Sharp-edged pencil type ZnO flowers and BiOI flakes combined with carbon nanofibers as heterostructured hybrid photocatalysts for the removal of hazardous pollutants from contaminated water

The growth of advanced micro-and nanostructures with metal oxides has consistently generated extraordinary interest in energy and environmental applications. Cutting-edge nanostructures exhibit superior reactive sites and surface areas, thus improving the performance in crucial domains. In this study, sharp-edged pencil-type ZnO flowers and BiOI flakes as pristine materials, and their composition with carbon nanofibers (CNFs) (ZnO-BiOI@CNFs) as a hetero hybrid catalyst as well as binary compositions such as ZnO-BiOI, ZnO@CNFs, and BiOI@CNFs catalysts were fabricated using a simple and convenient hydrothermal synthesis process. The composition of newly produced innovative nanostructures was examined for azo dye degradation under solar simulator exposure. Dye degradation of similar to 95% was achieved by the hybrid catalyst (ZnO-BiOI@CNFs) during 120 min of irradiation, which was similar to 1.8 and 2.1-times higher than pristine ZnO and BiOI nanostructures, respectively. The improved hybrid catalysts were able to degrade methyl orange (MO) and rhodamine B (RhB) dyes. Importantly, mixed dyes RhB, MO, and azo dye demonstrated 47% dye degradation using a hybrid catalyst. These mixed dye-scalable hybrid catalyst performances offer additional insights into commercialization/indus-trialization. The outstanding performance of the hybrid catalyst is attributed to the unidirectional electron flow with pencil-like ZnO, a catalyst with a larger absorption zone, high surface area, and reactive sites, particularly ZnO and BiOI nanostructures, and decreased recombination rate with a heterojunction interface. In addition, CNFs can operate as electron traps and sinks, providing very quick redox reactions. To produce the sophisticated nanostructures with homogeneous morphologies, this work presents new insights into energy and environmental applications.

Automated summary

The study synthesizes sharp-edged pencil-type ZnO flowers and BiOI flakes using a hydrothermal process, and combines them with carbon nanofibers (CNFs) to form a hetero hybrid catalyst (ZnO-BiOI@CNFs). The hybrid catalyst exhibits significantly enhanced degradation of azo dyes under solar simulator exposure compared to pristine ZnO and BiOI nanostructures. The degradation rate of the hybrid catalyst reaches 95%, which is 1.8 times higher than ZnO and 2.1 times higher than BiOI nanostructures. The hybrid catalyst also demonstrates efficient degradation of mixed dyes, providing valuable insights for commercialization and industrialization. The superior performance is attributed to the unique structure of ZnO, larger absorption zone, high surface area, reactive sites, and reduced recombination rate with a heterojunction interface, as well as the electron trap and sink capability of CNFs.