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Many applications are suggested for Ti‐MXene motivating strong interest in studies of Ti3C2Tx synthesis by solution‐based methods. However, so far only ex situ studies of the synthesis are performed, mostly due to the difficulty of handling HF‐based solutions. Here the first time‐resolved in situ synchrotron radiation X‐ray Diffraction study of MXene synthesis performed using a plastic capillary‐size reaction cell directly in HF solution is reported. This study provides the first report on the structure of "pristine MXene" formed by Ti3AlC2 etching with LiF+HCl. The term "pristine" refers to the MXene structure found directly in HF solution. By comparing the interlayer distances of pristine MXene (≈13.5 Å), solvent‐free Li‐intercalated MXene (≈12.2 Å), and Li‐free MXene (≈10.7 Å), it can be concluded that the width of "slit pores" formed by terminated MX layers during the Al etching does not exceed ≈3 Å. The width of these slit pores is a key factor for HF etching of Al within the interlayers. This space constraint explains the slow kinetics of MXene formation in HF‐based synthesis methods. No intermediate phases are observed, suggesting that the crystalline MXene phase is formed by the simultaneous etching of Al and termination of Ti3C2 layers. [ABSTRACT FROM AUTHOR]

Swelling is the most fundamental property of graphite oxides (GO). Here, a structural study of Brodie graphite oxide (BGO) swelling in a set of long chain 1‐alcohols (named C11 to C22 according to the number of carbons) performed using synchrotron radiation X‐ray diffraction at elevated temperatures is reported. Even the longest of tested alcohols (C22) is found to intercalate BGO with enormous expansion of the interlayer distance from ≈6Å up to ≈63Å, the highest expansion of GO lattice ever reported. Swelling transitions from low temperature α‐phase to high temperature β‐phase are found for BGO in all alcohols in the C11–C22 set. The transitions correspond to decrease of inter‐layer distance correlating with the length of alcohol molecules, and change in their orientation from perpendicular to GO planes to layered parallel to GO (Type II transitions). These transitions are very different compared to BGO swelling transitions (Type I) found in smaller alcohols and related to insertion/de‐insertion of additional layer of alcohol parallel to GO. Analysis of general trends in the whole set of 1‐alcohols (C1 to C22) shows that the 1‐alcohol chain length defines the type of swelling transition with Type I found for alcohols with C<10 and Type II for C>10. [ABSTRACT FROM AUTHOR]