Effectively enhanced catalytic effect of sulfur doped Ti₃C₂ on the kinetics and cyclic stability of hydrogen storage in MgH₂

Designing catalysts with high catalytic activity and stability is the key to achieve the commercial application of MgH₂. Herein, the sulfur doped Ti₃C₂ (S-Ti₃C₂) was successfully prepared by heat treatment of Ti₃C₂ MXene under Ar/H₂S atmosphere to facilitate the hydrogen release and uptake from MgH₂. The S-Ti₃C₂ exhibited pleasant catalytic effect on the hydriding/dehydriding kinetics and cyclic stability of MgH₂. The addition of 5 wt% S-Ti₃C₂ into MgH₂ resulted in a reduction of 114 ℃ in the starting dehydriding temperature compared to pure MgH₂. MgH₂ + 5 wt% S-Ti₃C₂ sample could quickly release 6.6 wt% hydrogen in 17 min at 220 ℃, and 6.8 wt% H₂ was absorbed in 25 min at 200 ℃. Cyclic testing revealed that MgH₂ + 5 wt% S-Ti₃C₂ system achieved a reversible hydrogen capacity of 6.5 wt%. Characterization analysis demonstrated that Ti-species (Ti⁰, Ti²⁺, Ti–S, and Ti³⁺) as active species significantly lowered the dehydrogenation temperature and promoted the re-/dehydrogenation kinetics of MgH₂, and sulfur doping can effectively improve the stability of Ti⁰ and Ti³⁺, contributing to the improvement of cyclic stability of MgH₂. This study provides strategy for the construction of catalysts for hydrogen storage materials.