Photothermal Mineralization of Polyolefin Microplastics via TiO 2 Hierarchical Porous Layer-Based Semiwetting Air-Plastic-Solid Interfaces.

Photo-mineralization of microplastics under mild conditions has emerged as a promising solution to plastic waste disposal. However, the inadequate contact between oxygen, water-insoluble polyolefin microplastics, and photocatalysts remains a critical issue. In this study, a TiO 2 hierarchical porous layer (TiO 2 -HPL) photocatalyst is presented to establish air-plastic-solid triphase interfaces for the photothermal mineralization of polyolefins. The wettability of the TiO 2 -HPL-based triphase interface is finely controlled from plastophobic to plastophilic. High-resolution imaging and finite element simulation demonstrate the significance of a semiwetting state in achieving multidirectional oxygen diffusion through the hierarchical pore structure while maintaining sufficient contact between the plastic phase and photocatalysts. For low-density polyethylene, the TiO 2 -HPL achieves a photothermal mineralization rate of 5.63 mmol g -1 h -1 and a conversion of 26.3% after 20 h of continuous irradiation. Additionally, the triphase photocatalytic system with semiwetting gas-plastic-solid interfaces shows good universality for various polyolefin reagents and products, illustrating its potential in achieving efficient photothermal mineralization of non-degradable microplastics.