Room-temperature synthesis of yellow TiO2 nanoparticles with enhanced photocatalytic properties

Anatase titanium dioxide (TiO2) nanoparticles have been successfully synthesized through a simple approach at low temperature. Particularly yellow TiO2 is well obtained at room temperature (25 °C). TiO2 samples are characterized by XRD, Raman, XPS, TEM, BET, UV–Vis, and Zeta Potential. The zeta potential value of TiO2 samples can be tuned from −26.8 to +13.6 mV by different reaction temperature. The yellow TiO2 has more oxygen vacancies and Ti3+ compared with other samples, which reduces the band gap from 3.1 to 2.9 eV and made the conduction band positively shift about 0.2 eV. Electrochemical impedance spectroscopy and Mott-Schottky plots reveal that the yellow TiO2 nanocrystals had higher carrier density and better conductivity for electron transfer. According to the XPS analysis, the Ti3+ content in different samples is 8.1%, 7.8%, 6%, 1%, and zero, respectively. The decomposition rate of Rhodamine B under UV light and visible light was 99.7% and 70.0%, and the NO removal efficiency in 5 min is 84.8% for yellow TiO2, respectively. The enhanced photocatalytic performance can be attributed to the presence of more oxygen vacancies in yellow TiO2 that can act as traps to reduce the recombination of e−/h+ pairs.