Enhanced De/hydrogenation\nKinetics and Cycle Stability\nof Mg/MgH<sub>2</sub> by the MnO<sub><i>x</i></sub>‑Coated\nTi<sub>2</sub>C<i>T</i><sub><i>x</i></sub> Cataly

MXene based catalysts can significantly enhance hydrogenation\nand\ndehydrogenation (de/hydrogenation) kinetics of Mg/MgH<sub>2</sub>,\nbut they suffer from uncontrollable catalysts–hydrogen bond\nstrength and structural instability. Here, we propose <i>T</i><sub><i>x</i></sub> density control of MXene-based catalysts\nand MnO<sub><i>x</i></sub> coating as a promising solution.\nThe MnO<sub><i>x</i></sub>@Ti<sub>2</sub>C<i>T</i><sub><i>x</i></sub>-catalyzed Mg/MgH<sub>2</sub> can release\n5.97 wt % H<sub>2</sub> at 300 °C in 3 min and 5.60 wt % H<sub>2</sub> at 240 °C in 15 min with an activation energy of 75.57\nkJ·mol<sup>–1</sup>. In addition, the samples showed \nexcellent de/hydrogenation-cycle stability, and the degradation of\nhydrogen storage capacity is negligible even after 100 cycles. DFT\ncalculations combined with XPS analysis showed that the <i>T</i><sub><i>x</i></sub> defect on the surface of the MnO<sub><i>x</i></sub>@Ti<sub>2</sub>C<i>T</i><sub><i>x</i></sub> catalyst could optimize the strength of the Ti–H\nbond, accelerating both hydrogen dissociation and diffusion processes.\nThe catalyst’s surface properties were protected by the MnO<sub><i>x</i></sub> coating, achieving high chemical and catalytic\nstability. These findings offer a strategy for surface structure optimization\nand protection of MXene-based catalysts, realizing controllable catalyst–hydrogen\nbond strength.