Piezocatalytic degradation of pollutants in water: Importance of catalyst size, poling and excitation mode

Piezocatalysis is a promising area of research that would enable new advances in environmental catalytic processes independent of energy sources such as light or electricity. To shed more light on this field, theoretical and experimental studies were conducted using poled and unpoled BF-KBT-PT ceramics as catalysts in order to investigate the effect that piezocatalyst size, piezocatalyst poling/unpoling and agitation mode have on the degradation of a dye, Rhodamine B (RhB), in water. While an apparently contradictory trend in the theoretical and experimental results was observed in relation to piezocatalyst size, poling indeed had a significant effect on the degradation of RhB, indicating that a complex combination of different phenomena such as ‘top-to-bottom’ electric potential difference due to ‘bulk’ piezoelectric polarisation, nanoscale piezoelectric response and sonocatalysis may result in the overall catalytic degradation of RhB. However, the greatest contribution to the degradation of the dye would come from sonochemistry, as ultrasound in absence of a catalyst already achieved a remarkable degradation of RhB. This study therefore demonstrates the complexity of piezocatalysis, and why other phenomena besides bulk piezoelectric polarisation of catalysts must be taken into account in piezocatalysis research.