Search

Reactivity of single-vacancy defective graphene (DG) and DG-supported Pd n and Ag n ( n = 1, 13) for mercury (Hg 0 ) adsorption has been studied using density functional theory calculation. The results show that Pd n binds defective site of DG much stronger than the Ag n , while metal nanocluster binds DG stronger than single metal atom. Metal clustering affects the adsorption ability of Pd composite while that of Ag is comparatively less. The binding strength of −8.49 eV was found for Pd 13 binding on DG surface, indicating its high stability. Analyses of structure, energy, partial density of states, and d-band center (ɛ d ) revealed that the adsorbed metal atom or cluster enhances the reactivity of DG toward Hg adsorption. In addition, the Hg adsorption ability of M n -DG composite is found to be related to the ɛ d of the deposited M n , in which the closer ɛ d of M n to the Fermi level correspond to the higher adsorption strength of Hg on M n -DG composite. The order of Hg adsorption strength on M n -DG composite are as follows: Pd 13 (−1.68 eV) >> Ag 13 (−0.67 eV) ∼ Ag 1 (−0.69 eV) > Pd 1 (−0.62 eV). Pd 13 -DG composite is therefore more efficient sorbent for Hg 0 removal in terms of high stability and high adsorption reactivity compared to the Ag 13 . Further design of highly efficient carbon based sorbents should be focused on tailoring the ɛ d of deposited metals. [ABSTRACT FROM AUTHOR]

Tetramer clusters of platinum (Pt), palladium (Pd), gold (Au) and silver (Ag) deposited on pristine and defective graphenes were studied as potential adsorptive materials for m-xylene using density functional theory (DFT) calculations including van der Waals contributions to the Hamiltonian. Structural, energetic and electronic (i.e. d-band center, partial density of state and explicit charge) properties have been investigated for understanding the m-xylene adsorption process. The m-xylene adsorption capability of these materials has been compared. The calculation results revealed that Pt4- and Pd4–DG adsorb m-xylene via a chemisorption process, while Au4- and Ag4–DG adsorb m-xylene via physisorption. These insights are valuable for applying and developing carbon-based materials for volatile organic compound (VOC) removal applications, since physisorption-driven materials are suitable as sorbents while their chemisorption counterparts are suitable as catalysts in an oxidation reaction. Those properties in turn can be tuned by modulating metal adsorption on the carbon-based materials. [ABSTRACT FROM AUTHOR]