DFT-based investigation of efficient hydrogen storage in novel cubic hydrides and multiple bond analysis

At present, in response to the challenges of energy scarcity and environmental change, clean and renewable hydrogen energy has become a focal topic. Efficient hydrogen storage is one of the key technologies for hydrogen utilization. A series of cubic hydrides is studied by first-principles calculations in this study. Five stable hydrides, including NaCa 3 LiH 8 , NaSc 3 LiH 8 , NaTi 3 LiH 8 , LiCa 3 NaH 8 , and LiSc 3 NaH 8 , have been obtained by screening the formation energy and elastic stability criteria. Their structural stability is further confirmed through the phonon spectra. Among them, NaTi 3 LiH 8 and LiCa 3 NaH 8 are ductile materials with potential for flexible devices. From the analysis of band structures, except for two Ca-based hydrides with narrow direct bandgaps (0.574 eV and 0.833 eV, respectively), the remaining hydrides have a metallic nature, indicating that they and their derivatives have potential application in optoelectronic devices. The bond analysis suggests that the centered alkali metal may play a more significant role in binding hydrogen for efficient storage. The hydrogen storage capacity of five materials in more than 4.4 wt% verifies their great potential for hydrogen storage. Considering the appropriate desorption temperatures for maximum hydrogen release, NaCa 3 LiH 8 (295.9 K) and NaSc 3 LiH 8 (335.3 K) warrant further investigation in the future. • Stable NaDM 3 LiH 8 and LiDM 3 NaH 8 are studied by first principles calculations. • NaCa 3 LiH 8 and LiCa 3 NaH 8 are direct semiconductors with 0.574 eV and 0.833 eV bandgaps. • Multiple bond analysis are used to discuss the hydrogen storage performance. • The NaCa 3 LiH 8 and NaSc 3 LiH 8 have proper desorption temperatures of 295.9 K and 335.3 K. • The hydrogen storage capacities are over 4.4 wt%.