Theoretical investigations on C₂H₄Nb complex as a potential hydrogen storage system, using moller–plesset (MP2) and density functional theory

Abstract

Calculations based on second-order Moller-Plesset and density functional theory (DFT) methods using different exchange and correlation functionals are performed on C 2 H 4 Nb organometallic complex for its hydrogen storage capacity. We found that this complex can store up to a maximum of 14 H 2 molecules using Becke-3 Lee-Yang-Parr (B3LYP)/LanL2DZ method, with a gravimetric H 2 uptake capacity of 18.92 wt% and average binding energy of 0.52 eV/H 2 . The evaluation of the temperature dependence of the Gibbs free energy change (DG) of H 2 adsorption process indicates that the adsorption of H 2 molecules is energetically favorable below 250 K using B3LYP (LanL2DZ) and PBEPBE (LanL2MB, LanL2DZ) level of theories. On the basis of the DFT descriptors, calculated at B3LYP (LanL2DZ) and B3PW91 (LanL2MB) level of theory, we found that the stability of the complex increases with increase in the number of H 2 molecules adsorbed by the complex.

Hydrogen storage: Materials, methods and perspectives

“…The conceptual DFT reactivity descriptors like electronegativity (χ, eV), hardness (η, eV) and electrophillicity (ω, eV) have been used to predict the stability of the complex. Increase in hardness and decrease in both electronegativity and electrophilicity upon the addition of H 2 indicates the stability and rigidity of the complex [113,127,136] (Fig. 7).…”

“…7). The temperature dependence of the Gibbs free energy change (ΔG) has been used to obtain an optimum temperature range required for adsorption of H 2 molecules on various complexes [120,127] (Fig. 8).…”

“…6). The complexes like Ti-polyacetylene complex [118], Scandium and vanadium based ethylene and propane complexes [119][120][121], alkane complexes [122][123][124], Sc atoms and Ti decorated on the C 60 and C 48 B 12 [125,126], niobium based ethene complex [127], TM-doped organosilica complexes [128], metal-decorated bucky balls [129,130] and multidecker Organometallic complexes are some of the well known hydrogen storing complexes. These complexes not only possess high binding energy but also have fast hydrogen adsorption and desorption cycles.…”

“…8). The energy scan carried by variation of single point energies as a function of radial distance of the H 2 molecule from the centre of the H 2 adsorbing system to the outside surface has been used to locate the position where hydrogen molecules are actually getting adsorbed on the chemical system [95,127] (Fig. 9).…”

A new solid material for hydrogen storage

“…The development and utilization of new clean energy sources is very important for the future of modern industrialized societies. It is widely recognized that hydrogen is a promising candidate to carry energy obtained renewably as it burns cleanly, it is the most abundant element in the universe and it is the lightest fuel with the highest energy per unit mass [3,4]. However, issues surrounding hydrogen storage remain unresolved.…”