Exceptional photocatalytic performance of hexagonal ZnO nanorods for anionic and cationic dyes degradation

Abstract

This study presents an in-depth investigation of zinc oxide hexagonal nanorods (ZnO NRs) synthesized via a hydrothermal approach at three pH basic values conducted in high-pressure laboratory reactor provided by Parr Instrument Company. The research evaluates the catalytic properties of the ZnO NRs, highlighting their potential for environmental applications. The as-fabricated samples are characterized by various techniques including the X-ray diffraction (XRD), UV–visible spectroscopy, Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) analysis, Field emission-scanning electron microscopy (FE-SEM), energy dispersive X-ray analysis (EDAX) and high-resolution transmission electron microscopy (HR-TEM). Rietveld refinement of X-ray diffraction data reveals the formation of high-purity hexagonal Wurtzite-type ZnO phase. Further, it is investigated that by decreasing the pH values, the grain size of ZnO NRs increases from 25.70 nm to 29.91 nm. SEM analyses further confirmed the hexagonal nanorod-shaped morphology of ZnO. The photocatalytic degradation performance of the as-fabricated ZnO NRs for Methylene Blue (MB) and Methyl Orange (MO) dyes increased with the increase in pH value, reaching almost 95 % and 64 %, respectively, after 30 min of UV irradiation. The optimum degradation is achieved at a pH value of 11.