Ni-Doped Pd/TiO 2 as a High-Efficiency Nanocatalyst for Hydrogen Storage of Magnesium Hydride

Magnesium hydride is regarded as a promising candidate for hydrogen storage and transportation owing to its substantial hydrogen capacity, affordability, and ecological compatibility. Nevertheless, its practical application is constrained by a relatively high operating temperature and unsatisfactory hydrogen absorption/desorption kinetics. Herein, a Ni-doped Pd/TiO2 nanocatalyst was successfully synthesized, and its effective catalysis on enhancing the hydrogen storage performance of MgH2 was systematically studied via combined experimental and density functional theory (DFT) approaches. At 275 °C, the MgH2–NiPd/TiO2 composite desorbs 6.09 wt % H2 within 1800 s, significantly higher than that of MgH2–Pd/TiO2 (5.41 wt %) and as-milled MgH2 (0.1 wt %) under the same conditions. Moreover, NiPd/TiO2 helps to decrease the dehydrogenation activation energy from 153 to 71.60 kJ/mol. MgH2–NiPd/TiO2 also shows an excellent cyclic stability with an average attenuation rate of less than 1% for each cycle. The DFT calculations also confirm that metal atoms more easily interact with hydrogen atoms than TiO2. The adsorption energy of hydrogen is 0.781 eV for TiO2, which is reduced to −0.938 eV for Pd/TiO2, and it further reduces to −1.227 eV for NiPd/TiO2. Electronic structure simulations suggest that the narrower the band gap, the more easily hydrogen diffuses. This work demonstrates that nano-NiPd/TiO2 effectively promoted the dehydrogenation of MgH2.