Enhancing Cs ₂ AgBiBr ₆ Photocatalysis via Rationalizing S-Scheme Heterojunction with Zinc Phthalocyanine as the Reductive Side

Lead-free double perovskite Cs₂AgBiBr₆ (CABB) has emerged as a promising photocatalytic material, but its efficiency is limited by rapid electron-hole recombination and insufficient active sites. Herein, an S-scheme heterojunction photocatalyst was constructed through the <i>in situ</i> growth of CABB nanosheets on a zinc phthalocyanine (ZnPc) substrate, where ZnPc acted as the reduction site with abundant high-energy electrons. Comprehensive characterizations confirmed the formation of robust interfacial Zn-Br bonds, ensuring intimate contact between ZnPc and CABB. Under visible-light irradiation, the optimized 0.05ZnPc/CABB composite exhibited significantly enhanced photocatalytic activity, achieving complete degradation of Rhodamine B (RhB) within 20 min, which outperformed pristine CABB and ZnPc. Mechanistic investigations involving photoelectrochemical measurements and density functional theory calculations revealed that the S-scheme band alignment, driven by the interfacial Zn-Br bonds and the built-in electric field, significantly enhanced charge separation and transfer. Additionally, the composite displayed excellent stability, maintaining 99% RhB degradation efficiency after five cycles. This work provides a novel strategy to enhance CABB photocatalysis via constructing S-scheme heterojunctions with ZnPc, highlighting potential applications in environmental remediation.