Photocatalytic degradation of methylene blue under visible light using carbon dot/titanium dioxide nanohybrid

Abstract

Due to the large band gap and the rapid recombination of electron-hole pairs of TiO2, carbon quantum dots (CQDs) modified TiO2 photocatalyst had been given intensive attention in visible light photodegradation. In this study, the oil palm frond-derived NCQDs/TiO2 was adopted for the first time in the photodegradation of Methylene Blue (MB) under visible light irradiation. TiO2 photocatalyst and NCQDs/TiO2 nanocomposites with different NCQDs contents were successfully synthesised through a facile in-situ hydrothermal method. The surface morphology and crystalline structure of NCQDs-decorated semiconductor photocatalyst were characterized by high-resolution transmission electron microscope (HRTEM), field emission scanning electron microscope (FESEM) and X-ray diffraction (XRD), respectively. Fourier transform infrared spectroscopy (FTIR) and energy dispersive X-ray (EDX) were utilized to prove the successful attachment and the uniform dispersion of NCQDs on TiO2 surface, respectively. The best-performed photocatalyst with the optimum amount of NCQDs (NCQDs/TiO2-1) displayed a degradation efficiency of 40.9% within 60 minutes, which is 2.6 times faster than that of pure TiO2 (15.6%). The improved photocatalytic performance could be attributed to the better charge separation since NCQDs act as an electron reservoir which impeded the recombination of electron-hole pairs. The present work proposed a simple synthetic route for the preparation of NCQDs/TiO2 nanocomposites and the use of biomass as a natural precursor which contributed to green and sustainable fabrication of photocatalyst in environmental application.