Reinvestigation of Water Oxidation Catalyzed by a Dinuclear Cobalt Polypyridine Complex: Identification of CoO_<i>x</i> as a Real Heterogeneous Catalyst

Abstract

Recently, a dinuclear cobalt complex, [(TPA)CoIII(μ-OH)(μ-O2)CoIII(TPA)](ClO4)3 (1; TPA = tris(2-pyridylmethyl)amine), has been reported as a homogeneous catalyst for electrochemical and photochemical water oxidation (Angew. Chem. Int. Ed. 2014, 53, 14499). During the reinvestigation of the reported water oxidation catalyst (WOC) of 1, several characterizations such as EDTA and bipyridine titrations, electrochemistry, SEM, EDX, ICP-AES, TEM, XPS, and UV–vis spectroscopy have revealed that the water oxidation may happen due to the formation of CoOx as a real heterogeneous WOC, and 1 itself lacks the ability to catalyze water oxidation. This paper presents a practical and simple procedure to clarify whether the water oxidation is truly catalyzed by a molecular catalyst or not.