Graphene Quantum Dots-Decorated 2D CuInP2S6 Nanosheets with Specially Enhanced Heterojunction-Associated Photocatalytic Activity for High-Performance Water Decontamination

Abstract

The significant environmental challenges of dye-contaminated wastewater necessitate efficient photocatalyst for pollutant degradation. Herein, a novel graphene quantum dots (GQDs) modified CuInP₂S₆ composite (GQDs@CuInP₂S₆) with a type-II band alignment has been successfully synthesized via laser liquid phase melting technology. Under visible light, GQDs@CuInP₂S₆ achieves 98.3% degradation of Rhodamine B (RhB) within 8 min, exhibiting a kinetic rate constant 2–3 orders of magnitude higher than pristine CuInP₂S₆. Density functional theory calculations reveal this enhancement stems from unique electronic modulation of CuInP₂S₆ by GQDs. Notably, irrespective of van der Waals or covalent GQDs-CuInP₂S₆ interactions, the composite transitions from pristine CuInP₂S₆'s a indirect bandgap to a direct bandgap, with chemisorbed GQDs further narrowing the gap, which facilitates electron transition and broadens light absorption spectrum. Additionally, the band alignment and partial charge density confirm a type-II heterojunction in chemisorbed GQDs@CuInP₂S₆. Holes from GQDs@CuInP₂S₆ and electrons from CuInP₂S₆ generate an internal electric field, suppressing charge carrier recombination and significantly enhancing photocatalytic performance. This work pioneers a synthesis approach for quantum dot-decorated surface composite and theoretically elucidates the quantum dot modification mechanisms, advancing a new innovative photocatalytic material design.