Catalytic Activity of an Iron-Based Water Oxidation Catalyst: Substrate Effects of Graphitic Electrodes

The
synthesis, characterization, and electrochemical studies of
the dinuclear complex [(MeOH)­Fe­(Hbbpya)-μ-O-(Hbbpya)­Fe­(MeOH)]­(OTf)4 (1) (with Hbbpya = N,N-bis­(2,2′-bipyrid-6-yl)­amine)
are described. With the help of online electrochemical mass spectrometry,
the complex is demonstrated to be active as a water oxidation catalyst.
Comparing the results obtained for different electrode materials shows
a clear substrate influence of the electrode, as the complex shows
a significantly lower catalytic overpotential on graphitic working
electrodes in comparison to other electrode materials. Cyclic voltammetry
experiments provide evidence that the structure of complex 1 undergoes reversible changes under high-potential conditions, regenerating
the original structure of complex 1 upon returning to
lower potentials. Results from electrochemical quartz crystal microbalance
experiments rule out that catalysis proceeds via deposition of catalytically
active material on the electrode surface.