DFT Insights into the C2N Monolayers and Transition Metal Decorating C2N for Hg0 Removal

Mercury is a dangerous heavy metal for the environment and human health. In this study, density functional theory (DFT) is employed to investigate the effect of the transition metals (TM) decoration on the C2N for Hg0 removal applications. These findings indicate that the adsorption energy of Hg0 on the C2N surface is low (−0.16 eV), however, the Mn, Fe, and Co atoms decoration on the C2N monolayer can enhance the adsorption energy. Specifically, the Fe@C2N exhibits the highest Hg0 adsorption energy. The work function of the C2N monolayer increases after the adsorption of the Hg0 and TM, due to the surface charge density redistribution. The impact of the Hg0 coverage and the number of the Fe atoms on the adsorption energy is also studied. The optimal number of the Hg0 atoms adsorbed on the Fe@C2N is two, while the Fe3 cluster decorated on the C2N monolayer can accommodate three Hg atoms. The presence of the CO molecule cannot affect Hg0 adsorption on the Fe@C2N, but the presence of the H2O molecule causes the surface to bend. This study can provide insight into the application of the C2N monolayer for Hg0 removal and provides a deep understanding of the adsorption process.