Structural, magnetic, thermal and visible light-driven water oxidation studies of heterometallic Mn/V complexes

Photoinduced hole transfer from tris(bipyridine)ruthenium dye to a high-valent iron-based water oxidation catalyst

An efficient water oxidation system is a prerequisite for developing solar energy conversion devices. Using advanced time-resolved spectroscopy, we study the initial catalytic relevant electron transfer events in the light-driven water oxidation system utilizing [Ru(bpy)3]2+ (bpy = 2,2'-bipyridine) as a light harvester, persulfate as a sacrificial electron acceptor, and a high-valent iron clathrochelate complex as a catalyst. Upon irradiation by visible light, the excited state of the ruthenium dye is quenched by persulfate to afford a [Ru(bpy)3]3+/SO4˙- pair, showing a cage escape yield up to 75%. This is followed by the subsequent fast hole transfer from [Ru(bpy)3]3+ to the FeIV catalyst to give the long-lived FeV intermediate in aqueous solution. In the presence of excess photosensitizer, this process exhibits pseudo-first order kinetics with respect to the catalyst with a rate constant of 3.2(1) × 1010 s-1. Consequently, efficient hole scavenging activity of the high-valent iron complex is proposed to explain its high catalytic performance for water oxidation.

Copper-containing hybrid compounds based on extremely rare [V2Mo6O26]6– POM as water oxidation catalysts

Hybrid Cu/V/Mo compounds with rare [α-V₂Mo₆O₂₆]^6– and oxides prepared by their thermal degradation were used as catalysts for water oxidation.

A small bandgap semiconductor, p-type MnV2O6, active for photocatalytic hydrogen and oxygen production

Visible-light active MnV₂O₆ with suitable band positions for both water oxidation and reduction.

Homogeneous Cobalt/Vanadium Complexes as Precursors for Functionalized Mixed Oxides in Visible-Light-Driven Water Oxidation

The heterometallic complexes (NH₄ )₂ [Co(H₂ O)₆ ]₂ [V₁₀ O₂₈ ]⋅4 H₂ O (1) and (NH₄ )₂ [Co(H₂ O)₅ (β-HAla)]₂ [V₁₀ O₂₈ ]⋅4 H₂ O (2) have been synthesized and used for the preparation of mixed oxides as catalysts for water oxidation. Thermal decomposition of 1 and 2 at relatively low temperatures (<500 °C) leads to the formation of the solid mixed oxides CoV₂ O₆ /V₂ O₅ (3) and Co₂ V₂ O₇ /V₂ O₅ (4). The complexes (1, 2) and heterogeneous materials (3, 4) act as catalysts for photoinduced water oxidation. A modification of the thermal decomposition procedure allowed the deposition of mixed metal oxides (MMO) on a mesoporous TiO₂ film. The electrodes containing Co/V MMOs in TiO₂ films were used for electrocatalytic water oxidation and showed good stability and sustained anodic currents of about 5 mA cm^-2 at 1.72 V versus relative hydrogen electrode (RHE). This method of functionalizing TiO₂ films with MMOs at relatively low temperatures (<500 °C) can be used to produce other oxides with different functionality for applications in, for example, artificial photosynthesis.

Visible-Light-Driven Water Oxidation by a Molecular Manganese Vanadium Oxide Cluster

Photosynthetic water oxidation in plants occurs at an inorganic calcium manganese oxo cluster, which is known as the oxygen evolving complex (OEC), in photosystem II. Herein, we report a synthetic OEC model based on a molecular manganese vanadium oxide cluster, [Mn4 V4 O17 (OAc)3 ](3-) . The compound is based on a [Mn4 O4 ](6+) cubane core, which catalyzes the homogeneous, visible-light-driven oxidation of water to molecular oxygen and is stabilized by a tripodal [V4 O13 ](6-) polyoxovanadate and three acetate ligands. When combined with the photosensitizer [Ru(bpy)3 ](2+) and the oxidant persulfate, visible-light-driven water oxidation with turnover numbers of approximately 1150 and turnover frequencies of about 1.75 s(-1) is observed. Electrochemical, mass-spectrometric, and spectroscopic studies provide insight into the cluster stability and reactivity. This compound could serve as a model for the molecular structure and reactivity of the OEC and for heterogeneous metal oxide water-oxidation catalysts.