Fig. 1: Evolution of LA sites on the FeOCl piezocatalyst.

a TEM images of FeOCl. b Butterfly-shaped amplitude curve and hysteresis loop of FeOCl. c KPFM image and the surface potential of FeOCl. d Dynamic pyridine adsorption on FeOCl. e Pyridine-FTIR spectra of FeOCl before and after ultrasonic vibration. f Concentration of LA sites on FeOCl derived from the Pyridine-FTIR spectra before and after ultrasonic vibration. US denotes ultrasonic vibration. The error bars represent the standard deviation, calculated from at least two independent experiments.