Proton‐Mediated and Ir‐Catalyzed Iron/Iron‐Oxide Redox Kinetics for Enhanced Rechargeability and Durability of Solid Oxide Iron–Air Battery
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The Mantoverde iron oxide-copper-gold (IOCG) deposit, Chile, contains hundreds of millions of tonnes (Mt) of mineable iron oxide and copper sulfide ore.While there is an agreement that mineralization at Mantoverde was caused by hydrothermal fluid(s), there is a lack of consensus for the role(s) that non-magmatic vs. magmatic fluid(s) played during the evolution of the mineralized system. In order to overcome the hydrothermal overprint at Mantoverde, which is known to disturb most conventional stable isotope systems (e.g., oxygen), we report the first δ56Fe and δ18O pairs for early-stage magnetite and late-stage hematite that provide information on the source reservoir of the hydrothermal fluids. Magnetite δ56Fe values range from 0.46 ± 0.04 to 0.58 ± 0.02‰and average 0.51 ± 0.16‰(n = 10; 2σ). Three hematite δ56Fe values were measured to be 0.34 ± 0.10, 0.42 ± 0.09, and 0.46 ± 0.06. Magnetite δ18O values range from 0.69 ± 0.04 to 4.61 ± 0.05‰ and average 2.99 ± 2.70‰ (n = 9; 2σ). Hematite δ18O values range from − 1.36 ± 0.05 to 5.57 ± 0.05‰and average 0.10 ± 5.38‰(n = 6; 2σ). These new δ56Fe and δ18O values fingerprint a magmatic-hydrothermal fluid as the predominant ore-forming fluid responsible for mineralization inmore »
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Mononitrosyl and dinitrosyl iron species, such as {FeNO} 7 , {FeNO} 8 and {Fe(NO) 2 } 9 , have been proposed to play pivotal roles in the nitrosylation processes of nonheme iron centers in biological systems. Despite their importance, it has been difficult to capture and characterize them in the same scaffold of either native enzymes or their synthetic analogs due to the distinct structural requirements of the three species, using redox reagents compatible with biomolecules under physiological conditions. Here, we report the realization of stepwise nitrosylation of a mononuclear nonheme iron site in an engineered azurin under such conditions. Through tuning the number of nitric oxide equivalents and reaction time, controlled formation of {FeNO} 7 and {Fe(NO) 2 } 9 species was achieved, and the elusive {FeNO} 8 species was inferred by EPR spectroscopy and observed by Mössbauer spectroscopy, with complemental evidence for the conversion of {FeNO} 7 to {Fe(NO) 2 } 9 species by UV-Vis, resonance Raman and FT-IR spectroscopies. The entire pathway of the nitrosylation process, Fe( ii ) → {FeNO} 7 → {FeNO} 8 → {Fe(NO) 2 } 9 , has been elucidated within the same protein scaffold based on spectroscopic characterization and DFT calculations. Thesemore »
