Relating X-ray photoelectron spectroscopy data to chemical bonding in MXenes

Abstract

The relationship between core level binding energy shifts, available through X-ray photoelectron spectroscopy, and chemical bonding is analysed for a series of MXenes, a new family of two-dimensional materials with many applications in nanotechnology.

Effect of oxygen termination on the interaction of first row transition metals with M2C MXenes and the feasibility of single-atom catalysts

“…The former is favorable in the MXenes composed of metals from the d 2 -(Ti, Zr, and Hf) and d 3 -(V, Nb, and Ta) metals, and d 4 -(Cr). 54 Alternatively, we found that the MXenes composed of d 4 -(Mo and W) metals prefer BABCB stacking, which is consistent with previous studies. [57][58][59] Here, it should be noted that Tan et al 59 claimed that BABCB stacking was preferred by Cr 2 CO 2 .…”

“…Similar models were used in a previous work analyzing the effect of O-terminations on the core level binding energy (CLBE) shis in this type of system. 54 A vacuum of 16 A along the c-axis was selected to ensure a negligible interaction between replicated slabs. The interaction between the transition metal atoms and O-terminated MXene carbides with M 2 CO 2 stoichiometry was established from the calculated adsorption energy, E ads , which is dened as follows:…”

Charge transport mechanisms in inkjet-printed thin-film transistors based on two-dimensional materials

“…The asymmetric Ti-C (2p 3/2 ∼ 454.8 eV and 2p 1/2 ∼ 460 eV) peak which is commonly associated with MXene flakes is shifted to a larger binding energy compared to its precursor MAX phase powder. This is attributed to the Al in the MAX phase powder (Ti-C 2p 3/2 ∼ 454.6 eV) being replaced by a more electronegative termination group like -F, -O, and -OH [120,[122][123][124].…”

Peculiar opportunities given by XPS spectroscopy for the clinician

“…This is done in order to minimize the fictitious repulsion between the replicas. Recent studies have reported the JS to provide ∆BEs of gas phase molecules and periodic surfaces [82,83] in good agreement with experiments, when adopting a PAW description of the atomic cores (implemented on VASP).…”

“…As a drawback, the periodic ∆SCF calculations imply the use of approaches in order to prevent the spurious core electron holes' interaction between the replica of the final system (N − 1 electron), that would lead to Coulomb divergence. The introduction of a uniform background opposite charge [82] and the addition of electrons in the conduction band [76,83] of the final systems have been the two main approaches adopted to circumvent such problem. However, the addition of fictitious counter charges in the final system can introduce spurious effects in the calculated values of core level BEs and ∆BEs [84].…”