First-principles study on the atomistic corrosion processes of iron

Abstract

The corrosion of iron presents an important scientific problem and a serious economic issue. It is also one of the most important subjects in materials science because it is basically an electrochemical process and closely related to other topics such as the electrocatalysis of the oxygen reduction reaction. So far, many studies have been conducted to address the corrosion of iron, a very complicated process that occurs when iron is exposed to oxygen and water. An important question is, at which site of the iron surface the corrosion starts and how it results in the final stage of the corrosion. In the present study, as an example of superficial defects, Fe dimers sticking out of Fe(100) surfaces are considered in order to understand the iron corrosion process from first-principles using density functional theory. We found that the Fe dimers spontaneously react with O and HO to form Fe(OH) + 4OH. Here, it is interesting to note that the Fe dimer plays the role of a water splitting catalyst, because the space above it is always vacant and can accept oxygen molecules many times for reacting with the surrounding water molecules. Then, if the Fe(OH) molecules are detached from the surface, they react with O to form FeO(OH) without an activation barrier, and, in turn, the FeO(OH) and HO molecules react to form Fe(OH) complexes with an activation energy of 0.653 eV. If these complexes further dissociate into Fe(OH) molecules, they react with each other to form FeO·2HO with an activation energy of 0.377 eV. This work may provide useful information on possible iron corrosion processes by water in the air.

Evolution of waste iron rust into α-Fe2O3/CNF and α-Fe2O3/PANI composites as an efficient positive electrode for sustainable hybrid supercapacitor

“…The products of reactions at cathode and anode are Fe +2 and OHions respectively, migrates toward each other and meet in between to form molecular, hydrous Fe(OH)2, FeOOH as initial products of corrosion. These molecular particles grow further via combinations of Fe +2 and OHions to get clusters, where nanosized particles are loosely held together via weak Vander-Waals and Hydrogen bondings [37,38]. The corrosion product is porous, so that corrosion continues further till access of environmental water and oxygen is present that follows exponential decay.…”

“…However, to the best of our knowledge, there are no reports on the use of rust derived nano α-Fe2O3 for application as hybrid supercapacitor. The rusting process called corrosion is a weathering phenomenon capable of giving aggregates of nano scaled iron oxide, a rust product [37].…”

Oxyhydroxide of metallic nanowires in a molecular H2O and H2O2 environment and their effects on mechanical properties

“…1,4,5,[7][8][9] Generally, in aqueous working conditions, metallic Fe materials commonly produce various crystalline phases of Fe oxide and oxyhydroxide such as green rust (Fe(OH) 2 ), goethite (a-FeOOH), etc. 3,6,[10][11][12][13] Overall, progressive oxidation of metallic Fe materials is usually associated with corrosion, and the corresponding detrimental effects are prevalent in many practical applications of the materials. [1][2][3]6,10 The environmental conditions dictate the strength, lifetime, and failure of reactive metallic materials.…”

“…3,6,[10][11][12][13] Overall, progressive oxidation of metallic Fe materials is usually associated with corrosion, and the corresponding detrimental effects are prevalent in many practical applications of the materials. [1][2][3]6,10 The environmental conditions dictate the strength, lifetime, and failure of reactive metallic materials. 3,14,15 In particular, the resulting oxide shell layer drastically alters the physical and chemical properties of the exposed surface layer, and as a result, eventually, the strength of Fe NWs may be weakened substantially compared to the corresponding un-oxidized counterparts.…”

“…3,14,15 In particular, the resulting oxide shell layer drastically alters the physical and chemical properties of the exposed surface layer, and as a result, eventually, the strength of Fe NWs may be weakened substantially compared to the corresponding un-oxidized counterparts. 2,3,10,16,17 However, the presence of undesirable oxide shell layer (or desirable oxide-coating) on the free Fe NW surfaces is associated with surface/interface finite-size effects which help distinctly to achieve potentially additional interesting and unique chemical, 3 physical, 8 optical, 18 mechanical, 17 and magnetic properties 5,8,11 as compared to the un-oxidized counterparts. 4,10,12,[19][20][21] All of these unique features make oxide-coated Fe-based nanomaterials very promising in many different research areas.…”