Catalytic mechanisms of nickel nanoparticles for the improved dehydriding kinetics of magnesium hydride

•Ni nanoparticles dispersed inside mesoporous carbon are synthesized.•The peak temperature of dehydrogenation of MgH2 is reduced by 142.5 °C.•The dehydriding activation energy of MgH2Ni@C nanocomposite is largely lowered.•The microscopic catalytic mechanisms of Ni are well examined by TEM observation.•In-situ formed Mg2Ni plays a dominant catalytic role in the decomposition of MgH2.