In Situ AlNi Derived from Ni/Dual-Phase TiO₂ for Hydrogen Storage Enhancement of MgH₂

Though recognized as a highly promising solid-state hydrogen storage material, magnesium hydride (MgH₂) in application is hindered by sluggish kinetics and high operating temperatures. Alloying and catalyzing are proven effective to enhance the hydrogen storage performance of MgH₂. Herein, the dual-phase TiO₂ (anatase/rutile TiO₂) supported Ni nanoparticle (Ni/Dp-TiO₂) were fabricated and incorporated into Mg₉₀Al₁₀. Mg₉₀Al₁₀-10 wt.% Ni/Dp-TiO₂ can absorb 4.28 wt.% H₂ at 150°C and desorb 3.86 wt.% H₂ at 250°C within 2500 s, outperforming Mg₉₀Al₁₀, which achieves 0.96 wt.% H₂ absorption and 0.27 wt.% H₂ desorption under identical conditions. Notably, the dehydrogenation activation energy (E_a) of Mg₉₀Al₁₀-10 wt.% Ni/Dp-TiO₂ is dramatically reduced to 56.36 kJ mol^-1, accompanied by significant decreases in the hydrogenation and dehydrogenation enthalpies (ΔH_abs and ΔH_des) to -66.25 and 68.18 kJ mol^-1, respectively. Both Density Functional Theory (DFT) calculations and experimental results demonstrate that the simultaneous enhancement of the kinetics and thermodynamics of Mg₉₀Al₁₀-10 wt.% Ni/Dp-TiO₂ originates from the electron-mediating effect of the in situ formed AlNi/Dp-TiO₂ and of Al species (including Mg-Al solid solution, Mg₁₇Al₁₂, and Mg₂Al₃). This work provides a viable strategy for the rational design of highly efficient catalysts toward advanced MgH₂-based hydrogen storage systems.