Enhancing the cycling stability of MgH2 using nitrogen modified titanate

Abstract

By introducing nitrogen anions, we obtained a N-doped K₂Ti₆O₁₃ (N-KTiO) catalyst with a considerably reduced band gap. The experimental results showed that N-KTiO could improve the de/re-hydrogenation kinetics and long-term cycling stability of the Mg/MgH₂ system. In particular, the peak temperature of MgH₂ with a 5 wt% N-KTiO catalyst was ca. 45 °C and 80 °C lower than those of TiO₂ catalysed and pure ones, respectively. After full dehydrogenation, 4.6 wt% H₂ was absorbed in 1 hour, even under room temperature. Moreover, after cycling for two hundred times at 300 °C, the H₂ capacity remained at 6.8 wt% with a retention as high as 94.4%, which is significantly better than those of the reported MgH₂-TiO₂ composites. Further investigation reveals that band structure changes of the catalyst may affect the catalytic effects, and the reversible changes in the valence state of the titanium species in catalysts are intrinsically associated with the enhanced kinetic properties and stability. This research may offer novel insights into developing effective catalysts for light metal hydrogen storage materials.