Photoreactive carbon dots modified g-C3N4 for effective photooxidation of bisphenol-A under visible light irradiation

• Main Authors: Iqbal, Anwar, Shittu, Fatimah Bukola, Mohamad Ibrahim, Mohamad Nasir, Abu Bakar, N. H. H., Yahaya, Noorfatimah, Rajappan, Kalaivizhi, Hussin, Mohd. Hazwan, Danial, Wan Hazman, Wilson, Lee D.
• Format: Article
• Language: English; English
• Published: Multidisciplinary Digital Publishing Institute (MDPI) 2022
• Subjects: QD Chemistry
• Online Access: http://irep.iium.edu.my/101534/7/101534_Photoreactive%20carbon%20dots%20modified%20g-C3N4_SCOPUS.pdf; http://irep.iium.edu.my/101534/8/101534_Photoreactive%20carbon%20dots%20modified%20g-C3N4.pdf; http://irep.iium.edu.my/101534/; https://www.mdpi.com/2073-4344/12/11/1311/pdf?version=1667801502; https://doi.org/10.3390/catal12111311

A series of carbon dots (CDs) modified g-C3N4 (xCDs/g-C3N4; x = 0.5, 1.0, and 1.5 mL CDs solution) was synthesized via the microwave-assisted hydrothermal synthesis method for the photooxidation of bisphenol-A (BPA) under visible light irradiation. The X-ray diffraction (XRD) analysis indicates that the CDs may have a turbostratic structure and the resulting photocatalysts have distorted crystal structure, as compared with pure g-C3N4. The high-resolution transmission electron microscope (HR-TEM) analysis revealed amorphous, mono-disperse, spherical CDs with an average particle size of 3.75 nm. The distribution of CDs within the matrix of g-C3N4 appear as small dark dot-like domains. The N2 adsorption-desorption analysis indicates that the nanocomposites are mesoporous with a density functional theory (DFT) estimate of the pore size distribution between 2–13 nm. The CDs quantum yield (QY) was determined to be 12% using the UV-vis spectral analysis, where the CDs/g-C3N4 has improved absorption in the visible region than g-C3N4. The higher BET surface area of CDs/g-C3N4 provided more adsorption sites and the ability to yield photogenerated e−/h+ pairs, which caused the 1.5 CDs/g-C3N4 to have better photocatalytic efficiency compared to the rest of the systems. The highest removal, 90%, was achieved at the following optimum conditions: BPA initial concentration = 20 mg L−1, catalyst dosage = 30 mg L−1, and pH = 10. The photooxidation process is mainly driven by photogenerated holes (h+) followed by •OH and O2•−. The synthesis of the 1.5 CDs/g-C3N4 system is simple and cost-effective, where this photocatalyst is highly stable and reusable versus other systems reported in the literature.