Photocatalytic Degradation of p-Nitrophenol in Aqueous Suspension by Using Graphene/ZrO2 Catalysts

A series of reduced graphene oxide (rGO) supported zirconia (ZrO2) nanocomposites with 1, 2 and 5 wt.% GO were synthesized using the sol-gel technique. The reduced graphene oxide/zirconia composites were characterized by X-ray powder diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM) high resolution transmission electron microscopy (HRTEM), ultraviolet-visible (UV-Vis) and, X-ray photoelectron spectroscopy (XPS), and N-2 adsorption and desorption measurements. The photocatalytic performance of the prepared samples was evaluated by monitoring the degradation of p-nitrophenol in aqueous suspension under UV illumination. The photocatalytic activity is strongly affected by the concentration of graphene in the ZrO2. The band gap values calculated from the Kubelka-Munk method showed a pronounced decrease upon increasing the amount of GO from 3.05 eV for pure ZrO2 to 2.77 eV for 5 wt.% rGO/ZrO2. Graphene serves as a good electron collector and transporter that effectively hindered the recombination of photo-generated electron-hole pairs resulting in high performance of photocatalytic degradation of p-nitrophenol.