Impact of Etching Conditions on Structural and Vibrational Characteristics of Novel i-MXene (Mo_2/3Er_1/3)₂C

The 2D i-MXenes represent a relatively new class of layered materials derived from quaternary (M’_2/3M”_1/3)₂AlC i-MAX phases. These i-MXenes are synthesized using conventional methods, similar to those employed for preparing MXenes from ternary MAX phases. However, during the synthesis of i-MXenes, the extent of M” etching occurs alongside Al, as the bonds between M”-C are relatively weaker compared to M’-C bonds. Consequently, the degree of M” etching can vary significantly based on the etching conditions, leading to the formation of novel inplane-ordered i-MXenes with distinctive properties. When M” is completely etched out, it results in vacancy-ordered i-MXenes, which are known for their outstanding conductivity, rendering them ideal for energy storage applications. Further investigation is essential to refine the synthesis process and produce diverse MXene structures. In this study, we explored the etching conditions of the (Mo_2/3Er_1/3)₂AlC MAX phase by employing both strong and mild etching methods to optimize the synthesis parameters such as time and temperature for preparing i-MXene. This was followed by structural characterizations using XRD, SEM, and Raman spectroscopy. Additionally, X-ray photoelectron spectroscopy and EDS were employed to identify and quantify the percentage of Erbium and the surface terminations groups on the resulting i-MXene. Our work highlights the tunability of synthesis conditions, paving the way for new types of MXenes and further expanding the MXene family.