Investigation On Photocatalytic And Piezoelectric Dye Decomposition Of ZnSnO₃ Nanomaterials

Green water and green mountains are golden mountains and silver mountains.Environmental pollution is a serious problem facing human society.Among them,the printing and dyeing industry is a major emitter of industrial wastewater.There are many methods for the degradation of printing and dyeing wastewater.Among them,photocatalytic technology,as an efficient,safe and environmentally friendly method for the degradation of advanced oxidation dye wastewater,has developed rapidly.Solar energy is a kind of clean energy.In addition to solar energy,vibration energy in the environment is also a common clean energy in nature.Since the process of photocatalysis is divided into two steps,namely,the process of photocatalysis of catalyst materials and the process of electrocatalytic reaction in dye wastewater solution.In theory,piezoelectric catalysis can also be realized by using the ability of piezoelectric materials to generate electricity,and piezoelectric materials can be used as catalysts to degrade dye wastewater under the action of vibration.As one of the typical ferroelectric lead-free nanomaterials,ZnSnO₃has attracted extensive attention for its photocatalytic,and piezoelectric properties.In this paper,we mainly studied the performance of ZnSnO₃ferroelectric nanomaterials in photocatalytic decomposition of dyes,and the improvement of the photocatalytic performance of ZnSnO₃with the assistance of cold-hot cycles and mechanochemical milling,the piezoelectric catalytic performance of ZnSnO₃ferroelectric nanomaterials in dye decomposition,and the improvement of piezoelectric catalytic degradation with the help of the mechanochemical milling.The details are as follows:（1）The enhanced photocatalytic performance of ZnSnO₃nanomaterial with the assistance of cold-hot cyclesThe ZnSnO₃nanomaterials were synthesized by sol-gel method.The photocatalytic properties of ZnSnO₃nanomaterials were studied with the aqueous solution of 5 mg/L Rh B organic dye as the decomposition target.It was found that ZnSnO₃nanoparticles could decompose 76.8%of dye solution in 80 min under UV irradiation.To improve the photocatalytic performance of ZnSnO₃,we used the cold-hot cycle assisted photocatalysis method to enhance the photocatalytic performance.Using the ZnSnO₃as the catalyst,the decomposition ratio of dyes increased by 21.3%compared with the single photocatalysis.Cold-hot cycle can promote the separation of photogenerated electron hole pairs in ZnSnO₃,which can enhance the decomposition ratio of photocatalysis for dye wastewater.（2）Adjusting the stoichiometric ratio of ZnSnO₃to improve the performance of piezoelectric catalysis for dye degradationZnSnO₃nanomaterials with different stoichiometric ratios were synthesized by hydrothermal method,and their photocatalytic and piezocatalytic properties for degradation of5 mg/L Rh B dye solution were studied.The decomposition ratio of ZnSnO₃and Zn_1.03Sno₃to Rh B solution were 90.6%and 95.7%respectively after 90 min of UV irradiation.After ultrasonic vibration for 40 min,the degradation rates of Rh B dye solution by ZnSnO₃and Zn_1.03Sn O₃were 86.1%and 98.4%respectively.The reaction rate constants for Rh B are0.0623 min^-1and 0.1251 min^-1,respectively.The reason why the nonstandard stoichiometric Zn_1.03Sn O₃has higher photocatalytic and piezocatalytic performance may be due to the increase of oxygen vacancies in the catalyst,which promotes the charge separation in catalysis.（3）The enhanced photocatalytic performance of ZnSnO₃through the mechanical millingThe effect of mechanical milling on the catalytic performance of ZnSnO₃nanomaterials was studied by simulating dye wastewater with 10 mg/L Rh B dye solution.The internal polarization and surface active sites of ZnSnO₃nanomaterials were enhanced by mechanical milling,so as to improve the photocatalytic and piezoelectric properties of the catalysts.It was found that the photocatalytic and piezoelectric degradation rates of ZnSnO₃after 60 min mechanical grinding were 93.6%and 93.8%respectively,which were much higher than59.3%and 40.4%of ZnSnO₃without milling.According to the performance characterization of the catalyst and related literature reports,mechanical milling increased the specific surface area of ZnSnO₃catalyst,thus increasing the reaction active sites.At the same time,the mechanical pressure in the milling process induced the ZnSnO₃ferroelectric material to be electrodeposited,which improved the internal polarization strength of the catalyst,and enhanced the photocatalytic and piezoelectric catalytic properties of ZnSnO₃.