Synthetization pill-like C-doped ZnO nano-photocatalyst for removing ofloxacin and methylene blue under visible light

• Published in: Journal of sol-gel science and technology 2024-04, Vol.110 (1), p.204-220
• Main Authors: Luu, Thi Viet Ha, Tho, Nguyen Thi Mai, Thuy, Tran Thi Thanh, Thong, Le Nhat, Dung, Nguyen Trung, Dang, Phuc Huu
• Format: Article
• Language: English
• Subjects: Carbon; Ceramics; Chemistry and Materials Science; Composites; Energy gap; Glass; Hydroxyl radicals; Inorganic Chemistry; Materials Science; Methylene blue; Morphology; Nanotechnology; Natural Materials; Optical and Electronic Materials; Organic compounds; Original Paper; Photocatalysis; Photocatalysts; Photodegradation; Photoelectric effect; Photoelectric emission; Zinc oxide; Zinc oxides
• ISSN: 0928-0707; 1573-4846
• DOI: 10.1007/s10971-024-06348-2

Carbon-doped zinc oxides were synthesized with different concentrations corresponding to PVA/Zn2+ molar ratios between 5 and 15% by the hydrothermal method. The XRD and SEM results show that the obtained materials have high crystallinity and a pill-like morphology. Carbon dopant significantly decreased band gap energy (EgCZ3 = 2.77 eV), improving the optical absorption of ZnO in the visible and ultraviolet regions. Generally, the catalyst with carbon doped 1.49% (CZ3), corresponding to the molar ratio of PVA/Zn 2+ = 15%, showed the highest photocatalytic efficiency of ofloxacin (Ofx) and methylene blue (MB) and was higher than pure ZnO. This is possibly attributed to its morphology with good uniformity and porosity; the specific surface area of SCZ3 is 26 m 2 /g which is 1.5 times higher than ZnO. Moreover, it is also relative to the stable and highest saturation photocurrent density of CZ3, which is ∼6.4 µA.cm −2 , 4.15 times higher than pure ZnO. In addition, trapping experiments showed that positive holes and hydroxyl radicals were the predominant active agents. Finally, COD and TOC analysis results suggested that the photodegradation progress of MB and Ofx formed organic compounds with smaller structures and proved that over 78% of MB and 66% of Ofx were converted entirely to simple inorganic substances such as CO2, H2O, etc. Graphical Abstract Highlights The pill-like nano-photocatalysts of C-doped ZnO (CZ) were prepared by the hydrothermal method with various PVA/Zn 2+ molar ratios (5, 10, and 15%). The C doping significantly decreased the band gap of pure ZnO (from 3.1 to 2.77 eV). Enhancing the photoinduced charge separation, observing that photocurrent is about 5.5 times greater than pure ZnO. Excellent performance in the decomposition of ofloxacin (Ofx) and methylene blue (MB) under visible light illumination and sunlight. The role of photoactive species in the reaction process was ordered as follows: h + > H O . > e − .