Probing Local Environments of Oxygen Vacancies Responsible for Hydration in Sc-doped Barium Zirconates at Elevated Temperatures: In Situ X-ray Absorption Spectroscopy, Thermogravimetry, and Active Learning Ab Initio Replica Exchange Monte Carlo Simulations

Proton-conducting oxides, specifically heavily Sc-doped barium zirconate perovskite, have attracted attention as electrolytes for intermediate-temperature protonic ceramic fuel cells because of their high proton conductivity and high chemical stability against carbon dioxide in that temperature regime. Hydration is a key reaction for incorporating protons by filling oxygen vacancies, VO, with hydroxyl groups and activating proton conduction in the perovskite. However, probing the local environment of oxygen vacancies responsible for hydration is challenging because the behavior depends on the temperature and water partial pressure, which necessitates in situ observations and calculations of the local environments at elevated temperatures. To obtain such information, we combined in situ X-ray absorption spectroscopy (XAS) for both the Sc and Zr K-edges, thermogravimetry, X-ray diffractometry, and active learning ab initio replica exchange Monte Carlo (RXMC) simulations in undoped and 20–40 at% Sc-doped barium zirconates at and below 800 °C. The presence of oxygen vacancies adjacent to Sc and Zr in the dehydrated samples and the hydration of these oxygen vacancies under a wet atmosphere were probed by in situ XAS for Sc and Zr pre-edges at elevated temperatures. Here, the microscopic hydration linearly responds to the macroscopic degree of hydration. RXMC sampling further supports the presence of Sc-VO-Zr and Sc-VO-Sc environments. An initial hydration occurs in the Sc-VO-Zr environment at and above 600 °C, but the Sc-VO-Sc environment contribution is greater at higher degrees of hydration. The Zr-Vo-Zr environment is the least abundant among them for the whole temperature range examined and thus has a negligible impact

Probing Local Environments of Oxygen Vacancies Responsible for Hydration in Sc-doped Barium Zirconates at Elevated Temperatures: In Situ X-ray Absorption Spectroscopy, Thermogravimetry, and Active Learning Ab Initio Replica Exchange Monte Carlo Simulations

Proton-conducting oxides, specifically heavily Sc-doped barium zirconate perovskite, have attracted attention as electrolytes for intermediate-temperature protonic ceramic fuel cells because of their high proton conductivity and high chemical stability against carbon dioxide in that temperature regime. Hydration is a key reaction for incorporating protons by filling oxygen vacancies, VO, with hydroxyl groups and activating proton conduction in the perovskite. However, probing the local environment of oxygen vacancies responsible for hydration is challenging because the behavior depends on the temperature and water partial pressure, which necessitates in situ observations and calculations of the local environments at elevated temperatures. To obtain such information, we combined in situ X-ray absorption spectroscopy (XAS) for both the Sc and Zr K-edges, thermogravimetry, X-ray diffractometry, and active learning ab initio replica exchange Monte Carlo (RXMC) simulations in undoped and 20–40 at% Sc-doped barium zirconates at and below 800 °C. The presence of oxygen vacancies adjacent to Sc and Zr in the dehydrated samples and the hydration of these oxygen vacancies under a wet atmosphere were probed by in situ XAS for Sc and Zr pre-edges at elevated temperatures. Here, the microscopic hydration linearly responds to the macroscopic degree of hydration. RXMC sampling further supports the presence of Sc-VO-Zr and Sc-VO-Sc environments. An initial hydration occurs in the Sc-VO-Zr environment at and above 600 °C, but the Sc-VO-Sc environment contribution is greater at higher degrees of hydration. The Zr-Vo-Zr environment is the least abundant among them for the whole temperature range examined and thus has a negligible impact.</jats:p

Carbon monoxide reduces pulmonary ischemia–reperfusion injury in miniature swine

ObjectivesCarbon monoxide is produced endogenously as a by-product of heme catalysis and has been shown to reduce ischemia–reperfusion injury in a variety of organs in murine models. The aims of this translational research were to establish an in situ porcine lung model of warm ischemia–reperfusion injury and to evaluate the cytoprotective effects of low-dose inhaled carbon monoxide in this model.MethodsWarm ischemia was induced for 90 minutes by clamping the left pulmonary artery and veins in 8 Clawn miniature swine (Japan Farm CLAWN Institute, Kagoshima, Japan). The left main bronchus was also dissected and reanastomosed just before reperfusion. Four animals were treated with inhaled carbon monoxide at a concentration of approximately 250 ppm throughout the procedure. Lung function and structure were serially accessed via lung biopsy, chest x-ray films, and blood gas analysis.ResultsCarbon monoxide inhalation dramatically decreased the lung injury associated with ischemia and reperfusion. Two hours after reperfusion, the arterial oxygen tension of the carbon monoxide–treated group was 454 ± 34 mm Hg, almost double the arterial oxygen tension of the control group (227 ± 57 mm Hg). There were fewer pathologic changes seen on chest x-ray films and in biopsy samples from animals in the carbon monoxide–treated group. Animals in the carbon monoxide–treated group also had fewer inflammatory cell infiltrates and a markedly smaller increase in serum concentrations of the proinflammatory cytokines interleukin 1β, interleukin 6, and high-mobility group box 1 after ischemia–reperfusion injury.ConclusionsThe perioperative administration of low-dose inhaled carbon monoxide decreases warm ischemia–reperfusion injury in lungs in miniature swine. This protective effect is mediated in part by the downregulation of proinflammatory mediators

Probing Local Environments of Oxygen Vacancies Responsible for Hydration in Sc-Doped Barium Zirconates at Elevated Temperatures: In Situ X‑ray Absorption Spectroscopy, Thermogravimetry, and Active Learning Ab Initio Replica Exchange Monte Carlo Simulations

Proton-conducting oxides, specifically heavily Sc-doped barium zirconate perovskite, have attracted attention as electrolytes for intermediate-temperature protonic ceramic fuel cells because of their high proton conductivity and high chemical stability against carbon dioxide in that temperature regime. Hydration is a key reaction for incorporating protons by filling oxygen vacancies, VO, with hydroxyl groups and activating proton conduction in the perovskite. However, probing the local environment of oxygen vacancies responsible for hydration is challenging because the behavior depends on the temperature and water partial pressure, which necessitates in situ observations and calculations of the local environments at elevated temperatures. To obtain such information, we combined in situ X-ray absorption spectroscopy (XAS) for both the Sc and Zr K-edges, thermogravimetry, X-ray diffractometry, and active learning ab initio replica exchange Monte Carlo (RXMC) simulations in undoped and 20–40 at % Sc-doped barium zirconates at and below 800 °C. The presence of oxygen vacancies adjacent to Sc and Zr in the dehydrated samples and the hydration of these oxygen vacancies under a wet atmosphere were probed by in situ XAS for Sc and Zr pre-edges at elevated temperatures. Here, the microscopic hydration linearly responds to the macroscopic degree of hydration. RXMC sampling further supports the presence of Sc-VO-Zr and Sc-VO-Sc environments. An initial hydration occurs in the Sc-VO-Zr environment at and above 600 °C, but the Sc-VO-Sc environment contribution is greater at higher degrees of hydration. The Zr-Vo-Zr environment is the least abundant among them for the whole temperature range examined and thus has a negligible impact