Full spectrum light driven photocatalytic in-situ epitaxy of one-unit-cell Bi2O2CO3 layers on Bi2O4 nanocrystals for highly efficient photocatalysis and mechanism unveiling

In-situ epitaxial growth is a fascinating strategy to nicely couple two low dimensional semiconductors as highly efficient composite photocatalysts. Meanwhile, organic contaminants in the photocatalytic process are usually decomposed into greenhouse gas (CO2) that can't be reused. Herein, we reported a green full spectrum light (UV, visible and NIR lights) induced epitaxial growth strategy to synthesize highly efficient Bi2O4/Bi2O2CO3 heterostructure photocatalyst by reusing waste carbon source, in which one-unit-cell Bi2O2CO3 layers (1.0 run) in situ grew on the surface of Bi2O4 nanocrystals during the photocatalytic degradation of rhodamine B (RhB) or phenol. More importantly, C-13 nuclear magnetic resonance (NMR) spectroscopy confirmed that the carbon element in Bi2O2CO3 was from the photocatalytic degradation of organic contaminations. Furthermore, density functional theory (DFT) calculations confirm that the Bi2O4 nanocrystals with exposed {-101} facets have the larger percentage of undercoordinated Bi atoms, which provided favorable conditions for the in-situ epitaxy of Bi2O2CO3 during the photocatalytic reaction. Additionally, the increased charge density near the Fermi level resulted in improved photoresponsivity of Bi2O4/Bi2O2CO3 composite and the coalescence of Bi2O4 and Bi2O2CO3 could favor the travel of photogenerated carriers from one to another owing to the close work functions for Bi2O4 (4.295 eV) and Bi2O2CO3 (4.410 eV). As we expected, the Bi2O4/Bi2O2CO3 composite presented higher photocatalytic activity for phenol and ciprofloxacin (CIP) degradation than pure Bi2O4 nano crystals. The possible degradation pathway of CEP in aqueous solution and photocatalytic mechanism of Bi2O4/Bi2O2CO3 composite were also proposed based on liquid chromatography mass spectrometer (LC MS) analysis and experimental results. This work provides a green strategy for designing highly efficient photocatalysts.