Coverage dependent H2 desorption energy: a quantitative explanation based on encounter desorption mechanism

Abstract

ABSTRACT Recent experiments show that the desorption energy of H2 on a diamond-like carbon surface depends on the H2 coverage of the surface. We aim to quantitatively explain the coverage dependent H2 desorption energy measured by the experiments. We derive a math formula to calculate an effective H2 desorption energy based on the encounter desorption mechanism. The effective H2 desorption energy depends on two key parameters, the desorption energy of H2 on H2 substrate and the ratio of H2 diffusion barrier to its desorption energy. The calculated effective H2 desorption energy qualitatively agrees with the coverage dependent H2 desorption energy measured by the experiments if the values of these two parameters in literature are used in the calculations. We argue that the difference between the effective H2 desorption energy and the experimental results is due to the lack of knowledge about these two parameters. So, we recalculate these two parameters based on experimental data. Good agreement between theoretical and experimental results can be achieved if these two updated parameters are used in the calculations.