Microwave-assisted Synthesis of Carbon Nanodots/TiO₂ Composite with Enhanced Photocatalytic Oxidation of VOCs in a Continuous Flow Reaction

In this research, carbon nanodots decorated TiO2 (CDs/TiO2) were prepared by the microwave method and used as the catalyst for the photo-oxidation of several volatile organic compounds (VOCs), including formaldehyde, acetone, and toluene, in a continuous flow under UV-A radiation. The catalyst was characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), high-resolution transmission electron microscopy (HRTEM), scanning electronic microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), thermogravimetric analysis (TGA), and photoluminescence spectroscopy (PL). The results confirm the vital role of carbon nanodots in the improvement of photocatalytic activity of TiO2 via extending the light absorption into the visible range and lengthening the existence of photoelectrons and holes. The synthetic catalyst exhibited superior photocatalytic performance than the pristine TiO2. The removal rate of formaldehyde, acetone, and toluene in a continuous flow and under humid conditions are 0.38, 0.22, and 0.2 mmol g(- 1) h(- 1), respectively. While the change in relative humidity had significant impacts on the photocatalytic activity of TiO2, CDs/TiO2 still exhibited a very high and stable VOCs conversion efficiency. Moreover, the photo-oxidation efficiency of formaldehyde on the CDs/TiO2 photocatalyst was maintained the same after 8 cycles.