Photoelectrocatalytic Synthesis of Hydrogen Peroxide by Molecular Copper‐Porphyrin Supported on Titanium Dioxide Nanotubes

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.