Defect Control Of Barium Titanate And Its Catalytic Performance

With the industrialization and the urbanization industry,the pollution of water resources by organic pollutants has caused severe environmental problems.It even threatens human health and life.Therefore,it is urgent to address wastewater and improve the ecological environment.Recently,piezocatalysis has attracted a lot of attention because it can degrade organic pollutants and purify water using the widely distributed mechanical vibration in nature.BaTiO₃（BTO）is a typical ferroelectric material with a piezoelectric coefficient(d₃₃)as high as 190 pm/V.It has attracted much attention in the field of piezoelectric catalysis.In order to promote the practical application of BTO materials,it is necessary to further improve their piezoelectric catalytic performance and enhance their degradation rate of dye.It is remarkable that the continuous ultrasonic vibration will not only cause the piezoelectric effect of the piezoelectric material,but also bring about the ultrasonic cavitation effect.Ultrasonic cavitation（the formation,growth,and implosive collapse of bubbles）could lead to high temperatures and pressures,resulting in the thermal decomposition of water vapor to produce different reactive radicals,such as?OH、?H,which can degrade organic dyes.So,the actual degradation rate of organic pigments can be further enhanced by the synergistic effect of both the piezocatalysis and the ultrasonic cavitation in the in-situ ultrasound-induced piezocatalysis.Defect engineering is a general method to adjust the electronic structure and properties of materials.In this work,by introducing oxygen vacancies into BTO materials,the migration and separation of carriers were promoted,the catalytic performance was improved,and the degradation rate of dye wastewater was further improved by the synergistic ultrasonic cavitation effect,which opens a feasible way for the industrial treatment of dye wastewater in the future.The main results are as follows:（1）Through the room temperature reduction method of lithium metal,BTO powders with different oxygen vacancy concentrations were obtained by grinding BTO powder with different ratios of lithium powder,and the relationship between oxygen vacancy concentration,ultrasonic cavitation and piezoelectric catalytic coupling on the catalytic activity of BTO powder was systematically investigated.Under the conditions of applied ultrasonic vibration（40 k Hz,150 W）and UV light（125 W,365 nm）irradiation,BTO-5wt%（Barium titanate powder treated with 5 wt%lithium powder）has excellent piezoelectric catalytic performance,and the reaction rate constant is as high as 0.1721 min^-1during the piezoelectric catalytic reaction in20 min,which is 3.8 times higher than that of the original BTO.The corresponding piezoelectric catalytic mechanism was established by radical trapping experiments and first principles calculations.（2）Dispersion of nano/micron-scale particulate piezoelectric catalysts in solution may cause secondary pollution to the environment and is not easily recoverable.BTO films with different oxygen vacancy concentrations were synthesized by pulsed laser deposition method under different oxygen pressures.By applying ultrasonic vibration（40 k Hz,150 W）,BTO-1（Barium titanate synthesized with an oxygen pressure of 1m Torr）exhibits excellent piezoelectric catalytic performance with 97.2%degradation of Rh B during the piezoelectric catalytic reaction in 50 min.The BTO film samples are easily recovered and have good cycling stability.