Improved hydrogen storage properties of Li-Mg-N-H system by lithium vanadium oxides

The Mg(NH ₂) ₂ -2LiH system is considered as one of the most potential hydrogen storage materials due to its high hydrogen storage capacity (5.6 wt%) and excellent reversible hydrogen adsorption and desorption performance. However, its poor kinetic characteristics of hydrogen absorption and desorption limit its practical application. In this work, Li ₃VO ₄ @LiVO ₂ was synthesized by a hydrothermal method, and was then introduced into Mg(NH ₂) ₂ -2LiH system to enhance the hydrogen absorption and desorption kinetic characteristics. The results show that the hydrogen storage properties were greatly improved with addition of 10 wt% Li ₃VO ₄ @LiVO ₂ addition. As for the hydrogen absorption and desorption kinetics, the average hydrogen absorption rate of 10 wt% Li ₃VO ₄ @LiVO ₂ modified Li-Mg-N-H sample within 20 min at 200 ℃ increased by 95.2% compared with that of the pristine Li-Mg-N-H sample, and the average hydrogen desorption rate of 10 wt% Li ₃VO ₄ @LiVO ₂ modified sample within 30 min at 180 ℃ increased by 42% compared with that of the pristine sample. The E _a of hydrogen desorption decreased from 117.86 kJ/mol to 99.43 kJ/mol, which also indicates that Li ₃VO ₄ @LiVO ₂ catalyst effectively improved the kinetic performance of hydrogen desorption and desorption of Li-Mg-N-H. Moreover, the hydrogen desorption capacity and hydrogen absorption capacity of 10 wt% Li ₃VO ₄ @LiVO ₂ modified Li-Mg-N-H increased by 18.4% and 13.8% compared with that of the pristine sample. The catalytic mechanism of Li ₃VO ₄ @LiVO ₂ was discussed based on XRD, XPS and FTIR analysis results.