Formation of surface protons from hydrogen molecule was observed for Pt/SO_4~(2-)-ZrO_2, and the protons act as catalytically active sites for several acid catalyzed reactions. The surface protons exist only when hydrogen molecules are present in gas phase, and disappear from the surface when hydrogen molecules are removed from gas phase. The proton is formed via dissociative adsorption of hydrogen, spillover of hydrogen atom onto support, surface diffusion of the spiltover hydrogen to Lewis acid site, and donation of an electron from hydrogen atom to Lewis acid site. Promotive effects of hydrogen on acid-catalyzed reactions are observed not only for the Pt/SO_4~(2-)-ZrO_2, but also for other catalysts which are composed of hydrogen activation sites and Lewis acid sites. A molecular hydrogen-riginated protonic acid site is proposed as a widely applicable concept for generation of protonic acid sites.
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