A perspective on defect chemistry in MXenes revealed by electron paramagnetic resonance (EPR) techniques

Official URL: https://dx.doi.org/10.1039/d6ta04398d

Defect structures play a defining role in the performance of MXenes across diverse applications, from energy storage and catalysis to sensing and electronics. Electron Paramagnetic Resonance (EPR) spectroscopy, with its exceptional sensitivity to unpaired electrons and local magnetic environments, offers a uniquely powerful probe of these defect states. However, despite the rapid expansion of MXene research, EPR studies have largely remained limited to qualitative signal identification, leaving the underlying defect physics and spin interactions insufficiently explored. This perspective style review article highlights the opportunities offered by advanced EPR methodologies, including pulsed, high-frequency, in situ, and dynamic nuclear polarization (DNP)-assisted approaches, for achieving a more comprehensive understanding of defect chemistry in MXenes. We outline a framework that integrates quantitative EPR analysis, spin Hamiltonian modeling, and coordination symmetry considerations to resolve the complexity of paramagnetic centers in these two-dimensional (2D) materials. By linking spectroscopic insight with defect chemistry frameworks such as the Newman Superposition Model (NSM) and Kröger–Vink notation, we propose a pathway toward spin-resolved defect engineering in MXenes, particularly in emerging systems involving dopants, surface functionalization, and complex defect environments. Ultimately, expanding the methodological scope of EPR can provide deeper insight into structure–property relationships and accelerate the rational design of MXene-based functional materials.