Surface intermediates steer the pathways of CO2 hydrogenation on Pt/γ-Al2O3: Importance of the metal-support interface

A variety of adsorbed intermediates have been extensively assigned during CO 2 hydrogenation on Pt/γ-Al 2 O 3 . However, the surface sites where the surface species reside have not been well resolved, which are extremely important to depict the reaction pathways of CO 2 hydrogenation. In the current work, surface species adsorbed on three regions were distinguished by in situ diffuse-reflectance infrared Fourier transform spectroscopy, i.e., contiguous Pt region of Pt nanoparticle, interfacial Pt int -O-Al int region between Pt nanoparticle and γ-Al 2 O 3 , and surface region of γ-Al 2 O 3 away from Pt nanoparticle. The dynamics of adsorbed H species, carbonyl species, bicarbonates, formate species, and adsorbed CO 2 , were identified at different sites, proving that the reaction occurs at the Pt/γ-Al 2 O 3 interface. We found that only the C-containing species at the Pt perimeter are directly active intermediates for the reaction. Such spatial analysis bridges the gap between the hydrogen activation and CO 2 activation, providing a deep understanding of CO 2 hydrogenation. In addition, the interface structure with oxygen vacancy is important for CO 2 activation, driving the reaction through carboxylate (*HOCO) pathway to form CO at the interface rather than formate (*HCOO) pathway and then be hydrogenated at the Pt surface.