Resonance of KNbO3 nanofibers is effectively stimulated by ultrasound with low frequency and low power to enhance piezocatalytic activity

Abstract

Ultrasound is commonly employed as a source of mechanical energy in piezocatalysis, where it serves as an external excitation source inducing piezopotential that drives surface chemical reactions on the catalysts. The augmentation of mechanical energy generally amplifies the piezoelectric potential on the surface of the piezoelectric catalyst, thereby augmenting its piezoelectric catalytic activity. However, increasing the input of mechanical energy results in elevated equipment energy consumption, particularly for ultrasound generators. Therefore, it is imperative to develop a methodology capable of imparting significant mechanical energy to the piezoelectric catalyst while minimizing energy dissipation. In general, the resonance frequency is where the largest amplitude is accessible. Therefore, excitation of the matching piezocatalyst at this frequency should result in a higher level of piezocatalytic activity and an improvement in energy conversion efficiency. In this study, we proposed that the length of piezoelectric KNbO₃ nanofibers is fixed to match the low-frequency ultrasound (LFUS) and calculated the length of the KNbO₃ nanofibers at low-frequency resonance through simulation. The piezocatalytic activity of KNbO₃ nanofibers at matched and unmatched natural and ultrasonic frequencies was investigated. Even at a reduced ultrasound power of 25 W, a notably high piezocatalytic activity was observed under the resonance, offering strong evidence for resonance-enhanced piezocatalysis. This work presents a fresh way for LFUS-activated piezocatalysis to achieve efficient degradation, which is of practical significance in energy-saving water treatment.