CO₂-derived carbon support with controlled morphology for synergistic kinetic enhancement of MgH₂ hydrogen storage

Magnesium hydride (MgH₂) offers high theoretical hydrogen storage capacity but suffers from low kinetics and high desorption temperatures. In this study, CO₂-derived carbon materials with controlled morphologies were synthesized via a template-directed magnesiothermic reduction and used as a support of MgH₂. Compared between sheet-like and rod-like carbon structures, the sheet-like carbon, with larger pore size and volume, improved interfacial contact and H₂ diffusion. Incorporating Ni into Mg/C sheet produced a synergistic catalytic–structural effect, reducing the desorption onset to ∼235 °C (vs. ∼285 °C for pure Mg) and lowering activation energy from 155 to 143 kJ mol−1. Capacity remained stable at ∼5.6–5.7 wt%, with a gradual decline to ∼5.0 wt% after 10 cycles. This work highlights an effective CO₂ utilization for application in hydrogen storage for improving MgH₂ dehydrogenation kinetics while maintaining high storage capacity.