Near-ambient X-ray photoemission spectroscopy and kinetic approach to the mechanism of carbon monoxide oxidation over lanthanum substituted cobaltites

Hueso, José L.; Martínez-Martínez, D.; Caballero, A.; González‐Elipe, Agustín R.; Mun, Bongjin Simon; Salmerón, Miquel

doi:10.1016/j.catcom.2009.06.022

Cited by 23 publications

(16 citation statements)

References 30 publications

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“…The gaseous oxygen is represented by two peaks (538.8 and 539.9 eV) that are ~1.1 eV apart ( Fig. 2 ), reflecting the 1s level of spin splitting of the paramagnetic nature of O 2 33 34 .…”

Section: Resultsmentioning

confidence: 99%

Characterization of photocatalytic TiO2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

Krishnan

Liu

Itty

et al. 2017

Sci Rep

112

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Consecutive eight study phases under the successive presence and absence of UV irradiation, water vapor, and oxygen were conducted to characterize surface changes in the photocatalytic TiO2 powder using near-ambient-pressure X-ray photoelectron spectroscopy (XPS). Both Ti 2p and O 1s spectra show hysteresis through the experimental course. Under all the study environments, the bridging hydroxyl (OHbr) and terminal hydroxyl (OHt) are identified at 1.1–1.3 eV and 2.1–2.3 eV above lattice oxygen, respectively. This enables novel and complementary approach to characterize reactivity of TiO2 powder. The dynamic behavior of surface-bound water molecules under each study environment is identified, while maintaining a constant distance of 1.3 eV from the position of water vapor. In the dark, the continual supply of both water vapor and oxygen is the key factor retaining the activated state of the TiO2 powder for a time period. Two new surface peaks at 1.7–1.8 and 4.0–4.2 eV above lattice oxygen are designated as peroxides (OOH/H2O2) and H2O2 dissolved in water, respectively. The persistent peroxides on the powder further explain previously observed prolonged oxidation capability of TiO2 powder without light irradiation.

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“…The gaseous oxygen is represented by two peaks (538.8 and 539.9 eV) that are ~1.1 eV apart ( Fig. 2 ), reflecting the 1s level of spin splitting of the paramagnetic nature of O 2 33 34 .…”

Section: Resultsmentioning

confidence: 99%

Characterization of photocatalytic TiO2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

Krishnan

Liu

Itty

et al. 2017

Sci Rep

112

View full text Add to dashboard Cite

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“…At higher temperature, with conversions higher than 80 %, the slope of the activity curve declines, being better the performance of the La 0.5 Sr 0.5 CoO 3-d perovskite, which achieves total oxidation at 245°C. These effects might be related with either a change in the oxidation mechanism [38] or the partial segregation of the perovskite phase in the presence of toluene at high temperatures [14].…”

Section: Catalytic Oxidation Of Toluenementioning

confidence: 99%

Study of Oxygen Reactivity in La1−x Sr x CoO3−δ Perovskites for Total Oxidation of Toluene

et al. 2012

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The total oxidation of toluene is studied over catalytic systems based on perovskite with general formula AA 0 CoO 3-d (A = La, A 0 = Sr). The systematic and progressive substitution of La 3? by Sr 2? cations in the series (La 1-x Sr x CoO 3-d system) of the perovskites have been studied to determine their influence in the final properties of these mixed oxides and their corresponding reactivity performance for the total oxidation of toluene as a model volatile organic compound with detrimental effects for health and environment. The structure and morphology of the samples before and after reaction have been characterized by XRD, BET and FE-SEM techniques. Additional experiments of temperature programmed desorption of O 2 in vacuum and reduction in H 2 were also performed to identify the main surface oxygen species and the reducibility of the different perovskites. It is remarkable that the La 1-x Sr x CoO 3-d series presents better catalytic performance for the oxidation of toluene, with lower values for the T 50 (temperature of 50 % toluene conversion) than the previously studied LaNi 1-y Co y O 3 series.

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“…We can analyze physicochemical properties on catalyst surfaces within a probing depth below 1–3 nm using a soft X-ray source (e.g., Al Kα: 1486.6 eV). The synchrotron-based XPS can provide an opportunity for analysis in even less than 1 nm of probing depth for a specific core-level state of the catalyst. − However, the conventional XPS setup was ordinarily running in UHV because of the limitation of inherent energy-loss and photoelectron scattering at the gas–solid interface. So, the XPS technique with a soft X-ray source was far from a useful characterization tool for catalysts in working conditions, because the inelastic mean-free path of photoemitted electrons sharply decreases at atmospheric pressure .…”

Section: Introduction To Operando Surface Chemistry On Model Catalyst...mentioning

confidence: 99%

Operando Surface Studies on Metal-Oxide Interfaces of Bimetal and Mixed Catalysts

et al. 2021

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The formation of metal-oxide interfaces in catalytic systems exhibits a synergistic phenomenon between metal and reducible oxides, often referred to as the strong metal−support interaction (SMSI). This unusual characteristic has been connected to the origin of highly enhanced catalytic performance for decades, but the mechanistic explanation of SMSI remains a long-standing issue in heterogeneous catalysis. To understand this matter at the molecular level, geometric and electronic functions of metal-oxide interfaces during catalytic reactions should be clearly interpreted using advanced microscopic and spectroscopic analysis techniques. In this Review, we highlight recently performed investigations at metal-oxide interfaces by operando characterization tools to identify active sites in working conditions. We introduce two kinds of catalysts, platinum-based bimetallic alloys and mixed metal-oxide catalysts. Selected operando techniques reveal their atomic-scale morphology, surface electronic structure, and charge transfer/transport at surfaces under oxidation, reduction, and gas mixture environments. With bimetallic model catalysts, topographic morphology observations present critical evidence for the structural modulation between the topmost layer and the subsurface lattice in oxygen conditions. For the mixed metal-oxide catalysts, we note that metal nanoparticles on reducible oxides demonstrate the catalytic activity enhancement, which is obviously influenced by the change of oxidation states at the metal-oxide interface. Environmental transmission electron microscopy images unveil the atomic-scale redox behaviors at the nanoparticle interfaces with evolutions of the reducible oxide under the catalytic reaction. The important role of reactive interfaces between the transition metal atom and oxide-support explains the surface chemistry and heterogeneous catalysis over active sites on well-defined single crystal model surfaces, as well as nanoparticle catalysts. Overall, operando studies for metal-oxide interfaces can shed light on mechanistic insights into the tuning of catalytic activity at the molecular level and on improving catalytic performance by the SMSI effect.

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Near-ambient X-ray photoemission spectroscopy and kinetic approach to the mechanism of carbon monoxide oxidation over lanthanum substituted cobaltites

Cited by 23 publications

References 30 publications

Characterization of photocatalytic TiO2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

Characterization of photocatalytic TiO2 powder under varied environments using near ambient pressure X-ray photoelectron spectroscopy

Study of Oxygen Reactivity in La1−x Sr x CoO3−δ Perovskites for Total Oxidation of Toluene

Operando Surface Studies on Metal-Oxide Interfaces of Bimetal and Mixed Catalysts

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