Document Type : Research Article
Authors
1
Department of Chemistry, Faculty of Science, University of Arak, Arak, Iran
2
Department of Physics, the Institute of Science, Dr. Homi Bhabha State University, Mumbai 400032, India
10.22091/jaem.2025.13007.1025
Abstract
This study evaluates the hydrogen storage capabilities of NH2M+ compounds (where M = Be, Li, Sc, Ti, V, Ca) using density functional theory (DFT) and second-order Møller-Plesset (MP2) methods with the 6-31++G(d,p) basis set. Our findings demonstrate that NH2Be+, NH2Li+, NH2Sc+, NH2Ti+, NH2V+, and NH2Ca+ complexes can bind up to three, five, six, six, five, and eight H2 molecules, respectively, achieving gravimetric hydrogen uptake capacities of 19.3%, 30.3%, 16.4%, 15.8%, 12.9%, and 22.2%. These capacities significantly surpass the U.S. Department of Energy's 2025 target of 5.5 wt%. Gibbs free energy-corrected adsorption energy analyses indicate that H2 adsorption on NH2Be+, NH2Ti+, and NH2V+ complexes is thermodynamically favorable at room temperature across a broad pressure and temperature range (50–400 K, 50–400 atm). In contrast, adsorption on NH2Li+, NH2Sc+, and NH2Ca+ complexes is viable below 85 K, 135 K, and 75 K, respectively. High desorption temperatures for NH2Be+, NH2Sc+, NH2Ti+, and NH2V+ complexes reflect their robust interactions with H2 molecules compared to other NH2M+ variants. Molecular dynamics simulations using atom-centered density matrix propagation (ADMP) at ambient conditions reveal that some adsorbed H2 molecules dissociate from the complexes. Overall, NH2Ti+ emerges as a particularly promising candidate for efficient hydrogen storage due to its favorable adsorption characteristics and high capacity.
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