MoS<sub>2</sub>@MWCNTs with Rich Vacancy Defects for Effective Piezocatalytic Degradation of Norfloxacin via Innergenerated-H<sub>2</sub>O<sub>2</sub>: Enhanced Nonradical Pathway and Synergistic Mechanism with Radical Pathway
Xueyao Wang, Xuyang Hu, Zhengjun Qu, Ting Sun, Huang Li-hui, Shimin Xu
Abstract
Molybdenum disulfide (MoS 2 )-based materials for piezocatalysis are unsatisfactory due to their low actual piezoelectric coefficient and poor electrical conductivity. Herein, 1T/3R phase MoS 2 grown in situ on multiwalled carbon nanotubes (MWCNTs) was proposed. MoS 2 @MWCNTs exhibited the interwoven morphology of thin nanoflowers and tubes, and the piezoelectric response of MoS 2 @MWCNTs was 4.07 times higher than that of MoS 2 via piezoresponse force microscopy (PFM) characterization. MoS 2 @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 2 •– ) and nonfree radical ( 1 O 2, key role) pathways, together with the innergenerated-H 2 O 2 promoting the degradation rate. 1 O 2 can be generated by electron transfer and energy transfer pathways. The presence of oxygen vacancies (OVs) induced the transformation of O 2 to 1 O 2 by triplet energy transfer. The fast charge transfer in MoS 2 @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.