Engineering surface polarization on bismuth titanate for efficient piezo-catalytic water purification

The utilization of mechanical energy to drive piezo-catalytic water purification holds significant promise for practical applications. However, severe charge recombination and sluggish reaction kinetics on catalyst surface limit the catalytic activity. In this study, we report a strategy for boosting charge separation and surface reactions by modulating the surface polarization of bismuth titanate (Bi4Ti3O12; BTO) via iodine grafting. Kelvin probe force microscopy (KPFM), theoretical calculations and piezoresponse force microscopy (PFM) indicate that iodine grafting significantly enhances surface polarization via enlarging interlayer potential difference and expanding the ferroelectric domain on BTO surface. The enhanced surface polarization not only improves the piezoelectric coefficients (d33) and piezoelectric current of BTO by factors of 1.8 and 4, respectively, but also promotes oxygen adsorption and the formation of the key intermediate *OOH, which accelerates singlet oxygen generation. As a result, the iodine-grafted BTO (BTO-I) exhibits an efficient piezo-catalytic tetracycline degradation of 96.6% within 60 minutes, which is 3.5 times faster than that of pristine BTO. Meanwhile, the degradation system also shows excellent stability, broad applicability, and ecological friendliness. This study provides new insights into the design of piezo-catalytic materials through surface polarization engineering and highlights their potential for environmental remediation.