A cobalt-tripeptide complex (CoGGH) is developed as an electrocatalyst for the selective sixelectron, eight-proton reduction of nitrite to ammonium in aqueous buffer near neutral pH. The onset potential for nitrite reduction occurs at −0.65 V vs Ag/AgCl (1 M KCl). Controlled potential electrolysis at −0.90 V generates ammonium with a faradaic efficiency of 90 ± 3% and a turnover number of 3550 ± 420 over 5.5 h. CoGGH also catalyzes the reduction of the proposed intermediates nitric oxide and hydroxylamine to ammonium. These results reveal that a simple metallopeptide is an active functional mimic of the complex enzymes cytochrome c nitrite reductase and siroheme-containing nitrite reductase.
Catalytic reduction of nitrite by an iron complex in water near neutral pH to form hydroxylamine and ammonium is reported. The catalyst is an iron center coordinated by the pentadentate macrocycle 2,13-dimethyl-3,6,9,12,18-pentaazabicyclo[12.3.1]octadeca-1(18),2,12,14,16-pentaene (FeN5H2). Catalysis is observed by cyclic voltammetry at a half-wave potential of E p/2 = −0.98 V vs Ag/AgCl (1 M KCl) when FeN5H2, nitrite, and a buffer (pH 7.2) are present. Controlled potential electrolysis of FeN5H2 and nitrite in pH 7.2 buffer at −0.98 V produces hydroxylamine (faradaic efficiency > 90%). FeN5H2 catalyzes ammonium production by disproportionation of hydroxylamine with concomitant formation of nitrous oxide and dinitrogen. These results are a rare example of multielectron electrocatalytic nitrite reduction by an iron complex near neutral pH.
The potential of time-of-flight secondary ion mass spectrometry (ToF-SIMS) is explored as a unique analytical tool to complement current analyses in wood polymer composites (WPC) research. ToF-SIMS is examined due to its chemical imaging abilities with both high spatial resolution for imaging and high depth resolution going from the surface into the bulk of the material, as well as its low detection limits. The ToF-SIMS method is introduced and preliminary data are discussed, demonstrating ToF-SIMS analyses of commercial WPCs before and after weathering. Controlled weathering exposed samples to rain, ultraviolet radiation, and freeze-thaw cycles, both alone and in combination. The surfaces of the samples were analyzed using ToF-SIMS at five different stages of the weathering process. Topography was also analyzed using scanning electron microscopy and the durability of the samples was measured at the end of weathering using three-point flexural strength testing. Analysis of the ToF-SIMS spectra using multivariate statistical methods demonstrated that ToF-SIMS distinguished samples that underwent various weathering conditions. ToF-SIMS images of WPC samples illustrated the spatial heterogeneity of the chemical components detected, and assisted with understanding changes observed in comparisons of the mass spectra. A depth profile indicated that some of the nitrogen-containing species observed in the spectra of the WPC were isolated to the surface of the sample. Throughout the discussion of this first analysis of WPC with ToF-SIMS, a focus is placed on the opportunities that exist for ToF-SIMS analysis of WPCs, along with the challenges that will need to be overcome for reliable interpretation of future data.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.