Synergistic interaction in metal oxide/silicon bulk heterostructures for efficient photo-carrier generation and photodegradation of toxic dye contaminants

A facile non-equilibrium mechanochemical technique has been adopted for the synthesis of silicon based bulk heterojunctions viz. ZnO/Si and CuO/Si, by discretely combining ZnO and CuO with Si through the process of microstructural refinement. Structural, morphological, thermal and optical properties of the prepared materials have been investigated in detail. Photogenerated charge carriers are the key to the efficient photocatalysis and proper cultivation of such charge carriers can take place by restricting their recombination. This can be achieved through suitable band alignment between the constituting semiconductors; in this case, ZnO/Si and CuO/Si. Such bulk heterojunction results from the mechanochemical process provide a significantly higher exposed surface area than the thin film like 2D heterojunctions. The photocatalytic activity of ZnO/Si and CuO/Si binary systems were evaluated by observing the changes in absorption peak intensity at specific wavelength of the dyes in aqueous medium when irradiated with artificial light source. Such systems were found to be proficient towards the photodegradation of four major hazardous industrial effluents viz. Alizarin Red S, Methylene Blue, Rose Bengal and Indigo Carmine owing to its higher specific surface area and minimized carrier recombination due to synergistic interaction between Si and the metal oxide semiconductor.