Synthesis and Characterization of Nitrogen-Doped TiO₂ Nanophotocatalyst with High Visible Light Activity

TLDR

Nitrogen doping improves TiO₂ photocatalytic activity by narrowing its band gap for visible‑light absorption and suppressing electron–hole recombination. The authors synthesized homogeneous anatase TiO₂ nanocatalysts doped with nitrogen via a microemulsion–hydrothermal process using organic nitrogen sources such as triethylamine, urea, thiourea, and hydrazine hydrate. Raman and XPS confirmed successful nitrogen incorporation in Ti–O–N and O–Ti–N sites, leading to a red‑shifted absorption edge and enhanced visible‑light photocatalytic degradation of rhodamine B and 2,4‑dichlorophenol, with triethylamine‑doped TiO₂ exhibiting the highest activity at an optimal doping level.

Abstract

Nitrogen-doped TiO2 nanocatalysts with a homogeneous anatase structure were successfully synthesized through a microemulsion−hydrothermal method by using some organic compounds such as triethylamine, urea, thiourea, and hydrazine hydrate. Analysis by Raman and X-ray photoemission spectroscopy indicated that nitrogen was doped effectively and most nitrogen dopants might be present in the chemical environment of Ti−O−N and O−Ti−N. A shift of the absorption edge to a lower energy and a stronger absorption in the visible light region were observed. The results of photodegradation or the organic pollutant rhodamine B in the visible light irradiation (λ > 420 nm) suggested that the TiO2 photocatalysts after nitrogen doping were greatly improved compared with the undoped TiO2 photocatalysts and Degussa P-25; especially the nitrogen-doped TiO2 using triathylamine as the nitrogen source showed the highest photocatalytic activity, which also showed a higher efficiency for photodecomposition of 2,4-dichlorophenol. The nitrogen doping concentration had an optimal value, and accordingly, the photocatalyst showed the highest photocatalytic activity. This suggested that nitrogen doping has important effects on the improvement of photocatalytic activity: on one hand, nitrogen doping could narrow the band gap of titania to extend the adsorption of catalyst to the visible light region; on the other hand, nitrogen doping could inhibit the recombination of the photoinduced electron and thereafter increase the efficiency of the photocurrent carrier.