Desorption of Zn from ZnO single-crystal surfaces during temperature programmed decomposition of methanol, formic acid, and 2-propanol

Desorption of Zn atoms at temperatures lower than the sublimation temperature of Zn from ZnO was observed during the temperature programmed decomposition (TPD) of methanol, formic acid, formaldehyde, and 2-propanol on a Zn-polar surface of ZnO. It was observed for formic acid, methanol, and formaldehyde on a stepped (5051) surface, 2-propanol and methanol on an O-polar surface, but not for 2-propanol on a stepped (5051) surface. The areas of the Zn desorption peaks were usually less than 10% of the areas of the other products, but the decomposition of methanol on the Zn-polar surface was exceptionally efficient in causing Zn desorption. Zn desorption was also enhanced by adsorbed triethylamine and prolonged exposure to D₂. It was suppressed by the presence of gaseous O₂. It was not enhanced by adsorbed O₂, CO, CO₂, H₂O, or NH₃. The enhanced Zn desorption was attributed to reduction of the ZnO surfaces. The desorption temperatures of various products in this work were lower than those previously reported. These more correct temperatures were reported.