Experimental and first-principles
studies were conducted to understand
the adsorption mechanism of elemental mercury on FeCl3-
and CuCl2-impregnated activated carbons. Activated carbon
was impregnated with either FeCl3 or CuCl2,
and their adsorption of elemental mercury was evaluated using a laboratory-scale
fixed-bed system. The fixed-bed tests were carried out by injecting
only nitrogen gas to investigate the interaction between mercury and
the chemical compound impregnated on the activated carbon. The test
temperature was 140 °C to simulate the temperature in a particulate
matter control device of full-scale facilities, such as coal-fired
power plants and waste incinerators. Based on the results, CuCl2-impregnated activated carbons showed much higher adsorption
efficiencies for elemental mercury than both activated carbons and
FeCl3-impregnated activated carbons. Density functional
theory (DFT) calculations revealed that the mercury adsorbates were
adsorbed more strongly on the CuCl2(110) surface than on
the FeCl3(001) surface. Electronic property analyses revealed
that the CuCl2 surface was more efficient as a mercury
removal adsorbent because more electrons were shared between Hg- and
Cu-influenced Cl bonds than those between Hg- and Fe-influenced Cl
bonds, which resulted in the stronger Hg adsorption of the former.
Mackinawite (FeS) has sulfur-deficient
surfaces and may have played
a role in the prebiotic chemistry of the Earth because of its catalytic
CO2-to-organic conversion ability, suggesting its suitability
for electrochemical carbon dioxide reduction (CO2RR) for
environmentally friendly and sustainable technologies. To exploit
this catalyst, an atomic understanding of the CO2RR mechanism
on sulfur-deficient FeS(001) surfaces is required, which we have explored
using dispersion-corrected density functional theory calculations.
The adsorption energies of CO2 on pristine and S-deficient
FeS(001) surfaces are −0.17 and −1.62 eV, respectively,
indicating that sulfur deficiency favors CO2 activation
and reduction. In addition, Bader charge population, density of states,
and charge density difference analyses confirmed the activation of
CO2 molecules via charge transfer (0.89e) from the Fe atoms to the adsorbates. We also found that the electrochemical
CO2RR over the studied surfaces favors methane in the potential-limiting
*CHO → *CH2O (ΔG
diff = 1.27 eV) and *OHCH2O → *CH2O (ΔG
diff = 0.78 eV) steps for reverse water–gas
shift and formate pathways, respectively. Concerning C2 species, a high surface concentration of the *CO intermediate on
the catalyst was found to be crucial, yielding ethane through a potential-limiting
*CH–CH2 → *CH2–CH2 step (ΔG
diff = 1.00 eV).
Nanocarbon based Frustrated Lewis Pair (FLP) bifunctional catalysts, on account of their un-quenched electron transfer property, are becoming increasingly attractive as catalysts for CO2 re-duction reaction via dissociative chemisorption of...
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