Enhanced photocatalytic activities of CeO2@ZnO core-shell nanostar particles through delayed electron hole recombination process

Abstract

Crystalline CeO2@ZnO core-shell nanostars were fabricated through hydrothermal and precipitation methods further characterized by XRD, UV-DRS, FT-IR, FE-SEM, EDAX, HR-TEM, SAED, AFM, XPS, BET and EPR analyses. The core-shell nanostar particles consist of ceria as core and zinc oxide as which were confirmed by FE-SEM and HR-TEM analysis. XRD analysis confirmed that the core-shell nanostar particles were highly crystalline in nature and nanosized. AFM analysis showed that the core-shell nanostar particles were highly porous with high surface roughness of 91.64 nm. The photocatalytic activity of CeO2@ZnO nanostars were evaluated by photocatalytic degradation of a model pollutant such as Orange-G (OG) under UV and visible light irradiations. The in-situ generation of OH. radicals was confirmed by EPR analysis. The maximum 90% of photocatalytic degradation of dye was observed by CeO2@ZnO CNS compared to pristine ZnO (>60% degradation) in neutral pH under UV and visible light irradiations. The pseudo-order rate constants were varied from 158 to 12 and 12 to 2 kobs × 10−3 (min−1) under UV and visible irradiations respectively for the different initial dye concentration from 5 to 25 ppm using CeO2@ZnO CNS. The higher photo activities of the core-shell nanostars are due to 4f shell of Ce4+ which traps the excited electron and further controls the rate of electron-hole pair recombination process under UV and visible light irradiations. The core-shell nanostars retain its photo activities for more than three cycles of reusability with better stability.