Enhancement of piezocatalytic activity at the ferro-paraelectric phase transition of Ba1-xSrxTiO3 nanopowders

Nanocrystalline Ba 1- x Sr x TiO 3 ( x  = 0–0.3) powders were investigated with special interest in their piezocatalytic performance for degradation of organic pollutants. A great improvement of piezocatalytic activity was obtained for the compositions x  = 0.2, in which the polarization shows a large change under external stress. Furthermore, with the increase of working environment temperature, the piezocatalytic performance of Ba 0.8 Sr 0.2 TiO 3 increases firstly and then decreases, giving the best piezocatalytic performance near its Curie temperature . For a better understanding of the piezocatalytic mechanism, the dynamics of charge carriers transfer on solid/liquid interface was discussed with respect to activation energy and overpotential of catalyst. It was suggested that the enhanced piezocatalytic activity of Ba 1- x Sr x TiO 3 comes from two aspects: (1) the overpotential provided by the piezoelectric effect decreases with the increasing Sr content, (2) the activation energy for the piezocatalytic reaction is greatly reduced at ferro-paraelectric phase transition. Combination of these two aspects gives rise to the nonlinear dependence of piezocatalytic activity on Sr content.