First-principles study of the hydrogen storage properties of hydride perovskites XCuH3 (X = K, Rb) for hydrogen storage applications.

In this paper, the structure, hydrogen storage capacity, mechanical, electronic, optical and thermodynamic properties of hydride perovskites KCuH 3 and RbCuH 3 are systematically studied via using density functional theory (DFT) for the first time. The formation energies and mechanical properties of XCuH 3 (X = K, Rb) hydrides indicate that KCuH 3 and RbCuH 3 are both thermodynamically and mechanically stable. The values of Pugh's index and Cauchy pressure for KCuH 3 and RbCuH 3 indicate that they are both brittle materials. In addition, their bonding types are mainly ionic bonds. Electronic properties show that these compounds are metallic. The hydrogen storage capacities of KCuH 3 and RbCuH 3 are calculated to be 2.78 wt% and 1.95 wt%, respectively. The optical properties indicate that KCuH 3 and RbCuH 3 both have high dielectric functions in the visible range and their absorption coefficient peak in the ultraviolet range. Additionally, the thermodynamic properties, including free energy, Debye temperature, melting temperature, entropy and heat capacity are calculated. The analyzed physical properties of KCuH 3 and RbCuH 3 perovskite hydrides suggest that they have great prospect in hydrogen applications. All the above parameters are calculated for the first time, which could contribute significantly to the development of sustainable energy technologies. • XCuH 3 (X = K, Rb) perovskite have been investigated using the first principles. • XCuH 3 perovskite exhibit thermodynamic and mechanical stability. • The gravimetric hydrogen storage capacity is found to be 2.78 wt% for KCuH 3. [ABSTRACT FROM AUTHOR]