Efficiency enhancement of cobalt tungstate by fabrication of heterojunction nanocomposite for photodegradation of pollutants

Design and preparation of a novel heterojunction photocatalyst, including cobalt tungstate, Ni(OH) 2 , and reduced graphene oxide (Co/Ni/RGO) were reported. To investigate the straightforward preparation of Co/Ni/RGO, different characterization methods including FTIR, XRD, FESEM, UV–Vis DRS, EDX, PL, TEM, XPS, and EIS were utilized. The prepared photocatalyst was used for the photocatalytic degradation of DR16 under incident visible light irradiation. Effect of different crucial parameters such as time of illumination, catalyst loading, DR16 concentration, pH of the solution, reusability function of the catalyst, turbidity of the solution in the presence of the catalyst, and scavenger experiments was checked. Trapping tests showed that the photogenerated O 2 •− plays the main role in the photocatalytic process. The stability and reproducibility of the photocatalyst were also evaluated. Based on Mott–Schottky plots all samples showed a positive slope which showed n-type semiconductor behavior. Also, N D values for pure RGO and Co/RGO were lower than Co/Ni/RGO nanocomposite which shows the enhancement of the electrical conductivity as well as charge transport in Co/Ni/RGO nanocomposite. Results evaluated by Nyquist plots confirmed higher photoactivity of Co/Ni/RGO compared with RGO or Co/RGO due to decreasing of the charge transfer resistance in Co/Ni/RGO. Bode plots showed that lifetime was not the reason for higher photoactivity of Co/Ni/RGO compared with Co/RGO and RGO.