Breaking Interfacial Charge Transport Limitations of Carbon Nitride-Based Homojunction by Lattice-Matched Interfacial Engineering for Enhanced Photocatalytic Overall Water Splitting

Constructing S-scheme heterojunctions is widely recognized as an effective strategy to enhance the photocatalytic overall water-splitting performance of polymeric carbon nitride. However, carbon nitride-based S-scheme heterojunctions are frequently constrained by a low lattice matching degree, weak interfacial adhesion, and high interfacial trap density, which significantly impede interface electron transport efficiency. To address these limitations, we fabricate a crystalline Rb doped polyheptazine imide (Rb-PHI)/melon (P&M) homojunction with tiny lattice mismatches by the flux-assisted synthesis method. Structural characterizations confirm that the flux-assisted synthesis method can effectively regulate the interface structure between PHI and melon, thus forming a crystalline and coherent homointerface. Moreover, kinetic analysis reveals that fabricating a nanoscale lattice-matched homointerface can generate a robust interfacial electric field, thereby facilitating the directed migration and spatial separation of photoexcited electrons and holes. More importantly, we find that the photocatalytic overall water-splitting activity and interfacial charge transfer efficiency of P&M homojunction depend on the degree of interfacial lattice matching and crystallinity. This study underscores the significance of interfacial structure for enhancing the charge transfer efficiency in S-scheme homojunctions and offers valuable insights and methodologies for developing high-performance S-scheme homojunctions.