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

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. Magnesium hydride stores abundant hydrogen but releases and absorbs it too slowly and at high temperatures. A dual-atom Ni–Co catalyst on titanium oxide tunes its electronic structure, speeding hydrogen storage kinetics and improving cycling stability.