First-principles study of Ti-decorated graphene-based single-atom catalyst for MgH2 dehydrogenation

Graphene-based single-atom catalysts (G-SACs) have been demonstrated to have significant role in enhancing the hydrogen storage performance of MgH 2 . In this work, single Ti atom was incorporated in various modified graphene, including pristine graphene (G), graphene with single vacancy (SVG) and double vacancy (DVG), and N-decorated graphene with single vacancy (N3G) and double vacancy (N4G). The effects of coordination environments of the Ti-decorated G-SACs on the dehydrogenation properties of MgH 2 were systematically investigated by first-principles calculations based on MgH 2 /G-SACs heterojunction model. It was found that the defective graphenes can prevent Ti atoms from agglomeration, whereas pristine graphene fails to do so. Structural analysis reveals that the introduction of Ti-decorated G-SACs induces elongation of Mg–H bonds and reduction of effective charge of H atoms at the interface, suggesting the Mg–H bonds tend to weaken. As for dehydrogenation thermodynamics, it was found that Ti-decorated G-SACs reduce the hydrogen desorption energies of MgH 2 , with the most significant effect observed for the G-SAC with N3G coordination environment (Ti@N3G). Interestingly, Ti@N3G also poses the greatest enhancement effect on the hydrogen diffusion kinetics, as revealed by ab initio molecular dynamics simulation, indicating that the MgH 2 /Ti@N3G interface serves as a fast diffusion channel for H atoms. • Systematic study of Ti-decorated graphene-based single-atom catalysts (G-SACs) for MgH 2 dehydrogenation. • Defective and N-doped graphene effectively anchor Ti atoms, preventing agglomeration. • Ti@N3G shows the greatest reduction in hydrogen desorption energy among the G-SACs studied. • MgH 2 /Ti@N3G interface acts as a fast diffusion channel, enhancing hydrogen diffusion kinetics.