  First-principles density functional theory (DFT) is employed to investigate
the interactions of CO2 gas molecules with pristine and lithium-functionalized
germanene. It is discovered that although a single CO2 molecule is weakly
physisorbed on pristine germanene, a significant improvement on its adsorption
energy is found by utilizing Li-functionalized germanene as the adsorbent.
However, the moderate adsorption energy at high CO2 coverage predicts an easy
release step. More excitingly, the structure of Li-functionalized germanene can
be fully recovered after removal of CO2 gas molecules. Our results suggest that
Li-functionalized germanene show promise for CO2 sensing and capture with a
storage capacity of 12.57 mol/kg.
