Importance of Metal-Support Interactions for CO 2 Hydrogenation: An Operando Near-Ambient Pressure X-ray Photoelectron Spectroscopy Study on Gold-Loaded In 2 O 3 and CeO 2 Catalysts.

Metal-support interactions, which are essential for the design of supported metal catalysts, used, e.g., for CO 2 activation, are still only partially understood. In this study of gold-loaded In 2 O 3 and CeO 2 catalysts during CO 2 hydrogenation using near-ambient pressure X-ray photoelectron spectroscopy, supported by near edge X-ray absorption fine structure, we demonstrate that the role of the noble metal strongly depends upon the choice of the support material. Temperature-dependent analyses of X-ray photoelectron spectra under reaction conditions reveal that gold is reduced on CeO 2 , enabling direct H 2 activation, but oxidized on In 2 O 3 , leading to decreased activity of Au/In 2 O 3 compared to bare In 2 O 3 . At elevated temperatures, the catalytic activity of the In 2 O 3 catalysts strongly increases as a result of facilitated CO 2 and (In 2 O 3 -based) H 2 activation, while the catalytic activity of Au/CeO 2 is limited by reoxidation by CO 2 . Our results underline the importance of operando studies for understanding metal-support interactions to enable a rational support selection in the future.