H₂ generation from aqueous ethanol over ZnO nanowires, the photo-transformation of surface species

ZnO nanowires (NWs) with wurzite structure and a very high [0001] preferred orientation were grown on a ZnO thin film, from a gas-solid process, in the absence of catalyst. ZnO NWs were characterized by FESEM, XRD, HRTEM, XPS, PL and Raman spectroscopy and used as photocatalysts for the photo-transformation of ethanol(aq) in the gas phase. The existence of different defects such as oxygen vacancies was evidenced. The photocatalytic process was followed by in-situ diffuse reflectance infrared spectroscopy (DRIFTS) coupled to on-line mass spectrometry (MS) analysis. The surface species determined during the irradiation (lambda = 365 nm) of ZnO NWs under ethanol/water vapor flow at room temperature are related with the hydrogen production and carboncontaining products evolved.