Surface Structure Related WO₃ Gas-sensing Properties And BaTiO₃ Photocatalytic/photovoltaic Properties And Their Physical Mechanisms

In this paper,after one-step hydrogenation of WO3 nanoparticles,the relationship between its gas sensitivity and surface structure was studied.The reactive site of the sensing reaction on molecular level is proposed and the fundamental gas sensing mechanism was clearly described.In addition,BaTiO3 nanowires grows along the direction of[001],BaTiO3 microplates exposed {001} surface and BaTiO3 nanoparticles with randomly oriented were prepared by the melting salt method.Through analysis photocatalytic properties of the BaTiO3 samples exposed different crystal faces and photovoltaic properties of the BaTiO3 composite films with different orientations,the concept of ferroelectric spontanoeus electric field and its driven charge separation mechanism are proposed from the atomic level for the first time.The above studies aims to explore the relationship between structure and performance of material and the specific mechanism of catalytic and gas sensing.The specific exploration contents are as follows:(1)WO3 nanoparticles were heated in pure H2 gas flow for different times to obtain the hydrogenated samples.The sensors response of WO3 nanoparticles before and after hydrogenated to ethanol,methanol and formaldehyde indicated hydrogenated WO3 has enhanced gas sensing properties.And with the extension of hydrogenated time,the response is further improved.In order to explore the influence mechanism of hydrogenation on gas sensing performance,X-ray diffraction(XRD),field emission electron microscope(FESEM).Fourier infrared spectrometer(FTIR)and multifunctional imaging photoelectron spectrometer(XPS)were used to characterize the morphological and structure of samples.The concept that unsaturated W atom with suspension bond is the sensing reactivity potential is proposed.It provides theoretical guidance for studying the sensing reaction mechanism and designing more excellent sensing materials.(2)Tetragonal BaTiO3 microplates and nanowires were prepared by molten salt method.XRD,FESEM,field emission transmission electron microscopy(FETEM)and physical adsorption were used to study the exposed crystal face and specific surface area of the two kinds of BaTiO3 sample,And the photocatalytic activities of them with different exposed facets in degradation of malachite green(MG)and methylorange(MO)were studied and compared,the results showed that the BaTiO3 microplates exposed {001} facets but with smaller specific surface area have better photocatalytic performance.The exposed {001} facets were found to be the active facets,and a sponstaneous electric field(Es)is created between polar Ba-BaTIO3(001)and O-BaTiO3(00 1)surfaces by the spontaneous polarization,which drives separation of the photomduced electrons and holes.The charge separation model affords guidance to give foll play to the potential value of ferroelectric materials in the field of photocatalysis and others.(3)[001]oriented and randomly oriented PVDF/BaTiO3 films were prepared from BaTiO3 micro-nanosheets exposed {001} facets and non-oriented BaTIO3 nanoparticles respectively,and ITO was used as the top and bottom electrodes of the films.The IV curve test found that the[001]oriented PVDF/BaTiO3 film has enhanced photovoltaic properties and rectification characteristics.By exploring the crystal structure of BaTiO3 in[001]direction,the physical mechanism of spontaneous electric field in spontaneous polarization direction of ferroelectric material BaTiO3 is proposed,which provided a new ideas for researching and designing better ferroelectric materials in optoelectronic applications.