Abstract
We report on a self-assembled system comprising a molecular copper-porphyrin photoelectrocatalyst, 5-(4-carboxy-phenyl)-10,15,20-triphenylporphyrinatocopper(II) (CuTPP-COOH), covalently bound to self-organized, anodic titania nanotube arrays (TiO(2) NTs) for photoelectrochemical reduction of oxygen. Visible light irradiation of the porphyrin-covered TiO(2) NTs under cathodic polarization up to -0.3 V vs. Normal hydrogen electrode (NHE) photocatalytically produces H(2)O(2) in pH neutral electrolyte, at room temperature and without need of sacrificial electron donors. The formation of H(2)O(2) upon irradiation is proven and quantified by direct colorimetric detection using 4-nitrophenyl boronic acid (p-NPBA) as a reactant. This simple approach for the attachment of a small molecular catalyst to TiO(2) NTs may ultimately allow for the preparation of a low-cost H(2)O(2) evolving cathode for efficient photoelectrochemical energy storage under ambient conditions.