Unveiling Local Atomic Ordering of Nb_αV_2-αCT_<i>x</i> MXenes for Lithium-Ion Storage

The demand for innovative materials in energy storage and generation necessitates precise atomic-scale chemical control in nanomaterials. Double-transition metal (DTM) MXenes have expanded the chemical diversity of layered 2D materials, exhibiting unique physicochemical properties. However, the atomic ordering of DTMs and its impact on lithium storage performance require further investigation. Here, we report the synthesis of two-dimensional niobium–vanadium carbides (NbαV2-αCTx) by Lewis acid etching strategy, a previously unexplored class of DTM MXenes. By utilizing X-ray absorption fine structure (XAFS) spectra, we demonstrate that adjusting the Nb/V ratio enables tuning of the coordination number of Nb/V in NbαV2-αCTx. As a result, the resulting Nb1.4V0.6CTx with enhanced local atomic ordering exhibited excellent rate performance and remarkable cycling stability. This study highlights the atomic-scale characterization of local structures using advanced X-ray spectroscopic techniques, expanding the diversity of the MXenes family.