Synthesis of Cu/TiO2 catalysts by reactive magnetron sputtering deposition and its application for photocatalytic reduction of CO2 and H2O to CH4

Abstract In the present work, a series of Cu/TiO2 catalysts were successfully synthesized by using pulsed direct current (DC) reactive magnetron sputtering of Cu targets under Ar atmosphere onto various TiO2 supports. The physiochemical properties of the catalysts were characterized by using inductive coupled plasma spectroscopy (ICP), X-ray diffraction (XRD), UV–Vis spectroscopy, N2 physisorption, transmission electron microscopy (TEM), PL spectroscopy, and X-ray photoelectron spectroscopy (XPS). The photocatalytic activities of all the catalysts were studied via the photocatalytic reduction of CO2 and H2O to CH4 under UV light irradiation. The Cu/TiO2 catalysts exhibited higher photocatalytic activity than the uncoated TiO2 supports and the ones made using an impregnation technique. The electron trapping of copper species, which prolonged the electron-hole recombination process, promoted photocatalytic activity of the Cu-doped catalysts. Moreover, the specific morphologies of the Cu species deposited on TiO2 supports and the smaller change of bandgap energy of the sputter coated catalysts also resulted in an improvement of photocatalytic activity under UV light irradiation.