Copper tungstate (CuWO4)/graphene quantum dots (GQDs) composite photocatalyst for enhanced degradation of phenol under visible light irradiation

Photocatalysis is one of the most preferred methods for the degradation of organic pollutants as it can lead to complete mineralization of organic pollutants employing sunlight as an energy source. Until so far enormous number of investigations have been done regarding the development of visible light responsive, stable, and cost effective photocatalysts. In the present work, owing to objectives mentioned above, an attempt was made to develop an efficient, cheaper, and visible light active composite photocatalyst consisting of moderate band gap, CuWO4 with electron conductive graphene quantum dots. A series of photocatalysts was prepared by varying the amount of CuWO4 while keeping the amount of GQDs fixed, and their activity was evaluated for the phenol degradation under visible light irradiation. The prepared photocatalysts were characterized by using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Raman spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, and Photoluminescence (PL) for the evaluation of crystallinity, functional groups, and properties of charge carrier separation, respectively. The maximum efficiency of photodegradation of phenol simulated wastewater was achieved by sample 0.5GCW (optimized sample having 0.5 wt% of CuWO4 with respect to fixed amount of GQDs), 53.41%, as compared to the pure CuWO4 sample, which exhibited 19.08% efficiency. A possible mechanism for enhanced activity of CuWO4 is proposed mainly due to efficient transfer of electrons from CuWO4 to graphene quantum dots. The results show that the graphene quantum dots GQDs with the CuWO4 significantly contributes to the improvement of photocatalytic performance.

Automated summary

Photocatalysis is an effective method for degrading organic pollutants using sunlight. This study developed a composite photocatalyst consisting of CuWO4 and graphene quantum dots (GQDs) to achieve better visible light activity. Different amounts of CuWO4 were used to prepare a series of photocatalysts, and their activity for phenol degradation was evaluated. The optimized sample, 0.5GCW, showed the highest efficiency of 53.41%, compared to the pure CuWO4 sample with 19.08% efficiency. Enhanced activity of CuWO4 is attributed to efficient electron transfer to GQDs. The results indicate that GQDs significantly contribute to the improvement of photocatalytic performance with CuWO4.