Sonochemically assisted fabrication of highly photoactive novel ZnO/MoO3 binary nanotubes anchored with Bi2O3 nanosheet for solar light-driven photocatalytic activity

Abstract

In this work, we present the fabrication of a direct Z-scheme photocatalyst, ZnO/MoO3/Bi2O3 by using a sonochemical-assisted biochemical (leaf extract of Moringa oleifera) process. The structural, surface and morphological characteristics of the manufactured composite were comprehensively studied by using various techniques including UV–Visible spectroscopy, X-ray diffraction, FTIR, SEM/EDX analysis, HRTEM imaging, XPS for chemical composition investigation, and BET surface area analysis. Our findings reveal that the nanotubes of ZnO/MoO3 are exquisitely aligned and interconnected well with Bi2O3 sheets which can be ascribed to the effective prevention of photoinduced electron-hole (e−-h+) pairs recombination. Moreover, the ternary hybrid possesses low band gap energy of 2.26 eV which suggest that sensitivity toward visible light and a large surface area, thereby increasing the active sites on its surface. ZnO/MoO3 with Bi2O3 enhances interfacial electron translocation efficiency, leading to a slower recombination rate of hole-electron pairs. Consequently, the one-pot combinative synthesis demonstrates a synergistic effect on the separation rate of active charge carriers, resulting in improved production and transmission of photo-excited electrons consequently enhancing its photocatalytic activity. In contrast to ZnO, MoO3, Bi2O3 and ZnO/MoO3, the ZnO/MoO3/Bi2O3 composite exhibited an impressive 98.8 % degradation efficiency of malachite green (MG) dye within 48 min under direct sunlight radiation, under optimized conditions (pH 13, 75 mg photocatalyst dose). The photocatalytic degradation process exhibited a rate constant of 0.090 min−1, following first-order reaction kinetics. Additionally, inhibitor studies allowed us to propose a mechanism that highlights the significant contributions of h+ (holes) and •O2− in the photocatalytic process.