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

• Increasing the hydrogen reduction time causes the decreasing of Pd2 + ion and PdO.
• Increasing the hydrogen reduction time results in the increasing of Pd metal.
• The optimal TiO2–Pd240 nanoparticle exhibits the highest photocatalytic activity.

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 (Pd2 +) 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.