经典文章精读 | 如何发现了MXene插层剂？| 2013年Yury Gogotsi

预计阅读时间约为6min

• pdf直接下载2Intercalation and delamination of layered carbides and carbonitrides..pdf

文章标题：

Intercalation and delamination of layered carbides and carbonitrides

DOI: 10.1038/ncomms2664

1. “Ti3C2(OH)xOyFz”

“It is important to note at the outset that the 2D MXene surfaces are not M-terminated, but covered with oxygen-containing groups, such as OH, and fluorine (F) introduced after etching with aqueous hydrofluoric acid (HF). The chemistry of exfoliated MXene produced by HF etching of Ti3AlC2 is much closer to Ti3C2(OH)xOyFz than to the idealized structure of a pure carbide layer Ti3C2. Henceforth, and for brevity’s sake, f-Ti3C2 will be used instead of the more cumbersome Ti3C2(OH)xOyFz. ”

“首先要注意的是，二维MXene表面不是M端，而是覆盖着含氧基团，如OH，以及用氢氟酸水溶液（HF）蚀刻后引入的氟（F）。通过HF蚀刻Ti3AlC2而产生的剥落MXene的化学性质要比纯碳化物层Ti3C2(OH)xOyFz的理想化结构更接近于Ti3C2。因此，为了简洁起见，将使用f-Ti3C2而不是更麻烦的Ti3C2（OH）xOyFz。”

2. 插层剂的发现

“The original aim of this work was to reduce the f-Ti3C2 surfaces to create Ti-terminated surfaces that theory predicts would be magnetic.A perusal of the graphene literature made it clear that hydrazine monohydrate N2H4·H2O (HM) dissolved in ,-dimethylformamide (DMF) is the reactant of choice. Since in our case, HM was found to primarily act as an intercalant rather than a reducing agent, the research objectives were redirected towards intercalation and delamination of MXenes. Furthermore, as the layered structures of the MXenes retain some similarities to clays, we reviewed the intercalation chemistries of the latter. Numerous compounds, such as formamide and its derivatives, dimethyl sulphoxide (DMSO), urea and long-chain alkylamines, among others have been shown to intercalate clays. For clays, HM is probably the most common intercalant; its intercalation results in the increase of kaolinite’s -lattice parameter (LP) from 7.2 to 10.3–10.4 Å ”

“这项工作的最初目的是减少f-Ti3C2的表面，以创造理论预测的Ti端面，使之具有磁性。仔细阅读石墨烯文献后，发现溶解在N,N-二甲基甲酰胺（DMF）中的一水肼N2H4-H2O（HM）是首选的反应剂。由于在我们的案例中，HM被发现主要作为插层剂而不是还原剂，研究目标被重新定向到MXenes的插层和分层。此外，由于MXenes的层状结构与粘土有一些相似之处，我们审查了后者的插层化学。许多化合物，如甲酰胺及其衍生物、二甲基亚砜（DMSO）、尿素和长链烷基胺等已被证明可以使粘土插层。对于粘土，HM可能是最常见的插层剂；它的插层导致高岭土的c-lattice参数（c-LP）从7.2增加到10.3-10.4 Å ”

3. 插层前后电阻率变化

“In addition, the electrical resistivities of non-intercalated MXenes and MXenes treated with HM were measured. The resistivity values of all intercalated samples were higher than those of non-intercalated MXenes presumably owing to the increase of their -LPs after intercalation . The differences in the magnitudes of the resistivity increases for different intercalated MXenes, at relatively the same expansion, can be partially explained by the different number of MXene atomic layers. In case of M3X2 (five atomic layers), the resistivity increases by an order of magnitude, whereas an increase by two orders is observed for the M2C (three atomic layers) compounds.”

“此外，还测量了非插层MXenes和用HM处理的MXenes的电阻率。所有插层样品的电阻率值都高于非插层MXenes，这可能是由于插层后其c-LPs的增加（补充表S1）。在相对相同的膨胀下，不同的插层MXenes的电阻率增加的幅度不同，可以部分地解释为MXene原子层的数量不同。在M3X2（五个原子层）的情况下，电阻率增加了一个数量级，而M2C（三个原子层）的化合物则增加了两个数量级。”

4. MXene分层

“We also tried to intercalate thiophene, ethanol, acetone, tetrahydrofuran, formaldehyde, chloroform, toluene, hexane, DMF, DMSO and urea into f-Ti3C2 at room temperature. Of these, only DMSO and urea resulted in an increase in the -LPs from 19.5±0.1 Å to 35.04±0.02 Å and 25.00±0.02 Å, respectively . ”

“我们还尝试在室温下将插进f-Ti3C2。其中，只有DMSO和尿素导致c-LPs从19.5±0.1 Å分别增加到35.04±0.02 Å和25.00±0.02 Å（补充图S5）。由此可见，DMF只在有HM的情况下插进f-Ti3C2。不管是不是巧合，在上述的有机化合物列表中，只有DMSO和尿素插层成功。”

5. 分层MXene的储能应用

“To date, our Li-ion work was carried out on stacked multilayer particles. The breakthrough presented herein, however, allowed us to measure Li-ion uptake on d-Ti3C2 ‘paper’. As shown in Fig. 4d, the capacity of the latter is a factor of 4 higher than that of as-synthesized f-MXene.”

“到目前为止，我们的锂离子工作是在堆叠的多层颗粒上进行的。然而，本文提出的突破使我们能够测量d-Ti3C2 "纸 "上的锂离子吸收量。如图4d所示，后者的容量比合成的f-MXene的容量高4倍。”

6. 插层方法

“To intercalate f-MXene with HM, the f-MXene powders were suspended either in HM or a 1:3 mixture of HM and DMF, and magnetically stirred for 24 h , either at room temperature (RT) or at 80 °C. In all cases, the weight ratio of HM:MXene was 10:1. When the treatment involved only HM, the suspensions were filtered and washed with ethanol. In case of intercalation with HM/DMF mixture, DMF was used for washing instead of ethanol. The powders were then dried in a desiccator under vacuum (<10 Torr) at RT for 24 h or in the vacuum oven (~10−2 Torr) at 120 °C for 24 h.

Intercalation of other organic compounds was attempted. Those included DMSO, urea, DMF, acetone, ethyl alcohol, tetrahydrofuran, chloroform, toluene, thiophene and formaldehyde. In all cases, the intercalation procedure was the same: (i) 0.3 g of f-Ti3C2 were mixed with 5 ml of each of the organic compounds listed above (excluding urea), then magnetically stirred for 24 h at RT; (ii) in the case of urea, 5 ml of 50 wt.% aqueous solution of urea was added to 0.3 g of f-Ti3C2 and stirred for 24 h at 60 °C. Later, the resulting colloidal solutions were filtered and dried in a desiccator under vacuum (<10 Torr) at RT. A detailed experimental section (materials used, techniques of material preparation and de-intercalation of MXenes) can be found in the Supplementary Methods. ”

“为了使f-MXene与HM插层，将f-MXene粉末悬浮在HM或HM与DMF的1:3混合物中，并在室温（RT）或80℃下磁力搅拌24小时。在所有情况下，HM：MXene的重量比为10：1。当处理只涉及HM时，悬浮液被过滤并用乙醇洗涤。在用HM/DMF混合物进行插层的情况下，用DMF代替乙醇进行洗涤。然后将粉末在真空（<10 Torr）下的干燥器中干燥24小时，或在120℃的真空炉（~10-2 Torr）中干燥24小时。

还尝试了其他有机化合物的夹层。这些包括DMSO、尿素、DMF、丙酮、乙醇、四氢呋喃、氯仿、甲苯、噻吩和甲醛。在所有情况下，插层程序是相同的：（i）将0.3克f-Ti3C2与上述每种有机化合物（不包括尿素）的5毫升混合，然后在RT磁力搅拌24小时；（ii）在尿素的情况下，将5毫升50重量％的尿素水溶液加入0.3克f-Ti3C2中，在60℃搅拌24小时。之后，将得到的胶体溶液过滤，并在RT的真空（<10托）下在干燥器中进行干燥。详细的实验部分（所用材料、材料制备技术和MXenes的去插层）可以在补充方法Microsoft Word - Intercalation and Delamination Supporting info - clean copy[3].docx (springer.com)中找到。”

【MXene】平台将致力于MXene研究工作内容的分享和报道，关注MXene在光电、医学、传感、电磁干扰屏蔽和催化等领域的最新研究进展。诚挚邀请各位教授、研究者和同行们在MXene平台上积极分享和讨论MXene的相关工作，欢迎关注我们，一起建立一个属于MXene的超高质量平台。如有侵权，请联系我们。

小编邮箱：mxene2011@163.com