Imperial College London
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Dr Steph Pendlebury

Faculty of Engineering

IMSE Institute Manager
 
 
 
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Contact

 

+44 (0)20 7594 0901s.pendlebury Website

 
 
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Location

 

Level 2 Office, Central LibraryAbdus Salam LibrarySouth Kensington Campus

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Summary

 

Publications

Citation

BibTex format

@article{Kafizas:2017:10.1021/acscatal.7b01150,
author = {Kafizas, A and Ma, Y and Pastor, E and Pendlebury, SR and Mesa, C and Francas, L and Le, Formal F and Noor, N and Ling, M and Sotelo-Vazquez, C and Carmalt, CJ and Parkin, IP and Durrant, JR},
doi = {10.1021/acscatal.7b01150},
journal = {ACS CATALYSIS},
pages = {4896--4903},
title = {Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO2 Photoanode: A Rate Law Analysis},
url = {http://dx.doi.org/10.1021/acscatal.7b01150},
volume = {7},
year = {2017}
}
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RIS format (EndNote, RefMan)

TY  - JOUR
AB  - It has been more than 40 years since Fujishima and Honda demonstrated water splitting using TiO2, yet there is still no clear mechanism by which surface holes on TiO2 oxidize water. In this paper, we use a range of complementary techniques to study this reaction that provide a unique insight into the reaction mechanism. Using transient photocurrent and transient absorption spectroscopy, we measure both the kinetics of electron extraction (t50% ≈ 200 μs, 1.5VRHE) and the kinetics of hole oxidation of water (t50% ≈ 100 ms, 1.5VRHE) as a function of applied potential, demonstrating the water oxidation by TiO2 holes is the kinetic bottleneck in this water-splitting system. Photoinduced absorption spectroscopy measurements under 5 s LED irradiation are used to monitor the accumulation of surface TiO2 holes under conditions of photoelectrochemical water oxidation. Under these conditions, we find that the surface density of these holes increases nonlinearly with photocurrent density. In alkali (pH 13.6), this corresponded to a rate law for water oxidation that is third order with respect to surface hole density, with a rate constant kWO = 22 ± 2 nm4·s–1. Under neutral (pH = 6.7) and acidic (pH = 0.6) conditions, the rate law was second order with respect to surface hole density, indicative of a change in reaction mechanism. Although a change in reaction order was observed, the rate of reaction did not change significantly over the wide pH range examined (with TOFs per surface hole in the region of 20–25 s–1 at ∼1 sun irradiance). This showed that the rate-limiting step does not involve OH– nucleophilic attack and demonstrated the versatility of TiO2 as an active water oxidation photocatalyst over a wide range of pH.
AU  - Kafizas,A
AU  - Ma,Y
AU  - Pastor,E
AU  - Pendlebury,SR
AU  - Mesa,C
AU  - Francas,L
AU  - Le,Formal F
AU  - Noor,N
AU  - Ling,M
AU  - Sotelo-Vazquez,C
AU  - Carmalt,CJ
AU  - Parkin,IP
AU  - Durrant,JR
DO  - 10.1021/acscatal.7b01150
EP  - 4903
PY  - 2017///
SN  - 2155-5435
SP  - 4896
TI  - Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO2 Photoanode: A Rate Law Analysis
T2  - ACS CATALYSIS
UR  - http://dx.doi.org/10.1021/acscatal.7b01150
UR  - http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000405360800084&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
UR  - http://hdl.handle.net/10044/1/50880
VL  - 7
ER  -
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