Superior photopiezocatalytic performance by enhancing spontaneous polarization through post-synthesis structure distortion in ultrathin Bi2WO6 nanosheet polar photocatalyst

[Display omitted] •Post-synthesis etching treatment by dilute NaOH aqueous solution at room temperature.•Enhanced polyhedron distortion in ultrathin Bi2WO6 nanosheets.•Much higher piezoelectricity due to higher degree of polyhedron distortions.•Improved charge carrier separation/transfer behavior from stronger piezoelectricity.•Superior photopiezocatalytic SMX degradation efficiency (∼33.9 times). The internal polarizations of polar photocatalysts could be enhanced through unit cell structure modulations to improve their photocatalytic performances. In this work, a simple, robust and low-cost NaOH etching process is developed to treat ultrathin Bi2WO6 nanosheets after their creation, resulting in a higher degree of polyhedron distortion (∼141 %) and an enhanced piezoelectricity (∼260 % the maximum effective piezoelectric coefficient d33). Compared with pristine ultrathin Bi2WO6 nanosheets, these etched samples demonstrate an improved charge carrier separation and transfer behavior due to their enhanced internal polarization with the assistance of richer oxygen vacancies, which largely enhance their piezocatalysis (∼4.6 times), photocatalysis (∼14.3 times) and especially coupled photopiezocatalysis (∼33.9 times) performances as demonstrated in their sulfamethoxazole (SMX) degradation performances. ·O2–, 1O2 and h+ are proven to be main reactive oxygen species (ROSs) during their photopiezocatalytic process and they could also work well in the real water matrix.