N‑Doped Bi₂O₂CO₃/Graphene Quantum Dot Composite Photocatalyst: Enhanced Visible-Light Photocatalytic NO Oxidation and In Situ DRIFTS Studies

In the present work, we have synthesized N-doped Bi₂O₂CO₃/graphene quantum dots composite (N-BOC/GQDs) under ambient environment for the first time. The as-prepared samples show notable improvement for visible light photocatalytic removal of indoor air pollutant NO in ppb level with comparison to the pristine N-BOC. X-ray diffraction (XRD) and transmission electron microscopy (TEM) characterization show that GQDs has no obvious influence on the structure and morphology of N-BOC; but GQDs could modify the surface of N-BOC to some extent, judging from the X-ray photoelectron spectroscopy (XPS). Moreover, results from UV–vis diffuse and reflectance spectroscopy (DRS), photoluminescence spectroscopy, and photoelectrochemical experiments altogether manifest that the efficiency of both light harvesting and charge separation of N-BOC/GQDs during the photocatalytic process is enhanced. Electron paramagnetic resonance (EPR) spectroscopy and thermodynamic analysis shows that superoxide radicals should be the main active species during the photocatalytic process. In addition, in situ diffuse reflectance infrared Fourier-transform spectroscopy (DRIFTS) reveals us the specific changes of NO_x related species during the whole reaction process. We believe that the present work could offer a new way to improve the phtocatalytic efficiency of bismuth compounds.