Experimental and Theoretical Research on Enhanced Visible Light Photocatalytic Performance of N-Doped TiO₂ Dielectrics

In this paper, in order to improve the response of functional dielectric TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> to visible light, doping modification method was adopted to realize the degradation of organic pollutants under natural light. The sol-gel method was used to prepare pure TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and N-doped TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> nanoparticle with doping ratio of 5at%, 10at% and 20at%. Photocatalytic properties of the samples were evaluated under UV and visible light respectively. The results show that N successfully enters the crystal lattice of anatase TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> and the N-doping modification significantly improves the absorption ability of TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> at visible wavelengths. The 10at% doped samples showed the best photocatalytic degradation efficiency under two kinds of light conditions. The results of density functional calculation of two N doping structures (substitution-doping and gap-doping) show that N doping introduces impurity levels from the hybridization of N 2p into the band gap of TiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2,</inf> reduces the effective band gap width, and causes the absorption edge to redshift, which gives a reasonable explanation for the experimental phenomenon.