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

The Mg(NH2)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, Li3VO4 @LiVO2 was synthesized by a hydrothermal method, and was then introduced into Mg(NH2)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% Li3VO4 @LiVO2 addition. As for the hydrogen absorption and desorption kinetics, the average hydrogen absorption rate of 10 wt% Li3VO4 @LiVO2 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% Li3VO4 @LiVO2 modified sample within 30 min at 180 ℃ increased by 42% compared with that of the pristine sample. The Ea of hydrogen desorption decreased from 117.86 kJ/mol to 99.43 kJ/mol, which also indicates that Li3VO4 @LiVO2 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% Li3VO4 @LiVO2 modified Li-Mg-N-H increased by 18.4% and 13.8% compared with that of the pristine sample. The catalytic mechanism of Li3VO4 @LiVO2was discussed based on XRD, XPS and FTIR analysis results. •Li3VO4 @LiVO2 was synthesized to enhance the hydrogen storage properties of Li-Mg-N-H.•The average hydrogen absorption rate of 10 wt% Li3VO4 @LiVO2 modified Li-Mg-N-H within 20 min increased by 95.2%.•The hydrogen desorption capacity increased by 18.4% after addition of 10 wt% Li3VO4 @LiVO2.