Preparation of One Dimensional Ultrathin Niobate Nanomaterials and Their Photocatalytic Activity
Author:Cheng Fang Rui
Supervisor:zhang ze peng jing xi ping
One-dimensional(1D)niobate nanomaterials,owing to their unique morphology and large specific surface area,have many potential applications in various fields.All of the 1D niobate nanostructures were prepared by bottom-up approachs,such as molten salt method and hydrothermal method,etc.Owing to their unique three-dimentional crystal structures,it was seldom reported that 1D niobate nanostructures were exfoliated from their parent materials.In this work,the rod-like RbNbO3(RNO)was synthesized by solid state reactions,and then 1D ultrathin niobate nanobelts and nanowires were prepared through a Top-Down sonication-assisted and soft-chemistry liquid exfoliation from the parent material RNO.The restacked nanobelts and nanowires were prepared via a drop-wise addition of acid aqueous solution to the nanobelts and nanowires suspensions,which have good photocatalytic activity.The main results are concluded as follows:(1)RNO prepared at atmospheric pressure is not stable in ambient,and is very sensitive to humidity.The raw materials were weighed and ground in a glovebox with dry argon atmosphere,and then synthesized at 900℃.As-produced RNO consists of rod-like primary particles.The XRD pattern of the RNO powder sample was collected in the isolated air condition,the profile fitting and following Rietveld refinement of the RNO structure was conducted by using GSAS.The result indicated that the prepared RNO powder sample is phase pure.(2)By using the liquid exfoliation method with the assistance of sonication,the 1D ultrathin niobate nanobelts from RNO were prepared in water.In this process,no other impurity phases were introduced.The original driving force for the exfoliation is the combination of the hydration of Rb+ and the hydrolysis of(NbO3)nn-.The 1D ultrathin nanobelts are intermediate state,which may be further exfoliated to the monodispersed nanochain structure.To understand the exfoliation mechanism may help the further exfoliation of the nanobelts,(3)1D ultrathin niobate nanowires were prepared through a soft chemistry liquid exfoliation from the parent material RNO.In appropriate concentration of ethylamine(EA)solution,the niobate nanochains with the diameter around 1 nm were observed.The original driving force for the exfoliation is the combination of the hydration of Rb+,the hydrolysis of(NbO3)nn-and acid-base neutralization reaction.(4)The restacked 1D nanobelts and nanowires tend to amorphous,but the the shape and size of them were not changed significantly.The restacked 1D nanobelts and nanowires show high photocatalytic activity for hydrogen generation under UV-light.After the co-catalyst Pt(0.5 wt%)was loaded,the restacked 1D nanowires showed quite high rate of the hydrogen generation of 17.6 mmol/h/g,which is 1.7 times of that of restacked ID nanobelts(10.2 mmol/h/g),and even higher than that of TiO2(P25,11.9 mmol/h)and anatase Ti02(99.8%metal bases,100 nm,12.2 mmol/h).