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The existence form and effect of La on the phase composition,morphology,recombination of photocarriers,and optical absorptivity of La-F codoped TiO2 were investigated.Experimental results indicate that all the phase composition of samples is anatase TiO2,the grain sizes decrease with the increasing of La content.The catalysts have a well-defined spherical structure with an average size of 12 -14 nm,and the doping elements are uniformly dispersed.Compared with pure TiO2,the absorption edge of La1.5F5-TiO2 red shifts from 388 to 437 nm,accordingly the energy gap (Eg) reduces from 3.2 to 2.84 eV.Besides,the recombination rate of electron-holes in La1.5F5-TiO2 is the weakest among the prepared samples,and the specific surface area of La1.5F5-TiO2 reaches 105.27 m2/g.The apparent reaction rate constant k of La1.5F5-TiO2 for methylene blue (MB) degradation under visible light obtained from the apparent first-order model achieves 0.0166 + 0.52 min-1,which is greater than 0.0033 ± 0.09 min-1 of TiO2.Moreover,high-resolution transmission electron microscopy (HRTEM) observation reveals that there coexist La2O3 particles in the co-doped TiO2.