Photocatalytic Performance of Undoped and Al-Doped ZnO Nanoparticles in the Degradation of Rhodamine B under UV-Visible Light:The Role of Defects and Morphology

• Published in: International journal of molecular sciences 2022-12, Vol.23 (24), p.15459
• Main Authors: Piras, Alessandra, Olla, Chiara, Reekmans, Gunter, Kelchtermans, An-Sofie, De Sloovere, Dries, Elen, Ken, Carbonaro, Carlo Maria, Fusaro, Luca, Adriaensens, Peter, Hardy, An, Aprile, Carmela, Van Bael, Marlies K
• Format: Article
• Language: English
• Subjects: Al-doped ZnO; Aluminum; Aquatic life; Aqueous solutions; Catalysts; Chemical reactions; Climate change; Dyes; Efficiency; Fourier transforms; green light-irradiation; Light irradiation; Morphology; Nanomaterials; Nanoparticles; Nanotechnology; Nitrogen; NMR; NMR spectroscopy; Nuclear magnetic resonance; Organic contaminants; Photocatalysis; Photodegradation; Photoluminescence; Photons; Pollutants; Rhodamine; Rhodamine B; Solid phases; Spectroscopy, Fourier Transform Infrared; Spectrum analysis; Ultraviolet Rays; Zinc oxide; Zinc Oxide - chemistry; Zinc oxides; ZnO
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms232415459

Quasi-spherical undoped ZnO and Al-doped ZnO nanoparticles with different aluminum content, ranging from 0.5 to 5 at% of Al with respect to Zn, were synthesized. These nanoparticles were evaluated as photocatalysts in the photodegradation of the Rhodamine B (RhB) dye aqueous solution under UV-visible light irradiation. The undoped ZnO nanopowder annealed at 400 °C resulted in the highest degradation efficiency of ca. 81% after 4 h under green light irradiation (525 nm), in the presence of 5 mg of catalyst. The samples were characterized using ICP-OES, PXRD, TEM, FT-IR, Al-MAS NMR, UV-Vis and steady-state PL. The effect of Al-doping on the phase structure, shape and particle size was also investigated. Additional information arose from the annealed nanomaterials under dynamic N at different temperatures (400 and 550 °C). The position of aluminum in the ZnO lattice was identified by means of Al-MAS NMR. FT-IR gave further information about the type of tetrahedral sites occupied by aluminum. Photoluminescence showed that the insertion of dopant increases the oxygen vacancies reducing the peroxide-like species responsible for photocatalysis. The annealing temperature helps increase the number of red-emitting centers up to 400 °C, while at 550 °C, the photocatalytic performance drops due to the aggregation tendency.