Integration of hydrogen production, storage, and optical properties of X2CaZnH6 (X = Li, Na, K): A DFT study

The current study utilizes the ab-initio calculations to delve into the structural, electronic, mechanical, hydrogen storage, photocatalytic water splitting, and optical properties of hydride perovskites X 2 CaZnH 6 (X = Li, Na, K). The negative formation enthalpy Δ H f (−2.81, −2.85, −2.76 eV/atom) and Goldschmidt tolerance factors ( t = 0.84, 0.91, 0.97) for X 2 CaZnH 6 (X = Li, Na, K) implies that these system are chemically stable with remarkable cubic phase. The thermodynamical stabilities are confirmed via well-known molecular dynamic simulation (AMID) based on Newtons law of energy conservation. These hydrides X 2 CaZnH 6 (X = Li, Na, K) reveals an indirect bandgaps of 1.93, 2.0, and 2.51 eV which are crucial for photocatalytic activities for water splitting. To performs these photocatalytic activities the values of band-edge potentials E V B (1.57, 1.55, 1.64 eV) and E C B (−1.35, −0.44, −0.85 eV) are calculated for X 2 CaZnH 6 (X = Li, Na, K) which highlights that these material suitable for water-splitting as X 2 CaZnH 6 fulfill the upper H ∗ /H 2 and lower limit O 2 /H 2 O of V vs. NHE (pH=0). Furthermore, the gravimetric ratio (C w t % ) of these X 2 CaZnH 6 (X = Li, Na, K) are also calculated as 4.75, 4.52, and 4.18 wt%, respectively. The storage capacity (C w t % ) values closely aligns with (US-DOE) target. In order, to check the practical feasibility of dehydrogenation the desorption temperature T d e s is computed as 477.17, 499.38, and 446.50 K for these X 2 CaZnH 6 (X = Li, Na, K). Additionally, a diverse nature of the dielectric constant ϵ ( ω ), suggests that these are potential materials for clean and renewable energy applications.