Catalytic effect of MOF-derived transition metal catalyst FeCoS@C on hydrogen storage of magnesium

Abstract

• The FeCo@C and FeCoS@C catalysts are derived from ZIF-67. • A heterogeneous C supported Mg 2 Co, α-Fe, Co 3 Fe 7 and MgS catalyst system is formed. • The MgH 2 -FeCoS@C composite can absorb 4.56 wt% hydrogen within 900 s at 473 K. • The initial dehydrogenation temperature of MgH 2 -FeCoS@C composite is 550 K. • The dehydrogenation activation energy of MgH 2 is reduced to 91.9 kJ mol −1 . The introduction of the heterogeneous catalysts with high activity can significantly improve hydrogen storage performance of MgH 2 , therefore, in this paper, we synthesize a carbon-supported transition metal compound, FeCoS@C derivative from ZIF-67, by utilizing the in situ formed C dispersive multiphase Mg 2 Co, α-Fe, Co 3 Fe 7 , and MgS to implement catalysis to MgH 2 . Noteworthily, MgH 2 -FeCoS@C rapidly absorbs 6.78 wt% H 2 within 60 s at 573 K and can also absorb 4.56 wt% H 2 in 900 s at 473 K. Besides, the addition of FeCoS@C results in decreasing of the initial dehydrogenation temperatures of MgH 2 from 620 to 550 K. The dehydrogenation activation energy of MgH 2 decreases from 160.7 to 91.9 kJ mol –1 . Studies show that the Mg 2 Co, α-Fe, and Co 3 Fe 7 act as “hydrogen channels” to accelerate hydrogen transfer due to the presence of transition metals, and MgS with excellent catalytic effect formed from MgH 2 -FeCoS@C provides a strong and stable catalytic effect. Besides, the carbon skeleton obtained by the carbonization of ZIF-67 not only serves as a dispersion for the multiphase catalytic system, but also provides more active sites for the catalysts. Our study shows that the multiphase and multiscale catalytic system provides an effective strategy for improving the hydrogen storage performance of MgH 2 .