Designing spinel NiCr2O4 loaded Bi2O3 semiconductor hybrid for mitigating the charge recombination and tuned band gap for enhanced white light photocatalysis and antibacterial applications

Abstract This study investigates the enhancement of Bi2O3 activity as photocatalyst by loading NiCr2O4 as an effective catalyst. High-resolution transmission electron microscopy (HRTEM) analysis revealed the attachment of NiCr2O4 nanospheres on surface of sheet-like Bi2O3 nanoparticle (NPs). X-ray powder diffraction (XRD) revealed the successful fabrication of crystalline nanocomposites (NCs) with coexistence of NiCr2O4 and Bi2O3. X-ray photoelectron spectroscopy (XPS) and energy-dispersive X-ray spectroscopy (EDAX) confirmed the elemental composition (Ni, Cr, Bi and O) with no trace of impurity. Peaks related to tetrahedral and the octahedral oxygen-metal ion bonds were observed in fourier-transform infrared spectroscopy (FTIR). BET analyzer indicates presence of more reactive sites in NCs than individual NPs. UV–vis diffuse reflectance spectroscopy (DRS) showed shift in band gap of NiCr2O4 (2.1 eV) and Bi2O3 (2.8 eV) to 2.3 eV for NiCr2O4-Bi2O3 NCs with visible light sensitization. The life time of charge carriers in NCs was greatly improved and it was revealed by photoluminescence (PL) study. The photocatalytic performance of NiCr2O4-Bi2O3 NCs was higher with apparent kinetic constant (kapp) of 0.012 min−1 which was 4 to 6 times boosted than its pure individual parts (Bi2O3 = 0.003 min−1; NiCr2O4 = 0.002 min−1). The study identified that ·OH play major role in dye degradation. The NiCr2O4-Bi2O3 NCs exhibited a stable photocatalysis performance with good photostability after sixth cycles. In addition, NCs exhibited excellent antimicrobial activity against Escherichia coli and Bacillus subtilis. The potential usage of visible-light energy and operation simplicity prompted NiCr2O4-Bi2O3 NCs as a promising magnetically removable candidate for photodegradation of toxic organic contaminants in the aqueous solutions and for antimicrobial applications.