Accelerated photocatalytic degradation of tetracycline hydrochloride over CuAl2O4/g-C3N4 p-n heterojunctions under visible light irradiation

In current study, the CuAl2O4/g-C3N4 p-n heterojunctions were synthesized by a self-assembly route in isopropanol, in which a tight loading structure achieved by immobilizing the p-type CuAl2O4 nanoplates on the n-type g-C3N4 nanosheets was established and verified by morphological and microstructural observations. The catalytic activity of the resultant p-n heterojunctions was examined for the photodegradation of tetracycline hydrochloride (TCH) under illumination of visible light. The results indicate that the p-n heterojunctions containing 10 wt% CuAl2O4 (10 wt% CuAl2O4/g-C3N4) showed the maximum activity and high structural stability although after multiple cycles. Photocatalytic experiments with the addition of trapping agents and spin-trapping electron paramagnetic resonance (EPR) analysis clearly revealed that the photocatalytic TCH degradation in these p-n heterojunctions mainly proceeds via superoxide radicals (O2−) and photogenerated holes (h+). The significant enhancement of photocatalytic activity is attributed to the construction of abundant p-n heterojunctions, which effectively accelerate the separation of charge pairs, and thereby improve the catalytic activity towards TCH photodegradation.