A critical analysis of the X-ray photoelectron spectra of Ti3C2Tz MXenes

Abstract

Since their discovery in 2011, the 2D transition metal carbide, nitrides, and carbonitridesdubbed MXenes -have garnered a lot of worldwide interest. Given their 2D structure, surface, or termination, chemistries play a vital role in most applications. X-ray photoelectron spectroscopy, XPS, is one of the most common characterization tools for quantifying surface terminations and overall chemistry. Herein we critically review the XPS fitting models proposed for Ti 3 C 2 T z MXene in the literature and make the case that they are at best incomplete and at worst contradictory. We propose a new fitting algorithm based on all the data obtained from previously published studies. In our approach, we assign the Ti 2p peak at 455.0 eV, to the C-Ti-O\O\O and C-Ti-C octahedra. The peaks at 456.0, 457.0, 457.9, and 459.6 eV are assigned to C-Ti-O\O\F, C-Ti-O\F\F, C-Ti-F\F\F, and TiO 2-x F 2x , respectively. The first four represent possible Ti atom terminations; the last is an oxyfluoride. In our proposed model we do not distinguish between O and OH terminations in the Ti 2p spectra; we only do so in the O spectra. Lastly, we propose and recommend a method for quantifying the surface terminations in Ti 3 C 2 T z .

Water-dispersible Ti3C2Tz MXene nanosheets by molten salt etching

“…High-resolution spectra for the Ti 2p, C 1s and Sn 3d binding energies are shown in Figures 5B-5D, respectively. The high-resolution XPS spectra of Ti 2p (Figure 5B) region were deconvoluted into Ti-C, Ti 2+ , Ti 3+ , TI-F, and TiO 2 , which matches with prior studies (Halim et al, 2016;Magnuson et al, 2018;Natu et al, 2021;Naguib et al, 2011). The presence of the Ti-C peak at binding energy of 455 eV in Ti 2p spectra indicates the removal of aluminum from MAX phase and formation of Ti 3 C 2 T z MXene nanosheets.…”

“…( Naguib et al., 2011 ). The high-resolution spectra of C 1s region ( Figure 5 C) of the powder show three prominent peaks at 282, 284.6, and 286.6 eV, which corresponds to Ti-C, C-C, and C-O, respectively ( Halim et al., 2016 ; Naguib et al., 2011 ; Natu et al., 2021 ). The presence of Ti-C peak in C 1s spectra confirms the formation of MXene ( Ghidiu et al., 2014b ; Halim et al., 2016 ; Naguib et al., 2011 ).…”

Carbon-Coated Three-Dimensional MXene/Iron Selenide Ball with Core–Shell Structure for High-Performance Potassium-Ion Batteries

“…The Ti 2p spectrum (Fig. 2c) showed multiple component peaks corresponding to Ti-C, Ti 3+ , Ti 4+ , and C-Ti-F bonds, indicating that the MXene nanosheets with the chemical formula of Ti n+1 C n F x were partially oxidized during the spray pyrolysis process [34][35][36][37]. The C 1s (Fig.…”

“…2d) spectrum could be deconvoluted into five peaks for Ti-C (282.5 eV), C=C (284.0 eV), C-C (285.2 eV), C-O (286.1 eV), and O=C-O (288.1 eV) bonds. The presence of the Ti-C bond was ascribed to MXene [37,38].…”

Investigating the rheology of 2D titanium carbide (MXene) dispersions for colloidal processing: Progress and challenges

“…Therefore, the chemical make-up of MXenes significantly impacts their colloidal rheology [49], and this should be characterised as fully as possible. Whilst we accept that it is currently difficult to quantify the proportions and spatial arrangement of functional groups which are typically denoted with an ambiguous "T x ", the present authors hope that developments in techniques such as hard X-ray photoelectron spectroscopy (HAXPES) will make the composition of MXenes better understood in the future [8,16,[62][63][64]. As well as this, it is important to note the age of samples at the time of rheological measurement, because this will affect both the degree of oxidation (which decreases surface charge) and flocculation (which decreases surface charge and increases average particle size and shape) [65].…”