Preparation And Piezo-Photocatalytic Performance Of Sodium Niobate Based Composite Catalyst

Semiconductor photocatalysis technology is widely recognized as one of the important strategies to solve the environmental pollution and energy crisis.Therefore,the improvement of catalytic performance is the focus of researchers.Currently,the photocatalytic performance was mainly improved by developing new photocatalytic materials and improving the separation efficiency of photo-generated carriers.In recent years,inspired by piezoelectric effect,researchers combine it with photocatalysis,namely piezo-photocatalysis.The polarization electric field induced by piezoelectric effect can effectively separate photo-generated carriers and significantly improve photocatalysis performance.Based on piezo-photocatalysis,sodium niobate（NaNbO₃）nanowires with piezoelectric properties were prepared in this paper,which were combined with photocatalytic materials.In addition,the piezo-photocatalytic performance of the composite catalyst was explored,and the possible enhancement mechanism was also studied.The specific research contents are as follows:（1）The NaNbO₃ nanowires were synthesized successfully via hydrothermal method.By means of X-ray diffraction（XRD）,scanning electron microscopy（SEM）and X-ray photoelectron spectroscopy（XPS）,the preparation process of NaNbO₃ nanowires were characterized and the optimum technological parameters of NaNbO₃ nanowires were determined.In addition,the piezo-photocatalytic performance of NaNbO₃ nanowires was studied with Rhodamine B（RhB）as the simulated pollutant.The results show that:NaNbO₃nanowires were successfully synthesized when the hydrothermal temperature and time are150℃ and 4 h,and the annealing temperature and time are 500℃ and 8 h,respectively.Under the condition of piezo-photocatalysis,the contribution rate of piezoelectricity to the whole catalytic process is 23.94%,which is attributed to the promotion of the separation efficiency of photogenerated carrier by the internal polarization field of NaNbO₃ nanowires.（2）The NaNbO₃/WO₃ composite catalyst was prepared via hydrothermal method.The phase structure and morphology of the catalyst were characterized by XRD,Fourier transform infrared spectroscopy（FT-IR）,XPS and SEM.The optical properties of the catalyst were analyzed by UV-Vis diffuse reflection spectroscopy（UV-Vis DRS）and fluorescence spectroscopy（PL）.In addition,RhB was used as a simulated pollutant to investigate the piezo-photocatalytic performance of the catalysts.The results show that:The 5%NaNbO₃/WO₃composite catalyst has the most excellent piezo-photocatalytic performance.The piezo-photocatalytic degradation efficiency of RhB can reach 73.7%within 120 min,which increases by 30.1%compared with the single photocatalysis.This is because the photo-generated carriers of WO₃ are driven to opposite directions under the action of polarization electric field.Thus,the separation efficiency of photo-generated carriers has been improved.After four cycles of experiments,the piezo-photocatalysis performance of the catalyst is almost unchanged,indicating that the composite catalyst has good stability.（3）NaNbO₃/g-C₃N₄ composite catalyst was prepared by ultrasonic composite method.The phase structure and morphology of the catalyst were obtained by XRD,FT-IR and Raman spectroscopy.The optical properties of the samples were evaluated by UV-Vis DRS and PL.In addition,the piezo-photocatalytic performance of NaNbO₃/g-C₃N₄ catalysts with different composite ratios was investigated by using RhB as the simulated pollutant.The experimental results show that:5%NaNbO₃/g-C₃N₄ catalyst has the best piezo-photocatalytic performance.The degradation efficiency of RhB can reach 95.9%within 30 min,which is 16.3%higher than that of single photocatalysis.It is attributed to the formation of heterojunction within the composite catalyst and the internal electric field generated by piezoelectric effect.The synergistic effect between the heterojunction and the internal electric field improves the separation efficiency of carriers.After four cycles,the degradation efficiency of the composite catalyst can still reach more than 80%.Combined with the XRD pattern,it can prove that the piezoelectric catalyst has a good cyclic stability.