DFT study of Hg adsorption on M-substituted Pd(111) and PdM/γ-Al2O3(110) (M = Au, Ag, Cu) surfaces

The adsorption of Hg-n (n = 1-3) on the Au-, Ag-, Cu-substituted Pd(1 1 1) surfaces as well as the PdM/gamma-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces has been investigated using spin-polarized density functional theory calculations. It is found that M-substituted Pd(1 1 1) surfaces show as good Hg adsorption capacity as the perfect Pd(1 1 1) at low Hg coverage, while the Hg adsorption capacity is only slightly weakened at high Hg coverage. On the basis of stepwise adsorption energies analysis, it is concluded that M-substituted Pd(1 1 1) surfaces can contribute to the binding of Hg atom on the surfaces at high Hg coverage. The electronic properties of the second metal atoms are the main factor contributes to the Hg adsorption capacity. Gas phase Pd-2 shows better Hg adsorption capacity than Pd-2/gamma-Al2O3, while PdM/gamma-Al2O3 can adsorb Hg more efficiently than bare PdM clusters. It suggests that the gamma-Al2O3 support can enhance the activity of PdM for Hg adsorption and reduces the activity of Pd-2. It is also found that Pd is the main active composition responsible for the interaction of mercury with the surface for PdM/gamma-Al2O3 sorbent. Taking Hg adsorption capacity and economic costs into account, Cu addition is a comparatively good candidate for Hg capture. (C) 2015 Elsevier B.V. All rights reserved.