Preparation of Highly Active TiO2 Nanocrystals and Their Photocatalytic Property
Enhancing the exposure ratio of high-energy{001}crystalline surfaces can effectively improve the photocatalytic activity of TiO2,and a crystal surface control agent is usually used to expose the high-energy{001}crystalline surfaces,but the morphology of the synthesized TiO2 is unstable and the particle size is large due to a variety of factors,so it is necessary to realize the stable synthesis of TiO2 nanocrys-tals and reduce the size of the particles.In this paper,TiO2 nanocrystals were synthesized using potas-sium titanate nanowires as precursors.Firstly,TiO2 octahedral bipyramidal morphology was achieved through acid treatment,and the particle size of TiO2 nanocrystals was reduced by decreasing the K+con-tent in potassium titanate nanowires.The study demonstrated that the photocatalytic activity of TiO2-H7-0 sample was the strongest,which synthesized through acid treatment of potassium titanate nanowires for 7 hours,resulted in an 86%reduction in particle size compared to the untreated sample.Furthermore,the activity of degrading methylene blue was 7.4 times higher than that of the original anatase TiO2.In order to further improve the photocatalytic activity of TiO2 nanocrystals,using(NH4)2CO3 as a morphol-ogy control agent to control the exposure ratio of{001}crystalline surfaces through the variation of(NH4)2CO3 concentration.The precursor without acid-treated series samples with(NH4)2CO3 crystal fac-ets modulation could effectively enhance the photocatalytic activity.The TiO2-0.14 synthesized at the(NH4)2CO3 concentration of 0.14 mmol/L exhibits 2.6 times greater degradation activity than that of the original anatase TiO2.However,the photocatalytic activity of the acid-treated for 7 h TiO2 samples were suppressed by introducing(NH4)2CO3 for crystal surface regulation,which might be caused by the lower percentage of{001}crystal surface exposure under the same(NH4)2CO3 concentration,as well as the increase of the particle size with the increase in the concentration of(NH4)2CO3,with the consequent decrease in the content of the oxygen vacancies.In this study,it was found that treating potassium tita-nate nanowire precursors with acid could synthesize octahedral bipyramidal TiO2 nanocrystals and reduce its particle size,which could improve the photocatalytic activity of TiO2.However,the extent of the acid treatment would impact the exposure ratio of the{001}facets and the crystallinity of the TiO2 nanocrys-tals.The relationship between acid treatment and crystal facet modulation needs to be thoroughly explored to further enhance the photocatalytic activity of TiO2 nanocrystals.
万方数据
