The in-situ construction of 2D/2D Bi2O2CO3/Bi2MoO6 Z-scheme heterojunction photocatalysts via the shared [Bi2O2]2 + layers in Bi2O2CO3 for efficient photocatalytic oxidation of Hg0

Abstract

Hg⁰ pollutants in the flue gas of coal-fired power plants pose a significant threat to the environment. Exploring the efficient removal of Hg⁰ using environmentally friendly photocatalytic technology is of great importance. Bi-based photocatalysts have become a research hotspot in the field of photocatalysis due to their tunable bandgap and excellent catalytic performance. The 2D/2D Bi₂O₂CO₃/Bi₂MoO₆ Z-scheme heterojunction composite photocatalyst was constructed via in situ epitaxial growth of Bi₂MoO₆ nanosheets on Bi₂O₂CO₃ through their highly similar [Bi₂O₂]²⁺ layered structures, achieving exceptional photocatalytic Hg⁰ oxidation efficiency in flue gas (with an efficiency of up to 92.21 %). The 2D/2D configuration provides an extensive contact area, making it an ideal optoelectronic platform for exploring heterojunction designs. The structure of the composite photocatalyst was characterized using XRD, SEM, TEM, BET, and AFM, confirming the successful construction of the 2D/2D heterojunction. The optimal sample, BOC-BMO-2, exhibited excellent photoelectrochemical performance and photocatalytic stability, attributed to the strong bonding between the [Bi₂O₂]²⁺ layers of Bi₂O₂CO₃ and the [MoO₄]²⁻ layers of Bi₂MoO₆. Combined XPS, ESR, and DFT analyses elucidated the Z-scheme heterojunction's regulatory role in charge carrier dynamics, where the synergistic interplay between the intrinsic internal electric field (IEF) and engineered oxygen vacancies (O_v) significantly enhanced charge separation and directional migration. Leveraging the exceptional charge separation efficiency of the 2D/2D Bi₂O₂CO₃/Bi₂MoO₆ photocatalyst, this work successfully identified the reaction mechanism and detailed pathway for Hg⁰ oxidation. The findings provide a groundbreaking strategy for constructing stable and efficient Z-scheme heterojunctions, with far-reaching applications in air purification and global mercury management.