Structural, photocatalytic and photoelectrochemical characteristics of ZnO nanoparticles synthesized by a glycine-nitrate process

Abstract

Zinc oxide is a semiconductor material which still, after a century of scientific research, shows great potential in modern day utilisements such as heterogenous photocatalysis of organic pollutants and as a photoanode material for efficient water splitting and oxygen generation. In this work zinc oxide was synthesized by a glycine-nitrate combustion process, which is a cheap, simple and efficient method for synthesizing transition metal oxides. The obtained powder was calcined at 400 and 500 °C and samples were characterized in detail using X-ray powder diffraction (XRPD), Fourier-trasform infrared spectroscopy (FTIR), Raman spectroscopy, field emission scanning electron microscopy (FESEM), photoluminescence spectroscopy (PL) and UV-Vis diffuse reflectance spectroscopy (DRS). Photoelectrocatalytic properties were investigated via electrochemical methods: linear voltammetry (LV), chronoamperometry (CA) and impedance spectroscopy (EIS). The results show that the obtained samples are nanocrystalline wurtzite zinc oxide with no impurities, with average particle diameters of 33 nm (annealed at 400 °C) and 48 nm (annealed at 500 °C). Both samples show significant amounts of various crystal deffects. The determined zinc oxide band gap was lower than the band gap of bulk zinc oxide. Photoelectrochemical measurements revealed that this material is photostable and reactive to light. Water oxidation is enhanced by exposing the light. Finally, photocatalytic properties were tested via determining kinetic parameters of organic pollutant decomposition. Both samples showed excellent photocatalytic activity by decomposing methylene blue and phenol.