Unification of hot spots and catalytic sites on isolated boron centers in porous carbon nitride nanosheets for efficient photocatalytic oxygen evolution

The quest for maximum photocatalysis necessitates the unification of hot spots and catalytic sites on photocatalysts. Herein, boron atoms were successfully incorporated into the tri-s-triazine unit of C3N4 (PCN-B-X), in the form of isolated B-N coordination. In-situ experimental and simulation analyses collectively demonstrated that the resulting atomic B centers and cyano groups functioned as hot spots to amplify charge dynamics and localized charge density. Concurrently, B-N coordination served as catalytic sites, reducing the activation energy for oxygen evolution reaction. Whereas, excessive B precursor led to partial B-B bonding, adversely affecting optical absorption and charge separation. Consequently, the optimal photocatalytic activity was achieved at an oxygen evolution rate of 248.9 µmol h−1 g−1 (λ > 420 nm), when the hot spots and catalytic sites were harmoniously aligned on isolated B coordination in PCN-B-20, surpassing that of C3N4 by 5.2 times. This study provides insights into photocatalytic mechanism and suggests approaches to develop robust metal-free photocatalysts for solar fuel production.