P-N bonds in P-modified biochar/g-C3N4 composite constructed via mechanochemical method to enhance photodegradation of indigo carmine

Photodegradation of indigo carmine (IC) in wastewater has received much attention in recent decades. However, the current photocatalysts used for IC photodegradation suffer from an unsatisfactory efficiency due to low yield of reactive species. Herein, a P-modified biochar/g-C3N4 (P-BC/CN) photocatalyst was fabricated by mechanochemical method using P-modified biochar and g-C3N4 as precursors. It is discovered that PN bonds were constructed between P-modified biochar and g-C3N4, and these bonds served as the active sites to promote the generation of •O2− during the photodegradation process. The biochar component in P-BC/CN composite is conducive to transfer the photogenerated carriers, thereby avoiding their recombination. The photodegradation experiment showed that the P-BC/CN composite exhibits an impressive photodegradation performance towards IC (C0 = 50 mg/L) with a photodegradation rate of 95.3% in 120 min. This work provides a green and efficient method to design biochar-based photocatalyst with PN active sites for advanced wastewater purification.