Combustion-synthesized ZnO-CeO2 heterojunctions for advanced photocatalytic dye degradation

ZnO-CeO2 heterojunctions were successfully synthesized utilizing a simple combustion approach employing equimolar solutions of the precursor chemicals. The morphology, content, crystallinity, purity, crystal size and bandgap energy features of the synthesized heterojunctions were carefully investigated utilizing various analytical methods. FESEM investigation indicated a heterogeneous flake or sheet-like appearance, as well as a rough and granular surface for the heterojunctions. XRD study found that the average crystallite size for ZnOCeO2 heterojunctions was 5.38 nm. The absorbance spectrum showed a peak absorption at 372 nm and a band gap energy value of 2.1 eV. The photocatalytic activity of the synthesized ZnO-CeO2 heterojunctions towards three model dyes, CR, RhB, and MB dyes, were investigated. Percent degradations of 96.61 % and 98.11 %, respectively were achieved for CR and MB dyes within 30 min, while 98.25 % photodegradation was observed for RhB dye within 60 min of UV irradiation. The rapid degradation of CR and MB dyes suggests their high susceptibility to the photocatalytic action of ZnO-CeO2 heterojunctions as compared to RhB dye. Kinetic analysis indicated that the degradation of dyes followed a pseudo-first-order kinetic model. Finally, for the photocatalytic activity of the as-synthesized heterojunctions, a photodegradation mechanism was also postulated.