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.
