The ability of Nature to achieve high-efficiency catalytic water oxidation in plants and cyanobacteria using the earth-abundant metals Mn and Ca sets the standard for artificial systems targeted at development of new energy technologies based on the water reserves of the planet. Most of the latter have been based on 4d and 5d metals such as Ru and Ir, but more recently the development of water oxidation catalysts (WOCs) using earth-abundant 3d metals such as Mn, Co and Cu has become more intensely investigated. Homometallic, high oxidation state Mn and Co systems have been extensively researched as WOCs over the past 20 years, but only recently has an efficient Mn-based WOC been reported, the [Mn12O12(dhb)16(H2O)4] (dhb- = 3,5-dihydroxybenzoate) cluster, which is a water oxidation electrocatalyst with a low overpotential of 0.33 V. While very active, the catalysis begins to decay within a few hours, assigned to slow degradation of the cluster. Since several robust Co/O clusters containing kinetically-inert CoIII have also been reported to be good WOCs, we have initiated a program seeking to amalgamate the benefits of the two areas by developing mixed-metal high nuclearity Co/Mn/O/RCO2- clusters. In this presentation will be described the development of a synthetic route to a new family of high oxidation state CoIII/MnIV/O clusters and their characterization by X-ray crystallography, magnetic studies, and other techniques, as well as the results from an investigation of its water oxidation activity.

Cobalt-manganese-oxide clusters as water oxidation catalysts

2019 Spring National Meeting

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