Study of Homologous Elements: Fe, Co, and Ni Dopant Effects on the Photoreactivity of TiO2Nanosheets

Despite sustained effort over the years, additional investigations into the relationship between doping elements and the photocatalytic properties of TiO2 are needed. In this work, Fe-group(Fe, Co, Ni)-doped anatase TiO2 nanosheets with exposed {0 0 1} facets are prepared by using a facile solvothermal synthetic route. A change in the type and concentration of the doping element consequently leads to a change in the size and percentage of {0 0 1} facets in the TiO2 nanosheets, and finally causes a significant difference in the photocatalytic activities of the as-prepared TiO2 samples. In this case, the performance of doped TiO2, which serves as the photocatalyst, is investigated by directly assessing its effect on the photodegradation of azo dyes (methylene blue) under UV and visible light irradiation, respectively. Importantly, for the first time these studies reveal that the order of the activities of the doped TiO2 is Ni>Co>Fe, and the optimal value of the percentage of the doping ions to Ti ions is 0.75 %. Electrochemical impedance spectra, photocurrent, and photoluminescence measurements indicate that the charge separation and transportation rate is mainly influenced by the type and concentration of doping ions, which determines the photodegradation activities of the TiO2 host.