Piezo-photocatalytic reforming of end-of-life plastic waste into syngas over defective BaxSr1-xTiO3-y solid solutions

Piezo-photocatalytic upcycling of plastic waste into added-value hydrocarbon fuel leverages mechanical and solar energy to reintegrate end-of-life plastics into the carbon cycle. This work reports a process that converts PET-derived ethylene glycol (EG) into syngas under ambient conditions using defect-engineered Ba x Sr 1−x TiO 3−y (BSTO) catalysts. A three-stage process produces graded oxygen-vacancy and Ti 3+ surface concentrations. Combination with optimized band structure yields catalysts of strong piezo-photo responses. Photoelectrochemical measurements confirm accelerated light-induced charge separation and transfer, while Kelvin probe force microscopy and DFT simulations corroborate defect-amplified piezoelectric polarization. Using this catalyst, EG solutions derived from PET microplastics and textile fibers demonstrate selective syngas compositions, confirming applicability to real-world PET waste. Mechanistic studies show that piezo-photo-reforming of EG achieves respective H 2 and CO evolution rates of 1062 and 646 μmol/g/h, >90% syngas selectivity, and an H 2 /CO ratio (~1.6), representing nearly a 20-fold increase in gas yield over photocatalysis alone. Control experiments demonstrate that catalyst composition and activation govern both catalytic activity and syngas ratio tunability. In situ ATR-FTIR identifies surface formate as a key intermediate, while 1 H NMR detects glycolic acid/glycolate in the liquid phase. DFT calculations indicate that lattice-oxygen-assisted C–C bond cleavage is significantly promoted within the reaction pathways. An advanced defect-engineered Ba x Sr 1−x TiO 3−y (BSTO) catalyst couples light and mechanical energy to convert end-of-life polyester textiles and PET microplastics into syngas under ambient conditions. Its defect-rich surface enhances charge separation and C–C bond cleavage, producing selective H 2 /CO mixtures as feedstock for sustainable aviation fuel production and closing the plastic carbon loop. • Strategic solid-solution design with defect engineering optimizes piezo-photocatalysts. • Defect gradients accelerate charge separation and transfer, and amplify piezoelectric polarization • Selective and efficient syngas production was achieved from ethylene glycol (EG) derived from microplastics and textile fibers, and laboratory-grade PET via piezo-photocatalysis. • In situ ATR-FTIR and ¹H NMR reveal formate and glycolate as key intermediates, while DFT calculations demonstrate lattice-oxygen-assisted C–C bond cleavage as the dominant reaction pathway.