TY - JOUR

T1 - Understanding the degradation pathways of oxalic acid in different photocatalytic systems

T2 - Towards simultaneous photocatalytic hydrogen evolution

AU - AlSalka, Y.

AU - Hakki, A.

AU - Fleisch, M.

AU - Bahnemann, D.W.

N1 - © 2018 Elsevier B.V. All rights reserved.

PY - 2018/11/1

Y1 - 2018/11/1

N2 - The photocatalytic degradation of aqueous oxalic acid has been investigated employing different photocatalytic systems under constant pH conditions. A self-prepared TiO 2 was utilized during the photocatalytic investigations in a bare and a platinized form. The synthesized pure anatase phase TiO 2 had a 10 nm grain size and a BET surface area of ca. 121 m 2 g −1 with relatively higher photocatalytic activity compared to the commercially available TiO 2 photocatalyst UV100. Complete photocatalytic degradation of oxalic acid was observed within 60 min of illumination under aerobic condition with no by-product been detected. In the absence of molecular oxygen, a perceptible amount of formic acid was formed in the liquid phase, as determined quantitatively by means of ion chromatography. The formation of formic acid suggests that a photo-Kolbe reaction tacks place under oxygen-free conditions. The formation of formic acid was also noticed when platinized TiO 2 (0.25 wt.%) was employed, together with an enhancement of the reactions photonic efficiency to the quadruple. A hydrogen evolution could only observe under oxygen-free condition with, again, a higher formation rate over the platinized material. However, upon complete photoreforming of oxalic acid the overall amount of the photocatalytically evolved hydrogen using Pt 0.25%/TiO 2 represented only 60% of the theoretical amount. Therefore, it is suggested that the source of H atoms could be the HC 2O 4 − species rather than molecular oxalic acid. A detailed mechanism for the photocatalytic degradation of aqueous oxalic acid at different photocatalytic conditions is proposed and discussed.

AB - The photocatalytic degradation of aqueous oxalic acid has been investigated employing different photocatalytic systems under constant pH conditions. A self-prepared TiO 2 was utilized during the photocatalytic investigations in a bare and a platinized form. The synthesized pure anatase phase TiO 2 had a 10 nm grain size and a BET surface area of ca. 121 m 2 g −1 with relatively higher photocatalytic activity compared to the commercially available TiO 2 photocatalyst UV100. Complete photocatalytic degradation of oxalic acid was observed within 60 min of illumination under aerobic condition with no by-product been detected. In the absence of molecular oxygen, a perceptible amount of formic acid was formed in the liquid phase, as determined quantitatively by means of ion chromatography. The formation of formic acid suggests that a photo-Kolbe reaction tacks place under oxygen-free conditions. The formation of formic acid was also noticed when platinized TiO 2 (0.25 wt.%) was employed, together with an enhancement of the reactions photonic efficiency to the quadruple. A hydrogen evolution could only observe under oxygen-free condition with, again, a higher formation rate over the platinized material. However, upon complete photoreforming of oxalic acid the overall amount of the photocatalytically evolved hydrogen using Pt 0.25%/TiO 2 represented only 60% of the theoretical amount. Therefore, it is suggested that the source of H atoms could be the HC 2O 4 − species rather than molecular oxalic acid. A detailed mechanism for the photocatalytic degradation of aqueous oxalic acid at different photocatalytic conditions is proposed and discussed.

KW - Hydrogen evolution

KW - Oxalic acid

KW - Photocatalysis

KW - Photocatalytic reforming

KW - Solar fuel

KW - TiO

UR - http://www.scopus.com/inward/record.url?scp=85045558842&partnerID=8YFLogxK

U2 - 10.1016/j.jphotochem.2018.04.008

DO - 10.1016/j.jphotochem.2018.04.008

M3 - Article

VL - 366

SP - 81

EP - 90

JO - Journal of Photochemistry and Photobiology A: Chemistry

JF - Journal of Photochemistry and Photobiology A: Chemistry

SN - 1010-6030

ER -