Boron substitution effect on adsorption of H2 molecules on organometallic complexes

Abstract

Abstract Hydrogen adsorption properties of Be/Sc doped pentalene complexes are investigated using second ordered Moller-Plesset method (MP2). In order to study the boron substitution effect, pentalene is further modified by substituting two and four boron atoms for carbon atoms at different positions and named as TBP1 and TBP2 for two boron atom substituted structures and FBP1 and FBP2 for four boron atom substituted structures. Two H2 molecules get adsorbed on each Be doped complex and having 3.25, 3.31, 3.31, 3.38 and 3.38\xa0wt% H2 uptake capacity for C8H6Be2, TBP1Be2, TBP2Be2, FBP1Be2 and FBP2Be2 complexes respectively. All Sc doped pentalene and boron substituted pentalene complexes can interact with nine H2 molecules except TBP2Sc2 complex. The TBP2Sc2 complex can adsorb eight H2 molecules. The H2 uptake capacity is found to be 8.63, 8.73, 7.84, 8.83 and 8.83\xa0wt% for C8H6Sc2, TBP1Sc2, TBP2Sc2, FBP1Sc2 and FBP2Sc2 complexes respectively. Gibbs free energy corrected adsorption energy plots show that the H2 adsorption on all Be doped complexes is possible at all temperatures and pressures considered here. The TBP1Sc2 complex seems to be more promising hydrogen storage material among all Sc doped complexes over a wide range of temperature and pressure. The H2 desorption temperatures obtained for the Be doped complexes are higher than the Sc doped complexes. Stability of the complexes is predicted with the help of the gap between the highest occupied molecular orbitals and the lowest unoccupied molecular orbitals.