A porphyrin-stabilized iridium oxide water oxidation catalyst

Colloidal solutions of iridium oxide hydrate (IrO₂· nH₂O) were formed using porphyrin stabilizers bearing malonate-like functional groups at each of the four meso positions of the porphyrin ring. Cyclic voltammetry and monitoring of solution oxygen concentrations under constant applied potential demonstrated the electrochemical catalytic activity of the porphyrin-IrO₂·nH₂O complexes for the oxidation of water to oxygen. Quenching of the porphyrin fluorescence in the complex implies strong interaction between the porphyrin and the IrO ₂·nH₂O. These results mark a step toward developing a porphyrin-based photoanode for use in a photoelectrochemical water-splitting cell.