Photocatalytic property of MWCNTs/BiOI with rich oxygen vacancies

In this paper, BiOI was surface decorated by multiwall carbon nanotubes (MWCNTs) via a hydrothermal method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscope (HRTEM), UV–Vis diffusion reflectance spectrometry (DRS), X-ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPS), and electron spin-resonance (ESR). Rich oxygen vacancies (OVs) were generated on the surface of BiOI, confirmed by ESR and XPS characterization. Trapping tests prove that superoxide (•O2−) is the key active species. When the mass ratio of MWCNTs/BiOI is 1.0%, the photocatalytic activity of MWCNTs/BiOI is 5.6 times of that of the bare BiOI. Finally, photocatalytic enhancement mechanism was proposed based on the experimental consequences. After surface modification by MWCNTs, electrons will transfer to MWCNTs due to the strong interaction between MWCNTs and BiOI, and the excellent conductivity of MWCNTs, significantly boosting the separation of e−/h+ pairs.