Interfacial Z-Scheme Heterostructure in Porous MXene-Fe3O4@Ag Nanocomposites toward Doxycycline Disintegration

Abstract

Nanoscale electronic structure at heterointerfaces critically governs charge-transfer pathways and photocatalytic efficiency, yet direct experimental insight remains limited. Herein, we report an interfacial Z-scheme heterostructure in a porous MXene-Fe3O4@Ag nanocomposite, allowing direct resolution and correlation of nanoscale electronic properties with efficient doxycycline disintegration under ambient solar irradiation. Hybrid integration of plasmonic Ag and magnetic Fe3O4 nanoparticles onto conductive Ti3C2 MXene sheets generates densely coupled heterointerfaces with pronounced electronic reconstruction. Scanning tunneling microscopy and spectroscopy, complemented by Kelvin probe force microscopy, reveal local density-of-states modulation and nanoscale band bending at the MXene-Fe3O4@Ag junctions before and after illumination, while X-ray photoelectron spectroscopy confirms interfacial charge redistribution. Together, these experimental observations provide direct evidence for a Z-scheme charge-transfer architecture. Enabled by this optimized interfacial electronic landscape, the nanocomposite achieves complete doxycycline disintegration with a substantially enhanced apparent quantum yield and significantly reduced solar energy consumption. The photocatalytic performance remains robust in complex real water matrices, including tap water, river water, and wastewater. Reactive species trapping experiments identify •OH radicals as the dominant oxidative species, elucidating the Z-scheme-driven photocatalytic mechanism. This study establishes nanoscale electronic-structure engineering as a key design principle for MXene-based Z-scheme photocatalysts for sustainable pharmaceutical wastewater remediation.