TY - JOUR

T1 - Photocatalytic conversion of acetate into molecular hydrogen and hydrocarbons over Pt/TiO2

T2 - pH dependent formation of Kolbe and Hofer-Moest products

AU - Hamid, S.

AU - Ivanova, I.

AU - Jeon, T.H.

AU - Dillert, R.

AU - Choi, W.

AU - Bahnemann, D.W.

N1 - Publisher Copyright: © 2017 Elsevier Inc. Copyright: Copyright 2018 Elsevier B.V., All rights reserved.

PY - 2017/5

Y1 - 2017/5

N2 - The photocatalytic generation of H 2 and hydrocarbons from aqueous acetic acid has been studied employing TiO 2 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 2 and hydrocarbons were found to be higher for Pt-loaded TiO 2 than for bare TiO 2. 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 2, CO 2, and CH 4. Furthermore, traces of C 2H 6, C 3H 8, CO, CH 3CHO, HCHO, CH 3OH, C 2H 5OH, and HCOOH were also detected. After 15 h of illumination, the average formation rates of H 2, CO 2, CH 4, and C 2H 6 evolved at pH 2 were found to be 22, 65, 35, and 2 µmol/h, respectively. The ratio of H 2 to hydrocarbons strongly depends on the pH values, i.e., at acidic pH the ratio of H 2 to CH 4 formation was found to be 0.6. On the contrary, at neutral and basic pH values negligible amounts of hydrocarbons were formed and H 2 was found to be the main product with formation rates of 12 and 5 µmol/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.

AB - The photocatalytic generation of H 2 and hydrocarbons from aqueous acetic acid has been studied employing TiO 2 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 2 and hydrocarbons were found to be higher for Pt-loaded TiO 2 than for bare TiO 2. 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 2, CO 2, and CH 4. Furthermore, traces of C 2H 6, C 3H 8, CO, CH 3CHO, HCHO, CH 3OH, C 2H 5OH, and HCOOH were also detected. After 15 h of illumination, the average formation rates of H 2, CO 2, CH 4, and C 2H 6 evolved at pH 2 were found to be 22, 65, 35, and 2 µmol/h, respectively. The ratio of H 2 to hydrocarbons strongly depends on the pH values, i.e., at acidic pH the ratio of H 2 to CH 4 formation was found to be 0.6. On the contrary, at neutral and basic pH values negligible amounts of hydrocarbons were formed and H 2 was found to be the main product with formation rates of 12 and 5 µmol/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.

KW - Acetate

KW - Photocatalysis

KW - Platinized titania

KW - Solar fuel

KW - Surface charge

UR - http://www.scopus.com/inward/record.url?scp=85016407620&partnerID=8YFLogxK

U2 - 10.1016/j.jcat.2017.02.033

DO - 10.1016/j.jcat.2017.02.033

M3 - Article

VL - 349

SP - 128

EP - 135

JO - Journal of catalysis

JF - Journal of catalysis

SN - 0021-9517

ER -