In situ probing of surface sites on supported molybdenum nitride catalyst by CO adsorption

1997 ◽  
pp. 1247-1248 ◽  
Author(s):  
Shuwu Yang ◽  
Can Li ◽  
Jiang Xu ◽  
Qin Xin
Keyword(s):  
Co Adsorption ◽  
Molybdenum Nitride ◽  
Surface Sites

A topological quantum-chemical study of the chemisorption of carbon monoxide on the fcc (112) surfaces of Ni, Pt, Pd, Rh, and Ir

1990 ◽  
Vol 55 (8) ◽  
pp. 1907-1919
Author(s):  
Jiří Pancíř ◽  
Ivana Haslingerová
Keyword(s):  
Carbon Monoxide ◽  
Quantum Chemical ◽  
Co Adsorption ◽  
Quantum Chemical Study ◽  
Chemical Study ◽  
Dissociative Chemisorption ◽  
Frontier Orbitals ◽  
Surface Sites ◽  
Charged Surfaces ◽  
Topological Quantum

A semiempirical quantum-chemical topological method is applied to the study of the fcc (112) surfaces of Ni, Pt, Pd, Rh, and Ir and the nondissociative as well as dissociative chemisorption of carbon monoxide on them. On Ni, dissociative chemisorption is preferred to linear capture, whereas on Pd and Pt, linear capture is preferred although dissociative chemisorption is also feasible. On Rh and, in particular, on Ir, dissociative chemisorption is energetically prohibited. The high dissociative ability of the Ni surface can be ascribed to a rather unusual charge alteration and to the degeneracy of the frontier orbitals. Negative charges at the surface level are only found on the Ni and Pt surfaces whereas concentration of positive charges is established on the Rh and Ir surfaces; the Pd surface is nearly uncharged. Metals with negatively charged surfaces seem to be able to dissociate molecules of carbon monoxide. It is demonstrated that CO adsorption can take place on all metal surface sites, most effectively in the valley of the step. In all the cases studied, the attachment to the surface is found to be energetically more favourable for the carbon than for the oxygen.

scholarly journals Removal of Cd(II) from Micro-Polluted Water by Magnetic Core-Shell Fe3O4@Prussian Blue

Molecules ◽  
2021 ◽  
Vol 26 (9) ◽  
pp. 2497
Author(s):  
Xinxin Long ◽  
Huanyu Chen ◽  
Tijun Huang ◽  
Yajing Zhang ◽  
Yifeng Lu ◽  
...  
Keyword(s):  
Prussian Blue ◽  
Co Adsorption ◽  
Magnetic Core ◽  
Diameter Distribution ◽  
Polluted Water ◽  
Core Shell ◽  
Freundlich Model ◽  
Rate Limiting Step ◽  
Rate Limiting

A novel core-shell magnetic Prussian blue-coated Fe3O4 composites (Fe3O4@PB) were designed and synthesized by in-situ replication and controlled etching of iron oxide (Fe3O4) to eliminate Cd (II) from micro-polluted water. The core-shell structure was confirmed by TEM, and the composites were characterized by XRD and FTIR. The pore diameter distribution from BET measurement revealed the micropore-dominated structure of Fe3O4@PB. The effects of adsorbents dosage, pH, and co-existing ions were investigated. Batch results revealed that the Cd (II) adsorption was very fast initially and reached equilibrium after 4 h. A pH of 6 was favorable for Cd (II) adsorption on Fe3O4@PB. The adsorption rate reached 98.78% at an initial Cd (II) concentration of 100 μg/L. The adsorption kinetics indicated that the pseudo-first-order and Elovich models could best describe the Cd (II) adsorption onto Fe3O4@PB, indicating that the sorption of Cd (II) ions on the binding sites of Fe3O4@PB was the main rate-limiting step of adsorption. The adsorption isotherm well fitted the Freundlich model with a maximum capacity of 9.25 mg·g−1 of Cd (II). The adsorption of Cd (II) on the Fe3O4@PB was affected by co-existing ions, including Cu (II), Ni (II), and Zn (II), due to the competitive effect of the co-adsorption of Cd (II) with other co-existing ions.

In situ AFM and XPS Investigation of U6+ Reduction by Fe2+ on Hematite and Pyrite

2012 ◽  
Vol 1444 ◽  
Author(s):  
Jingjie Niu ◽  
Udo Becker ◽  
Rodney Ewing
Keyword(s):  
Charge Transfer ◽  
Co Adsorption ◽  
Reduction Rate ◽  
Mulliken Charge ◽  
Quantum Mechanical ◽  
Quantum Mechanical Calculations ◽  
Initial Ph ◽  
Adsorption Reduction ◽  
Tapping Mode Afm

ABSTRACTUranyl adsorption/reduction by Fe2+ on hematite and pyrite has been studied at neutral pH under anoxic and CO2-free conditions. XPS results confirm that more U3O8 precipitates on hematite than on pyrite reacted for 24 h in 160 μM uranyl nitrate and 160 μM Fe2+ solution at initial pH 7.3. These results are explained in terms of co-adsorption energy and U atom Mulliken charge transfer by quantum mechanical calculations. Moreover, in situ fluid tapping-mode AFM experiments on hematite indicate a deceleration of the U reduction rate within 24 h due to the passivation of the surface caused by the formation of orthorhombic U3O8 crystals. In addition, crystals observed using AFM show morphologies of orthorhombic schoepite appearing on hematite after 5 h.

The dissimilar twins – a comparative, site-selective in situ study of CO adsorption and desorption on Pt(322) and Pt(355)

2007 ◽  
Vol 601 (4) ◽  
pp. 1108-1117 ◽  
Author(s):  
B. Tränkenschuh ◽  
C. Papp ◽  
T. Fuhrmann ◽  
R. Denecke ◽  
H.-P. Steinrück
Keyword(s):  
Co Adsorption ◽  
Adsorption And Desorption ◽  
In Situ Study ◽  
Site Selective

Mechanistic Insights into the Spontaneous Reaction Between CO2 and La2-xSrxCuO4

2021 ◽  
Author(s):  
Alexander William Henry Whittingham ◽  
Jordan Lau ◽  
Rodney David Lucien Smith
Keyword(s):  
Electrochemical Impedance ◽  
Co2 Reduction ◽  
Active Surface ◽  
Structural Instability ◽  
Redox Couple ◽  
Surface Sites ◽  
Carbonate Ions ◽  
Redox Active ◽  
Spontaneous Reaction

Layered perovskites such as La2-xSrxCuO4 are active electrocatalysts for CO2 reduction, but they suffer from structural instability under catalytic conditions. This structural instability is found to arise from the reaction of CO2 with surface sites. Variable scan rate voltammetry shows the growth of a Cu-based redox couple when potentials cathodic of 0.6 V vs. RHE are applied in the presence of CO2. Electrochemical impedance spectroscopy identifies a redox active surface state at this voltage, whose concentration is increased by electrochemical reduction in the presence of CO2. In-situ spectroelectrochemical FTIR identifies surface bound carbonates as being involved formation of these surface sites. The orthorhombic lattice for La2-xSrxCuO4 is found to uniquely enable monodentate binding of (bi)carbonate ions from solution as well as bidentate carbonate ions through reaction with CO2. The incorporation of Sr(II) induces a transition to a tetragonal lattice, for which only monodentate carbonate ions are observed. It is proposed that the binding of carbonate ions in a bidentate fashion generates sufficient strain at the surface to result in amorphization at the surface, yielding the observed Cu(II)/Cu(I) redox couple.

scholarly journals Determining the Location of Co2+ in Zeolites by UV-Vis Diffuse Reflection Spectroscopy: A Critical View

Catalysts ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 123 ◽  
Author(s):  
Andrea Bellmann ◽  
Christine Rautenberg ◽  
Ursula Bentrup ◽  
Angelika Brückner
Keyword(s):  
Diffuse Reflection ◽  
Co Adsorption ◽  
In Situ Ftir ◽  
Diffuse Reflection Spectroscopy ◽  
Reflection Spectroscopy ◽  
Oxide Supports ◽  
In Situ Ftir Spectroscopy ◽  
Vis Spectroscopy

UV–Vis spectroscopy as well as in situ FTIR spectroscopy of pyridine and CO adsorption were applied to determine the nature of Co species in microporous, mesoporous, and mixed oxide materials like Co–ZSM-5, Co/Na–ZSM-5, Co/Al–SBA-15, and Co/Al2O3–SiO2. Because all sample types show comparable UV–Vis spectra with a characteristic band triplet, the former described UV–Vis band deconvolution method for determination and quantification of individual cationic sites in the zeolite appears doubtful. This is also confirmed by results of pyridine and CO adsorption revealing that all Co–zeolite samples contain two types of Co2+ species located at exchange positions as well as in oxide-like clusters independent of the Co content, while in Co/Al–SBA-15 and Co/Al2O3–SiO2 only Co2+ species in oxide-like clusters occur. Consequently, the measured UV–Vis spectra represent not exclusively isolated Co2+ species, and the characteristic triplet band is not only related to γ-, β-, and α-type Co2+ sites in the zeolite but also to those dispersed on the surface of different oxide supports. The study demonstrates that for proper characterization of the formed Co species, the use of complementary methods is required.

scholarly journals Catalytic Behaviour of Flame-Made CuO-CeO2 Nanocatalysts in Efficient CO Oxidation

Catalysts ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 256 ◽  
Author(s):  
Feng Zhao ◽  
Shuangde Li ◽  
Xiaofeng Wu ◽  
Renliang Yue ◽  
Weiman Li ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Water Vapor ◽  
Co Oxidation ◽  
Photoelectron Spectroscopy ◽  
Co Adsorption ◽  
Synergistic Interaction ◽  
Flame Spray ◽  
Oxidation Activity ◽  
X Ray

CuO-CeO2 nanocatalysts with varying CuO contents (1, 5, 9, 14 and 17 wt %) were prepared by one-step flame spray pyrolysis (FSP) and applied to CO oxidation. The influences of CuO content on the as-prepared catalysts were systematically characterized by X-ray diffraction (XRD), N2 adsorption-desorption at −196 °C, field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and hydrogen-temperature programmed reduction (H2-TPR). A superior CO oxidation activity was observed for the 14 wt % CuO-CeO2 catalyst, with 90% CO conversion at 98 °C at space velocity (60,000 mL × g−1 × h−1), which was attributed to abundant surface defects (lattice distortion, Ce3+, and oxygen vacancies) and high reducibility supported by strong synergistic interaction. In addition, the catalyst also displayed excellent stability and resistance to water vapor. Significantly, in situ diffuse reflectance infrared Fourier transform spectroscopy (in situ DRIFTS) showed that in the CO catalytic oxidation process, the strong synergistic interaction led readily to dehydroxylation and CO adsorption on Cu+ at low temperature. Furthermore, in the feed of water vapor, although there was an adverse effect on the access of CO adsorption, there was also a positive effect on the formation of fewer carbon intermediates. All these results showed the potential of highly active and water vapor-resistive CuO-CeO2 catalysts prepared by FSP.

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