Investigation of energy storage in layered perovskite-like oxides XCa₂Ta₃O₁₀ (X= Li, Na) using promised DFT+U approach

This study employed the DFT + U method to investigate and discuss the structural, mechanical, thermodynamic, optical, electronic, thermoelectric, and hydrogen storage properties of Dion-Jacobson-type XCa₂Ta₃O₁₀ (X = Li, Na) layered perovskite compounds. Mechanical stability is confirmed by elastic constants and Born criteria. A modest Poisson's ratio (∼0.31–0.32) and a B/G ratio above 1.75 indicate ductility associated with ionic bonding, making these materials suitable for hydrogen adsorption and release cycles. Electronic properties reveal indirect band gaps of 1.63 eV for LiCa₂Ta₃O₁₀ and 1.51 eV for NaCa₂Ta₃O₁₀, suggesting they could be effective in visible-light-driven photocatalysis. Optical analysis shows high dielectric constants (ε₁(0) ≈ 5.96 for Li and 5.84 for Na compounds), low reflectivity in the visible spectrum, and significant absorption (∼2.5 × 10⁴ cm⁻¹), indicating excellent light-harvesting abilities. The XCa₂Ta₃H₁₀ (X = Li, Na) hydrides are thermodynamically stable during hydrogenation, as evidenced by negative formation energies of −4.565 eV/atom (Li-based) and −4.508 eV/atom (Na-based), along with cohesive energies of 38.66 Ry/atom and 40.51 Ry/atom. The gravimetric hydrogen storage capacities are 3.56 wt% for LiCa₂Ta₃H₁₀ and 3.41 wt% for NaCa₂Ta₃H₁₀, with volumetric capacities of 7.44 % and 6.69 %, respectively, confirming their potential as solid-state hydrogen storage materials. Furthermore, D-J type XCa₂Ta₃O₁₀ (X = Li, Na) and related hydrides demonstrate promise for photocatalytic water splitting and hydrogen storage applications.