Promising Cr-Doped ZnO Nanorods for Photocatalytic Degradation Facing Pollution

Chromium (Cr)-doped zinc oxide (ZnO) nanorods with wurtzite hexagonal structure were prepared through a thermal decomposition technique. The concentration effect of the Cr doping on the structural, morphological, and optical properties of the ZnO nanorods was established by correlating various measurements: transmission electron microscopy (TEM), photoluminescence (PL), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and several UV-visible studies. The obtained nanorods were investigated as photocatalysts for the photodegradation process of methyl orange (MO), under UV-vis light illumination. Different weights and time intervals were studied. A 99.8% photodegradation of MO was obtained after 100 min in the presence of 1 wt.% Cr III acetate hydroxide and zinc acetate dehydrate "ZnO-Cr-1 ". The kinetic rate constant of the reaction was found to be equal to 4.451 x 10(-2) min(-1) via a pseudo-first order rate model. Scavenger radicals demonstrated the domination of OH & BULL; radicals by those of O-2 & BULL;(-) superoxide species during the photodegradation. The interstitial oxygen site O-i is proposed to play a key role in the generation of holes in the valence band under visible irradiation. The ZnO-Cr-1 photocatalyst displayed good cycling stability and reusability.