Noble metal intercalation effects on the dehydrogenation of MgH₂/γ-graphdiyne heterojunctions

Magnesium hydride (MgH₂) offers high gravimetric hydrogen storage capacity and good reversibility, but its high dehydrogenation temperature and sluggish kinetics limit practical applications. In this study, an MgH₂ (110)/γ-graphdiyne heterojunction model was developed using density functional theory (DFT), with Pd, Pt, Ru, Rh, Ir, and Os atoms intercalated into the interfacial gap to evaluate the dehydrogenation pathway and kinetics. Results show that the γ-graphdiyne-induced interfacial charge redistribution weakens the Mg-H interaction, lowering the dehydrogenation barrier from 2.54 eV to 2.12 eV. Noble metal intercalation further reduces the barrier, with the Rh-intercalated system showing the lowest value of 0.63 eV and a decreased reaction energy. Interestingly, the dehydrogenation barriers correlate well with reaction energies, following the Bell-Evans-Polanyi relationship (R² = 0.93). Furthermore, the noble metals' d-orbital electron count exhibits a segmented linear correlation with the barrier, providing a screening descriptor and predicting a barrier of approximately 1.32 eV for Ag- and Au-intercalated systems. This study offers insights into interfacial design and metal screening for catalytic dehydrogenation systems based on MgH₂.