A Biomimetic Copper Water Oxidation Catalyst with Low Overpotential

Simply mixing a Cu­(II)
salt and 6,6′-dihydroxy-2,2′-bipyridine
(H2L) in a basic aqueous solution afforded
a highly active water oxidation catalyst (WOC). Cyclic voltammetry
of the solution at pH = 12–14 shows irreversible catalytic
current with an onset potential of ∼0.8 V versus NHE. Catalytic
oxygen evolution takes place in controlled potential electrolysis
at a relatively low overpotential of 640 mV. Experimental and computational
studies suggest that the L ligand participates in electron
transfer processes to facilitate the oxidation of the Cu center to
lead to an active WOC with low overpotential, akin to the use of the
tyrosine radical by Photosystem II to oxidize the CaMn4 center for water oxidation.