Photocatalytic activation of sodium percarbonate by C3N5/C2N3 homojunction for rapid water purification: Efficient electron transfer of built-in electric field

Abstract

The sodium percarbonate (SPC) activation by photogenerated electron from metal-free semiconductors is a potential advanced oxidation process in water treatment. C2N3, a novel CxNy material, was used to construct a nonmetallic homojunction catalyst via loading C3N5. The C3N5/C2N3 homojunction catalyst was used to photocatalytic activate SPC to degrade acetaminophen (AP), sulfamethoxazole, tetracycline, oxytetracycline and acyclovir. The CN-2/SPC/Vis system can completely remove AP within 20 min at 15 °C, and achieve excellent removal rate in a wide pH range. Its reaction rate constant was 24 times higher than that of C3N5/C3N4/SPC/Vis system. The CN-2/SPC/Vis system showed outstanding removal efficiency in tap and lake water. Notably, CN-2 was prepared as a photocatalytic suspension sponge and exhibited superior practicability in secondary effluent simulation experiment. CN-2 sponge can completely degrade AP within 50 min. The dominant active species for AP removal were h+, •O2− and 1O2. DFT calculations and electrochemical experiments demonstrated that the built-in electric field of nonmetallic homojunction accelerated the carrier separation, and more photogenerated electrons activated SPC to generate ROS. This work provides new insights into the construction of heterojunction in photocatalytic system and reveals the application potential of homojunction in wastewater purification.