Issue 9, 2024

Sequential proton coupled electron transfer events from a tetraruthenium polyoxometalate in photochemical water oxidation

Abstract

The tetraruthenium polyoxometalate {RuIV(H2O)4(μ-OH)2(μ-O)4[SiW10O36]2}10− (Ru4POM) shows multiple oxidative proton coupled electron transfer (PCET) events in a [Ru(bpy)3]2+/S2O82− photochemical cycle for catalytic water oxidation, with electrons conveyed to the photogenerated [Ru(bpy)3]3+ oxidant and protons transferred to aqueous bases. As shown by laser flash photolysis, in aqueous phosphate buffer the consumption of the [Ru(bpy)3]3+ oxidant by Ru4POM shows bi-exponential kinetics with a fast component and a slow component that feed the Ru4POM catalyst with up to 6 oxidative equivalents through PCET in ca. 50 ms. The apparent rates of both the fast and slow components depend linearly on HPO42− and on the pH of the aqueous medium, suggesting the involvement of the buffer base, of water and of OH in assisting removal of the protons from Ru4POM. In particular, the beneficial role of HPO42− is reflected in a proportional improvement in the oxygen evolution activity, reaching quantum efficiency approaching 14%, although an excessive increase of buffer concentration is detrimental to the [Ru(bpy)3]3+ stability and leads to the abatement of the O2 evolution.

Graphical abstract: Sequential proton coupled electron transfer events from a tetraruthenium polyoxometalate in photochemical water oxidation

Supplementary files

Article information

Article type
Paper
Submitted
26 jan 2024
Accepted
16 mar 2024
First published
18 mar 2024
This article is Open Access
Creative Commons BY-NC license

Sustainable Energy Fuels, 2024,8, 1944-1952

Sequential proton coupled electron transfer events from a tetraruthenium polyoxometalate in photochemical water oxidation

E. Rossin, M. Bonchio, M. Natali and A. Sartorel, Sustainable Energy Fuels, 2024, 8, 1944 DOI: 10.1039/D4SE00146J

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