CuO-Assisted Deamination Molten-Salt Growth of Low-Defect CCN/LaOBr Heterojunctions for Efficient Overall Water Splitting

Abstract

Photocatalytic overall water splitting (OWS) is an eco-friendly method to produce high-purity hydrogen and oxygen using solar energy. Polymeric carbon nitride (PCN) is a promising photocatalyst, but its low polymerization degree and poor crystallinity hinder efficient charge separation and transport. Therefore, optimizing its intrinsic structure is crucial for enhancing performance. In this study, a crystalline carbon nitride (CCN)/LaOBr composite is synthesized via a CuO-assisted deamination molten-salt method. By combining CuO-catalyzed deammoniation with molten salt templating, this method reduces ammonia partial pressure and promotes precursor polycondensation, yielding CCN with high crystallinity and low defects. Enhanced crystallinity of CCN reduces charge recombination, while the CCN/LaOBr heterojunction improves charge separation and suppresses back reactions. The optimized CCN/LaOBr shows excellent photocatalytic activity, with H₂ and O₂ evolution rates of 24.2 and 10.8 μmol h⁻¹, twice those of PCN/LaOBr. This work provides insights into the designing highperformance carbon nitride-based photocatalysts through intrinsic PCN structure optimization and heterostructure formation.