Adsorption of chlorine on ZnO(0001)-Zn and coadsorption with HCOOH

The adsorption of Cl-2 on the zinc-terminated ZnO(0001) surface at 300 K wa s studied with low-energy ion-scattering spectroscopy (ISS), X-ray photoele ctron spectroscopy (XPS), angle-resolved XPS (ARXPS), and work-function and band-bending measurements. The surface saturated with similar to 0.30 chlo rine adatoms [Cl(a)] per zinc site, sitting above the zinc layer in no appa rent registry with the substrate. Combined work-function and band-bending m easurements indicate anionic Cl(a). Using formic acid to produce surface fo rmate, the effect of Cl(a) on formate decomposition was studied also. On th e chlorine-free ZnO(0001) surface, formate decomposes through two different pathways: dehydration and dehydrogenation. Pre-adsorbed chlorine suppresse s the amount of adsorbed formate produced, and enhances the selectivity for its dehydrogenation. (C) 2000 Elsevier Science B.V. All rights reserved.