FCC/α-Fe biphasic nano-sites synergize with CNTs to enhance reversible hydrogen storage of MgH2

Abstract

In this study, we successfully synthesized a ternary VTiFe solid solution alloy catalyst via mechanical alloying and strategically integrated it with carbon nanotubes (CNTs) through a two-step ball milling process, aiming to revolutionize the hydrogen storage performance of MgH₂. Comprehensive characterization revealed that the VTiFe alloy undergoes a remarkable microstructural evolution during ball milling, leading to the in situ formation of nanoscale FCC and α-Fe biphasic catalytic sites, which synergistically promote the reversible hydrogen storage process in Mg/MgH₂. The introduction of CNTs plays a vital role in regulating the surface morphology and aggregation behavior of the composite, facilitating long-range hydrogen diffusion within the material. Benefiting from the synergistic catalytic effects of the VTiFe alloy and CNTs, the MgH₂-6 wt% VTiFe-3 wt% CNTs composite achieves impressive hydrogen desorption capacities of 5.0 wt% and 5.5 wt% at 200 °C and 225 °C, respectively, while maintaining exceptional reversibility over 31 cycles. This work provides new insights and experimental evidence for the rational design and performance optimization of Mg-based hydrogen storage materials from the perspective of catalyst microstructure engineering and surface modification.