XPS spectra curve fittings of Ti3C2Tx based on first principles thinking

[Display omitted] •Perfect fits of the F 1s, O 1s, Ti 2p, and C 1s XPS spectra curve fitting.•Seven pieces of established XPS knowledge useful when to understand XPS spectra.•Can be used as a model for future curve fitting of conducting materials in general.•One O bonds toward two Ti atoms and another O bonds toward three Ti atoms.•The Ti3C2Tx termination shows two domains – only F (20%) and with both F and O. MXenes are an interesting family of 2D materials that have the potential to meet challenges in many applications. A useful tool in the work of understanding the nature of the MXenes, as well as exploring their capabilities, is X-ray photoelectron spectroscopy (XPS). In analyzing XPS spectra it might be necessary to use curve fitting to extract valuable information. However, approaches toward the curve fitting procedure have been different in many studies and introductions of questionable assumptions, unverified feature assignments, and inconsistent curve fitting have led to contrasting conclusions from XPS analysis. It is therefore motivated to show curve fittings of F 1s, O 1s, Ti 2p, and C 1s XPS spectra obtained from high quality Ti3C2Tx that are based on fundamental knowledge applied step by step through the strategy of first principles thinking. With the use of first principles thinking the curve fittings and the subsequent analysis became more realistic compared to what have been presented in recent studies. The results of the curve fittings presented in this work are well founded and can be used as a model for future curve fittings of MXenes. The strategy of first principles thinking is advantageous in XPS curve fittings in general.