Reverse Hydrogen Spillover on Metal Oxides for Water‐Promoted Catalytic Oxidation Reactions

Understanding the water‐involved mechanism on metal oxide surface and the dynamic interaction of water with active sites is crucial in solving water poisoning in catalytic reactions. Herein, this work solves this problem by designing the water‐promoted function of metal oxides in the ethanol oxidation reaction. In situ multimodal spectroscopies unveil that the competitive adsorption of water‐dissociated *OH species with O 2 at Sn active sites results in water poisoning and the sluggish proton transfer in CoO‐SnO 2 imparts water‐resistant effect. Carbon material as electron donor and proton transport channel optimizes the Co active sites and expedites the reverse hydrogen spillover from CoO to SnO 2 . The water‐promoted function arises from spillover protons facilitating O 2 activation on the SnO 2 surface, leading to crucial *OOH intermediate formation for catalyzing C‐H and C‐C cleavage. Consequently, the tailored CoO‐C‐SnO 2 showcases a remarkable 60‐fold enhancement in ethanol oxidation reaction compared to bare SnO 2 under high‐humidity conditions.