H2 storage and equilibrium isotope effect for Be, Li, and Ti-doped closoborate complexes

This work reports hydrogen uptake capacity and equilibrium isotope effect (EIE) for the Be, Li, and Ti-doped closoborate (B6H6) complexes using first-principles calculations at MP2/6-311++G** level. The EIE was obtained using vibrational frequencies of H-2 and D-2-adsorbed B6H6M (M = Be, Li, and Ti) complexes at MP2/6-311++G** level. Two, three, and four H-2/D-2 molecules get adsorbed on B6H6Be, B6H6Li, and B6H6Ti respectively. The gravimetric H-2(D-2) uptake capacity of B6H6Be, B6H6Li, and B6H6Ti complexes is found to be 4.8(9.5), 7.2(13.44), and 6.3(11.94) wt% respectively. H-2 adsorption is thermodynamically favorable on B6H6Ti at ambient conditions, whereas it is unfavorable on B6H6Li and B6H6Be complexes. Contribution from each vibrational mode in calculating the equilibrium isotope effect is obtained. The EIE calculated using vibrational frequencies for the B6H6Be(1H(2)/1D(2)), B6H6Be(2H(2)/2D(2)), B6H6Li(1H(2)/1D(2)), B6H6Li(2H(2)/2D(2)), B6H6Li(3H(2)/3D(2)), B6H6Ti(2H(2)/2D(2)), B6H6Ti(3H(2)/3D(2)), and B6H6Ti(4H(2)/4D(2)) complexes is found to be 0.56, 0.26, 0.76, 0.93, 1.05, 0.25, 0.05, and 0.75 respectively. In case of B6H6Ti(1H(2)) complex, the hydrogen is adsorbed in atomic form. It is found that D-2 binds better than the H-2 to the B6H6M (M = Be, Li, and Ti) complex.

Automated summary

This study investigates the hydrogen uptake capacity and equilibrium isotope effect for Be, Li, and Ti-doped closoborate (B6H6) complexes using first-principles calculations. Results show the adsorption of H-2/D-2 molecules on different complexes, and the calculated equilibrium isotope effect values for each complex. The study also reveals that D-2 binds better than H-2 to the B6H6M (M = Be, Li, and Ti) complexes.