Near UV-Irradiation of CuOx-Impregnated TiO2 Providing Active Species for H2 Production Through Methanol Photoreforming

Copper doped-TiO2 (P25) nanomaterials have been intensively studied as promising catalysts for H-2 production by photo-reforming of selected organic compounds. However, the role of copper oxidation states on the improvement of photocatalytic activity is still debated. In this work, CuOx-impregnated P25-TiO2 catalysts were used for photocatalytic production of hydrogen from methanol. Copper species/oxidation states both in the as-prepared catalysts and after the photocatalytic process were investigated. To this purpose, H-2 production rates were correlated to physico-chemical properties of the samples, both before and after photocatalytic process, by means of Raman, X-Ray Diffraction, Electron Paramagnetic Resonance spectroscopy, X-Ray Photoelectron Spectroscopy, Temperature-Programmed Reduction and High Resolution Transmission Electron Microscope techniques. Results revealed the presence of both Cu2O and CuO deposits on the samples surface after calcination. Notably, under near-UV irradiation, the fraction of highly dispersed CuO particles undergo a partial dissolution process, followed by reduction to metallic copper Cu-(s) by photogenerated electrons, boosting H-2 production rate. Our findings indicate that both Cu2O and Cu-(s) act as co-catalysts for H-2 generation, yet by different mechanisms. Overall this study, provides the basis to enhance catalytic performance of red-ox active systems through UV-irradiation approach.