Combining X‐Ray Photoelectron and Absorption Spectroscopies for Determining Surface Chemistry and Composition of Ti3C2Tx MXene

Abstract Surface chemistry and core composition of 2D MXenes play a major role in their interfacial properties, but the determination and quantification of their bonding environments remain challenging. X‐ray Photoelectron Spectroscopy (XPS) is a method of choice that is broadly utilized but is often hindered by large uncertainties and systematic bias due to adsorbed species such as adventitious carbon or etching residues. In this work, energy‐dependent XPS and depth profile modeling of the Ti 3 C 2 T x MXene surface are employed to differentiate the contributions from the MXene and the adsorbed species, thereby increasing the accuracy of quantification. In comparison, uncorrected lab‐based XPS suffers from a systematic overestimation of Ti vacancies by 7% and an underestimation of terminal atoms, particularly F, by as much as 15%. Interestingly, it is found that a simple inelastic mean free path correction is sufficient to address the issue and reveals extremely low defects in Ti 3 C 2 T x MXene synthesized using the HF/HCl etching route. Soft X‐ray Absorption Spectroscopy (XAS), supported by Density Functional Theory (DFT) calculations, also demonstrates a high chemical sensitivity of the surface terminations. This work provides novel insights into XPS quantification and the use of XAS for probing the carbide core and surface chemistry of Ti 3 C 2 T x MXenes.