scholarly journals Reaction-Induced Cluster Ripening and Initial Size-Dependent Reaction Rates for CO Oxidation on Ptn/TiO2(110)-(1×1)

2014 ◽  
Vol 136 (24) ◽  
pp. 8702-8707 ◽  
Author(s):  
Simon Bonanni ◽  
Kamel Aït-Mansour ◽  
Wolfgang Harbich ◽  
Harald Brune
Keyword(s):  
Co Oxidation ◽  
Reaction Rates ◽  
Initial Size ◽  
Size Dependent

Growth kinetic control over MgFe2O4 to tune Fe occupancy and metal–support interactions for optimum catalytic performance

CrystEngComm ◽  
2021 ◽  
Vol 23 (13) ◽  
pp. 2538-2546
Author(s):  
Min Yang ◽  
Guangshe Li ◽  
Huixia Li ◽  
Junfang Ding ◽  
Yan Wang ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Growth Kinetic ◽  
Catalytic Performance ◽  
Growth Behavior ◽  
Kinetic Control ◽  
Size Dependent ◽  
Metal Support ◽  
Support Size ◽  
Metal Support Interactions ◽  
First Time

For the first time, the growth behavior with size-dependent Fe occupancies at different sites of MgFe2O4 was examined. Hybrid catalysts of Pt/MgFe2O4 with a support size of 20.6 nm exhibited an optimal performance of CO oxidation.

Theoretical study of catalytic oxidation of CO on free PdxO2+ (x = 4–6) clusters: size dependent comparison of combustion

RSC Advances ◽  
2015 ◽  
Vol 5 (53) ◽  
pp. 42329-42340 ◽  
Author(s):  
Chandan Sahu ◽  
Deepanwita Ghosh ◽  
Abhijit K. Das
Keyword(s):  
Co Oxidation ◽  
Catalytic Oxidation ◽  
Theoretical Study ◽  
Dft Study ◽  
Oxidation Of Co ◽  
Catalytic Co Oxidation ◽  
Size Dependent ◽  
Catalytic Oxidation Of Co

A DFT study has been adopted to explore the catalytic CO oxidation on a free PdxO2+ (x = 4–6) cluster.

scholarly journals Size-dependent dynamic structures of supported gold nanoparticles in CO oxidation reaction condition

2018 ◽  
Vol 115 (30) ◽  
pp. 7700-7705 ◽  
Author(s):  
Yang He ◽  
Jin-Cheng Liu ◽  
Langli Luo ◽  
Yang-Gang Wang ◽  
Junfa Zhu ◽  
...  
Keyword(s):  
Co Oxidation ◽  
Oxidation Reaction ◽  
Au Nanoparticles ◽  
Working Condition ◽  
Ab Initio Molecular Dynamics ◽  
Present Observation ◽  
Size Dependent ◽  
Reaction Condition ◽  
Au Clusters ◽  
Co Oxidation Reaction

Gold (Au) catalysts exhibit a significant size effect, but its origin has been puzzling for a long time. It is generally believed that supported Au clusters are more or less rigid in working condition, which inevitably leads to the general speculation that the active sites are immobile. Here, by using atomic resolution in situ environmental transmission electron microscopy, we report size-dependent structure dynamics of single Au nanoparticles on ceria (CeO2) in CO oxidation reaction condition at room temperature. While large Au nanoparticles remain rigid in the catalytic working condition, ultrasmall Au clusters lose their intrinsic structures and become disordered, featuring vigorous structural rearrangements and formation of dynamic low-coordinated atoms on surface. Ab initio molecular-dynamics simulations reveal that the interaction between ultrasmall Au cluster and CO molecules leads to the dynamic structural responses, demonstrating that the shape of the catalytic particle under the working condition may totally differ from the shape under the static condition. The present observation provides insight on the origin of superior catalytic properties of ultrasmall gold clusters.

scholarly journals Modeling the effects of size on patch dynamics of an inert tracer

2009 ◽  
Vol 6 (2) ◽  
pp. 1735-1756
Author(s):  
P. Xiu ◽  
F. Chai
Keyword(s):  
Dilution Rate ◽  
Ocean Circulation ◽  
Three Dimensional ◽  
Circulation Model ◽  
Patch Dynamics ◽  
Initial Size ◽  
Phytoplankton Productivity ◽  
Size Dependent ◽  
Enrichment Experiments

Abstract. Mesoscale iron enrichment experiments have revealed that additional iron affects the phytoplankton productivity and carbon cycle. However, the role of initial size of fertilized patch in determining the patch evolution is poorly quantified due to the limited time of research vessels at sea. Using a three-dimensional ocean circulation model, we simulated different sizes of inert tracer patches that were only regulated by physical circulation and diffusion. Model results showed that during the first few days since release of inert tracer, the calculated dilution rate was found to be a linear function with time, which was sensitive to the initial patch size with steeper slope for smaller size patch. After the initial phase of rapid decay, the relationship between dilution rate and time became an exponential function, which was also size dependent. Therefore, larger initial size patches can usually last longer and ultimately affect biogeochemical processes much stronger than smaller patches.

scholarly journals The surface tension of surfactant-containing, finite volume droplets

2020 ◽  
Vol 117 (15) ◽  
pp. 8335-8343 ◽  
Author(s):  
Bryan R. Bzdek ◽  
Jonathan P. Reid ◽  
Jussi Malila ◽  
Nønne L. Prisle
Keyword(s):  
Surface Tension ◽  
Finite Volume ◽  
Climate Models ◽  
High Surface ◽  
Finite Size ◽  
Volume Ratio ◽  
Cloud Droplet ◽  
Reaction Rates ◽  
Hygroscopic Growth ◽  
Size Dependent

Surface tension influences the fraction of atmospheric particles that become cloud droplets. Although surfactants are an important component of aerosol mass, the surface tension of activating aerosol particles is still unresolved, with most climate models assuming activating particles have a surface tension equal to that of water. By studying picoliter droplet coalescence, we demonstrate that surfactants can significantly reduce the surface tension of finite-sized droplets below the value for water, consistent with recent field measurements. Significantly, this surface tension reduction is droplet size-dependent and does not correspond exactly to the macroscopic solution value. A fully independent monolayer partitioning model confirms the observed finite-size-dependent surface tension arises from the high surface-to-volume ratio in finite-sized droplets and enables predictions of aerosol hygroscopic growth. This model, constrained by the laboratory measurements, is consistent with a reduction in critical supersaturation for activation, potentially substantially increasing cloud droplet number concentration and modifying radiative cooling relative to current estimates assuming a water surface tension. The results highlight the need for improved constraints on the identities, properties, and concentrations of atmospheric aerosol surfactants in multiple environments and are broadly applicable to any discipline where finite volume effects are operative, such as studies of the competition between reaction rates within the bulk and at the surface of confined volumes and explorations of the influence of surfactants on dried particle morphology from spray driers.

New DRIFTS Cell Design for the Simultaneous Acquisition of IR Spectra and Kinetic Data Using On-Line Product Analysis

2001 ◽  
Vol 55 (11) ◽  
pp. 1537-1543 ◽  
Author(s):  
M. M. Schubert ◽  
T. P. Häring ◽  
G. Bräth ◽  
H. A. Gasteiger ◽  
R. J. Behm
Keyword(s):  
Co Oxidation ◽  
Gas Flow ◽  
Reaction Rates ◽  
Gas Analysis ◽  
Cell Design ◽  
Product Analysis ◽  
Kinetic Measurements ◽  
On Line ◽  
Improved Performance ◽  
Diffuse Reflectance Infrared

A new design for a DRIFTS (diffuse reflectance infrared Fourier transform spectrometry) cell for in situ studies in heterogeneous catalysis is presented, which allows for improved reaction control (i.e., gas flow, temperature, minimized background conversion) and for precise kinetic measurements via on-line gas analysis by a tandem-arranged gas chromatograph. Specifically, the very low background activity of the cell itself for CO and H2 oxidation makes it possible to study the preferential CO oxidation in H2-rich gases (PROX) at relevant reaction temperatures (150–350 °C) and reactant concentrations (≤1 kPa CO and O2). Comparison with results obtained in a quartz tube reactor shows excellent agreement with the reaction rates obtained in the DRIFTS cell. The improved performance of the new DRIFTS cell design is demonstrated by examining the influence of CO2 on the PROX reaction over a Au/Fe2O3 catalyst. The addition of CO2 to idealized reformate (varying CO and O2 partial pressures, 75 kPa H2, balance N2) significantly reduces both the CO oxidation rate and the selectivity of the PROX reaction on Au/α-Fe2O3 and strongly affects the frequency of the C–O stretch vibration of adsorbed CO due to CO2 coadsorption.

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