Synthesis and characterization of N-doped graphene oxide quantum dots/Fe-BDC composite for methylene blue decomposition

Abstract

In this work, we functionalized FeBDC by dosing Nitrogen-doped graphene quantum dots in order to improve the photocatalytic performance over Methylene Blue (MB) degradation. The novelty of this research is that N-doped graphene quantum dots (NGQ) were prepared by microwave irradiation Glycerol-Urea-Citric acid mixture, in which Glycerol could expand the sp² domain of the NGQ. The effect of NGQ dosage on crystalline phases and porous properties of NGQ/FeBDC were thoroughly studied using X-ray Diffraction, Fourier-transform Infrared spectroscopy, and Nitrogen adsorption isotherm measurement. The optimal catalyst was 4-NGQ/FeBDC, with the doping percentage of NGQ in NGQ/FeBDC composite being at 4%wt. of the precursors. Some of the noticeable improvements of the 4-NGQ/FeBDC over the original FeBDC sample included a larger BET surface area (141.8 m² g⁻¹), wider optical absorption edge, a smaller bandgap energy (2.42 eV), and faster degradation reaction. The optimal sample was able to completely decompose MB within 50 minutes and could be repeatedly exploited 4 times. The morphology of 4-NGQ/FeBDC particles was polyhedron shape with NGQ covering around, confirmed by Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) images. Some parameters that affect MB degradation of the 4-NGQ/FeBDC would be investigated, covering light irradiation, H₂O₂ presence, initial pH of MB solution, and reusability. The regeneration procedure of the optimal photocatalysts as well as the electron transfer mechanism within the photocatalytic system would be proposed in this paper.

Keywords:

• Dye degradation
• Fenton reaction
• graphene quantum dots
• metal-organic frameworks
• photocatalysis
• Methylene Blue

Declaration of competing interests

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This study was supported by the International Technology Center Pacific (ITC-PAC)’s program (US-ARMY). This work and paper were made with Government support under Contract No. FA520920P0139 awarded by the International Technology Center Pacific (ITC-PAC). The authors thank the supports of RoHan Program, DAAD, BMZ, and GeViCat Center, Hanoi University of Science and Technology (HUST) for the FTIR work.