Fabrication of tunable anatase/rutile heterojunction N/TiO2 nanophotocatalyst for enhanced visible light degradation activity

Abstract With special focus of the effect of dopant concentration on physicochemical properties, a series of visible light active nitrogen doped titania (N/TiO2) nanomaterials were successfully synthesized via sol-gel method of titanium butoxide in the presence of benign N dopant guanidium chloride. The resulting anatase/rutile (A/R) mixed phase materials were subjected to different characterization techniques, and their photocatalytic performance was evaluated against methylene blue (MB) dye under visible light irradiation. The results confirmed that the N was effectively doped in interstitial sites (7.2 atomic%) with Ti-N-O linkage, and the N/Ti mol ratio significantly dictated the physicochemical properties, and photodegradation of the photocatalysts. Notably, the mesoporous N/TiO2 (1:1 N/Ti, 42% A, 58% R with 2.91 eV band gap energy) demonstrated 97% photodegradation activity along with a fastest photodegradation rate of 0.033 min−1, which was 17 times faster than the undoped TiO2. Such excellent improvement was attributed to the synergistic effect of N-doping and optimal A/R phase composition that led to higher light absorption capacity and specific surface area, lower band gap energy and recombination rate as well as higher interstitial N in the crystal. Such promising green heterojunction photocatalysts have a broad range of applications from photocatalysis to photovoltaics.