Source abstract
Abstract
The mechanisms of photoelectrochemical water and methanol oxidation on TiO2 anatase (101) and rutile (110) surfaces have been studied using the intensity modulated photocurrent spectroscopy (IMPS) technique. The phenomenological rate constants for the photogenerated charge carriers transfer and recombination have been determined at different band bending values in the presence and absence of methanol as well as at different methanol concentrations. The obtained results have been analyzed based on the IMPS theory for a bulk semiconductor surface together with a model to define the nature of the surface-bound intermediates. The results of the analysis indicated that (i) water oxidation proceeds via coupling of two >OH•br radicals on both surfaces and the coupling of >OH•br radicals is about 1 order of magnitude faster on the anatase (101) surface than that on the rutile (110) surface; (ii) the rate constant of surface recombination at the flatband potential on anatase (101) surface is much lower than that on rutile (110) surface; and (iii) in the presence of methanol, the coupling of the >OH•br radicals on the anatase (101) surface is still the dominating reaction whereas on the rutile (110) surface the photogenerated >OH•br reacts rapidly with methanol, faster by a factor of 18 times than on anatase (101) surface so that the >OH•br coupling is less dominant. On the basis of those findings, it is concluded that the coupling of the >OH•br radicals is an essential step to trap the photogenerated holes and reduce the surface recombination on anatase (101) surface in the absence and presence of methanol. The faster reaction of methanol with the >OH•br on rutile (110) compared with that on anatase (101), while the former usually exhibits lower photocatalytic activity, indicates that the charge separation (not the charge transfer) is the rate controlling step in the photocatalytic process.
Source: openalex_inverted_index · Quality: baseline
Affiliations
Department of Chemistry, Faculty of Science, Sohag University, Sohag 82524, Egypt
Department of Chemistry, King Fahd University of Petroleum & Minerals (KFUPM), Dhahran 31261, Saudi Arabia
Researcher at K.A.CARE Energy Research & Innovation Center at Dhahran, Dhahran 31261, Saudi Arabia
Institute of Physical Chemistry and Electrochemistry, Leibniz Universität Hannover, Callinstrasse 3A, 30167 Hannover, Germany
Photocatalysis and Nanotechnology Research Unit, Institute of Technical Chemistry, Leibniz Universität Hannover, Callinstrasse 3A, 30167 Hannover, Germany
Laboratory for Nanocomposite Materials, Department of Photonics, Faculty of Physics, Saint-Petersburg State University, Ulianovskaia str. 3, Peterhof, Saint Petersburg 198504, Russia
Funding
Saint Petersburg State University · Deanship of Scientific Research, King Faisal University · King Abdullah City for Atomic and Renewable Energy