MoS@MWCNTs with Rich Vacancy Defects for Effective Piezocatalytic Degradation of Norfloxacin via Innergenerated-HO: Enhanced Nonradical Pathway and Synergistic Mechanism with Radical Pathway.

Molybdenum disulfide (MoS)-based materials for piezocatalysis are unsatisfactory due to their low actual piezoelectric coefficient and poor electrical conductivity. Herein, 1T/3R phase MoS grown in situ on multiwalled carbon nanotubes (MWCNTs) was proposed. MoS@MWCNTs exhibited the interwoven morphology of thin nanoflowers and tubes, and the piezoelectric response of MoS@MWCNTs was 4.07 times higher than that of MoS via piezoresponse force microscopy (PFM) characterization. MoS@MWCNTs exhibited superior activity with a 91% degradation rate of norfloxacin (NOR) after actually working 24 min (as for rhodamine B, reached 100% within 18 min) by pulse-mode ultrasonic vibration-triggered piezocatalysis. It was found that piezocatalysis for removing pollutants was attributed to the synergistic effect of free radicals (OH and O) and nonfree radical (O, key role) pathways, together with the innergenerated-HO promoting the degradation rate. O can be generated by electron transfer and energy transfer pathways. The presence of oxygen vacancies (OVs) induced the transformation of O to O by triplet energy transfer. The fast charge transfer in MoS@MWCNTs heterostructure and the coexistence of sulfur vacancies and OVs enhanced charge carrier separation resulting in a prominent piezoelectric effect. This work opens up new avenues for the development of efficient piezocatalysts that can be utilized for environmental purification.