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Articles >>
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Catalysts by Design for Syngas Cleanup

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Quantitative Relationship between Support Porosity and the Stability of Pore-Confined Metal Nanoparticles Studied on CuZnO/SiO2 Methanol Synthesis Catalysts

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Millifluidics for Time-resolved Mapping of the Growth of Gold Nanostructures

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Geometric optimization of liquid-liquid slug flow in a flow-focusing millifluidic device for synthesis of nanomaterials


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An article about EFRC Research featured on Materials360 Online: "Catalyst Durability Improved by Maximizing Metal Separation" by Tim Palucka


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Selectivity of CO2 reduction on copper electrodes: The role of the kinetics of elementary steps


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Towards stable catalysts by controlling collective properties of supported metal nanoparticles


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Artificial Evolution Helps Catalyst Discovery


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Structure and Mobility of Metal Clusters in MOFs: Au, Pd, and AuPd Clusters in MOF-74

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Iron Oxide Pins Gold Atoms In Place

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Developing a Millifluidic Platform for the Synthesis of Ultrasmall Nanoclusters: Ultrasmall Copper Nanoclusters as a Case Study

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Ultrasmall Nanocluster Fabrication With A Millifluidic Chip

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Synthesis, characterization, and testing of supported Au catalysts prepared from atomically-tailored Au38(SC12H25)24 clusters

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Methods for Computing Accurate Atomic Spin Moments for Collinear and Noncollinear Magnetism in Periodic and Nonperiodic Materials

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Rust Splits Water!

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Catalysts for Green Energy

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Articles
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Our team members serve on the Editorial Board of the Nationwide EFRC Newsletter.

space control Dr. Gareth Parkinson

Institute of Applied Physics,
Vienna University of Technology
E-mail: gareth.parkinson@tuwien.ac.at
  space control Dr. Sanchita Biswas

Center for Advanced Microstructures and Devices, Louisiana State Univeristy
E-mail: sbiswas@lsu.edu
             
space control Dr. Gonzalo Prieto

Debye Institute for Nanomaterials Science, Utrecht University
E-mail: G.PrietoGonzalez@uu.nl
       

Please contact them to discuss any potential newsletter items.

Link to EFRC Newsletter    

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  Jan 2012   Feb 2012   Mar 2012   Feb 2013  


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July 2014

Catalysts by Design for Syngas Cleanup

A cheap and recyclable solution to remove sulfur and tars from biofuels. This research was supported by the Center for Atomic-Level Catalyst Design, an Energy Frontier Research Center funded by the U.S. Department of Energy Office of Science's Office of Basic Energy Sciences.

Read more in EFRC Newsletter


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Feburary 2014

Quantitative Relationship between Support Porosity and the Stability of Pore-Confined Metal Nanoparticles Studied on CuZnO/SiO2 Methanol Synthesis Catalysts

Metal nanoparticle growth represents a major deactivation mechanism of supported catalysts and other functional nanomaterials, particularly those based on low melting-point metals. Here we investigate the impact of the support porous structure on the stability of CuZnO/SiO2 model methanol synthesis catalysts. A series of silica materials with ordered cagelike (SBA-16 mesostructure) and disordered (SiO2-gel) porosities and varying pore sizes were employed as catalyst supports. Nitric oxide moderated nitrate decomposition enabled the synthesis of catalytically active Cu nanoparticles (3-5 nm) exclusively inside the silica pores with short interparticle spacings. Under relevant reactive conditions, confinement of the Cu particles in cagelike silica pores notably enhances catalyst stability by limiting Cu particle growth as compared to catalysts deposited in SiO2-gel host materials with also 3D and highly interconnected though unconstrained porosity. For both pore morphologies, we find a direct relationship between catalyst stability and support porosity, provided the narrowest characteristic pore dimension is employed as a porosity descriptor. For cagelike porosities this corresponds to the size of the entrances to the nanocages. Our results point to nanoparticle diffusion and coalescence as a relevant growth mechanism under reactive conditions and underscore the significance of the narrowest pore constrictions to mitigate growth and improve catalyst stability. This finding contributes to the establishment of general and quantitative structure-stability relationships which are essential for the design of catalysts and related functional nanostructures with long lifetimes under operation conditions.

See Gonzalo Prieto , Mozaffar Shakeri , Krijn P. de Jong & Petra E. de Jongh

Article first published online: 10 Feb 2014
DOI: 0.1021/nn406119j

Read more in EFRC Newsletter



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April 2013

Quantitative Relationship between Support Porosity and the Stability of Pore-Confined Metal Nanoparticles Studied on CuZnO/SiO2 Methanol Synthesis Catalysts
Recent work by the EFRC group at the Utrecht University has appeared in Nature Materials. Supported metal nanoparticles play a pivotal role in areas such as nanoelectronics, energy storage and conversion, and catalysis, but their tendency to grow into larger crystallites is an issue for their stable performance. A strategy based on controlling not only size and composition but also the location of the metal nanoparticles, now reveals the impact of their three-dimensional nanospatial distribution on their catalytic stability.

See Gonzalo Prieto, Jovana Zecevic, Heiner Friedrich, Krijn P. de Jong & Petra E. de Jongh.
Article first published online: 11 Nov 2012 DOI:10.1038/nmat3471

Read more in EFRC Newsletter

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June 2013

CALCD research work finds mention in C&EN news: "CO Induces Clustering Of Metal Atoms" by Mitch Jacoby
To get the most out of particulate precious-metal catalysts, catalyst manufacturers strive to disperse the metal as finely as possible. The aim is to maximize the fraction of exposed atoms because atoms buried in a particle's interior are inaccessible to reactants and therefore uninvolved in catalysis. Some reaction processes thwart that aim, causing catalyst particles to coalesce, which deactivates them. Gareth S. Parkinson, Ulrike Diebold, and coworkers at Vienna University of Technology have uncovered the mechanism of one such process-and found a way to stop it. By using scanning tunneling microscopy to track individual palladium atoms on Fe3O4, a model catalyst system, the team finds that the presence of just a small amount of CO, which is common to many catalytic processes, causes otherwise stationary Pd atoms to form highly mobile Pd-CO species. As the Pd-CO species grow in number, they nucleate and form small Pd clusters that diffuse, coalesce, and grow into nanoparticles. The team also finds that surface OH groups impede this detrimental process (Nat. Mater. 2013, DOI: 10.1038/nmat3667). A surface hydroxyl coating could significantly improve catalyst stability, they suggest.

(Article By Mitch Jacoby)


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March 2013

Millifluidics for Time-resolved Mapping of the Growth of Gold Nanostructures

Innovative in situ characterization tools are essential in understanding the reaction mechanisms leading to the growth of nanoscale materials. Though techniques such as in situ transmission X - ray microscopy, fast single-particle spectroscopy, small-angle X-ray scattering etc. are currently being developed, these tools are complex, not easily access ible, and do not necessarily provide the temporal resolution required to follow the formation of these particles in realtime. Here, we demonstrate for the first time the utility of a simple millifluidic chip for an in situ real time analysis of morphology and dimension-controlled growth of gold nano- and micro-structures with a time resolution of 5 ms. The structures formed were characterized using synchrotron radiation based in situ X-ray absorption spectroscopy, 3-D X-ray tomography and high resolution electron microscopy. These gold nanostructures were found to be catalytically active for conversion of 4-nitrophenol into 4-aminophenol, providing an example of the potential opportunities for time resolved analysis of catalytic reactions. While the investigations reported here are focused on gold nanostructures, the technique can be applied to analyze the time-resolved growth of other types of nanostructured metals and metal-oxides. With the ability to probe at least a tenfold higher concentrations, in comparison with traditional microfluidics, the tool has potential to revolutionize a broad range of fields from catalysis, molecular analysis, biodefense, and molecular biology.

See Katla Sai Krishna, Chelliah V. Navin, Sanchita Biswas, Varshni Singh, Kyungmin Ham, G. Lisa Bovenkamp, Chandra S. Theegala, Jeffery T Miller, James J. Spivey, Challa S. S. R. Kumar

Article first published online: 15 Mar 2013
DOI:10.1021/ja400434c Click here to view full article



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February 2013

Geometric optimization of liquid - liquid slug flow in a flow-focusing millifluidic device for synthesis of nanomaterials

With recent increasing trend towards development of "easy to fabricate" and simple millifluidic systems that could provide required control as well as high throughput, we present here a demonstration of potential opportunities for controlled droplet/slug formation within a flow-focusing millifluidic chip. Numerical simulations supported by experimental evidence show that the millifluidic device provides similar control in slug formation as in the case of microfluidic devices. More specifically, our investigations reveal that the acquired slug volume depends on the squeezing volume (Vsqueeze) and blockage volume (Vblock) in the squeezing regime. While the squeezing volume (Vsqueeze) can be tuned by manipulating the flow rate of the continuous phase, the blockage volume (Vblock) depended only on the geometry of the focusing region. Based on numerical simulations, two millifluidic flow focusing channel designs to produce small slugs were suggested. The slugs were utilized for the synthesis of uniform copper nanoparticles. The findings are anticipated to have implications for a number fields ranging from fluid dynamics, lab-on-a-chip devices, chemical engineering, nanomaterials synthesis, protein crystallization to advanced drug delivery as well as chip fabrication.
See Yuehao Li, Dawit G. Yamane, Shuning Li, Sanchita Biswas, Rupesh K. Reddy, Jost S. Goettert, Krishnaswamy Nandakumar, Challa S.S.R. Kumar
Chemical Engineering Journal, Volume 217, Pages 447-459. Article first published online: 1 Feb 2013
DOI: 10.1016/j.cej.2012.11.111
Click here to view full article


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February 2013

An article about EFRC Research featured on Materials360 Online: "Catalyst Durability Improved by Maximizing Metal Separation" by Tim Palucka
The research work by Petra E. de Jongh and her colleagues at Utrecht University and Eindhoven University in the Netherlands is now featured on Materials360 Online (www.materials360online.com). The work was first published online in the journal Nature Materials (November 2012) under the title "Towards stable catalysts by controlling collective properties of supported metal nanoparticles", authored by Gonzalo Prieto, Jovana Zecevic, Heiner Friedrich, Krijn P. de Jong & Petra E. de Jongh. The work is largely supported as part of the Center for Atomic-Level Catalyst Design, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001058. Read More

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January 2013

Selectivity of CO2 reduction on copper electrodes: The role of the kinetics of elementary steps

The work by the EFRC group has appeared in Angewandte Chemie. Based on DFT calculations of the elementary activation barriers that incorporate the role of water solvation, a new path that leads to methane and ethylene for CO2 electroreduction on Cu(111) has been identified. Instead of proceeding through a CHO intermediate (which leads to methanol), methane formation goes through an alternative path proceeding via reduction of CO to COH, which eventually leads to CHx species that can produce both methane and ethylene as observed experimentally.

See Xiaowa Nie, Monica R. Esopi, Michael J. Janik, and Aravind Asthagiri.

Article first published online: 23 Jan 2013
DOI: 10.1002/anie.201208320 Click here to view full article



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November 2012

Towards stable catalysts by controlling collective properties of supported metal nanoparticles
Recent work by the EFRC group at the Utrecht University has appeared in Nature Materials. Supported metal nanoparticles play a pivotal role in areas such as nanoelectronics, energy storage and conversion, and catalysis, but their tendency to grow into larger crystallites is an issue for their stable performance. A strategy based on controlling not only size and composition but also the location of the metal nanoparticles, now reveals the impact of their three-dimensional nanospatial distribution on their catalytic stability.
See Gonzalo Prieto, Jovana Zecevic, Heiner Friedrich, Krijn P. de Jong & Petra E. de Jongh.
Article first published online: 11 Nov 2012 DOI:10.1038/nmat3471
Read more in EFRC Newsletter

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October 2012

Artificial Evolution Helps Catalyst Discovery

Genetic algorithm enables reliable modeling of catalytic metal clusters in a porous framework and sets the grounds for purpose design with atomic precision - Dr. Gonzalo Prieto


Taking the Guesswork out of Catalyst Design


Genetic algorithms allow modeling confined clusters that drive reactions



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August 2012

Structure and Mobility of Metal Clusters in MOFs: Au, Pd, and AuPd Clusters in MOF-74

Metal-organic frameworks, known as MOFs, are widely used in catalytic reactions to control the atomic-level structures of metal clusters by confining them within ultra-high surface area nanoporous crystals. Several experimental groups have reported incorporation of metal nanoclusters inside MOFs. However, David Sholl and collaborators at Georgia Tech now show for the first time that the structure and mobility of Au-, Pd-, and AuPd metal nanoclusters in MOFs can be reliably be predicted theoretically. Using combine density functional theory (DFT) calculations with a genetic algorithm (GA) to reliably predict the structure of the adsorbed clusters, they are able to compare hundreds of adsorbed configurations for each cluster. (Paper now published: Vilhelmsen et al., J. Am. Chem. Soc. 134 (2012) 12807).


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June 2012

Iron Oxide Pins Gold Atoms In Place

Recent work by the EFRC group at the Technical University of Vienna has been highlighted by C&E News. It shows how gold atoms can be stabilized on an iron oxide surface up to 400 °C, far higher temperatures than previously reported. Read more

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March 2012

Developing a Millifluidic Platform for the Synthesis of Ultrasmall Nanoclusters: Ultrasmall Copper Nanoclusters as a Case Study

The future of lab-on-a-chip devices for the synthesis of nanomaterials hinges on the successful development of high-throughput methods with better control over their size. While significant effort in this direction mainly focuses on developing "difficult to fabricate" complex microfluidic reactors, scant attention has been paid to the "easy to fabricate" and simple millifluidic systems that could provide the required control as well as high throughput. By utilizing numerical simulation of fluids within the millifluidic space at different flow rates, the results presented here show velocity profiles and residence time distributions similar to the case of microfluidics. By significantly reducing the residence time and residence time distribution, a continuous flow synthesis of ultrasmall copper nanoclusters (UCNCs) with exceptional colloidal stability is achieved. In-situ synchrotron-radiation-based X-ray absorption spectroscopy (XAS) reveal that the as-prepared clusters are about 1 nm, which is further supported by transmission electron microscopy and UV-vis spectroscopy studies. The clusters reported here are the smallest ever produced using a lab-on-a-chip platform. When supported on silica, they are found to efficiently catalyze C-H oxidation reactions, hitherto unknown to be catalyzed by Cu. This work suggests that a millifluidic platform can be an inexpensive, versatile, easy-to-use, and powerful tool for nanoparticle synthesis in general, and more specifically for ultrasmall nanoclusters (UNCs).
See Sanchita Biswas, Jeffrey T. Miller, Yuehao Li, Krishnaswamy Nandakumar, Challa S. S. R. Kumar, Article first published online: 6 Mar 2012
DOI: 10.1002/smll.201290031 Click here to view full article


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Feburary 2012

Ultrasmall Nanocluster Fabrication With A Millifluidic Chip

"We are trying to bridge the current gap between exotic microfluidic reactors and well-established flask reactors for controlled synthesis of nanomaterials" , Dr. Challa Kumar

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Feburary 2012

Synthesis, characterization, and testing of supported Au catalysts prepared from atomically-tailored Au38(SC12H25)24 clusters

This cover (on right) shows how Au38 clusters are prepared in solution (lower left), supported on TiO2 (upper left), and treated to remove the thiol ligands that are necessary for the synthesis process (upper right). The image on the front cover describes work supported as part of the Center for Atomic Level Catalyst Design, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences under Award Number DE-SC0001058.
For the full article, see S. Gaur et al. Phys. Chem. Chem. Phys., 2012, 14, 1627-1634. Click here to view full article


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January 2012

Methods for Computing Accurate Atomic Spin Moments for Collinear and Noncollinear Magnetism in Periodic and Nonperiodic Materials

The cover (on right) shows the spin orbit coupling potential energy surface for the single molecule magnet Fe4C40H52N4O12 which exhibits noncollinear magnetism. Center: Relative energies are shown in color for 60 global rotations of the spin magnetization density. The computed magnetic anisotropy barrier of 2.9 meV is in good agreement with the 2.4 meV published experimental value. Border: Atomic spin moments are shown as vectors superimposed on the molecular structure. Only moments for Fe atoms (orange) are large enough to be visible.
See Manz, T. A.; Scholl, D. S. J. Chem. Theory Comput. 2011, 7, 4146-4164.


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January 2012

Rust Splits Water!

Understanding water splitting on an iron oxide surface opens the door to a new line of research in hydrogen production
- Dr. Sanchita Biswas

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April 2010

"Catalysts for Green Energy", Chemistry World