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RISS 인기검색어
- 검색키워드
- 저자 : Dillert, R. (검색결과 3 건)
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Kandiel, Tarek A.,Dillert, Ralf,Bahnemann, Detlef W. Korean Society of Photoscience 2009 Photochemical & photobiological sciences Vol.8 No.5
Titanium dioxide was modified with Pt-polypyrrole nanocomposites through the in situ simultaneous reduction of Pt(IV) and the oxidative polymerization of pyrrole monomers at ambient temperature. The modified powders were characterized using X-ray photoelectron spectroscopy (XPS), dark-field scanning transmission electron microscopy (DF-STEM), infrared spectroscopy (IR) and by the determination of the BET surface area by nitrogen adsorption. Photocatalytic hydrogen production tests were performed employing 75 ml aqueous solution containing $2250\;{\mu}mol$ methanol as the sacrificial electron donor. The obtained results show that 0.5 and 1.0 wt% Pt and polypyrrole, respectively, are the optimum ratios for high photocatalytic $H_2$ production rates. The amount of $H_2$ evolved during 5 h of UV-vis illumination of the suspension of Pt-polypyrrole modified $TiO_2$ powder is three times higher than that obtained with Pt-loaded $TiO_2$ prepared by a photochemical deposition method. The photonic efficiencies of the $H_2$ production employing 75 ml aqueous solution containing 370 mmol methanol were calculated to be $10.6{\pm}0.5$ and $4.5{\pm}0.2%$ for $TiO_2$ modified with Pt-polypyrrole nanocomposites and for Pt-loaded $TiO_2$ prepared by a photochemical deposition method, respectively. A synergistic effect between Pt nanoparticles and polypyrrole leading to a better separation of the charge carriers is proposed to explain the enhanced reactivity of the newly synthesized photocatalyst.
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Hamid, Saher,Ivanova, Irina,Jeon, Tae Hwa,Dillert, Ralf,Choi, Wonyong,Bahnemann, Detlef W. Elsevier 2017 Journal of catalysis Vol.349 No.-
<P><B>Abstract</B></P> <P>The photocatalytic generation of H<SUB>2</SUB> and hydrocarbons from aqueous acetic acid has been studied employing TiO<SUB>2</SUB> P25-based photocatalyst particles. The effect of pH on the distribution of reaction products and their formation rates during the photochemical as well as the photoelectrochemical oxidation of acetic acid has been investigated. The photocatalytic formation rates for H<SUB>2</SUB> and hydrocarbons were found to be higher for Pt-loaded TiO<SUB>2</SUB> than for bare TiO<SUB>2</SUB>. The major reaction products resulting from the photocatalytic decomposition of aqueous acetic acid, as determined quantitatively in the gas phase, were found to be H<SUB>2</SUB>, CO<SUB>2</SUB>, and CH<SUB>4</SUB>. Furthermore, traces of C<SUB>2</SUB>H<SUB>6</SUB>, C<SUB>3</SUB>H<SUB>8</SUB>, CO, CH<SUB>3</SUB>CHO, HCHO, CH<SUB>3</SUB>OH, C<SUB>2</SUB>H<SUB>5</SUB>OH, and HCOOH were also detected. After 15h of illumination, the average formation rates of H<SUB>2</SUB>, CO<SUB>2</SUB>, CH<SUB>4</SUB>, and C<SUB>2</SUB>H<SUB>6</SUB> evolved at pH 2 were found to be 22, 65, 35, and 2µmol/h, respectively. The ratio of H<SUB>2</SUB> to hydrocarbons strongly depends on the pH values, <I>i.e.,</I> at acidic pH the ratio of H<SUB>2</SUB> to CH<SUB>4</SUB> formation was found to be 0.6. On the contrary, at neutral and basic pH values negligible amounts of hydrocarbons were formed and H<SUB>2</SUB> was found to be the main product with formation rates of 12 and 5µmol/h at pH 7 and 11, respectively. It is therefore assumed that the hydroxide ion has a significant effect on the reaction pathways. Due to the fact that methanol and ethanol are formed as reaction products, water or hydroxide ions are apparently required for the formation of the major oxidizing agent, that is the hydroxyl radical. Herein, a detailed mechanism for the photocatalytic decomposition of acetic acid at different pH values is presented.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Photocatalytic decomposition of acetic acid results in formation of H<SUB>2</SUB>, CH<SUB>4</SUB>, and C<SUB>2</SUB>H<SUB>6</SUB>. </LI> <LI> pH greatly influences product distribution and formation rates. </LI> <LI> Photocatalytic transformation of acetate proceeds by Kolbe reaction at pH<7. </LI> <LI> Photocatalytic transformation of acetate proceeds by Hofer-Moest reaction at pH≥7. </LI> <LI> A significant formation rate for H<SUB>2</SUB> was found for 2≤pH≤9. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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