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.
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