A reversible switch for hydrogen adsorption and desorption: electric fields

Abstract

Implementation of hydrogen storage systems requires moderate bonding strength. However, this goal has remained a challenge, either due to the weak physisorption or extremely strong chemisorption. Here, we report on a new phenomenon, namely that H₂ binding can be externally enhanced (or weakened) via superimposition of a positive (or negative) electric field. We demonstrate this concept using an 8-Li-doped carbon nanotube. The calculated adsorption energy E_ad = −0.58 eV/H₂ under F = +0.010 au is 93.33% lower than that under 0.000 au (F indicates the field intensity). This is because the positive field produces an extra dipole moment. In contrast, E_ad increases from −0.30 to −0.20 eV/H₂ when F = −0.010 au. In view of the fact that storage systems are insensitive to small unexpected field fluctuations, the application of the electric field as a reversible switch makes practical sense.