Enhanced photoactivity of Sm, N, P-tridoped anatase-TiO2 nano-photocatalyst for 4-chlorophenol degradation under sunlight irradiation

A novel high-performance Sm, N, P-tridoped anatase-TiO2 nano-photocatalyst (SNPTO) was successfully prepared by a modified sol–solvothermal process. The physicochemical properties of as-prepared samples were characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption–desorption isotherm, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, UV–vis absorbance spectroscopy, photoluminescence spectroscopy, and zeta potential measurements. The results showed that, among as-prepared undoped, single-doped, and codoped samples, SNPTO presented the highest photoactivity for degrading 4-chlorophenol (4-CP) under simulated sunlight irradiation with the apparent rate constant of 2.83 × 10−2 min−1, which was 3.98 times more than that of commercial P25 TiO2 (kapp = 7.11 × 10−3 min−1). The TOC removal rate for 4-CP solution (20 mg L−1) in the presence of SNPTO (0.4 g L−1) reached 87.13% after simulated sunlight irradiation for 120 min, indicating that 4-CP could be mineralized efficiently. Experiments concerning radical scavengers indicated that OH in the solution was the main reactive species. The enhanced photoactivity of SNPTO was attributed to a synergistic effect of the more efficient inhibition of the recombination of photogenerated electrons and holes, the increase in the visible light absorption ability, surface hydroxyl and specific surface area, as well as the improvement of the surface textural properties. SNPTO exhibited good photochemical stability and could be reused for 5 times with less than 1.6% decrease in the 4-CP removal efficiency.