Photochemistry of Fe:H₂O Adducts in Argon Matrixes: A Combined Experimental and Theoretical Study in the Mid-IR and UV–Visible Regions

Abstract

The photochemistry of Fe:HO adducts is of interest in fields as diverse as catalysis and astrochemistry. Industrially, iron can be used as a catalyst to convert HO to H, whereas in the interstellar medium it may be an important component of dust grains, influencing the chemistry on their icy surfaces. This study consisted of the deposition and spectral characterization of binary systems of atomic iron with HO in cryogenic argon matrixes. In this way, we were able to obtain information about the interaction of the two species; we observed the formation of adducts of iron monomers and dimers with water molecules in the mid-IR and UV-visible spectral domains. Upon irradiation with a UV radiation source, the iron species were inserted into the water molecules to form HFeOH and HFeOH, leading in some cases to the formation of FeO possibly accompanied by the production of H. DFT and correlated multireference wave function calculations confirmed our attributions. This combination of IR and UV-visible spectroscopy with theoretical calculations allowed us to determine, for the first time, the spectral characteristics of iron adducts and their photoproducts in the UV-visible and in the OH stretching region of the mid-IR domain.

Separate Silicate and Carbonaceous Solids Formed from Mixed Atomic and Molecular Species Diffusing in Neon Ice

“…On the other hand, reactions of H 2 O with C and with Fe were studied at low temperature in He droplets and in Ar ice. They were found to give the weakly bond compounds H 2 O C (Krasnokutski & Huisken 2014a) and H 2 O Fe (Krasnokutski & Huisken 2014b;Deguin et al 2018).…”

The Doping Effect of 13-Atom Iron Clusters on Water Adsorption and O–H Bond Dissociation

“…5 With the use of argon matrices, a joint experimental and theoretical photochemistry study was conducted in the mid-IR and UV− visible regions, verifying the existence of HFeOH and HFe 2 OH indicative of a dissociated O−H bond on the iron atom and the dimer. 6 On the other hand, there are a few previously published theoretical studies addressing the interactions between water and small cluster Fe n (n = 1−4), 7 illustrating the determining role of the H-bond in stabilizing water molecules adsorbed on iron surfaces, 8 as well as water activation on Fe(100). 9−11 It is generally recognized that hydrogen evolution from iron clusters is energetically favorable but there are exceptions such as FeH 2 O + and Fe 4 H 2 O + cations, and occasionally the local and nonlocal correlation functionals could be sensitive to the calculation results.…”