Advanced computational screening of X2CaH4 (X = Rb and Cs) for hydrogen storage applications

Abstract

Utilizing cutting-edge computational screening methods, this study explores the hydrogen storage capacity of two complex metal hydrides, Cs2CaH4 and Rb2CaH4. We perform a thorough analysis of their structural, electrical, optical, and hydrogen storage properties using density functional theory (DFT). Within the I4/mmm space group, both compounds display stable tetragonal crystal structures, and their thermodynamic stability is confirmed by their formation energies. Notably, compared to Rb2CaH4, Cs2CaH4 is more stable. With band gaps of 2.99 eV for Cs2CaH4 and 3.28 eV for Rb2CaH4, the electronic properties show insulating behavior, which is beneficial for reducing electronic interference during hydrogen absorption and desorption. A comparative research reveals that the potential gravimetric hydrogen storage capacities of Cs2CaH4 (1.28%) and Rb2CaH4 (1.86%) are comparable to, albeit marginally less than, those of materials that are frequently explored, such as lithium borohydride. With their individual absorption and reflectivity peaks, the optical characteristics offer more information about how they interact with electromagnetic radiation, information that may be useful for improving their performance in real-world applications. Our results imply that Cs2CaH4and Rb2CaH4 have considerable potential for use in practical hydrogen storage systems, especially in situations where stability and minimal electronic interference are essential. Subsequent research endeavors may concentrate on enhancing the hydrogen storage capacity of these materials, so rendering their incorporation into existing hydrogen storage methods more feasible.