ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Exploring the world of metal nitrides as hydrogen storage materials: a DFT study

Saba Niaz and Altaf Hussain Pandith

Department of Chemistry, University of Kashmir, Srinagar, India

E-mail: sobnewtonn@gmail.com

Received: 18 December 2020  Accepted: 8 May 2021

Abstract:

Efficient storage of hydrogen is one serious impediment in using H₂ as an alternate clean fuel, at a larger scale, in the context of alarming levels of global warming and fast depleting fossil fuel resources. Metal nitrides such as Li₂N₄, Na₂N₄ and K₂N₄ using density functional theory with PBE1PBE and B3LYP functional and 6-31G (d,p), 6–31 ++ G (d,p) and 6–311 ++ G (d,p) as basis sets. This has revealed that doping of alkali metal atoms on the nitride systems increases their hydrogen adsorption ability, due to the electron transfer that occurs from the metal atom to the nitrogen surface. The charged surface created around the metal atom is found to enhance the hydrogen adsorption capacity of the complex from 9 to 16.79wt% with an average binding energy from 0.06 to 0.30 eV/H₂. Various conceptual reactivity descriptors, bond parameters, Gibbs free energy change (ΔG) and energy gap values support the idea that the stability of the complex increases on hydrogen uptake.

Graphic abstract

Efficient storage of hydrogen is one serious impediment in using H₂ as an alternate clean fuel, at large scale, in the context of alarming levels of global warming and fast depleting fossil fuel resources. Herein, we report theoretical studies on some novel metal nitrides in order to probe its hydrogen storage potential. M₂N₄ systems (where M = Li, Na, K) can store hydrogen around 5–12 H₂ molecules with an gravimetric density of 9–16.79 wt% and an average binding energy in the range of 0.06–0.30 eV/H₂. It was found that among all the three metal nitrides Li₂N₄ is found to possess highest binding energy and energy gap, whereas K₂N₄ adsorbs maximum number of H₂ molecules.

Keywords: Metal nitrides; Density functional theory; Physisorption; Hydrogen storage

Full paper is available at www.springerlink.com.

DOI: 10.1007/s11696-021-01695-8

Chemical Papers 75 (9) 4831–4848 (2021)