Explicit solvation effects on low-index Fe surfaces and small particles as adsorbents of Arsenic species: A DFT study

Abstract

Density functional theory (DFT) calculations were carried out on hydroxylated and solvated (H&S) Fe substrates. Fe (110) and (111) extended surfaces as well as clusters of 32 and 59 atoms, and a nanoparticle of 80 atoms were studied as adsorbent substrates of harmful As species. Arsenious (H3AsO3) and arsenic (H3AsO4) acids are physisorbed on the H&S Fe(110) but chemisorbed on the H&S Fe(111) surface. The open-packed plane of the (111) surface, with free active sites, allows better interaction with the acid molecules. The small hydroxylated cluster, Fe32, has shown the best activity as adsorbent of H3AsO3. Electronic charge transfer occurs not only from Fe atoms that directly interact with the acid molecule, but neighbouring Fe atoms are also oxidized. This work presents clear evidence that these spherical Fe aggregates, formed mainly by (111) faces and with an important percentage of low-coordination sites, are excellent adsorbent substrates of H3AsO3 and should be considered as a reference to search for new supported catalysts.