Improved charge carrier dynamics in rationally designed F-g-C3N4/In2O3 type II heterojunction for efficient pollutant removal: Mechanistic insights, real-world applications, and toxicity study

Herein, we present a simple chemical bath/impregnation method for synthesizing fluorine (F)-doped graphitic carbon nitride (g-C₃N₄)/indium oxide (In₂O₃) type-II heterojunction for enhanced photocatalytic degradation of methylene blue (MB) and tetracycline (TC), and reduction of Cr(VI) pollutants under visible light irradiation. Heterojunction formation and F-doping were confirmed using several physicochemical characterization techniques. The synthesized F-doped g-C₃N₄/In₂O₃(FCN/INO) photocatalyst demonstrated remarkable degradation efficiencies, achieving 97 % MB degradation in 60 min, 97 % TC degradation in 35 min, and 96 % Cr(VI) reduction in 40 min. The FCN/INO sample exhibited exceptional photocatalytic activity for pollutant degradation in tap and lake water, and also for effectively degrading MB + TC mixtures. It demonstrated outstanding stability over five cycles, confirming excellent recyclability. Strong anti-interference activity ensured robustness against co-existing ions, and toxicity studies confirmed the formation of non-toxic degradation products, highlighting its suitability for long-term environmental applications. The improved photocatalytic performance of FCN/INO is ascribed to its exceptional optical, electronic, and surface properties, which promote efficient electron-hole pair generation, separation, and rapid transport, as confirmed by photoluminescence (PL), electrochemical impedance spectroscopy, and photocurrent density data. The charge carrier lifetime, as determined via time-resolved PL, was found to be significantly longer in FCN/INO than in its bare counterparts.