Bidirectional catalysts with dual-atom dynamic d-band centre modulation and support self-reconstruction for de/hydrogenation in MgH₂/Mg.

Abstract

High-capacity solid-state hydrogen storage using MgH₂ requires high de/hydrogenation temperatures and exhibits sluggish kinetics. Although catalytic modification of MgH₂ has been extensively studied, existing catalysts largely focus on unidirectional optimisation, failing to simultaneously and efficiently optimise the reversible hydrogen-storage properties of the MgH₂/Mg system. Herein, we rationally design and construct a heteronuclear dual-atom catalyst, Ni₁Co₁@TiO₂. In this system, Ni and Co bidirectionally modulate the d-band centres, enabling synergistic and complementary catalysis. Specifically, Ni serves as the primary active site for Mg-H bond cleavage during dehydrogenation, facilitated by Co-induced d-band centre downshift. Conversely, Co acts as the primary active site for H₂ dissociation during hydrogenation via Ni-triggered d-band centre upshift. Simultaneously, self-reconstruction of titanium species and oxygen vacancies, coupled with strong metal-support interactions (Ni/Co-TiO₂), accelerate interfacial electron transfer and inhibit metal atom migration. This synergy significantly enhances both reaction kinetics and cycling stability, showing great promise for large-scale hydrogen-storage applications.