Efficient Light-Driven Carbon-Free Cobalt-Based Molecular Catalyst for Water Oxidation

Abstract

The abundant-metal-based polyoxometalate complex [Co(4)(H(2)O)(2)(PW(9)O(34))(2)](10-) is a hydrolytically and oxidatively stable, homogeneous, and efficient molecular catalyst for the visible-light-driven catalytic oxidation of water. Using a sacrificial electron acceptor and photosensitizer, it exhibits a high (30%) photon-to-O(2) yield and a large turnover number (>220, limited solely by depletion of the sacrificial electron acceptor) at pH 8. The photocatalytic performance of this catalyst is superior to that of the previously reported precious-metal-based polyoxometalate water oxidation catalyst [{Ru(4)O(4)(OH)(2)(H(2)O)(4)}(γ-SiW(10)O(36))(2)](10-).

Splitting Water with Cobalt

“…Quantum yields of 30 % and turnover number of more than 220 were obtained. [223] It should be noted that the experimental conditions used for such photocatalytic assays should be controlled precisely, in particular by well-defined control experiments. For example, Collomb and co-workers observed that O 2 is produced from irradiated pH 3 aqueous solutions of [Ru(bipy) 3 ] 2+ and peroxodisulfate in the absence of any catalyst.…”

Improving Singlet Oxygen Resistance during Photochemical Water Oxidation by Cobalt Porphyrin Catalysts

“…[19] Despite this limitation, this system has been widely employed as a facile means of generating [Ru(bpy) 3 ] 3 + upon visible light irradiation, which then serves as a sacrificial chemical oxidant. [15,20,21] No attention has been given to the formation of 2 + -sensitized WO catalysis. [17] Similar ringopened products are known to result from the attack of 1 O 2 on porphyrin complexes.…”

Conversion of CO2 via Visible Light Promoted Homogeneous Redox Catalysis

“…There are some reports of photocatalytic water oxidation in homogeneous systems such as molecular ruthenium complexes [125][126][127][128][129][130][131][132][133][134][135], as well as earth abundant metal complexes [136][137][138] in the presence of sacrificial electron acceptors. In this case, a recently published mononuclear ruthenium complex shows TOF values up to 0.32 s −1 [139].…”