Theoretical study of efficiency of metal cations (Mg⁺, Ca⁺, and Ag⁺) for effective hydrogen storage

Abstract

The interaction between the metal cations and H₂ molecule has been investigated using dispersion-corrected and -uncorrected hybrid density functional and CCSD(T) methods in conjunction with the correlation consistent triple-ζ quality basis sets for the storage of the H₂ molecule. The molecular properties, potential energy surfaces, stability, binding energy and well-depth have been computed for the metal cation–dihydrogen (M⁺–H₂, M = Mg, Ca, and Ag) complexes in the gas phase. The results obtained by the dispersion-corrected hybrid density functional B2PLYP-D method agree very well with the earlier experimental and theoretical results wherever available. Different components of the interaction energy have been estimated by the symmetry adapted perturbation theory (SAPT) to get physical insight into the interaction energy. Among the three complexes, only Ag⁺–H₂ is the most stable complex and it accumulates more H₂ molecules as the interaction between the metal cation Ag⁺ and the H₂ molecule is the greatest.

Keywords:

• hydrogen storage
• complexes
• metal cation–dihydrogen
• dispersion correction
• hybrid density functionals
• equilibrium bond distance
• dissociation energy
• depth of the potential well
• potential energy surface (PES)
• binding energy
• CCSD(T)
• SAPT

Acknowledgements

A.K. Das is grateful to the Council of Scientific and Industrial Research (CSIR), Government of India, for a research grant under scheme number: 03(1168)/10/EMR-II. We thank Prof. Mike Schmidt, Iowa State University, USA, for his assistance. Kaushik Sen and Chandan Sahu are grateful to the Council of Scientific and Industrial Research (CSIR), Government of India, for providing research fellowships. We thank Professor Prasanta Kumar Mukherjee, Ramkrishna Mission, Vivekananda University, Belur Math, for his valuable suggestions. We also thank Dr Bhaskar Mandol, University of Strathclyde, Glasgow, UK, for his suggestions.