よりきれいな水をつくる手がかり(The Clues for Cleaner Water)

2024-05-06 ピッツバーグ大学

＜関連情報＞

• https://news.engineering.pitt.edu/the-clues-for-cleaner-water/
• https://pubs.acs.org/doi/10.1021/acscatal.4c01317

電気化学的オゾン生成における触媒腐食と均一系活性酸素種の相互作用 Interplay between Catalyst Corrosion and Homogeneous Reactive Oxygen Species in Electrochemical Ozone Production

Rayan Alaufey, Lingyan Zhao, Andrew Lindsay, Tana Siboonruang, Qin Wu, John A. Keith, Ezra Wood, and Maureen Tang
ACS Catalogy  Published:April 18, 2024
DOI:https://doi.org/10.1021/acscatal.4c01317

Abstract

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.