Hierarchical ZnO-TiO2 nanoheterojunction: A strategy driven approach to boost the photocatalytic performance through the synergy of improved surface area and interfacial charge transport

Current research emphasizes on the development of metal oxide-based nanostructured heterojunction for efficient photocatalytic applications. As of now, commercially available photocatalysts cannot satisfy the everexpanding challenges in energy and environmental sectors. Thus, the present work demonstrates the influence of hierarchical ZnO-TiO2 heterojunction on improved physicochemical and photocatalytic properties. The morphological modifications of ZnO-TiO2 heterojunction is achieved via tuning of composite ratio. Consequently, the formation of well-crafted hierarchical ZnO-TiO2 heterojunction exhibits enhanced photocatalytic performance for methylene blue (MB) and methyl orange (MO) dye degradation. This combined approach of structural tuning and heterojunction formation delivers the advantage of the improved surface area along with effective charge carrier separation. Accordingly, ZnO-TiO2 with optimal composite ratio (1:1) showed superior photocatalytic performance than the remaining samples. Various structural, surface, optical and photoelectrochemical assessments were employed to examine those exceptional modifications encountered in optimally designed ZnO-TiO2 heterojunction. It has been found that the utilization of such an optimized photocatalyst not only ensures better light-harvesting capability but also diminishes the charge carrier recombination rate through appropriate surface defects and suitable band alignment. Furthermore, a probable mechanism accountable for the improved photocatalytic performance is also proposed and explained.