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

<jats:title>Abstract</jats:title>
<jats:p>Due to the large band gap and the rapid recombination of electron-hole pairs of TiO<jats:sub>2</jats:sub>, carbon quantum dots (CQDs) modified TiO<jats:sub>2</jats:sub> photocatalyst had been given intensive attention in visible light photodegradation. In this study, the oil palm frond-derived NCQDs/TiO<jats:sub>2</jats:sub> was adopted for the first time in the photodegradation of Methylene Blue (MB) under visible light irradiation. TiO<jats:sub>2</jats:sub> photocatalyst and NCQDs/TiO<jats:sub>2</jats:sub> 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 TiO<jats:sub>2</jats:sub> surface, respectively. The best-performed photocatalyst with the optimum amount of NCQDs (NCQDs/TiO<jats:sub>2</jats:sub>-1) displayed a degradation efficiency of 40.9% within 60 minutes, which is 2.6 times faster than that of pure TiO<jats:sub>2</jats:sub> (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/TiO<jats:sub>2</jats:sub> nanocomposites and the use of biomass as a natural precursor which contributed to green and sustainable fabrication of photocatalyst in environmental application.</jats:p>