Single-atom iron on penta-graphene assisted with non-bonding interaction as superior demercurizer: A DFT exploration

Elemental mercury (Hg-0) released from coal-fired power plants causes global concern. Magnetic adsorbents have attracted extensive attention due to their high adsorption performance, but carbon-based sorbents with magnetism for Hg-0 removal are rarely studied. Having excellent adsorption activity, single-atom Fe adsorbents on penta-graphene (PG) substances might be promising magnetic materials for Hg-0 removal. In this study, six different PG-based single-atom Fe adsorbents are designed by nitrogen doping, concluding that FeN3 on singlevacancy defective PG (Fe/SVN123) is an effective Hg-0 adsorbent due to the larger adsorption energy ( 0.87 eV) based on density functional theory (DFT) calculations. The electron density difference (EDD) and density of states (DOS) results demonstrate the existence of chemical bonding between Hg-0 and the adsorbents. Non-covalent interaction (NCI) analysis verifies the important contribution of non-bonding interactions to adsorption strength. The temperature has an inhibitory effect on Hg-0 adsorption. When the temperature reaches similar to 520 K, Hg-0 desorbs from Fe/SVN123, leading to adsorbent regeneration. The potentially detrimental effect of SO2 and NO on Hg-0 adsorption on Fe/SVN123 is deeply discussed by configuration analysis and ab initio molecular dynamics (AIMD) simulation. This work enriches the fundamentals of single-atom catalysts (SACs) and opens up new insight into non-bonding interactions on SACs.