Platinum Nanoparticles Supported on Anatase Titanium Dioxide as Highly Active Catalysts for Aerobic Oxidation under Visible Light Irradiation

Abstract

Visible light irradiation (λ >450 nm) of platinum (Pt) nanoparticles supported on anatase titanium dioxide (TiO 2 ) promotes efficient aerobic oxidation at room temperature. This occurs via the electronic excitation of Pt particles by visible light followed by the transfer of their electrons to anatase conduction band. The positively charged Pt particles oxidize substrates, whereas the conduction band electrons are consumed by the reduction of molecular oxygen. The activity of this photocatalysis depends on the height of Schottky barrier and the number of perimeter Pt atoms created at the Pt/anatase heterojunction, which are affected by the amount of Pt loaded and the size of Pt particles. The catalyst loaded with 2 wt % Pt, containing 3−4 nm Pt particles, creates a relatively low Schottky barrier and a relatively large number of perimeter Pt atoms and, hence, facilitates smooth Pt→anatase electron transfer, resulting in very high photocatalytic activity. This catalyst is successfully activated by sunlight and enables efficient and selective aerobic oxidation of alcohols at ambient temperature.

Analysis of the Promoted Activity and Molecular Mechanism of Hydrogen Production over Fine Au–Pt Alloyed TiO2 Photocatalysts

“…1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 band at λ> 400 nm due to the inter-band transition of Pt NPs. 18 The Au/TiO 2 NPs exhibited an intense absorption band centred at 540 nm, which could be assigned to the SPRof the Au NPs. 7 We note that this SPR peak wavelength is slightly blue-shifted as compared to our previously reported Au/TiO 2 synthesized by a sol-gel hydrothermal method, suggesting a decrease of the Au particle size.…”

Selective Photocatalytic Oxidation of Aniline to Nitrosobenzene by Pt Nanoparticles Supported on TiO2 under Visible Light Irradiation

“…After evacuation, the sample was measured at 77 K. The signals observed for the Pt/anatase sample (b) under the dark condition (g = 2.029 and 2.001) are assigned to O − formed via a dissociative adsorption of O 2 onto the oxygen vacancy sites of the anatase TiO 2 surface, which was also observed for bare anatase TiO 2 . 24 The broad g = 1.980 signal (spectrum a) is assigned to the Ti 3+ species formed on rutile TiO 2 . 45 irradiation of this sample (blue), however, creates distinctive signals assigned to a superoxide-type oxygen anion (O 2 − ; g xx = 2.002, g yy = 2.009, g zz = 2.028) stabilized on the TiO 2 surface.…”

“…This is due to the sintering of Pt particles by a high-temperature treatment. 24,25 Figure 8b shows the results obtained via a 12 h photoreaction with respective catalysts. Although the nitrosobenzene selectivities are similar, the activity significantly decreases with an increase in the size of Pt particles because the number of surface Pt atoms decreases with an increase in the size of Pt particles.…”

Photoelectrocatalytic selective oxidation of 4-methoxybenzyl alcohol in water by TiO2 supported on titanium anodes

“…Visible-light-driven partial photocatalytic oxidation of alcohols was achieved over Pt nanoparticles supported on anatase TiO 2 [18], single-crystalline rutile TiO 2 nanorods [19] and over pure TiO 2 with selectivity of 99% [20]. It has been found that the addition of Brønsted acids [21] adsorbed onto TiO 2 dramatically accelerated the photocatalytic oxidation of alcohols without any loss of selectivity.…”