高活性TiO_(2)纳米晶的制备及其光催化性能

Preparation of Highly Active TiO_(2) Nanocrystals and Their Photocatalytic Property

提升高能{001}晶面的暴露比例可有效提高TiO_(2)的光催化活性,通常采用晶面控制剂暴露高能{001}晶面,但受多种因素影响合成的TiO_(2)形貌不稳定,且粒径较大,有必要在缩小粒径的基础上实现TiO_(2)纳米晶的稳定合成。基于此,本文以钛酸钾纳米线为前驱体稳定合成TiO_(2)纳米晶,首先通过酸处理保证TiO_(2)八面双锥体形貌,并通过降低钛酸钾纳米线中K+含量来减小TiO_(2)纳米晶的粒径。研究表明,以钛酸钾纳米线为前驱体酸处理7 h合成的TiO_(2)-H7光催化活性最强,其粒径比未酸处理时缩小了近86%,降解亚甲基蓝的活性是原始锐钛矿型TiO_(2)的7.4倍。在此基础上,以(NH_(4))_(2)CO_(3)为形貌控制剂,通过改变(NH_(4))_(2)CO_(3)浓度来调控{001}晶面的暴露比例进一步提高TiO_(2)纳米晶的光催化活性。前驱体未酸处理系列(NH_(4))_(2)CO_(3)晶面调控后可有效提升光催化活性,(NH_(4))_(2)CO_(3)的浓度为0.14 mmol/L时合成的TiO_(2)-0.14是原始锐钛矿型TiO_(2)降解活性的2.6倍。以酸处理7 h的钛酸钾纳米线引入(NH_(4))_(2)CO_(3)进行晶面调控后,光催化活性反而受到了抑制,可能是{001}晶面暴露比例不足,且颗粒粒径随(NH_(4))_(2)CO_(3)浓度的增加而增加,氧空位含量随之减少导致的。本研究发现酸处理钛酸钾纳米线前驱体可合成八面双锥体TiO_(2)纳米晶并缩小颗粒尺寸,进而提高TiO_(2)的光催化活性。但酸处理程度会影响后续晶面调控{001}晶面的暴露比例和纳米晶结晶度,要想进一步提升TiO_(2)纳米晶的光催化活性还需深入探究酸处理与晶面调控之间的构效关系。

Enhancing the exposure ratio of high-energy{001}crystalline surfaces can effectively improve the photocatalytic activity of TiO_(2),and a crystal surface control agent is usually used to expose the highenergy{001}crystalline surfaces,but the morphology of the synthesized TiO_(2) is unstable and the particle size is large due to a variety of factors,so it is necessary to realize the stable synthesis of TiO_(2) nanocrystals and reduce the size of the particles.In this paper,TiO_(2) nanocrystals were synthesized using potas‐sium titanate nanowires as precursors.Firstly,TiO_(2) octahedral bipyramidal morphology was achieved through acid treatment,and the particle size of TiO_(2) nanocrystals was reduced by decreasing the K+ content in potassium titanate nanowires.The study demonstrated that the photocatalytic activity of TiO_(2)-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 TiO_(2).In order to further improve the photocatalytic activity of TiO_(2) nanocrystals,using(NH_(4))_(2)CO_(3) as a morphol‐ogy control agent to control the exposure ratio of{001}crystalline surfaces through the variation of(NH_(4))_(2)CO_(3) concentration.The precursor without acid-treated series samples with(NH_(4))_(2)CO_(3) crystal fac‐ets modulation could effectively enhance the photocatalytic activity.The TiO_(2)-0.14 synthesized at the(NH_(4))_(2)CO_(3) concentration of 0.14 mmol/L exhibits 2.6 times greater degradation activity than that of the original anatase TiO_(2).However,the photocatalytic activity of the acid-treated for 7 h TiO_(2) samples were suppressed by introducing(NH_(4))_(2)CO_(3) for crystal surface regulation,which might be caused by the lower percentage of{001}crystal surface exposure under the same(NH_(4))_(2)CO_(3) concentration,as well as the increase of the particle size with the increase in the concentration of(NH_(4))_(2)CO_(3),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 TiO_(2) nanocrystals and reduce its particle size,which could improve the photocatalytic activity of TiO_(2).However,the extent of the acid treatment would impact the exposure ratio of the{001}facets and the crystallinity of the TiO_(2) nanocrys‐tals.The relationship between acid treatment and crystal facet modulation needs to be thoroughly explored to further enhance the photocatalytic activity of TiO_(2) nanocrystals.