Piezo-photoelectric Synergistic Catalytic Performance Of Sodium Niobate-based Piezoelectric Ceramics

NaNbO₃ is an n-type semiconductor with strong redox ability,but its wide band gap and low light utilization efficiency limit its application in the field of photocatalysis.NaNbO₃ also has excellent piezoelectricity,and the use of piezoelectric polarization can significantly improve the problem of low light utilization efficiency.Therefore,in this paper,NaNbO₃ powders with different morphologies were synthesized by hydrothermal and solid-state methods,respectively.The effect of their morphologies on the piezoelectric-photoelectric catalytic performance was explored.Further,Ag nanoparticles were deposited on the surface of NaNbO₃ particles and oxygen vacancies were introduced inside to achieve semiconducting,and the mechanism of their piezoelectric-photoelectric synergistic catalytic degradation of organic pollutants was further studied.The main research contents and conclusions of this paper are as following:（1）NaNbO₃ micropowders,NaNbO₃ microwires and NaNbO₃microsheets are synthesized by solid-phase and hydrothermal methods,and the effect of morphology on piezoelectric catalytic efficiency is studied.The results show that the NaNbO₃ micro-powder synthesized by the solid-phase method has the highest piezoelectric catalytic activity,and the reaction rate constant k is 0.08893 min^-1.The optimal piezoelectric-photosynthetic catalytic efficiency is exhibited under the conditions of light wavelength of 320-780 nm and ultrasonic frequency of45 k Hz,and the k value reaches 0.11001 min^-1.（2）Ag nanoparticles are deposited on the surface of NaNbO₃ by the photoreduction method,and the deposition amount is controlled by controlling the photoreduction time.The catalytic efficiency increases at first and then decreases with the increase of deposition time.Among them,NaNbO₃-0.75h Ag showed the best catalytic activity.The k value of electro-optical synergistic catalysis reaches 0.16314 min^-1.At the same time,NaNbO₃-0.75h Ag achieves good cycling stability,and it still keeps more than 87%of the original catalytic efficiency after 8 cycles.（3）The oxygen vacancies are successfully introduced into NaNbO₃by heat treatment to realize its semiconducting.The oxygen vacancy content is regulated by controlling the heat treatment temperature and time.The NaNbO₃-900℃-N₂ sample has the highest oxygen vacancy content.The oxygen vacancy content is the least.Increasing the heat treatment time of the sample in nitrogen,its catalytic efficiency increases at first and then decreases,among which NaNbO₃-3h-N₂ has the best catalytic activity,and the k value reaches 0.19175 min^-1.Lower than the original untreated sample.It shows that proper oxygen vacancy content is beneficial,but too high concentration is not conducive to the improvement of piezoelectric photocatalytic performance and piezoelectric catalytic performance.