TY - JOUR

T1 - Isotopic studies on the degradation of acetaldehyde on anatase surfaces

AU - Melchers, S.

AU - Schneider, J.

AU - Bahnemann, D.W.

N1 - Funding information: This work was funded by the German Federal Ministry of Education and Research (contract no. 13N13350, PureBau – Untersuchung von Werkstoffsystemen für photokatalytisch hocheffiziente Baustoffe- Teilvorhaben: Oberflächenchemie der Photokatalysatoren und der Werkstoffe). The authors wish to thank Juan F. Montoya for the synthesis of Ti 18 O 2 and Luis Granone for the Raman and XRD analysis.

PY - 2020/1/15

Y1 - 2020/1/15

N2 - Herein, we studied the role of bridging oxygen (O br 2−) in the photocatalytic degradation reaction of gaseous acetaldehyde under anaerobic conditions. Ti 16O 2 and the isotopologues Ti 18O 2 were treated with acetaldehyde in the dark and upon UV illumination and at the reactor outlet the evolved C 16O 2 and C 18O 16O were monitored by mass spectrometry (MS). Ti 16O 2 exhibited a constant C 18O 16O/C 16O 2 ratio in the dark and upon UV illumination. In the dark the C 18O 16O/C 16O 2 ratio obtained with Ti 18O 2 was similar to the ratio monitored with Ti 16O 2, while upon UV illumination the ratio increased evincing an incorporation of O br 2− into the formation of CO 2. Accordingly, a following reaction mechanism could be derived: upon UV illumination the generated holes are trapped by the bridging oxygens forming O br [rad]− , which then react with adsorbed acetaldehyde forming acetate that is decomposed into CO 2 and CH 4. The remaining oxygen vacancy is replenished by an oxygen atom supplied by adsorbed water. This is, to the best of our knowledge, the first time that the crucial role of O br 2− within the photocatalytic process has been described for a gas phase reaction.

AB - Herein, we studied the role of bridging oxygen (O br 2−) in the photocatalytic degradation reaction of gaseous acetaldehyde under anaerobic conditions. Ti 16O 2 and the isotopologues Ti 18O 2 were treated with acetaldehyde in the dark and upon UV illumination and at the reactor outlet the evolved C 16O 2 and C 18O 16O were monitored by mass spectrometry (MS). Ti 16O 2 exhibited a constant C 18O 16O/C 16O 2 ratio in the dark and upon UV illumination. In the dark the C 18O 16O/C 16O 2 ratio obtained with Ti 18O 2 was similar to the ratio monitored with Ti 16O 2, while upon UV illumination the ratio increased evincing an incorporation of O br 2− into the formation of CO 2. Accordingly, a following reaction mechanism could be derived: upon UV illumination the generated holes are trapped by the bridging oxygens forming O br [rad]− , which then react with adsorbed acetaldehyde forming acetate that is decomposed into CO 2 and CH 4. The remaining oxygen vacancy is replenished by an oxygen atom supplied by adsorbed water. This is, to the best of our knowledge, the first time that the crucial role of O br 2− within the photocatalytic process has been described for a gas phase reaction.

KW - Acetaldehyde

KW - Degradation mechanism

KW - Lattice oxygen

KW - Photocatalysis

KW - TiO

UR - http://www.scopus.com/inward/record.url?scp=85055838830&partnerID=8YFLogxK

U2 - 10.1016/j.cattod.2018.10.016

DO - 10.1016/j.cattod.2018.10.016

M3 - Article

VL - 340

SP - 318

EP - 322

JO - Catalysis today

JF - Catalysis today

SN - 0920-5861

ER -