Correlation between palladium chemical state and photocatalytic performance of TiO₂-Pd based nanoparticles

Photocatalytic processes can be used to illustrate both solar energy conversion and environmental friendly applications. In this study, we synthesize several titanium dioxide-palladium (TiO₂-Pd) based catalysts by wet impregnation method plus hydrogen-thermal reduction process in order to develop high-effective photocatalysts that can be easily produced even in industrial quantities. Moreover, we examine the effects of hydrogen-thermal reduction process on the photocatalytic performance of TiO₂-Pd based catalysts. From X-ray photoelectron spectroscopy analysis, increasing the hydrogen reduction process time results in the decreasing of palladium ion (Pd^{2 +}) and palladium oxide (PdO), but it causes the increasing of palladium (Pd) metal. The hydrogen reduction process is helpful for the preparation of TiO₂-Pd based catalysts with high photocatalytic decomposition of organic dyes (the apparent reaction rate constant ∼ 0.124 min^{- 1} under solar simulator irradiation) and excellent photocatalytic hydrogen production rate (∼ 26,000 μmol/g·h under UV-B irradiation). The TiO₂-Pd based catalysts prepared in this study exhibit high photocatalytic performance. They are also industrially relevant especially when the low cost of Pd metal is taken into consideration.