Gas Sensing, Photocatalytic, Piezoelectric, Photovoltaic And Rectification Properties And Physical Mechanisms Of PbTiO₃ Polar {001} Facets

In this paper,PbTiO3 nanosheets with exposed crystal faces of {001} were prepared by hydrothermal method.The surface of PbTiO3 nanosheet was optimized by hydrogenation treatment.At the same time,PbTiO3 nanowires grown in the direction of[001]was prepared by hydrothermal method,and the photocatalytic properties of the nanosheets and the nanowires were tested.In addition,PbTiO3 thin films with different[001]orientations were prepared by sol-gel method,and their piezoelectric,rectification and photovoltaic properties were tested under different conditions,the dependence of piezoelectric,rectification and photovoltaic properties on the orientation of[001]was studied.Based on the analysis of the atomic structure of PbTiO3,the relationship between the structure and the properties of PbTiO3 was studied,the fundamental reasons for the enhanced gas sensing,photocatalysis,piezoelectric,rectification and photovoltaic properties of PbTiO3 polar structure at the atomic level are described in detail.The specific research results are as follows:(1)PbTiO3 nanosheets were prepared by hydrothermal method,and the surface of PbTiO3 nanosheetts was optimized by hydrogenation method.The sensing properties of PbTiO3 nanosheets before and after hydrogenation were studied for acetone,ethanol and triethylamine.It was found that the sensing properties of PbTiO3 nanosheets prepared by hydrogenation were better than those prepared by non-hydrogenation.(2)The ratio of PbTiO3 nanowire exposed to {001} surface was further controlled by changing the reaction conditions,and the PbTiO3 nanowire grown along[001]direction was prepared by hydrothermal method,the photocatalytic degradation of methylene blue and rhodamine B(Rh B)by PbTiO3 nanosheets and nanowires exposed to different ratios of {001} crystal planes was investigated,it was found that the photocatalytic degradation of MB and Rh B on PbTiO3 nanowires exposed to{001} crystal plane was significantly better than that of PbTiO3 nanowires grown along[001]direction.This was because the ratio of PbTiO3 nanowires exposed to{001} surface was higher than that of PbTiO3 nanowires.A charge separation model driven by spontaneous electric field(Es)between the polar crystal planes of PbPbTiO3(001)and O-PbTiO3(001)was proposed.(3)PbTiO3 thin films with different[001]orientation were prepared by sol-gel method with different pretreatment time.The rectification,photovoltaic and piezoelectric properties of PbTiO3 thin films with different[001]orientations were studied,and the effects of[001]orientations on the rectification,photovoltaic and piezoelectric properties were investigated,it is shown that the rectification,photovoltaic and piezoelectric properties originate from the polar structure of PbTiO3,and a new physical mechanism of photovoltaic rectification and piezoelectric is proposed at the atomic level.