Unlocking the potential of magnetic nanomaterials in photocatalysis: a review of recent progress and future perspectives

Abstract

There has been considerable attention paid to magnetic nanomaterials (MNMs) for photocatalytic degradation of polluted water; however, their research progress has been hindered by a vague definition of the “synergistic effect,” shallow performance verification, and insufficient mechanism discussion. In this review, we introduce a critical analysis of MNM-based photocatalysis by addressing a tripartite synergy concept that includes (i) the advantage of operational magnetic recovery, (ii) the enhancement of interfacial charge transfer, and (iii) Fe2+/Fe3+-mediated redox shuttling. Synthetic routes are evaluated critically in terms of defect density, crystalline quality, magnetic saturation (Ms) retention, interface quality, scalability, and environmental impact rather than only morphological attributes. Charge-transfer dynamics are analyzed by categorizing conventional heterojunctions with S-scheme and Z-scheme systems, and ROS generation pathways are classified into semiconductor band-edge processes and Fenton/photo-Fenton chemistry. The review highlights the fact that mechanistic investigations require uniformity in terms of band-edge positions, carrier kinetics, and spectroscopic characterization. Performance evaluation is not confined to just degradation percentage and pseudo-first-order kinetics because it also considers the mineralization of intermediates, apparent quantum yield, toxicity of intermediates, energy requirements, effects of the water matrix, metal dissolution, and magnetic recovery. In conclusion, a comparative analysis indicates a persistent lack of real-water validation, performance standardization, stability assessment, and scale-up studies. By identifying the actual conditions under which magnetic, interfacial, and redox properties affect photocatalytic activity, this review offers guidelines for the development and evaluation of future magnetic photocatalysts for industrial-scale water purification.