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Photocatalytic water oxidation with cobalt-containing tungstobismutates: Tuning the metal core


Evangelisti, F; Car, P-E; Blacque, O; Patzke, Greta R (2013). Photocatalytic water oxidation with cobalt-containing tungstobismutates: Tuning the metal core. Catalysis Science & Technology, 3(12):3117.

Abstract

A new type of tungstobismutate water oxidation catalyst (WOC) with a disordered Co|W core, [{Co(H2O)3}2{CoBi2W19O66(OH)4}]10− (1) was tested for visible-light-driven performance and compared to a series of isostructural Co- and Mn-containing polyoxometalates with variable transition metal contents,([Co2.5(H2O)6{Bi2W19.5O66(OH)4}]8− (2) and [Mn1.5(H2O)6{Bi2W20.5O68(OH)2}]6− (3)). All compounds were structurally characterized, and no indications for significant decomposition under catalytic conditions for visible-light-driven water oxidation ([Ru(bpy)3]2+ as photosensitizer (PS) and {{S}2{O}8}2− as electron acceptor in different buffer systems) were found. For the first time, subtle differences in the core disorder patterns of isostructural POM-WOCs were revealed to be decisive for the catalytic activity of (1) (maximum TON of 21 with 97% oxygen yield for 115 μM (1)). Performance comparison of the POM series sheds new light on the structure–activity relationships for targeted POM-WOC construction. Indeed, the Co disorder differences between (1) and (2) exclusively affect the sterically more accessible external site of the two crystallographically independent Co core positions which has a 25% higher Co occupancy in (1). This points to a stereoselective reaction pattern for the tetranuclear POM core of WOC (1) which might open up novel construction strategies for the economic redesign of sandwich-type POM-WOCs. In parallel, we demonstrate for the POM series (1)–(3) that electrochemical measurements under catalytic conditions are a promising and convenient pre-screening strategy for WOC activity. Furthermore, POM/PS complex formation of (1) with [Ru(bpy)3]2+ is investigated in detail, and the different roles of Mn- and Co-centers in POM-WOC synthesis are compared.

Abstract

A new type of tungstobismutate water oxidation catalyst (WOC) with a disordered Co|W core, [{Co(H2O)3}2{CoBi2W19O66(OH)4}]10− (1) was tested for visible-light-driven performance and compared to a series of isostructural Co- and Mn-containing polyoxometalates with variable transition metal contents,([Co2.5(H2O)6{Bi2W19.5O66(OH)4}]8− (2) and [Mn1.5(H2O)6{Bi2W20.5O68(OH)2}]6− (3)). All compounds were structurally characterized, and no indications for significant decomposition under catalytic conditions for visible-light-driven water oxidation ([Ru(bpy)3]2+ as photosensitizer (PS) and {{S}2{O}8}2− as electron acceptor in different buffer systems) were found. For the first time, subtle differences in the core disorder patterns of isostructural POM-WOCs were revealed to be decisive for the catalytic activity of (1) (maximum TON of 21 with 97% oxygen yield for 115 μM (1)). Performance comparison of the POM series sheds new light on the structure–activity relationships for targeted POM-WOC construction. Indeed, the Co disorder differences between (1) and (2) exclusively affect the sterically more accessible external site of the two crystallographically independent Co core positions which has a 25% higher Co occupancy in (1). This points to a stereoselective reaction pattern for the tetranuclear POM core of WOC (1) which might open up novel construction strategies for the economic redesign of sandwich-type POM-WOCs. In parallel, we demonstrate for the POM series (1)–(3) that electrochemical measurements under catalytic conditions are a promising and convenient pre-screening strategy for WOC activity. Furthermore, POM/PS complex formation of (1) with [Ru(bpy)3]2+ is investigated in detail, and the different roles of Mn- and Co-centers in POM-WOC synthesis are compared.

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Additional indexing

Item Type:Journal Article, not refereed, original work
Communities & Collections:07 Faculty of Science > Department of Chemistry
Dewey Decimal Classification:540 Chemistry
Language:English
Date:2013
Deposited On:03 Feb 2014 15:50
Last Modified:07 Dec 2017 08:29
Publisher:R S C Publications
ISSN:2044-4753
Publisher DOI:https://doi.org/10.1039/C3CY00475A

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