Hydrogen retention in lithium and lithium oxide films

Pure lithium (Li) surfaces are difficult to maintain in fusion devices due to rapid oxide formation, therefore, parameterizing and understanding the mechanisms of hydrogen (H, D) retention in lithium oxide (Li₂O) in addition to pure Li is crucial for Li plasma-facing material applications. To compare H retention in Li and Li₂O films, measurements were made as a function of surface temperature (90–520 K) under ultrahigh vacuum (UHV) conditions using temperature programmed desorption (TPD). In both cases, the total retention dropped with surface temperature, from 95% at 90 K to 35% at 520 K Li₂O films retained H in similar amounts as pure Li. Molecular Dynamics (MD) modeling was used to elucidate the mechanisms of H retention, and results were consistent with experiments in terms of both retention fraction and the drop of retention with temperature.