Understanding Ti3C2Tx MXene Surface Chemistry with XPS Analysis

A recent study published in Advanced Materials Interfaces introduced a new method to accurately analyze the surface chemistry of Ti3C2Tx MXenes. The researchers utilized energy-dependent X-ray photoelectron spectroscopy (XPS) in combination with depth profile modeling to achieve this.

This approach enabled them to differentiate and quantify signals from the MXene material itself and from adsorbed species. In contrast, uncorrected lab-based XPS tended to overestimate titanium vacancies and underestimate surface terminal groups.

MXenes are a group of two-dimensional transition metal carbides and nitrides known for their unique chemical and physical properties. These properties make them valuable in various fields such as energy storage, water purification, catalysis, and gas separation. Understanding the surface chemistry and internal composition of MXenes is crucial for their applications, although it is challenging to achieve with high precision.

Various techniques, including XPS, are commonly used to study MXene chemistry. However, conventional XPS methods can produce biased results due to the presence of surface contaminants. To address this issue, the researchers employed synchrotron-based XPS, which allowed them to tune the probing energy and distinguish between signals from true MXene surfaces and external contaminants.

The study involved synthesizing Ti3C2Tx MXenes from Ti3AlC2 MAX phases using a mixture of hydrofluoric acid (HF) and hydrochloric acid (HCl) at different concentrations. Structural and surface analysis were conducted on the MXene films using various techniques, including XPS, XAS, and UV–vis–NIR spectroscopy. The results showed that the refined approach provided more accurate analysis of the surface composition and stoichiometry of Ti3C2Tx MXenes.

The comparison with traditional lab-based XPS highlighted the importance of excitation energy in obtaining reliable measurements. The study also demonstrated the effectiveness of XAS in studying surface chemistry in these materials. The methodology developed in this research could be applied to MXene samples prepared using different etching methods.

According to the source: AZoM.