Analyzing the temperature dependence of titania photocatalysis: kinetic competition between water oxidation catalysis and back electron–hole recombination
Author(s)
Type
Journal Article
Abstract
This study examines the kinetic origins of the temperature dependence of photoelectrochemical water oxidation on nanostructured titania photoanodes. We observe that the photocurrent is enhanced at 50 °C relative to 20 °C, with this enhancement being most pronounced (by up to 70%) at low anodic potentials (<+0.6 V vs RHE). Over this low potential range, the photocurrent magnitude is largely determined by kinetic competition between water oxidation catalysis (WOC) and recombination between surface holes and bulk electrons (back electron–hole recombination, BER). We quantify the BER process by transient photocurrent analyses under pulsed irradiation. Remarkably, we find that the kinetics of BER (∼90 ms half-time) are independent of temperature. In contrast, the kinetics of WOC, determined from the analysis of the photoinduced absorption of accumulated surface holes, are found to accelerate up to 2-fold at 50 °C relative to 20 °C. We conclude that the enhanced photocurrent densities observed in the low-applied potential region result primarily from the accelerated WOC, reducing losses due to the competing BER pathway. At higher applied potentials (>+0.6 V vs RHE), a smaller (∼10%) enhancement in photocurrent density is observed at 50 °C relative to 20 °C. Photoinduced absorption studies, correlated with studies using triethanolamine as a hole scavenger, indicate that this more modest enhancement at anodic potentials primarily results from an enhanced charge separation efficiency. We conclude by discussing the implications of these results for the practical application of photoanodic WOC under solar irradiation, influenced by these temperature-independent and -dependent underlying kinetic processes.
Date Issued
2024-11-01
Date Acceptance
2024-08-30
Citation
ACS Catalysis, 2024, 14 (21), pp.16543-16550
ISSN
2155-5435
Publisher
American Chemical Society (ACS)
Start Page
16543
End Page
16550
Journal / Book Title
ACS Catalysis
Volume
14
Issue
21
Copyright Statement
© 2024 The Authors. Published by American Chemical Society. This publication is licensed under
CC-BY 4.0 .
CC-BY 4.0 .
License URL
Identifier
https://doi.org/10.1021/acscatal.4c03685
Publication Status
Published
Date Publish Online
2024-10-24