Coprecipitation synthesis of N, Fe doped anatase TiO₂ nanoparticles and photocatalytic mechanism

N, Fe single doped and co-doped anatase TiO₂ nanoparticles were successfully prepared by coprecipitation method using TiCl₄, NH₄OH, Fe(NO₃)₃·9H₂O as raw materials and polyvinyl alcohol as dispersant. The samples were characterized by TG-DSC, FTIR, XRD, FESEM, EDS, XPS, and UV–Vis to investigate the influence of doping concentration on the thermal effect, crystal structure, morphology, composition, energy band gap and photocatalytic activity of TiO₂ nanoparticles. Results indicated that TiO₂ nanoparticles doped with 0.15 at.% N and 0.3 at.% Fe showed the best photocatalytic activity. N, Fe co-doping had a synergistic effect: (1) The transformation inhibition of anatase to rutile phase was achieved, leading to formation of high crystallized monophasic anatase TiO₂; (2) The bandgap narrowing effect was significant, increasing the light absorption range; (3) The small grain size of ~ 10 nm in diameter was obtained, resulting in effective separation of photo-induced electrons and holes.