Facile synthesis of a Ni₃S₂@C composite using cation exchange resin as an efficient catalyst to improve the kinetic properties of MgH₂

Carbon materials have excellent catalytic effects on the hydrogen storage performance of MgH₂. Here, carbon-supported Ni₃S₂ (denoted as Ni₃S₂@C) was synthesized by a facile chemical route using ion exchange resin and nickel acetate tetrahydrate as raw materials and then introduced to improve the hydrogen storage properties of MgH₂. The results indicated the addition of 10wt.% Ni₃S₂@C prepared by macroporous ion exchange resin can effectively improve the hydrogenation/dehydrogenation kinetic properties of MgH₂. At 100 ℃, the dehydrogenated MgH₂-Ni₃S₂@C-4 composite could absorb 5.68wt.% H₂. Additionally, the rehydrogenated MgH₂-Ni₃S₂@C-4 sample could release 6.35wt.% H₂ at 275 ℃. The dehydrogenation/hydrogenation enthalpy changes of MgH₂-Ni₃S₂@C-4 were calculated to be 78.5 kJ mol⁻¹/−74.7 kJ mol⁻¹, i.e., 11.0 kJ mol⁻¹/7.3 kJ mol⁻¹ lower than those of MgH₂. The improvement in the kinetic properties of MgH₂ was ascribed to the multi-phase catalytic action of C, Mg₂Ni, and MgS, which were formed by the reaction between Ni₃S₂ contained in the Ni₃S₂@C catalyst and Mg during the first hydrogen absorption–desorption process.