Efficient photocatalytic activity of Mo-doped ZnO-In2O3 type-II staggered heterostructure for dye degradation

ZnO is one of the most widely used materials in the domain of photocatalysis and offers potentially better performance as compared to other photocatalysts. However, the high recombination rate of photogenerated exciton and small absorption window of ZnO is the biggest hurdle in its way to scalability. This work presents the fabrication of Mo-doped zinc oxide (ZnO:Mo) and Mo-doped indium oxide (In2O3:Mo) type-II thin-film heterojunction deposited by thermal evaporation and its photocatalysis characteristics. XRD diffraction showed polycrystalline nature of ZnO:Mo, In2O3:Mo, and their heterostructure thin films. Morphological features showed clustered growth of the thin films. The energy band gap determined from the Tauc's plots was around 3.25 eV and 3.50 eV for ZnO:Mo and In2O3:Mo, respectively. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Zn, Mo, O, and In, extrapolation of valence band spectra supports the formation of type-II band alignment in heterostructure. Mo-doped zinc oxide and Mo-doped indium oxide heterostructure (ZnO:Mo/In2O3:Mo) showed better photodegradation efficiency for MB dye upon sun exposure as compared to ZnO:Mo and In2O3:Mo thin films, which was due to the formation of ZnO:Mo/In2O3:Mo type-II heterojunction that led to the efficient separation of photoinduced carriers with first-order degradation constant of 8 x 10(-3) min(-1). ZnO:Mo/In2O3:Mo heterojunction showed photodegradation efficiency of 92% and worked very well to reduce the recombination rate of photoinduced electron hole pair and broaden the photon absorption window from 310 to 350 nm.