Sol-gel Synthesis, Photo- and Electrocatalytic Properties of Mesoporous TiO₂ Modified with Transition Metal Ions

Mesoporous nanosized titania films modified with Co²⁺, Ni²⁺, Mn³⁺, and Cu²⁺ ions have been produced by templated sol-gel method and characterized by optical spectroscopy, X-ray diffraction (XRD), and Brunauer, Emmett, and Teller (BET) surface area measurement. Band gap energy and the position of flat band potentials were estimated by photoelectrochemical measurements. The films doped with transition metals possessed higher photocurrent quantum yield, as well as photo- and electrochemical activity compared to undoped samples. Mⁿ⁺/TiO₂ (M-Co, Ni, Mn, Cu) electrodes with low dopant content demonstrate high efficiency in electrocatalytic reduction of dissolved oxygen. Polarization curves of TiO₂, TiO₂/Ni²⁺, TiO₂/Co^2+/3+, and TiO₂/Mn³⁺ electrodes contain only one current wave (oxygen reduction current). It means that reaction proceeds without the formation of an intermediate product H₂O₂.