Single-phase Gd0.2La0.2Ce0.2Hf0.2Zr0.2O2 and Gd0.2La0.2Y0.2Hf0.2Zr0.2O2 nanoparticles as efficient photocatalysts for the reduction of Cr(VI) and degradation of methylene blue dye

We report for the first time the use of noble metal-free multi-component equiatomic oxide as photo-catalysts with excellent performance for natural sunlight driven degradation of Cr(VI) and methylene blue dye. The multi-component oxide nanoparticles with a composition Gd0.2La0.2Ce0.2Hf0.2Zr0.2O2 and Gd0.2La0.2Y0.2Hf0.2Zr0.2O2 were synthesized by simple co-precipitation followed by peptization in acid to obtain nanoparticle sol and calcined at 500 degrees C. The nanopowders were characterized by x-ray diffraction (XRD), UV-Visible spectroscopy (UV-Vis), and high-resolution transmission electron microscopy (HRTEM). The complete (similar to 100%) reduction of Cr(VI) to Cr(III) was observed after 90 and 100 min for the calcined Gd0.2La0.2Ce0.2Hf0.2Zr0.2O2 and Gd(0.2)La(0.2)Yo(0.20)Hf(0.2)Zr(0.2)O(2) respectively, under exposure to natural sunlight. In addition, 70% degradation of methylene blue is observed in 180 min. The effective photocatalytic activity of multi-component oxides can be attributed to their unique composition containing five components in equimolar amounts. The role of oxygen vacancies in photo-catalytic reduction of Cr(VI) and the degradation of methylene blue is also discussed. (C) 2020 Elsevier B.V. All rights reserved.

Automated summary

This study demonstrated the use of noble metal-free multi-component equiatomic oxides as efficient photo-catalysts for the degradation of Cr(VI) and methylene blue dye under natural sunlight, with complete reduction of Cr(VI) and significant degradation of methylene blue. The unique composition of these oxides, containing five components in equimolar amounts, played a key role in their effective photocatalytic activity. Additionally, the role of oxygen vacancies in the photo-catalytic reduction of Cr(VI) and degradation of methylene blue was discussed.