Rational design of visible-light-driven Pd-loaded α/β-Bi2O3 nanorods with exceptional cationic and anionic dye degradation properties

Abstract

Here, we report a simple sono-chemical method to fabricate Pd-loaded α/β-Bi2O3 nanorods with exceptional methylene blue (MB), brilliant green (BG) and acid red 1 (AR) dye degradation properties. The unique nanorods morphology was accomplished by treating of bismuth complexes with sodium hydroxide at room temperature. Palladium was introduced by UV-photo-deposition method from palladium (II) chloride source. The successful substitution of Bi3+ by Pd2+ in bulk of Pd-loaded α/β-Bi2O3 was confirmed by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). The surface presence of α-, β-Bi2O3, PdO and metallic Pd0 was confirmed by X-ray photoelectron spectroscopy (XPS). The rational design and fabrication approach is based on matching of (1) valence band (VB) and conduction band (CB) of as-prepared catalyst with redox potentials of dyes, (2) VB and CB with reactive oxygen species (ROS), and (3) redox potentials of dyes with ROS. By using the approach of rational design the material is able to degrade cationic MB (90.8%), BG (83.3%) and anionic AR (83.2%) dyes within 20 min under LED light irradiation (100 mW/cm2), as well as to degrade mixtures of cationic/anionic MB-AR and BG-AR dyes. Further optimization of dye degradation parameters, such as initial concentration of dye, amount of catalyst, and solution pH was carried out. A mechanism of dye degradation was proposed based on ROS scavenging experiments and mapping out of semiconductor band structures with redox potentials of dyes and ROS. Pd-loaded α/β-Bi2O3 catalyst has potential applications in wastewater treatment, water splitting and healthcare industries.