Single-Atom Cu Supported on Ti₃C₂T_<i>x</i> for Catalyzing Hydrogen Storage in MgH₂

Magnesium hydride (MgH₂) has been considered a promising hydrogen storage material, but its commercial application is severely limited by high operating temperature and slow de/hydrogenation kinetics. Herein, an efficient catalyst, Cu_SA/Ti₃C₂T_<i>x</i>, is successfully synthesized by introducing a Cu single-atom into Ti₃C₂T_<i>x</i> MXene nanosheets and applied to MgH₂. The synthesized MgH₂ + 5 wt %Cu_SA/Ti₃C₂T_<i>x</i> (Cu_SA/Ti₃C₂T_<i>x</i>/MgH₂) composite exhibits low initial dehydrogenation temperature (<i>T</i> = 241.73 °C) and rapidly dehydrogenation kinetics (<i>E</i>_a = 76.38 kJ/mol H₂). Impressively, the Cu_SA/Ti₃C₂T_<i>x</i>/MgH₂ composite desorbs 3.3 wt % of hydrogen within 240 min at 180 °C after 20 cycles, as well as an initial dehydrogenation temperature of 164.29 °C. The superior catalytic effect of Cu_SA/Ti₃C₂T_<i>x</i> catalyst is ascribed to the numerous catalytic active area, in-situ-formed active metallic Ti, and multivalent Ti species, accelerating the electron transfer and weakening the strength of Mg-H bonds. In particular, the Cu single-atom improved the stability of Ti⁴⁺ in Ti₃C₂T_<i>x</i>, thereby enhancing its catalytic ability. This work provides a new perspective for ameliorating the catalytic ability of MXene.