Regulation of phase composition and oxygen vacancy in hydrothermally synthesized NaNbO3 nanowire and its enhanced piezocatalytic activity for antibiotic elimination

Piezocatalysis based on piezoelectricity has shown potential for environmental remediation and production of clean energy, which, however, cannot meet the standard of practical application due to its insufficiency. Herein, we successfully regulated phase composition (monoclinic, orthogonal and amorphous) in NaNbO3 nanowire through controlling the annealing temperature and time, where the decreased structural symmetry at the twophase interface improved the piezoelectricity and meanwhile the increased oxygen vacancies in amorphous structure acted as active sites to promote charge separation and oxygen adsorption. As a result, the optimized NaNbO3 sample annealed under 350 degrees C for 2 h presented much higher piezocatalytic activity for antibiotic degradation than the pristine NaNbO3. In detail, the effects of pH, antibiotic concentration, antibiotic type and reusability on the piezocatalytic performance were systematically studied. The enhanced piezocatalytic activity of the annealed NaNbO3 was revealed through testing piezoelectric coefficient, surface potential, piezoelectric current response and generation rate of active oxygen species, and therefore a possible piezocatalytic mechanism was proposed. Based on the determined intermediate products in the antibiotic degradation process, the reasonable degradation pathway was suggested.