Investigation On Piezo–catalytic And Pyro–catalytic Dye Degradation And Mechanism Of Ba_xSr_1–xTiO₃

Due to the rapid development of printing and dyeing industry,a great amount of untreated wastewater containing organic dyes has been continuously discharged into rivers,which seriously threatens natural environment and ecological balance.In the past few decades,researchers have always devoted themselves to approach solutions of wastewater treatment and discovered some effective catalytic methods,such as electric field induced electrocatalysis and light induced photocatalysis.These two types of catalysis have shown great potential in terms of addressing environmental concerns and the growing need for clean energy sources.In addition to electric energy and light energy,there are many other clean energy sources in nature,e.g.,mechanical vibration energy,day and night temperature variation–induced energy,which can also be used to design catalysis,namely piezo–catalysis and pyro–catalysis.In this work,the piezo–catalytic and pyro–catalytic dye degradation and mechanism of Ba_xSr_1–xTiO₃ materials is studied.The main contents are as follows:1.Piezo–catalysis of Ba_xSr_1–xTiO₃ nanofibersBa_xSr_1–xTiO₃（0.70≤x≤0.90）nanofibers with different stoichiometric ratios are prepared through a hydrothermal method.The effect and mechanism of different stoichiometric ratios on the performance of piezo–catalytic dye decomposition is explored.After 60 min of ultrasonic vibration,the catalyst with the component x=0.75possesses the highest piezo–catalytic activity,with the rhodamine B dye decomposition ratio of 98%while the catalyst with the component x=0.90 possesses the lowest piezo–catalytic activity,with the rhodamine B dye decomposition ratio of 50%.The possible mechanism is that when x=0.75,the curie temperature of Ba_xSr_1–xTiO₃ is close to room temperature.The piezoelectric properties reach the maximum near the curie temperature.In addition,the effects of ultrasonic power,dye p H,concentration,type and amount of catalyst on piezo–catalytic performance are also explored.2.Pyro–catalysis of Ba_xSr_1–xTiO₃Ba_xSr_1–xTiO₃（1≤x≤0）nanofibers with different stoichiometric ratios are prepared through a hydrothermal method.The effect and mechanism of different stoichiometric ratios on the performance of pyro–catalytic dye decomposition is explored.After 84 heating–cooling cycles with the range of 28–60℃,Ba_0.8Sr_0.2TiO₃shows the highest pyro–catalytic activity,with the decomposition ratio of Rhodamine B dye of 90%.While Ba TiO₃ has the lowest pyro–catalytic activity with the 48%decomposition ratio.The possible mechanism is that when x=0.8,the curie temperature of Ba_0.8Sr_0.2TiO₃ is about 50°C,which is in the applied temperature range.The pyroelectric properties of the material reach the maximum near the Curie temperature,In addition,the Ba_xSr_1–xTiO₃（x=1）is chosen to explore the effect and mechanism of electric polarization on the pyro–catalytic performance of materials.After 140 cold–hot cycles（28–60℃）,decomposition ratio of rhodamine B dye using Ba_xSr_1–xTiO₃（x=1）poled under the poling field of 5.0 k V/mm reaches～56%,which is more than 7times that of unpoled Ba TiO₃.It is suggested that the electric polarization is helpful to improve the pyroelectric catalytic performance,which may be due to the improvement of the pyroelectric performance and the number of carriers in the pyroelectric catalytic process.