Nanocrystalline ZnO doped Dy2O3 a highly active visible photocatalyst: The role of characteristic f orbital's of lanthanides for visible photoactivity

•Novel highly visible active photo catalyst synthesized by ZnO doping on Dy2O3.•Change in absorption spectra of the photo catalyst from UV to visible region.•f Shells of lanthanides play critical role in e− trapping and recombination process.•Conformation of OH radical formation via EPR spin trapping technique.•Photo catalyst effectively degraded a model pollutant under visible light.

Nanocrystalline ZnO doped Dy2O3 has been prepared by a simple and efficient technique for exhibiting an enhanced visible light photocatalytic activity. The prepared catalysts were characterized by IR, UV-DRS, XRD, FESEM, EDAX, HRTEM, XPS, AFM and EPR analysis. XRD data showed that the particles were highly crystalline and nanosized. The size of the nanoparticle was 30–56 nm and found to be of mixed morphology. The surface of the catalyst was highly porous and had a surface roughness of 53.28 nm. ZnO was doped on Dy2O3 in various proportions and the best ratio was finalized by the determination of photodegradation efficiency employing a model pollutant for example, ORG under visible light irradiation. 50 mol% ZnO doped Dy2O3 possessed two fold photocatalytic activities than that of pristine ZnO and followed a pseudo-first-order degradation kinetics. The enhanced photocatalytic activity was due to the presence of f shells in the lanthanide oxide crystal lattice which traps the excited electrons further delaying the process of recombination of electron–hole pair. The dye degradation was initiated by the attack of OH radicals formed during the course of reaction and the formation of OH radicals was confirmed by EPR analysis. The 50 mol% ZnO doped Dy2O3 catalyst completely degraded ORG dye molecules in the aqueous phase and these were confirmed by UV–visible spectroscopy, COD and QTOF-Mass analyses.

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