Mechanisms of water oxidation to oxygen: cobalt(IV) as an intermediate in the aquocobalt(II)-catalyzed reaction

Abstract

Both heterogeneous and homogeneous catalyses of water oxidation to 02 have been recently reported for metal oxides1 and aquo-or hydroxo-metal complexes.2 One of the more efficient systems involves cobalt(II) catalysis of water oxidation by Ru-(bpy)33+ (£°(Ru(bpy)33+/2+) = 1.26 V), which occurs above pH ~52a (eq 1). We have studied the kinetics and product distri-Ru(bpy)33+ + V2H20 = Ru(bpy)32+ + H++ >/402 (1)

Solar Water Splitting: Progress Using Hematite (α‐Fe2O3) Photoelectrodes

“…For example, water oxidation by cobalt has been extensively studied and is known to be particularly rapid. [68] The treatment of Fe 2 O 3 photoanodes (prepared by a CVD method) with a monolayer of Co 2+ resulted in a ca. 0.1 V reduction of the photocurrent onset potential.…”

Splitting Water with Cobalt

“…This system was studied by Sutin and co-workers to further characterize the reaction mechanism, but the nature of the catalyst remains undefined. [179] Recently, Styring and co-workers observed that a colloidal catalyst with spherical nanoparticules (10-60 nm radius) is produced when methylenediphosphonate is added to the photolyzed solution. Oxygen (TON % 20) is produced in aqueous solution at pH 7 under visible irradiation with [Ru(bipy) 3 ] 2+ as the photosensitizer and peroxodisulfate as the electron acceptor.…”

Molecular complexes in water oxidation: Pre-catalysts or real catalysts

“…Less than 5% decomposition (Co 2+ ions) of 26 was detected after illumination, which is too small to drive water oxidation under the operational conditions. (2) According to previous research[109], high concentration of Co 2+ ions not only delay the onset time for liberation of O 2 , but also reduce the activity of water oxidation. In contrast, 26 exhibited no lag in catalysis under illumination.…”