Ternary MgO/ZnO/In2O3 heterostructured photocatalysts derived from a layered precursor and visible-light-induced photocatalytic activity

A visible-light-responsive MgO/ZnO/In2O3 mixed-metal oxide (MZI-MMO) heterostructured photocatalyst was derived from a Mg-containing ternary hydrotalcite-like precursor followed by controllable calcination. The photocatalysts were characterized by powder X-ray diffraction (XRD), UV–vis diffuse reflectance spectra (DRS), high-resolution transmission electron microscopy (HRTEM) and specific surface area measurements. The findings indicated that a single layered double hydroxide (LDH) precursor leads to a well-crystalline ternary oxide photocatalyst. The photocatalyst showed superior catalytic performance for the photodegradation of organic dye compared to a commercial P25 photocatalyst driven by visible light. MgO/ZnO/In2O3 heterojunctions were observed on the interfaces by HRTEM, which could play a vital role in enhancing photocatalytic performance. The role of MgO was discussed based on a possible inhibition of photo-generated carrier recombination during the photocatalytic degradation. The photo-generated electrons can be transferred through the conduction band of oxides and be effectively involved in the formation of radical O2-, confirmed by using radical scavengers. The radical O2- is mainly responsible for the photodegradation of methylene blue (MB). Furthermore, the MgO/ZnO/In2O3 photocatalysts possess excellent recycling performance with a negligible activity loss after a four-run use. The kinetic studies suggested that the degradation of MB complies with a pseudo-first-order kinetic behavior.