Iron Dissolution from Goethite (α-FeOOH) Surfaces in Water by Ab Initio Enhanced Free Energy Simulations

19 April 2018, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Dissolution of redox-active metal oxides plays a key role in a variety of phenomena including (photo)electrocatalysis, degradation of battery materials, corrosion of metal oxides and biogeochemical cycling of metals in natural environments. Despite its widespread significance, mechanisms of metal-oxide dissolution remain poorly understood at the atomistic level. This study is aimed at elucidating the long-standing problem of iron dissolution from Fe(III)-oxide, a complex process involving coupled hydrolysis, surface protonation, electron transfer, and metal-oxygen bond cleavage. We examine the case of goethite (α-FeOOH), a representative phase bearing structural similarities with many other metal (hydr)oxides. By employing quantum molecular dynamics simulations (metadynamics combined with the Blue Moon ensemble approach), we unveil the mechanistic pathways and rates of both nonreductive and reductive dissolution of iron from the (110) and (021) goethite facets in aqueous solutions at room temperature. Our simulations reveal the interplay between concerted internal (structural) and external (from solution) protonation as essential for breaking Fe-O bonds, as well as for stabilizing intermediate configurations of dissolving Fe. We demonstrate specifically how Fe(III) reduction to Fe(II) yields higher dissolution rates than the proton-mediated pathway, while the most rapid dissolution is expected for these two processes combined, in agreement with experiments.


Free energy calculations


Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.