Hydrogen adsorption on Ce-ethylene complex using quantum chemical methods

Abstract

Hydrogen storage capacity of Ce-ethylene complex is studied at MP2/SDD level. We have suggested suitable temperature and pressure range over which H2 adsorption on this complex is energetically favorable. The kinetic stability of H2 adsorbed complexes is verified by means of a gap between Highest Occupied Molecular Orbital (HOMO) and Lowest Unoccupied Molecular Orbital (LUMO). Six H2 molecules can be adsorbed on Ce-ethylene complex thereby showing the H2 uptake capacity of 6.71 wt % and satisfying the target set by US Department of Energy for vehicular application. Adsorption of all the six H2 is in molecular form so we expect faster adsorption and desorption kinetics for this complex. Temperature dependent study of H2 adsorption energy with Gibbs free energy correction has shown that H2 adsorption on Ce-ethylene complex is energetically favorable below 190 K. Interaction of Ce:C2H4 with adsorbed H2 molecules is found to be attractive in nature. The vibrational frequencies for H2 and D2 adsorbed complexes viz. Ce:C2H4(6H2) and Ce:C2H4(6D2) have been used to calculate the Equilibrium Isotope Effect (EIE) which is found to be 0.67.