Internal electric field at the Schottky junctions in an MXene–MnCdS heterostructure for complete uranium remediation

Abstract

The photocatalytic reduction of soluble U(VI) offers a sustainable pathway for nuclear wastewater remediation, yet conventional systems face persistent challenges including low efficiency, limited stability, and economic problems. Herein, we address these limitations by constructing a Schottky junction between Mn_0.3Cd_0.7S and Ti₃C₂T_x MXene via a hydrothermal strategy. The optimized heterostructure achieves complete U(VI) removal within 30 min under visible light without any sacrificial agents with a maximum capacity of 831.74 mg g⁻¹. Through combined Kelvin probe force microscopy (KPFM) and density functional theory (DFT) simulations, it is confirmed that the internal built-in electric field with band bending drives directional electron transfer from Mn_0.3Cd_0.7S to Ti₃C₂T_x, substantially enhancing charge separation. Furthermore, the MXene co-catalyst extends visible-light absorption, stabilizes photogenerated carriers, and provides abundant active sites, addressing key limitations of conventional semiconductor systems. This work establishes an efficient and stable non-precious-metal photocatalyst for uranium extraction, offering a general design principle for Schottky-based architectures targeting advanced environmental purification.