The molecular mixed metal oxide, [H9Cu25.5O8(Nb7O22)8]28-, is found to be active in water oxidation catalysis after dissolution in pH 12 aqueous solutions of KOH. The solution maintains catalytic activity for 24 hours under electrochemical water oxidation at a high overpotential with minimal loss in corresponding current density. No electrodeposition of copper oxides were detected on the surface of the working eletrode by SEM-EDX, XPS, and ATR. The copper containing species can be reused as a water oxidation catalyst after extraction. Additional SAXS studies indicate that the polyoxometalate cluster may be aggregating at higher pH values and that copper oxide formation is unlikely in this system. We demonstrate that by starting with the polyoxometalate, [H9Cu25.5O8(Nb7O22)8]28-, we are effectively using polyoxoniobate clusters to stablize molecular copper-oxo species under conditions that would otherwise readily lead to the formation of insoluble copper oxides and copper hydroxides. This marks a rare copper-based, base-compatible, molecular water oxidation catalyst. It further indicates the potential of polyoxometalates for use as stabilizing clusters to protect molecular catalysts under reactive conditions.

Stabilizing effects of polyoxoniobates on molecular copper-oxo species in alkaline water for water oxidation catalysis

254th National Meeting (2017)

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