Green synthesis of nitrogen-doped TiO2 nanoparticles with exposed {001} facets using Chromolaena odorata leaf extract for photodegradation of pollutants under visible light

Abstract

Facet-tailored TiO2 nanoparticles (NPs) exhibit exceptional properties due to high surface energy. Conventional strategies for the fabrication of such TiO2 NPs involve harmful chemicals, which necessitates the development of environmentally benign pathways. Plant extract-assisted synthesis has emerged as a promising green alternative to conventional nanomaterial synthesis. This work introduces an innovative method for the synthesis of nitrogen-doped TiO2 (N-TiO2) NPs with exposed {001} facets using the leaf extract of a weed plant Chromolaena odorata, which is commonly known as Siam weed. The synthesis was carried out by sol-gel process with triethylamine (TEA), hydrazine hydrate and urea being the nitrogen precursors. The synthesised N-TiO2 NPs exhibited exposed {001} facets and showed a reduction in band gap. Photo-induced degradation of methylene blue dye was used to analyse the photocatalytic capability of N-TiO2 NPs in the visible range. The effect of N precursor, N dosage and light exposure time on the catalytic efficacy was studied. N-TiO2 NPs derived from TEA with 1 mol.% dopant achieved 98 % degradation in 180 minutes, while those synthesized with hydrazine and urea attained 96 % and 93 %, respectively when compared to 90 % degradation for undoped samples. The N-doping leads to significant advancement of photocatalytic effectiveness of the TiO2 NPs by introducing mid-gap levels in the forbidden energy gap that diminishes the charge carrier-recombination and boost the charge-carrier mobility of TiO2. This along with the existence of high energy facets causes a substantial advancement in the photocatalytic function in the visible region. The proposed method is a sustainable way for synthesising N-TiO2 NPs with exposed {001} facets for environment remediation applications.