Issue 5, 2020

Multi-potential-step chronocoulospectrometry for electrocatalytic water oxidation by a mononuclear ruthenium aquo complex immobilized on a mesoporous ITO electrode

Abstract

A new mononuclear Ru aquo complex [Ru(C8Otpy)(H2dcbpy)(OH2)]2+ with 4,4′-dicarboxy-2,2′-bipyridine (H2dcbpy) and 4′-octyloxy-2,2′:6′,2′′-terpyridine (C8Otpy) ligands was synthesized to investigate electrocatalytic water oxidation by the complex immobilized on a mesoporous indium-doped tin oxide (meso-ITO) electrode using a multi-potential-step chronocoulospectrometric (MPSCCS) technique. UV-visible absorption spectroscopic data indicated that [Ru(C8Otpy)(dcbpy)(OH2)] (RuOH2) is deprotonated to [Ru(C8Otpy)(dcbpy)(OH)] (RuOH) on the meso-ITO surface even at pH 5.9 of the electrolyte solution. The cyclic voltammogram (CV) of the RuOH/meso-ITO electrode showed a pH-independent redox response at E1/2 = 0.80 V vs. Ag/AgCl in the pH range of 5–12, being assigned to a non-proton-coupled 1e redox process of RuIIOH/RuIIIOH. The MPSCCS measurement of the RuOH/meso-ITO electrode between 0.2 and 1.5 V vs. Ag/AgCl showed that RuIV species (tentatively RuIVO) exist in a steady state of the electrocatalysis in the initial stage. This suggests that the electrochemical oxidation from RuIVO to RuVO could compete with the water nucleophilic attack for O–O bond formation involved in the rate-determining step under the employed conditions. The possibility that the water nucleophilic attack on RuIVO could also compete with the electrochemical oxidation of RuIVO to RuVO was suggested by the electrocatalytic water oxidation at a low applied potential of 1.4 V prior to the formation potential of RuVO. The MPSCCS measurement at 1.4 V for 1 h showed that RuOH is gradually transformed into an alternative catalyst (most likely RuOx nanoparticles) on the electrode. The MPSCCS technique is promising to reveal the redox reactions and catalytic aspects of molecular catalysts immobilized on an electrode for water oxidation.

Graphical abstract: Multi-potential-step chronocoulospectrometry for electrocatalytic water oxidation by a mononuclear ruthenium aquo complex immobilized on a mesoporous ITO electrode

Supplementary files

Article information

Article type
Paper
Submitted
18 نومبر 2019
Accepted
23 دسمبر 2019
First published
23 دسمبر 2019

Dalton Trans., 2020,49, 1416-1423

Multi-potential-step chronocoulospectrometry for electrocatalytic water oxidation by a mononuclear ruthenium aquo complex immobilized on a mesoporous ITO electrode

Y. Tsubonouchi, J. Honta, T. Sato, E. A. Mohamed, Z. N. Zahran, K. Saito, T. Yui and M. Yagi, Dalton Trans., 2020, 49, 1416 DOI: 10.1039/C9DT04442F

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements