Influence of Thermal Activation of Titania on Photoreactivity of Pt/TiO2 in Hydrogen Production

Abstract

A series of Pt/TiO 2 photocatalysts was prepared by impregnation of fresh and thermal-activated titania (commercial Evonik Aeroxide P25 TiO 2 ) with an aqueous solution of H 2 PtCl 6 followed by reduction in an aqueous solution of NaBH 4 . The thermal activation was performed by annealing in air. The photocatalytic activity of the Pt/TiO 2 catalysts was measured for the hydrogen production from a mixture of glycerol under UV radiation. It was found that the activation at 300-600 °C provides an increase in the photoreactivity of resulting Pt/TiO 2 photocatalysts in the production of hydrogen while its structural and textural properties do not change. This effect is due to formation of cationic vacancies that limits fast electron-hole recombination. Keywords photocatalysis • XPS • NEXAFS • XRD • nanoparticles Catalysis Letters Catalysis LettersNaBH 4 (Acros Organics, 98%) at room temperature [7]. The photocatalysts were referred to as "T300", "T400", "T500", "T600", "T700", and "T800", respectively. The photocatalyst prepared without the thermal activation was referred to as "RT". Platinum content was approximately 1 wt% in all the photocatalysts. All the chemical reagents used in the experiments, excluding distilled water, were obtained from commercial sources as guaranteed-grade reagents and were used without further purification and treatment. MethodsThe photocatalysts were examined by UV-vis spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray absorption near edge structure (XANES) spectroscopy, and X-ray diffraction (XRD) and N adsorption techniques. The diffuse reflectance UV-vis spectra were obtained using a Shimadzu UV-2501 PC spectrophotometer with an ISR-240A diffuse reflectance unit. The specific surface area (SSA) was calculated by the Brunauer-Emmett-Teller method using nitrogen adsorption isotherms measured at liquid nitrogen temperatures with an automatic Micromeritics ASAP 2400 sorptometer. XRD patterns were recorded on a Bruker D8 Advance diffractometer in the 2θ range from 20° to 80° using the Cu Kα radiation. The mean sizes of crystallites in the samples were estimated from the full width at half maximum of corresponding peaks using the Scherrer formula. The phase composition of the photocatalysts was quantitatively analyzed using the Rietveld refinement method.The XPS study was performed using an X-ray photoelectron spectrometer (SPECS Surface Nano Analysis GmbH, Germany) equipped with a PHOIBOS-150 hemispherical electron energy analyzer, a XR-50M X-ray source, and an ellipsoidal crystal monochromator FOCUS-500. The core-level spectra were obtained under ultrahigh vacuum conditions using the monochromatic Al Kα radiation. The charge correction was performed by setting the Ti2p 3/2 peak at 459.0 eV [12]. In this case, the main peak in the C1s spectra was observed at 285.2±0.1 eV. Relative concentrations of elements were determined from the integral intensities of the core-level spectra using the cross sections according to Scofield [13]. For detailed analysis, the spectra were fitted in...

Photocatalytic activity of titanium dioxide produced by high-energy milling

“…On the other hand, rutile has a smaller band gap (3.0 eV) compared to anatase (3.2 eV) [19], which contributes to the absorption of light with a longer wavelength [20]. Previously, in our works, a strong influence of the phase composition of titanium dioxide on its photocatalytic activity was shown [21,22]. An affordable way to modify titanium dioxide is high-energy ball milling.…”

New titania-based photocatalysts for hydrogen production from aqueous-alcoholic solutions of methylene blue

“…All samples which were synthesized with the thermal treatment stage possessed higher activity in ethanol aqueous solutions. Recently, it has been shown, 19 that the thermal This journal is © The Royal Society of Chemistry 2020 activation of titania in the temperature range between 300 and 600 C leads to an increase in photoreactivity of platinized titania in the hydrogen production. According to the XPS study, this effect is due to formation of cationic vacancies that limit the fast electron-hole recombination.…”

“…According to the XPS study, this effect is due to formation of cationic vacancies that limit the fast electron-hole recombination. 19 Also, increased content of rutile can improve the activity of such complicated Cu 2 O/ CuO/TiO 2 photocatalysts.…”

“…18 Recently, preliminary thermal treatment of titanium dioxide was used in our group to obtain Pt/TiO 2 photocatalysts, which were active in the hydrogen production from glycerol aqueous solutions. 19…”

“…18 Recently, preliminary thermal treatment of titanium dioxide was used in our group to obtain Pt/TiO 2 photocatalysts, which were active in the hydrogen production from glycerol aqueous solutions. 19 It seems interesting to combine the photocatalytic oxidation of methylene blue with other processes. Earlier, it was demonstrated that the presence of titania allows oxidation of the dye and synthesis of hydrogen to occur simultaneously in seawater.…”