Wolkenstein’s Model of Size Effects in CO Oxidation by Gold Nanoparticles

The Wolkenstein’s theory of catalysis and the d-band theory of formation chemical bonds between transition metal catalysts and adsorbates were used to develop the approach applied to the kinetics of CO oxidation by gold nanoparticles. In the model, within the framework of the mechanism of the reaction going through dissociative adsorption of oxygen molecules and reaction with gas-phase CO molecules, weak and strong chemisorption states of intermediates (O, CO2) were taken into account in the kinetic equations by introducing reversible electronic steps corresponding to electron transfers between the intermediates and the catalyst. As a result, we obtain the expression for the reaction rate, which exhibits a volcano-shape dependence upon the size of the gold nanoparticles at the conditions when the intermediates fractions are not small compared to the empty active sites of the catalyst. It is supposed that the approach can be also applied to the Langmuir-Hinshelwood mechanism.

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CO Oxidation Efficiency and Hysteresis Behavior over Mesoporous Pd/SiO2 Catalyst

Catalysts ◽

10.3390/catal11010131 ◽

2021 ◽

Vol 11 (1) ◽

pp. 131 ◽

Cited By ~ 1

Author(s):

Rola Mohammad Al Soubaihi ◽

Khaled Mohammad Saoud ◽

Myo Tay Zar Myint ◽

Mats A. Göthelid ◽

Joydeep Dutta

Keyword(s):

Carbon Monoxide ◽

Catalytic Activity ◽

Co Oxidation ◽

Active Sites ◽

Bond Activation ◽

Dissociative Adsorption ◽

High Catalytic Activity ◽

Good Catalytic Activity ◽

Pretreatment Conditions ◽

Oxidation Efficiency

Carbon monoxide (CO) oxidation is considered an important reaction in heterogeneous industrial catalysis and has been extensively studied. Pd supported on SiO2 aerogel catalysts exhibit good catalytic activity toward this reaction owing to their CO bond activation capability and thermal stability. Pd/SiO2 catalysts were investigated using carbon monoxide (CO) oxidation as a model reaction. The catalyst becomes active, and the conversion increases after the temperature reaches the ignition temperature (Tig). A normal hysteresis in carbon monoxide (CO) oxidation has been observed, where the catalysts continue to exhibit high catalytic activity (CO conversion remains at 100%) during the extinction even at temperatures lower than Tig. The catalyst was characterized using BET, TEM, XPS, TGA-DSC, and FTIR. In this work, the influence of pretreatment conditions and stability of the active sites on the catalytic activity and hysteresis is presented. The CO oxidation on the Pd/SiO2 catalyst has been attributed to the dissociative adsorption of molecular oxygen and the activation of the C-O bond, followed by diffusion of adsorbates at Tig to form CO2. Whereas, the hysteresis has been explained by the enhanced stability of the active site caused by thermal effects, pretreatment conditions, Pd-SiO2 support interaction, and PdO formation and decomposition.

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Elucidation of Active Sites of Gold Nanoparticles on Acidic Ta2O5 Supports for CO Oxidation

ACS Catalysis ◽

10.1021/acscatal.0c01966 ◽

2020 ◽

Vol 10 (16) ◽

pp. 9328-9335

Author(s):

Mingyue Lin ◽

Chihiro Mochizuki ◽

Baoxiang An ◽

Yusuke Inomata ◽

Tamao Ishida ◽

...

Keyword(s):

Gold Nanoparticles ◽

Co Oxidation ◽

Active Sites

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Dissociative Adsorption of O2 on Clean and CO-Precovered Pt Surfaces

MRS Proceedings ◽

10.1557/proc-1084-s05-01 ◽

2008 ◽

Vol 1084 ◽

Author(s):

Bin Shan ◽

Ligen Wang ◽

Jangsuk Hyun ◽

Yang Sang ◽

Yujun Zhao ◽

...

Keyword(s):

Co Oxidation ◽

Density Functional ◽

Atomic Oxygen ◽

Activation Barrier ◽

Co Adsorption ◽

Dissociative Adsorption ◽

Binding Energies ◽

Critical Question ◽

Oxygen Dissociation ◽

Langmuir Hinshelwood Mechanism

ABSTRACTIt is generally accepted that CO oxidation on transition metals follows a Langmuir-Hinshelwood mechanism. The oxidation reaction takes place in two sequential steps where the oxygen molecule first dissociates into atomic oxygen and then reacts with an adsorbed CO to form CO2. One critical question concerning the reaction kinetics under high pressure is the probability of oxygen dissociation on a highly CO covered surface. On bare transition metal surfaces, molecularly adsorbed oxygen readily dissociates with little or no apparent activation barrier. In industrial diesel engine catalysis, the metal surface is initially packed with CO. Subsequent reactions such as oxygen dissociation must take place on a CO covered surface. In this paper, we performed density functional theory (DFT) calculations for O2 dissociation on Pt(111) in the presence of different CO adsorption environments. While several stable O2 molecular precursor states (top-bridge-top, top-fcc-bridge, and top-hcp-bridge) exist on a clean Pt(111) surface, these precursors become endothermic beyond a critical CO coverage of ∼0.44 ML. Furthermore, the reaction path for CO oxidation via dissociated atomic oxygen becomes less favorable at higher CO coverage, primarily due to competitive adsorption and lateral repulsion. It was found that the oxygen dissociation barrier and the binding energies of atomic oxygen are well correlated via the Evans-Polanyi relationship.

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Improved Catalytic Performance of Au/α-Fe2O3-Like-Worm Catalyst for Low Temperature CO Oxidation

Nanomaterials ◽

10.3390/nano9081118 ◽

2019 ◽

Vol 9 (8) ◽

pp. 1118 ◽

Cited By ~ 5

Author(s):

Qiuwan Han ◽

Dongyang Zhang ◽

Jiuli Guo ◽

Baolin Zhu ◽

Weiping Huang ◽

...

Keyword(s):

Electron Microscopy ◽

Gold Nanoparticles ◽

Co Oxidation ◽

Oxidation Reaction ◽

Active Sites ◽

Catalytic Performance ◽

Photoelectron Spectra ◽

Great Activity ◽

X Ray ◽

Co Oxidation Reaction

The gold catalysts supported on various morphologies of α-Fe2O3 in carbon monoxide (CO) oxidation reaction have been studied for many researchers. However, how to improve the catalytic activity and thermal stability for CO oxidation is still important. In this work, an unusual morphology of α-Fe2O3 was prepared by hydrothermal method and gold nanoparticles were supported using a deposition-precipitation method. Au/α-Fe2O3 catalyst exhibited great activity for CO oxidation. The crystal structure and microstructure images of α-Fe2O3 were carried out by X-ray diffraction (XRD) and scanning electron microscopy (SEM) and the size of gold nanoparticles was determined by transmission electron microscopy (TEM). X-ray photoelectron spectra (XPS) and Fourier transform infrared spectra (FTIR) results confirmed that the state of gold was metallic. The 1.86% Au/α-Fe2O3 catalyst calcined at 300 °C had the best catalytic performance for CO oxidation reaction and the mechanism for CO oxidation reaction was also discussed. It is highly likely that the small size of gold nanoparticle, oxygen vacancies and active sites played the decisive roles in CO oxidation reaction.

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Towards a Design of Active Oxygen Evolution Catalysts: Insights from Automated Density Functional Theory Calculations and Machine Learning

10.26434/chemrxiv.7926869 ◽

2019 ◽

Author(s):

Seoin Back ◽

Kevin Tran ◽

Zachary Ulissi

Keyword(s):

Machine Learning ◽

Oxygen Evolution ◽

Active Sites ◽

Density Functional ◽

Chemical Space ◽

Density Functional Theory Calculations ◽

Catalyst Design ◽

Transition Metal Catalysts ◽

Oxide Materials ◽

Design Strategies

<div> <div> <div> <div><p>Developing active and stable oxygen evolution catalysts is a key to enabling various future energy technologies and the state-of-the-art catalyst is Ir-containing oxide materials. Understanding oxygen chemistry on oxide materials is significantly more complicated than studying transition metal catalysts for two reasons: the most stable surface coverage under reaction conditions is extremely important but difficult to understand without many detailed calculations, and there are many possible active sites and configurations on O* or OH* covered surfaces. We have developed an automated and high-throughput approach to solve this problem and predict OER overpotentials for arbitrary oxide surfaces. We demonstrate this for a number of previously-unstudied IrO2 and IrO3 polymorphs and their facets. We discovered that low index surfaces of IrO2 other than rutile (110) are more active than the most stable rutile (110), and we identified promising active sites of IrO2 and IrO3 that outperform rutile (110) by 0.2 V in theoretical overpotential. Based on findings from DFT calculations, we pro- vide catalyst design strategies to improve catalytic activity of Ir based catalysts and demonstrate a machine learning model capable of predicting surface coverages and site activity. This work highlights the importance of investigating unexplored chemical space to design promising catalysts.<br></p></div></div></div></div><div><div><div> </div> </div> </div>

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Kinetics of the catalytic hydrodesulphurization reaction system; hydrogenolysis of thiophene

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19802728 ◽

1980 ◽

Vol 45 (10) ◽

pp. 2728-2741 ◽

Cited By ~ 7

Author(s):

Pavel Fott ◽

Petr Schneider

Keyword(s):

Atmospheric Pressure ◽

Active Sites ◽

Flow Reactor ◽

Kinetic Equations ◽

Reaction System ◽

Reaction Products ◽

Molybdenum Catalyst ◽

Cobalt Molybdenum Catalyst ◽

Kinetics Of ◽

Reaction Schemes

Kinetics have been studied of the reaction system taking place during the reaction of thiophene on the cobalt-molybdenum catalyst in a gradientless circulation flow reactor at 360 °C and atmospheric pressure. Butane has been found present in a small amount in the reaction products even at very low conversion. In view of this, consecutive and parallel-consecutive (triangular) reaction schemes have been proposed. In the former scheme the appearance of butane is accounted for by rate of desorption of butene being comparable with the rate of its hydrogenation. According to the latter scheme part of the butane originates from thiophene via a different route than through hydrogenation of butene. Analysis of the kinetic data has revealed that the reaction of thiophene should be considered to take place on other active sites than that of butene. Kinetic equations derived on this assumption for the consecutive and the triangular reaction schemes correlate experimental data with acceptable accuracy.

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Synergistic Effect of Alkali Na and K Promoter on Fe-Co-Cu-Al Catalysts for CO2 Hydrogenation to Light Hydrocarbons

Catalysts ◽

10.3390/catal11060735 ◽

2021 ◽

Vol 11 (6) ◽

pp. 735

Author(s):

Yuhao Zheng ◽

Chenghua Xu ◽

Xia Zhang ◽

Qiong Wu ◽

Jie Liu

Keyword(s):

Synergistic Effect ◽

Active Sites ◽

Intermediate Formation ◽

Active Phase ◽

Dissociative Adsorption ◽

Co2 Hydrogenation ◽

Chain Growth ◽

Co2 Conversion ◽

Light Hydrocarbons ◽

Active Centers

Alkali metal K- and/or Na-promoted FeCoCuAl catalysts were synthesized by precipitation and impregnation, and their physicochemical and catalytic performance for CO2 hydrogenation to light hydrocarbons was also investigated in the present work. The results indicate that Na and/or K introduction leads to the formation of active phase metallic Fe and Fe-Co crystals in the order Na < K < K-Na. The simultaneous introduction of Na and K causes a synergistic effect on increasing the basicity and electron-rich property, promoting the formation of active sites Fe@Cu and Fe-Co@Cu with Cu0 as a crystal core. These effects are advantageous to H2 dissociative adsorption and CO2 activation, giving a high CO2 conversion with hydrogenation. Moreover, electron-rich Fe@Cu (110) and Fe-Co@Cu (200) provide active centers for further H2 dissociative adsorption and O-C-Fe intermediate formation after adsorption of CO produced by RWGS. It is beneficial for carbon chain growth in C2+ hydrocarbons, including olefins and alkanes. FeCoCuAl simultaneously modified by K-Na exhibits the highest CO2 conversion and C2+ selectivity of 52.87 mol% and 89.70 mol%, respectively.

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Facet-Dependent Reactivity of Ceria Nanoparticles Exemplified by CeO2-Based Transition Metal Catalysts: A Critical Review

Catalysts ◽

10.3390/catal11040452 ◽

2021 ◽

Vol 11 (4) ◽

pp. 452

Author(s):

Michalis Konsolakis ◽

Maria Lykaki

Keyword(s):

Transition Metal ◽

Co Oxidation ◽

Critical Review ◽

Rational Design ◽

Metal Catalysts ◽

Co2 Hydrogenation ◽

Transition Metal Catalysts ◽

Fine Tuning ◽

Ceria Nanoparticles ◽

Highly Active

The rational design and fabrication of highly-active and cost-efficient catalytic materials constitutes the main research pillar in catalysis field. In this context, the fine-tuning of size and shape at the nanometer scale can exert an intense impact not only on the inherent reactivity of catalyst’s counterparts but also on their interfacial interactions; it can also opening up new horizons for the development of highly active and robust materials. The present critical review, focusing mainly on our recent advances on the topic, aims to highlight the pivotal role of shape engineering in catalysis, exemplified by noble metal-free, CeO2-based transition metal catalysts (TMs/CeO2). The underlying mechanism of facet-dependent reactivity is initially discussed. The main implications of ceria nanoparticles’ shape engineering (rods, cubes, and polyhedra) in catalysis are next discussed, on the ground of some of the most pertinent heterogeneous reactions, such as CO2 hydrogenation, CO oxidation, and N2O decomposition. It is clearly revealed that shape functionalization can remarkably affect the intrinsic features and in turn the reactivity of ceria nanoparticles. More importantly, by combining ceria nanoparticles (CeO2 NPs) of specific architecture with various transition metals (e.g., Cu, Fe, Co, and Ni) remarkably active multifunctional composites can be obtained due mainly to the synergistic metalceria interactions. From the practical point of view, novel catalyst formulations with similar or even superior reactivity to that of noble metals can be obtained by co-adjusting the shape and composition of mixed oxides, such as Cu/ceria nanorods for CO oxidation and Ni/ceria nanorods for CO2 hydrogenation. The conclusions derived could provide the design principles of earth-abundant metal oxide catalysts for various real-life environmental and energy applications.

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The Effect of Iron Impurities on Transition Metal Catalysts for the Oxygen Evolution Reaction in Alkaline Environment: Activity Mediators or Active Sites?

Catalysis Letters ◽

10.1007/s10562-020-03478-4 ◽

2020 ◽

Author(s):

Ioannis Spanos ◽

Justus Masa ◽

Aleksandar Zeradjanin ◽

Robert Schlögl

Keyword(s):

Transition Metal ◽

Oxygen Evolution ◽

Oxygen Evolution Reaction ◽

Active Sites ◽

Water Electrolysis ◽

Metal Catalysts ◽

Transition Metal Catalysts ◽

Alkaline Water Electrolysis ◽

Co Catalysts ◽

Model Transition

AbstractThere is an ongoing debate on elucidating the actual role of Fe impurities in alkaline water electrolysis, acting either as reactivity mediators or as co-catalysts through synergistic interaction with the main catalyst material. This perspective summarizes the most prominent oxygen evolution reaction (OER) mechanisms mostly for Ni-based oxides as model transition metal catalysts and highlights the effect of Fe incorporation on the catalyst surface in the form of impurities originating from the electrolyte or co-precipitated in the catalyst lattice, in modulating the OER reaction kinetics, mechanism and stability. Graphic Abstract

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