In less than a decade, we have witnessed significant advancement in the development of a new class of 2D materials known as MXenes, which are transition metal carbides, carbonitrides and nitrides. Due to their unique combination of physical and mechanical property attributes, a wide range of electrochemical energy storage, catalytic, electromagnetic interference shielding, nanoelectronics, optoelectronics, sensors, and biomedical applications have already been explored. From a fundamental standpoint, it is important to understand how the atomic structure and functional group chemistry govern nanoscale properties such that new insight can be gained in order to develop improved synthesis methods or to tune specific functional properties. (Scanning) transmission electron microscope (S/TEM) is ideally suited to characterize 2D MXenes using a combination of high spatial/temporal resolution imaging and analytical electron microscopy methods. In this talk, I will focus on three main topic areas of microscopy driven MXene research and detail how each microscopy technique is helping to better understand properties of MXene. <i>In situ</i> S/TEM is being used to determine ion intercalation mechanisms and kinetics by tracking the dynamic expansion of lattice planes during electrochemical biasing and the formation of interphase inorganic compounds. STEM, combined with electron energy loss spectroscopy (EELS), is being used to determine the bonding characteristics and electronic structure of intercalants and functional group chemistry due to its importance on ion transport and conductivity. EELS is also being used to map the plasmonic response of MXenes at high spatial resolution. Lastly, STEM based atomic fabrication methods are being explored to controllably manipulate the MXene atomic structure to realize new nanoelectronic devices.

Essential role of electron microscopy in fundamental MXene research

ACS Fall 2021

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