Metal Chalcogenide Modified Cobalt Oxide: Synthesis, Characterization and Photocatalytic Activity

Abstract

Due to increasing energy demands and environmental pollution, it is need of the hour to develop some eco-friendly technologies that can overcome these two major issues. Nanotechnology and photocatalysis provide best solution for the energy crisis and environmental pollution. Here, in this work, we report various metal chalcogenides modified cobalt oxide photocatalysts (Co3O4, CoTe, ZnSe, Co3O4/CoTe and Co3O4/ZnSe) for the photocatalytic degradation of Congo red, which is a major industrial waste and pollution causing agent. Synthesized photocatalysts are further characterized by various techniques including powder X-ray diffraction (XRD), scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX) and UV-Visible diffused reflectance spectroscopy. These techniques have confirmed that nanoparticles and their nanocomposites have been synthesized successfully. Among different synthesized photocatalysts, it was expected that nanocomposites (Co3O4/ZnSe, Co3O4/CoTe) would show better photocatalytic activities as compared to their individual counter parts which might be ascribed to the reduced electron-hole recombination. In case of Co3O4/CoTe nanocomposite photocatalytic activity is high, which was about 96 % in 60 min for the degradation of Congo red. But the photocatalytic activity of pure Co3O4, CoTe is just 20 % and 15 %, respectively. The higher photocatalytic activity of Co3O4/CoTe is attributed to high charge separation, better bandgap alignment and presence of common cation. As far as the photocatalytic activity of Co3O4/ZnSe nanocomposite is concerned, unexpected results were obtained because bare ZnSe has shown better photocatalytic activity which was about 98 % in 60 min as compared to its nanocomposite which was near 94 % in 60 min for the photodegradation of Congo red dye. This might be attributed to the presence of mixed phase of ZnSe i.e. cubic and hexagonal, which makes ZnSe itself a heterostructure to facilitate charge separation.