Facile Synthesis of ZnSe/Co₃O₄ Heterostructure Nanocomposites for the Photocatalytic Degradation of Congo Red Dye

In the present paper, simple hydrothermal and solid-state methods are reported for the synthesis of metal chalcogenide (ZnSe), metal oxide (Co3O4) and their nano-heterostructure (ZnSe/Co3O4 3:1, 1:1 and 1:3 ratios by weight), while their photocatalytic efficiencies are also investigated. The X-ray diffraction results corroborate the good crystallinity and purity of all synthesized products, i.e., ZnSe, Co3O4 and their nanocomposites. The scanning electron micro-images of ZnSe show a mixed morphology of nanoparticles (≈16 nm), including spherical and distorted cubes, while Co3O4 has a worm-like morphology (≈20 × 50 nm). The EDX results show that all the elements are present in accordance with their anticipated amounts in the products. The UV/visible absorption spectrum of ZnSe depicts a sharp absorption at around 480 nm, while Co3O4 demonstrates two prominent peaks, 510 nm and 684 nm. The prepared samples were employed for the photocatalytic degradation of Congo red dye and the nano-heterostructure (ZnSe/Co3O4 3:1) shows an exceptional photocatalytic degradation efficiency of 96%. This enhanced photocatalytic activity was due to the synergic effect of ZnSe and Co3O4 that reduced the electron/hole recombination and caused suitable bandgap alignment.