Double Hydride Perovskites as Promising Materials for Clean Energy Storage: A First-Principles (DFT) Study

Hydride materials are widely recognized for their significant potential in hydrogen storage, a crucial component of renewable energy systems. This study employs density functional theory (DFT) to investigate the structural, electronic, optical, and hydrogen storage properties of novel double hydride perovskites, such as Na₂LiXH₆ (X = Al, Ga). The materials crystallize in a cubic structure (Fm-3m), the optimized structural parameters are obtained through energy–volume (E-V) curve analysis, and the negative formation enthalpies confirm the thermodynamic stability of these compounds.

Electronic structure calculations reveal that Na₂LiAlH₆ and Na₂LiGaH₆ are semiconductors with indirect band gaps of approximately 2.60 eV and 0.66 eV, respectively. These values suggest potential applications in semiconductor-based devices. Optical analyses including the dielectric function, absorption coefficient, refractive index, extinction coefficient, and optical conductivity indicate strong absorption in the ultraviolet region, highlighting the materials’ potential for optoelectronic applications such as UV detectors and solar energy harvesting.

Moreover, the predicted gravimetric hydrogen storage capacities C_wt(%) are favorable, and the hydrogen desorption temperatures T_d are calculated to be 373.9 K for Na₂LiAlH₆ and 337.1 K for Na₂LiGaH₆. These properties indicate practical viability for energy storage applications. Together, these characteristics position Na₂LiXH₆ hydrides as promising multifunctional materials for next-generation clean energy technologies, combining efficient hydrogen storage with valuable electronic and optical features. This work contributes to the ongoing search for sustainable materials supporting the transition to renewable energy.