Fabrication of a novel Bi2O3 nanoparticle impregnated nitrogen vacant 2D g-C3N4 nanosheet Z scheme photocatalyst for improved degradation of methylene blue dye under LED light illumination

Abstract

Herein, we report the facile fabrication of a novel visible light active photocatalyst by hydrothermally loading Bi2O3 nanoparticles on nitrogen vacant 2D g-C3N4 nanosheets. It showed excellent photocatalytic efficiency toward refractory pollutant under LED light illumination. The nitrogen vacant 2D g-C3N4 nanosheets were prepared through thermal treatment of bulk g-C3N4 under alkaline condition. A wide range of characterization techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy (DRS), electron spin resonance spectroscopy (ESR), atomic force microscopy (AFM) and photoluminescence spectroscopy (PL) were employed to reveal the structural, morphological and optical properties of the nitrogen vacant material as well as of the composite. The nitrogen vacant material exhibited a significant red shift in the visible light absorption edge as compared to the bulk material. The photoluminescence spectra confirmed the enhanced electron hole separation efficiency of the nitrogen vacant g-C3N4 and the composite over the precursors. The enhanced photocatalytic activity toward methylene blue (MB) degradation could be attributed to the enhanced light absorption efficiency and the superior charge carrier separation of the nitrogen vacant material and the composite. The photocatalytic activity was assessed through the degradation of refractory MB dye under LED illumination. The composite material 2% Bi2O3/g-C3N4 displayed the highest degradation efficiency with a first order degradation rate constant of 0.040 min−1, which is 2.5 and 1.9 fold superior than the rate constants of bulk and nitrogen vacant 2D g-C3N4 nanosheet, respectively. Furthermore, based on the findings of the radical scavenging experiment, a direct Z scheme electron transfer mechanism has been proposed. This study would unlock a new direction toward further enhancing the efficiency of vacancy engineered materials.