Synergistic Catalytic Activity of Porous Rod-like TMTiO3 (TM = Ni and Co) for Reversible Hydrogen Storage of Magnesium Hydride

MgH2 contains a high content of 7.6 wt % H2. However, its poor kinetics and high thermodynamic stability exhibit unacceptably low energy efficiency. Catalyst doping is deemed as one of the most effective strategies to improve its kinetic performance. In this work, porous rod-like TMTiO3 (TM = Ni and Co) samples are designed and introduced into an MgH2 system for the first time. TMTiO3 exhibits a high catalytic effect on the hydrogen desorption performance of MgH2. In particular, MgH2–6% NiTiO3 possesses excellent catalytic efficiency with a relatively low dehydrogenation temperature (235 °C) and fast dehydrogenation rate (∼0.1842 wt %/min at 235 °C), and the sample exhibits wonderful cycling stability with respect to both capacity (6.4 wt %) and kinetics (∼0.64 wt %/min at 300 °C). Mechanistic research shows that the in situ-formed Mg2Ni/Mg2NiH4 phases are regarded as catalytically active species, which work as a "Hydrogen Pump" and make the hydrogen release easier. Meanwhile, the interconversion within multivalent titanium (Ti4+, Ti3+, and Ti2+) that acts as a carrier for electron transformation leads to easy H formation from H–. The synergetic catalytic effects between Mg2Ni/Mg2NiH4 and multivalent titanium result in favorable and lasting catalytic efficiency for the enhanced hydrogen desorption properties of the MgH2 system.