Modulating ion migration realizes both enhanced and long-term-stable nanozyme activity for efficient microplastic degradation

Degradation of microplastics represents a significant global environmental challenge, necessitating the development of bio-inspired catalysts with superior activity and stability, capable of mimicking natural plastic-degrading enzymes. Although nanozymes possess advantages such as low cost, ready availability, and multienzymatic activities, issues of self-consumption often hinder their practical application. Here, motivated by the acceleration of Li+ migration for improving the electrochemical reactivity and cycling stability of lithium iron phosphate (LFP), we engineered LFP by introducing Mn2+ to expand the lattice structure, resulting in Mn-doped LFP (LFMP) that modulates ion migration in nanozymes. Density functional theory (DFT) calculations reveal that Mn2+ doping expands the lattice structure of LFP while narrowing its bandgap, thereby significantly enhancing Li+ migration rates. Leveraging this design, LFMP exhibits enhanced peroxidase-like activity (3 times higher than that of LFP) and cycling stability (80% activity retention after 5 cycles versus 45% for LFP), enabling efficient degradation of microplastics made from polyamide 6, high-density polyethylene, and polypropylene. By exemplifying that the degradation efficiency achieved using LFMP nanozymes significantly exceeds that of traditional methods, we affirm that lattice expansion-driven ion migration may inspire future strategies to circumvent the self-consumption issue while maintaining high catalytic activity in nanozymes.