Lead-free double halide perovskite Cs2AgBiI6/g-C3N4 heterojunction photocatalysts for effective visible-light photocatalytic activity

Abstract

Perovskites are known for their exceptional photocatalytic properties, owing to their unique optoelectronic characteristics and structural versatility. However, the inherent instability and toxicity of conventional perovskites have restricted their practical application. The development of double perovskite materials has successfully addressed some of these issues. Nevertheless, problems such as significant charge recombination and slow surface catalytic reactions continue to hinder their practical application. In this study, we develop a novel and highly efficient composite, the Cs₂AgBiI₆/g-C₃N₄ (CABI/CN) heterojunction photocatalyst, synthesized through a simple anti-solvent recrystallization process. Under visible light (λ ≥ 420 nm, 300 W Xe lamp), the CABI/CN-20 composite achieved 97 % degradation of rhodamine B in 180 min, outperforming Cs₂AgBiI₆ by a factor of 1.3. In contrast, g-C₃N₄ showed minimal degradation under the same conditions. The enhanced photocatalytic performance of the CABI/CN-20 heterojunction is attributed not only to improved charge separation efficiency within the photocatalyst but also to the facilitation of photogenerated carrier transfer across the heterojunction interface due to the potential difference. Consequently, this leads to optimal redox capacity and significantly enhances the photocatalytic degradation performance. This study introduces novel methods for synthesizing Cs₂AgBiI₆/g-C₃N₄ heterojunctions and emphasizes their efficient separation of photogenerated carriers.