followed by further hydrogenation of the resulting intermediates on cobalt. Metal-support interactions can effectively modify the catalytic properties of heterogeneous composites. Here, the authors report the possibility of controlling the interaction between cobalt and a ceria-zirconia support by changing the particle size of the latter, resulting in a superior CO2 hydrogenation system.