Characterization of the hetero-system ZnCo2O4/ZnO prepared by sol gel: application to the degradation of Ponceau 4R under solar light

Ponceau 4R is successfully oxidized on the hetero-system ZnCo2O4/ZnO under the solar light. The spinel with a nano-morphology is elaborated by the sol gel method at ~ 850 °C. The X-ray diffraction pattern exhibits narrow peak characteristics that reveals a good crystallization. The capacitance−2–potential (C−2–E) plot of the semiconductor ZnCo2O4 indicates p type behavior from which a flat band potential of + 0.30 VSCE is determined. The energy band diagram, built from the physic-chemical properties, clearly predicts the electron transfer from the conduction band of ZnCo2O4 toward dissolved oxygen via ZnO. Indeed, the ZnCo2O4/ZnO composite improves the photocatalytic performance, where the colloidal photochemical hetero-system is successfully used for the light induced Ponceau 4R oxidation. The spinel dose and Ponceau 4R concentration are optimized. The conversion rate is controlled by UV–Visible spectrophotometry and, under the ideal conditions, the oxidation of 70% of Ponceau 4R (15 ppm) is obtained in aerated solution for less than 4 h when exposed to the solar light. The oxidation obeys a first order kinetic with a half-photocatalytic life of 130 min (k ~ 52 × 10−4 min−1).