Sodium percarbonate fuel-driven magnetic micromotor for rapid detection and efficient removal of tetracycline: Synergistic effect of oxygen vacancy and dissolved oxygen

Abstract

Micro/nanomotors (MNMs) propelled by hydrogen peroxide (H₂O₂) fuel have garnered significant interest in sensitive colorimetric detection and rapid catalytic degradation of organic pollutants. However, their practical applications remain constrained by multiple limitations including toxic high-concentration H₂O₂ requirements, sluggish Fe²⁺/Fe³⁺ redox cycling, and secondary contamination risks from metal ion leaching. Herein, we rationally developed a novel magnetic tubular FeCu@NC/MnO₂ micromotor through multistep fabrication using kapok-derived C microtubes as templates. The micromotor demonstrated remarkable propulsion (126.47 μm s⁻¹) under 0.5 M sodium percarbonate (SPC) solution and magnetic guidance, achieving eco-friendly fuel utilization by replacing unstable liquid H₂O₂ with solid SPC. Benefiting from abundant active sites and oxygen vacancy (O_V), the micromotor exhibited dual functionality in SPC activation with both sensitive colorimetric detection (LOD = 0.214 μM) and efficient catalytic degradation of tetracycline (TC, 93.73 % removal within 90 min). Quenching experiments and electron paramagnetic resonance (EPR) revealed a free radical and non-radical pathway involving hydroxyl radicals (•OH) and singlet oxygen (¹O₂) in TC degradation. More importantly, the O_V-mediated electron transfer facilitated Cu⁺/Cu²⁺, Fe²⁺/Fe³⁺, and Mn³⁺/Mn⁴⁺ redox cycling, while synergistic O_V and dissolved oxygen (DO) interactions promoted the generation and conversion of reactive oxygen species (ROS, •OH → O₂^•- → ¹O₂). This study provides fundamental insights into O_V- and DO- mediated ROS generation/transformation mechanisms and offers a paradigm for designing defect-engineered micromotor in environmental remediation.