DFT Insights into the C ₂ N Monolayers and Transition Metal Decorating C ₂ N for Hg ⁰ Removal

Abstract 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 C 2 N for Hg 0 removal applications. These findings indicate that the adsorption energy of Hg 0 on the C 2 N surface is low (−0.16 eV), however, the Mn, Fe, and Co atoms decoration on the C 2 N monolayer can enhance the adsorption energy. Specifically, the Fe@C 2 N exhibits the highest Hg 0 adsorption energy. The work function of the C 2 N monolayer increases after the adsorption of the Hg 0 and TM, due to the surface charge density redistribution. The impact of the Hg 0 coverage and the number of the Fe atoms on the adsorption energy is also studied. The optimal number of the Hg 0 atoms adsorbed on the Fe@C 2 N is two, while the Fe 3 cluster decorated on the C 2 N monolayer can accommodate three Hg atoms. The presence of the CO molecule cannot affect Hg 0 adsorption on the Fe@C 2 N, but the presence of the H 2 O molecule causes the surface to bend. This study can provide insight into the application of the C 2 N monolayer for Hg 0 removal and provides a deep understanding of the adsorption process.