Heteroatom sulfur exploration for enhancing MgH2 dehydrogenation: A theoretical and experimental analysis

Abstract

High operating temperatures and sluggish kinetics constrain the commercial application of magnesium-based hydrogen storage materials. To overcome these drawbacks, this work investigates heteroatom sulfur as a catalyst to improve the dehydrogenation of MgH2 using density functional theory (DFT) and experimental validation. Heteroatom sulfur can influence the dehydrogenation of MgH2 by modulating interfacial carbon-magnesium interactions and substituting surface hydrogen sites. In particular, DFT calculations reveal that sulfur functional groups facilitate charge transfer and significantly reduce the energy barrier of MgH2 by 0.32 eV–1.59 eV. Substitution of sulfur atoms at surface hydrogen sites of MgH2 notably improves dehydrogenation by weakening the Mg–H bond and enabling a sulfur-assisted two-step dehydrogenation mechanism. Experimental results further confirm these theoretical findings. The MgH2/900C–20SO2 sample exhibits that the peak dehydrogenation temperature and the onset dehydrogenation temperature were 19.8 °C and 64 °C lower than that of pure MgH2, and a significant reduction in activation energy from 134.52 kJ mol−1 to 92.12 kJ mol−1. This research provides a comprehensive understanding of the catalytic effects of heteroatom sulfur on MgH2 and offers crucial theoretical and practical insights for the development of more efficient magnesium-based hydrogen storage systems.