ZnMn2O4 hierarchical hollow Self-Assembly microspheres Bearing enhanced photocatalytic activity under visible light

Abstract

This study presents the successful synthesis of highly hierarchical ZnMn₂O₄ microspheres (HZM) through the self-assembly of nanoparticle arrays. HZM was prepared using a one-step hydrothermal method, without the use of sacrificial agents or templates, at three different hydrothermal times (20, 40, and 72 h). Increasing the hydrothermal time to more than 20 h resulted in the formation of well-defined hierarchically hollow microspheres. Analysis confirmed the proper crystallinity and phase purity of HZM, with regular nanoparticles arranged on their surface in a stacked configuration resembling a hedgehog shape. The photocatalytic characteristics of HZM were assessed through an investigation into the degradation of methylene blue (MB) under visible light. Among the synthesized HZMs, those processed for a duration of 72 h (HZM3) demonstrated an enhanced specific surface area and a reduced recombination rate of photogenerated electron-hole pairs. This improvement has garnered significant attention, resulting in the most effective photocatalytic oxidation of MB (>80 %) achieved within 180 min. The comprehensive evaluation and analysis of the photocatalytic properties of the synthesized hollow microspheres were conducted. The durability and stability of HZM3 in the tricycle indicate that these as-synthesized microspheres can serve as durable photocatalysts for the degradation of organic dye molecules.