Abstract
Polymeric carbon nitride (PCN) holds great promise for photocatalytic H(2)O(2) production owing to its excellent stability and structural tunability. However, the inferior overall photocatalytic performance of PCN owing to its limited charge separation efficiency is a longstanding challenge. Herein, a K⁺-doped bridge-type PCN featuring ─C≡N and ─OH surface groups is synthesized via thermal polymerization. K-PCN exhibits superior efficiency for photocatalytic H(2)O(2) production (8647.78 µM·h(-1)) with a quantum efficiency of 17.92% at 420 nm, remarkably surpassing that of PCN (86.96 µM·h(-1) and 0.129%). K⁺ ions tend to reside within the interlayers of PCN, where they create K(+)-bridges that reduce interlayer spacing, strengthen π-π stacking, and improve crystallinity, thereby accelerating charge transport by shortening carrier migration pathways and suppressing recombination. Moreover, K(+) perturbs the local electronic structure via interaction with nitrogen lone pairs, thereby narrowing the bandgap and enhancing visible-light absorption. The introduction of ─C≡N and ─OH groups enrich the surface with polar sites, with ─C≡N promoting O(2) adsorption and activation through electron delocalization and ─OH increasing hydrophilicity and O(2) concentration via hydrogen bonding. This study elucidates the pathway and mechanism of photocatalytic oxygen reduction and provides novel insights into the reasonable design of bridge-type group-modified PCN for efficient H(2)O(2) production.