First-Principle Study on Heterofullerenes: Effective and Multifunctional in Hg Removal

Abstract

Mercury control is very important with regard to the clean use of fossil fuels. Although both carbonaceous materials and metals can effectively remove Hg⁰, they still face great challenges. Single-atom loaded materials provide new ways for Hg species removal. Metal-substituted C60 has been predicted to have high chemical reactivity. Accordingly, the adsorption mechanisms of Hg species on 19 types of heterofullerenes (C59M, M = Ti, V, Mn, Fe, Co, Ni, Zn, Zr, Nb, Mo, Tc, Ru, Rh, Pd Cu, Au, W, Ir, and Ag) were studied by using DFT method. Most of the C59M can strongly adsorb Hg⁰, and C59Cu is the best one, with its adsorption energy being −0.67 eV. C59M′ (M′ = Fe, Co, Ni, Cu, Zn, and Mn) with strong interaction with Hg⁰ were chosen for further studying on their adsorption of HgCl and HgCl₂. Both HgCl and HgCl₂ prefer dissociative adsorption. Moreover, Hg⁰ adsorption on C59M′Cl and C59M′Cl₂ were checked. The results showed that Hg⁰ physically adsorbs on both C59M′Cl and C59M′Cl₂. Importantly, oxidative adsorption of Hg⁰ were also calculated on C59M′Cl₂. C59CoCl₂ shows excellent removal ability for Hg⁰ via oxidative adsorption due to the lowest activation barrier (0.89 eV), then C59CuCl₂ has the next-lowest barrier (1.00 eV). This study is of great significance for understanding the adsorption mechanisms and expands the theoretical system of carbon-based materials for Hg species removal.