Interparticle electron transfer in methanol dehydrogenation on platinum-loaded titania particles prepared from P25

Commercial titania sample (P25) was homogenized first (HomoP25), and then crystalline phases (anatase and rutile) were isolated from it by chemical dissolution methods followed by samples' purification by washing and annealing. The photocatalytic activities were tested for anaerobic methanol dehydrogenation in two reaction systems: (1) under UV/vis polychromatic irradiation with in situ platinum (Pt) deposition, and (2) under UV/vis monochromatic irradiation (action spectra) for ex situ platinum deposition. The properties of bare and modified titania samples were investigated by XRD, DRS, STEM, BET and zeta potential measurements. It was found that platinized rutile was more active than platinized anatase and platinized HomoP25, due to ability of photo-absorption of more photons (narrower band gap). Moreover, in HomoP25 sample, rutile was platinized first, probably due to positively charged surface allowing favorable adsorption of chloroplatinate ions. More than 10 times lower content of Pt (<0.1 wt%) deposited on annealed samples (forming aggregates with an increased interface between titania NPs) than that on HomoP25 (2 wt%) resulted in similar level of photocatalytic activity, suggesting an interparticle electron transfer (IPET) between titania NPs inside one aggregates (one Pt NP was sufficient for one aggregate).