Highly stretchable TPU/g-C3N4 composite nanofiber film for enhancing the piezo-photocatalytic sewage treatment by electrospinning-induced pretension

Enhancing the sustainability of catalysts is crucial for the practical application of piezo-photocatalytic degradation of sewage. This study introduces a novel approach by fabricating highly stretchable piezoelectric composite nanofiber films through electrospinning TPU/g-C3N4 mixture. The tight integration of TPU nanofibers with g-C3N4 few-layers pre-stresses g-C3N4 and strengthens the mechanical properties of the composite films, achieving a maximum tensile strain and stress of 862% and 6.90 MPa, respectively. With the assistance of 300 W ultrasound, the photocatalytic capability of the TPU/0.2g g-C3N4 composite nanofiber film is enhanced by 43% and maintains nearly 100% of its initial performance after 12 repeated experiments. The electronic, piezoelectric, and optical properties of uniaxial-strained monolayer g-C3N4 are studied by first-principles calculations, revealing that stretching in the armchair direction can double the in-plane piezoelectric coefficient, while compression in the armchair direction simultaneously alters the charge distribution within the heptazine rings and modulates the adsorption sites and energy for oxygen molecule. Therefore, ultrasound-induced dynamic strains can significantly enhance the photocatalytic effect. The degradation of electronic industrial wastewater demonstrates the practical application potential of the catalytic composite nanofiber film. This research offers a pioneering strategy for the development of efficient photocatalytic systems for sewage treatment.