Enhancing photocatalytic performance of TiO2 in H2 evolution via Ru co-catalyst deposition

A series of ruthenium catalysts supported into pure anatase titania were tested in the photo-production of hydrogen from methanol:water mixtures under UV and visible illumination conditions. Catalysts containing 1, 2, 3 and 5 wt.% of ruthenium were subjected to a characterization study with the help of X-ray diffraction, Raman, X-ray photoelectron spectroscopy, photoluminescence, morphology as well as scanning and transmission electron microscopy. Through the measurement of the optical properties of the suspension of the catalysts and the hydrogen photo-production reaction rate we calculate the true quantum efficiency. Optimum activity is presented by the catalyst with a 3 wt.% of Ru component, which shows quantum efficiency values of ca. 3.1 and 0.6% under, respectively, UV and visible light illumination. Careful examination of the physico-chemical properties of the solid allows to establish a correlation between the ruthenium surface exposed and the quantum efficiency. The implications of such result to justify chemical activity of the ruthenium supported samples are discussed both for UV and visible illumination conditions.