Novel Complex Hydrides ALi 3 H 9 (A = Zr, Nb, Ru, or Rh) for Solid‐Sate Hydrogen Storage: A First‐Principles Investigations

Hydrogen is a clean and promising future energy source. In this work, we study a new class of lithium–based complex hydrides, ALi 3 H 9 (A = Zr, Nb, Ru, and Rh), to explore their hydrogen storage potential through density functional theory (DFT) calculations. The stability of ALi 3 H 9 (A = Zr, Nb, Ru, and Rh) is confirmed by its negative formation energy. Ab initio molecular dynamics (AIMD) simulations up to 300 K demonstrate that ALi 3 H 9 (A = Zr, Nb, Ru, and Rh) remains thermally stable. ALi 3 H 9 (A = Zr, Nb, Ru, and Rh) hydrides exhibit high gravimetric hydrogen capacities of 7.49, 7.39, 6.93, and 6.83 wt%, respectively. ALi 3 H 9 (A = Zr, Nb, Ru, and Rh) hydrides show high volumetric capacities ranging from 138.6 to 169.4 gH 2 L −1 , substantially exceeding that of liquid hydrogen (~71 gH 2 L −1 ), highlighting their strong potential for compact solid‐state hydrogen storage applications. The corresponding desorption temperatures are 268.7 K (Zr), 201.13 K (Nb), 414.9 K (Ru), and 396.3 K (Rh), indicating that Nb‐ and Zr‐based compounds enable hydrogen release at comparatively lower temperatures. Electronic structure calculations performed using the hybrid HSE06 functional reveal that ZrLi 3 H 9 , NbLi 3 H 9 , and RhLi 3 H 9 exhibit metallic behavior due to band crossings at the Fermi level, while RuLi 3 H 9 shows semiconducting nature with a bandgap of 1.627 eV. The density of states (DOS) shows dominant transition‐metal d ‐states near the Fermi level with strong hybridization and symmetric spin channels, confirming robust bonding and nonmagnetic behavior. Mechanical analysis confirms that all ALi 3 H 9 (A = Zr, Nb, Ru, and Rh) hydrides satisfy the Born stability criteria, indicating structural stability, with Ru‐ and Rh‐based compounds showing higher stiffness, while Zr‐ and Nb‐based systems exhibit ductile behavior.