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

Abstract

The as-prepared CuAl 2 O 4 /g-C 3 N 4 hybrid systems by decorating p -type CuAl 2 O 4 nanoplates on the surface of n -type g-C 3 N 4 nanosheets exhibit enhanced photocatalytic activity for the degradation of tetracycline hydrochloride because of speedy charge separation driving by p-n heterojunctions. • CuAl 2 O 4 nanoplates assembled on g-C 3 N 4 nanosheets yield many p - n heterojunctions. • CuAl 2 O 4 /g-C 3 N 4 achieved 90% tetracycline hydrochloride photodegradation in 1 h. • Improved photocatalytic activity attributed to rapid charge separation and transfer. In current study, the CuAl 2 O 4 /g-C 3 N 4 p-n heterojunctions were synthesized by a self-assembly route in isopropanol, in which a tight loading structure achieved by immobilizing the p -type CuAl 2 O 4 nanoplates on the n -type g-C 3 N 4 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% CuAl 2 O 4 (10 wt% CuAl 2 O 4 /g-C 3 N 4 ) 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 ( O 2 − ) 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.