Active sites for H2 and H2O activation over bifunctional ZnO-Pt(1 1 1) model catalysts

Abstract Hydroxylated oxide surfaces play an important role in many catalysis, energy, and environment processes. In this work, surface hydroxylation of Zn oxide (ZnOx) overlayers grown on Pt(1 1 1) has been studied by X-ray photoelectron spectroscopy and high resolution electron energy loss spectroscopy in ultrahigh vacuum, H2, and H2O atmospheres, respectively. Surface science measurements and H-D exchange experiments confirm that surface dissociation of H2 and H2O results in the surface hydroxylation of ZnOx overlayers. Bare Pt surface and interface between ZnOx and Pt are critical in surface hydroxylation by H2, whereas ZnOx surface itself is active for H2O dissociation. H2O mainly reacts with O-deficient ZnOx overlayer, while reaction with H2 or atomic H species becomes dominant on O-rich ZnOx overlayer.