Preparation Of Nonmetal Doped NaTaO₃ By Hydrothermal Process And Studies Of Optical Properties

Recently,perovskite NaTaO₃ has become one of the popular research subjects in the field of photocatalysis for its unique structure.It is demonstrated that NaTaO₃ has a more attractive prospect than any other semiconductor photocatalytic material in the photocatalytic process including photocatalytic water-splitting to producing hydrogen, degradation of organic dyestuffs,photocatalytic reduction of CO₂. However,the large band gap of NaTaO₃ greatly reduces the utilization of solar energy.An effective approach to expand the scope of the optical response of NaTaO₃ could be obtained by doping nonmetal ions in NaTaO₃.In this work,I-doped NaTaO₃ has been successfully synthesized by a hydrothermal process.The structure of I-doped NaTaO₃ was characterized by XRD,TEM,XPS,UV-VIS.Meanwhile,the I,N,F, S,P and Cl-doped NaTaO₃ were studied depending on computational simulation in order to deeply understanding of the mechanism.For NaTaO₃ and I-doped NaTaO₃,transmission electron microscopy (TEM) and X-ray diffraction showed the well crystallized cubic morphology.Iodine ion was located at the site of Ta⁵⁺ and the lattice cell of NaTaO₃ was expanded after doping by I ions.The optical properties of I-doped NaTaO₃ were determined by UV-vis diffuse reflection spectroscopy(DRS).The result revealed that the absorption onsets of the doped samples have the slight red shift with the increased I ions content. The largest red shift was located at wavelength of 428 nm with a good excition absorption.The band gap was estimated to be 2.90 eV from the absorption edge by the formula,Eg(eV)= 1240/λ_g(nm).The photocatalytic activity of MB solution degraded by NaTaO₃ sample under ultraviolet (UV) light irradiation was determined.It showed that the photocatalyst activity was enhanced by the appropriate addition of I ions in NaTaO₃.The band structure and density of states for iodine ions were calculated using the first principles for the two different models.The I ion was located in the site of Ta⁵⁺ in the model I,whereas the I ions substituted the O^2- in the modelâ…¡.The band gap was narrowed in the modelâ… which is consistent with the experiment results.The same calculations were performed for N,F,S,P and Cl-doped NaTaO₃.It is found the band gap of F-doped NaTaO₃ was increased,and the optical absorption edge shifted up to the higher energy.However the band gap of N,S,P and Cl-doped NaTaO₃ was decreased,and the optical absorption edge shifted down to the lower energy.The greatest red shift was found in the models of N,P-doped NaTaO₃.