Doping a catalyst can efficiently improve the hydrogen
reaction
kinetics of MgH2. However, the hydrogen desorption behaviors
are complicated in different MgH2–catalyst systems.
Here, a carbon-encapsulated nickel (Ni@C) core–shell catalyst
is synthesized to improve the hydrogen storage properties of MgH2. The complicated hydrogen desorption mechanism of the MgH2–Ni@C composite is elucidated. The experimental and
theoretical calculation results indicate a short-range nanoreaction
effect on the hydrogen desorption behaviors of the MgH2–Ni@C composite. The Ni@C catalysts and the adjacent MgH2 form nanoreaction sites along with preferential hydrogen
desorption. The new interface between the in situ formed Mg and residual
MgH2 contributes to the subsequent hydrogen desorption.
With the nanoreaction sites increased via adding more catalyst, the
short-range nanoreaction effect is more prominent; as a comparison,
the interface effect becomes weaker or even disappears. In addition,
the core–shell structure catalyst shows ultrahigh structural
stability and catalytic activity, even after 50 hydrogen absorption
and desorption cycles. Hence, this study provides new insights into
the complicated hydrogen desorption behaviors and comes up with the
short-range nanoreaction effect in the MgH2–catalyst
system.
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