A high-frequency (95 GHz) electron paramagnetic resonance study of B-doped TiO2 photocatalysts

A high-field and high-frequency (HF, 95 GHz) electron paramagnetic resonance (EPR) study has been carried on B-doped TiO2. Several paramagnetic species are observed both in the dark and under UV irradiation which are resolved employing the high resolution of HFEPR. The behaviour of the EPR signals may be interpreted in terms of a sensitization of the B-doped TiO2 to visible light. A paramagnetic species interacting with a B atom is found. The Hamiltonian parameters of this species carry important information on its electronic structure. The analysis of the hyperfine values reveals that the spin density is mainly centred on the B and asymmetrically distributed in two p B orbitals. Insights into the B local structure in the semiconductor are gained.