Flower-like Ni/C scaffold enables efficient Mg utilization with in situ hydrogen-pump catalysis for durable hydrogen storage

Solution-reduced nano-Mg is uniformly dispersed in flower-like Ni/C(D). • Mg 2 Ni/Mg 2 NiH 4 pump and carbon confinement synergistically enhance kinetics. • 100% capacity retention over 90 cycles after activation. A rationally designed Mg-Ni/C(D) composite was synthesized by calcining a hydrothermally prepared Ni-MOF(BDC) precursor (from Ni 2 + and terephthalic acid, H 2 BDC) into flower-like porous Ni/C(D), followed by Mg loading via lithium-naphthalenide reduction. Spherical Ni/C(T) was prepared similarly using trimesic acid (H 3 BTC). Compared with Ni/C(T), Ni/C(D) possesses an effective hierarchical porous structure, enabling a higher effective reversible hydrogen storage capacity (based on the total composite mass) at a comparable dehydrogenation onset temperature. During hydrogen sorption, in situ-formed Mg 2 Ni acts as a reversible Mg 2 NiH 4 /Mg 2 Ni hydrogen pump, lowering the kinetic barrier and providing nucleation sites for the Mg/MgH 2 transformation, while the carbon matrix confines nanoparticles to prevent agglomeration. Notably, after 10 activation cycles, it retains nearly 100% capacity over the next 90 cycles. This synergy between catalytic pumping and nanoconfinement makes Mg-Ni/C(D) promising for solid-state hydrogen storage. Download: Download high-res image (156KB) Download: Download full-size image Through in situ lithium-naphthalenide reduction, nano-Mg is uniformly embedded in the flower-like Ni/C(D) scaffold. The Mg 2 Ni/Mg 2 NiH 4 hydrogen pump, coupled with carbon nanoconfinement, effectively lowers the kinetic barriers via interfacial electron transfer and hydrogen diffusion, yielding a low onset temperature of 223.38 °C and 100% capacity retention over 90 cycles after activation. This work demonstrates a rational strategy for designing high-performance Mg-based hydrogen storage materials.