Study of hydrogen storage potential, optoelectronic and thermoelectric response of double perovskites hydrides X2CuAlH6 (X = Li, Na) for renewable energy

Double perovskite (DP) hydrides have emerged as potential candidates for efficient hydrogen (H2) storage materials. The current study has elucidated the chemical composition, hydrogen storage, optical, and wasted heat transformation into power. The tolerance factor confirms the structural stability and the negative formation energies confirm their thermodynamic stability. Li2CuAlH6 and Na2CuAlH6 have revealed H2 storage capacities of 5.49 % and 4.25 %, respectively. Moreover, the volumetric storage capacity of 47.67 g.H2/L and 43.12 g.H2/L, respectively. The predicted mechanical constants indicate the mechanical stability of the DP hydrides. The predicted values of mechanical parameters have predicted the ductile nature and anisotropic characteristics. The electronic characteristics suggested that Li2CuAlH6 and Na2CuAlH6 have an energy gap of 0.84 and 0.71 eV. The optical properties, including absorption, reflectivity, and energy loss, have been calculated, which confirm the applicability of Li2CuAlH6 and Na2CuAlH6 for optoelectronics. Finally, the thermoelectric attributes and ZT parameters were computed, and they were found to be 0.74 and 0.44 for Li2CuAlH6 and Na2CuAlH6, respectively. This analysis shows that Li2CuAlH6 has a stronger potential for thermal power generation. Consequently, Li2CuAlH6 and Na2CuAlH6 are compelling candidates for hydrogen storage and energy conversion applications.