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Hydroxyl radicals (•OH) are well known as crucial chemicals for maintaining the normal activities of human cells; however, the excessive concentration of •OH disrupts their normal function, causing various diseases, including liver and heart diseases, cancers, and neurological disorders. The detection of •OH as a biomarker is thus essential for the early diagnosis of these serious conditions. Herein, a novel electrochemical sensor comprising a composite of cerium oxide nanoclusters, gold nanoparticles, and a highly conductive carbon was developed for detecting •OH. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were employed to characterize the signals generated by the interaction of the composite with •OH radicals. The CV results revealed that the developed sensor could accurately and selectively detect •OH in the Fenton reaction. The sensor demonstrated a linear relationship between the current peak and •OH concentration in the range 0.05 − 0.5 mM and 0.5 − 5 mM with a limit of detection (LOD) of 58μM. In addition, EIS studies indicated that this electrochemical sensor could distinguish between •OH and similar reactive oxygen species (ROS), like hydrogen peroxide (H2O2). It is also worth mentioning that additional merits, such as reproducibility, repeatability, and stability of the sensor were confirmed.
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Interplay between Catalyst Corrosion and Homogeneous Reactive Oxygen Species in Electrochemical Ozone Production
Electrochemical ozone production (EOP), a six-electron water oxidation reaction, offers promising avenues for creating value-added oxidants and disinfectants. However, progress in this field is slowed by a dearth of understanding of fundamental reaction mechanisms. In this work, we combine experimental electrochemistry, spectroscopic detection of reactive oxygen species (ROS), oxygen-anion chemical ionization mass spectrometry, and computational quantum chemistry calculations to determine a plausible reaction mechanism on nickel- and antimony-doped tin oxide (Ni/Sb–SnO2, NATO), one of the most selective EOP catalysts. Antimony doping is shown to increase the conductivity of the catalyst, leading to improved electrochemical performance. Spectroscopic analysis and electrochemical experiments combined with quantum chemistry predictions reveal that hydrogen peroxide (H2O2) is a critical reaction intermediate. We propose that leached Ni4+ cations catalyze hydrogen peroxide into solution phase hydroperoxyl radicals (•OOH); these radicals are subsequently oxidized to ozone. Isotopic product analysis shows that ozone is generated catalytically from water and corrosively from the catalyst oxide lattice without regeneration of lattice oxygens. Further quantum chemistry calculations and thermodynamic analysis suggest that the electrochemical corrosion of tin oxide itself might generate hydrogen peroxide, which is then catalyzed to ozone. The proposed pathways explain both the roles of dopants in NATO and its lack of stability. Our study interrogates the possibility that instability and electrochemical activity are intrinsically linked through the formation of ROS. In doing so, we provide the first mechanism for EOP that is consistent with computational and experimental results and highlight the central challenge of instability as a target for future research efforts.
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- PAR ID:
- 10518034
- Publisher / Repository:
- American Chemical Society
- Date Published:
- Journal Name:
- ACS Catalysis
- Volume:
- 14
- Issue:
- 9
- ISSN:
- 2155-5435
- Page Range / eLocation ID:
- 6868 to 6880
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1021/acscatal.4c01317
