Hydrogen Evolution\nReaction Activity in Mo<sub>2</sub>TiC<sub>2</sub>T<i>x</i> MXene Derived from Mo<sub>2</sub>TiAlC<sub>2</sub> MAX Phase: Insights\nfrom Compositional Transformations

MAX phases represent a crucial building block for the\nsynthesis\nof MXenes, which constitute an intriguing class of materials with\nsignificant application potential. This study investigates the catalytic\nproperties of the Mo<sub>2</sub>TiAlC<sub>2</sub> MAX phase and the\ncorresponding Mo<sub>2</sub>TiC<sub>2</sub>T<sub><i>x</i></sub> MXene for the hydrogen evolution reaction (HER). Characterization\nby X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive\nspectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) revealed\nthat despite the presence of secondary phases, the HER catalytic activity\nis primarily influenced by the MAX phase and its derived MXene. Interestingly,\nthe catalytic activity of the MXene improves over time, attributed\nto the formation of MoO<sub>2</sub> as identified by XPS. This work\nenhances the understanding of MXene-based materials for electrochemical\napplications, highlighting crucial structural and chemical transformations\nthat optimize their performance in energy conversion technologies.