Pd quantum dots loading Ti3+,N co-doped TiO2 nanotube arrays with enhanced photocatalytic hydrogen production and the salt ions effects

Pd quantum dots (QDs) loading Ti3+,N co-doped TiO2 nanotube array (NTA) films were prepared by anodic oxidation of Ti foils, followed by calcination at 400 °C and Pd photo-depositions using a PdCl2 solution. The photocatalytic hydrogen production activity of the Pd QDs loading Ti3+,N co-doped TiO2 NTA was tested under UV–vis light irradiation in a methanol aqueous solution and compared with those of Ag and Au loaded Ti3+,N co-doped TiO2 NTAs. The effects of Pd content, salt ions and catalytic reaction temperature on the photocatalytic activities of the Pd QDs loading Ti3+,N co-doped TiO2 NTA catalysts were explored systematically. The photocatalytic reaction mechanism was proposed based on the experimental results. The results show that the hydrogen evolution reaction (HER) rate (17.6 µmol cm−2h−1) over the Pd QDs loading TiO2NTA/Pd10 (10 cycles of Pd photo-depositions) was increased to 16 times higher than that of the unloaded TiO2NTA (1.1 µmol cm−2h−1). Interestingly, adding small amount of alkali salt (0.5 g L−1) in the preparation process of the TiO2 NTAs or in the photocatalytic reaction medium (1 g L−1) can further increase the HER rates distinctly (2.7–3.4 times).