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Interplay Between Charge Accumulation and Oxygen Reduction Catalysis in Nanostructured TiO 2 Electrodes Functionalized with a Molecular Catalyst
Author(s) -
Kim YeeSeul,
Kriegel Sébastien,
BessmertnykhLemeune Alla,
Harris Kenneth D.,
Limoges Benoît,
Balland Véronique
Publication year - 2021
Publication title -
chemelectrochem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.182
H-Index - 59
ISSN - 2196-0216
DOI - 10.1002/celc.202100424
Subject(s) - catalysis , electrochemistry , electrode , faraday efficiency , electron transfer , porphyrin , materials science , inorganic chemistry , redox , oxide , chemical engineering , photochemistry , chemistry , organic chemistry , engineering
The catalytic reduction of O 2 by a manganese(III) porphyrin immobilized in a nanostructured semiconductive transparent TiO 2 electrode is here investigated by UV‐Vis spectroelectrochemistry in an aqueous buffered medium. Analysis of the operando spectroelectrochemical data, collected for both the immobilized catalyst and the TiO 2 matrix, demonstrates the coexistence of two faradaic electrochemical processes, namely ( i ) irreversible interfacial electron transfer from TiO 2 to the immobilized porphyrin triggering the catalytic reduction of O 2 , and ( ii ) reversible proton‐coupled electrochemical reduction of TiO 2 leading to the accumulation of electrons in the TiO 2 bulk. The competition between these two processes is modulated by the local concentration of O 2 , which itself varies with the rate of the catalysis. Indeed, when O 2 is locally strongly depleted by catalysis, the process switches from catalysis to charge storage, like a battery. As a result, the electrons stored in TiO 2 were observed to pursue the catalysis even after the electrode polarization was switched‐off ( i. e ., under open circuit). This is an overlooked phenomenon that we believe is important to consider in applications relying on metal oxide‐based photoelectrodes operating in aqueous media.