Dario Stacchiola

Brookhaven National Laboratory, New York City, New York, United States

Are you Dario Stacchiola?

Claim your profile

Publications (108)514.06 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: doi: 10.1021/jp507966v
    The Journal of Physical Chemistry C 10/2014; · 4.84 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The transformation of CO2 into alcohols or other hydrocarbon compounds is challenging because of the difficulties associated with the chemical activation of CO2 by heterogeneous catalysts. Pure metals and bimetallic systems used for this task usually have low catalytic activity. Here we present experimental and theoretical evidence for a completely different type of site for CO2 activation: a copper-ceria interface that is highly efficient for the synthesis of methanol. The combination of metal and oxide sites in the copper-ceria interface affords complementary chemical properties that lead to special reaction pathways for the CO2→CH3OH conversion.
    Science 08/2014; 345(6196):546-50. · 31.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Understanding the mechanisms governing chemical and morphological changes induced by an ambient-pressure gas and how such changes influence the activity of heterogeneous catalysts is central to the formation of a predictive capability for structure–reactivity relationships. With techniques such as ambient-pressure photoelectron spectroscopy, scanning tunneling microscopy, and surface X-ray diffraction, active phases and reaction intermediates can be probed in situ on relevant samples to form a comprehensive picture of this dynamic interplay between gases and surfaces. Of particular interest is the interaction of oxygen and carbon monoxide with catalysts. We will describe how model systems of increased complexity can be used to investigate gas-mediated mass transfer processes that may occur even at relatively modest temperatures. Furthermore, we will discuss how the morphology may be tailored to study specific contributions from defect sites and charge transfer to catalytic activity.
    The Chemical Record 08/2014; · 4.38 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Abstract Formate species have been proposed to be either critical intermediates or spectators in the water–gas shift (WGS) and methanol synthesis processes. CeOx–CuyO/Cu(1 1 1) has been shown to be a very active inverse catalyst for the WGS reaction. We present here the study of formate species obtained from the deprotonation of formic acid (HCOOH) on the inverse catalysts. Exposure of CeOx–CuyO/Cu(1 1 1) to HCOOH at 300 K leads to the formation of formates on both ceria and Cu sites. The formates isolated on CeOx–CuyO/Cu(1 1 1) systems cannot be hydrogenated even at a pressure of 200 Torr H2 at 300–350 K. The formate species localized on ceria sites are thermally more stable than those on Cu sites, and the thermal decomposition of all of the formates occurs by dehydrogenation releasing CO2 and H2. Evidence of reverse spillover of formates from the oxide to the metal was observed on CeO2−x/Cu(1 1 1) inverse catalysts.
    Catalysis Today 07/2014; · 3.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The reducibility of metal oxides is of great importance to their catalytic behavior. Herein, we combined ambient-pressure scanning tunneling microscopy (AP–STM), X-ray photoemission spectroscopy (AP–XPS), and DFT calculations to study the CO titration of CuxO thin films supported on Cu(1 1 1) (CuxO/Cu(1 1 1)) aiming to gain a better understanding of the roles that the Cu(1 1 1) support and surface defects play in tuning catalytic performances. Different conformations have been observed during the reduction, namely, the 44 structure and a recently identified (5–7–7–5) Stone–Wales defects (5–7 structure). The DFT calculations revealed that the Cu(1 1 1) support is important to the reducibility of supported CuxO thin films. Compared with the case for the Cu2O(1 1 1) bulk surface, at the initial stage CO titration is less favorable on both the 44 and 5–7 structures. The strong CuxOCu interaction accompanied with the charge transfer from Cu to CuxO is able to stabilize the oxide film and hinder the removal of O. However, with the formation of more oxygen vacancies, the binding between CuxO and Cu(1 1 1) is weakened and the oxide film is destabilized, and Cu2O(1 1 1) is likely to become the most stable system under the reaction conditions. In addition, the surface defects also play an essential role. With the proceeding of the CO titration reaction, the 5–7 structure displays the highest activity among all three systems. Stone–Wales defects on the surface of the 5–7 structure exhibit a large difference from the 44 structure and Cu2O(1 1 1) in CO binding energy, stability of lattice oxygen, and, therefore, the reduction activity. The DFT results agree well with the experimental measurements, demonstrating that by adopting the unique conformation, the 5–7 structure is the active phase of CuxO, which is able to facilitate the redox reaction and the Cu2O/Cu(1 1 1)Cu transition.
    ChemCatChem 06/2014; · 5.18 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Reducible oxides have been shown to greatly improve the activity of water gas shift (WGS) catalysts. The precise mechanism for this effect is a matter of intense debate, but the dissociation of water is generally considered to be the key step in the reaction. We present here a study of the water activation on oxygen vacancies at the support as part of the mechanism of the WGS reaction on Pt supported on pure and gallium-doped ceria. Doping the ceria with gallium allows tuning the vacancies in the support while maintaining constant the metal dispersion. An inverse relationship was found between the catalytic activity to WGS and the amount of oxygen vacancies. In situ time-resolved X-ray diffraction, mass spectrometry, and diffuse reflectance infrared spectroscopy (DRIFT) showed that the oxygen vacancy filling by water is always fast in either Pt/CeO2 or Pt/CeGa. DFT calculation provides molecular insights to understand the pathway of water reaction with vacancies at the metal–oxide interface sites. Our results suggest that the activation of the water molecule in the WGS mechanism is not the rate-limiting step in these systems. Concentration-modulation spectroscopy in DRIFT mode under WGS reaction conditions allows the selective detection of key reaction intermediates, a monodentate formate (HCOO) and carboxylate (CO2δ−) species, which suggests the prevalence of a carboxyl (HOCO) mechanism activated at the oxide–metal interface of the catalyst.
    ACS Catalysis 05/2014; 4(6):2088–2096. · 5.27 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: doi: 10.1021/cs500148e
    ACS Catalysis 04/2014; · 5.27 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The oxidation of CO is the archetypal heterogeneous catalytic reaction and plays a central role in the advancement of fundamental studies, the control of automobile emissions, and industrial oxidation reactions. Copper-based catalysts were the first catalysts that were reported to enable the oxidation of CO at room temperature, but a lack of stability at the elevated reaction temperatures that are used in automobile catalytic converters, in particular the loss of the most reactive Cu+ cations, leads to their deactivation. Using a combined experimental and theoretical approach, it is shown how the incorporation of titanium cations in a Cu2O film leads to the formation of a stable mixed-metal oxide with a Cu+ terminated surface that is highly active for CO oxidation.
    Angewandte Chemie 04/2014;
  • [Show abstract] [Hide abstract]
    ABSTRACT: The oxidation of CO is the archetypal heterogeneous catalytic reaction and plays a central role in the advancement of fundamental studies, the control of automobile emissions, and industrial oxidation reactions. Copper-based catalysts were the first catalysts that were reported to enable the oxidation of CO at room temperature, but a lack of stability at the elevated reaction temperatures that are used in automobile catalytic converters, in particular the loss of the most reactive Cu+ cations, leads to their deactivation. Using a combined experimental and theoretical approach, it is shown how the incorporation of titanium cations in a Cu2O film leads to the formation of a stable mixed-metal oxide with a Cu+ terminated surface that is highly active for CO oxidation.
    Angewandte Chemie International Edition 04/2014; · 11.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The activation of gold in catalytic reactions has been the subject of intensive research that has led to the transformation of one of the least chemically reactive elements to a catalyst with excellent activity and selectivity. Scientists have performed numerous systematic experimental and theoretical studies using model systems, which have explained the role of Au in chemical reactions with progressively increasing degrees of structural and chemical complexity. We present an overview of recent studies of model Au(111), CeOx/Au(111), and Au/CeOx/TiO2(110) surfaces that use Au in different structural configurations specifically for the water-gas shift reaction (WGS, CO + H2O → CO2 + H2), an important industrial process for the purification of CO. We demonstrate the significance of key structural components of the Au-based supported catalysts such as the metal-oxide interface (Au-Ox) toward the WGS catalytic activity, a "structure-activity" relationship. In the WGS reaction, Au(111) or Au nanoparticles have poor catalytic performance due to their inability to activate one of the most important steps of the reaction, the breaking of O-H bonds in the dissociation of water (H2O → OH + H). The relatively large energetic barrier can be overcome by using O on Au(111) to facilitate the formation of OH at low temperatures, with eventual CO2 and H2 production upon reaction between CO and the adsorbed OH. However, the inability to replace the reacted O prevents a sustainable catalytic process from occurring on Au(111). The addition of a small concentration of CeOx nanoparticles on top of the Au(111) surface facilitates this rate-determining step and easily continues the catalytic cycle in the production of H2. We have discovered that CeOx nanoparticles in contact with Au(111) are rich in Ce(3+). They also have a distinct metal-oxide interface, which sustains excellent activity for the WGS reaction via the formation of a unique carboxylate intermediate, making CeOx/Au(111) more active than Cu/ZnO(0001̅), Cu(100), and Cu(111) which are the typical catalysts for this reaction. Taking this knowledge one step further, bringing these components (oxide and metal nanoparticles) together over a second oxide in Au/CeOx/TiO2 produces a system with unique morphological and electronic properties. The result is a superior catalyst for the WGS reaction, both as a model system (Au/CeOx/TiO2(110)) and as powder material (Au/CeOx/TiO2(anatase)) optimized directly in a series of systematic investigations.
    Accounts of Chemical Research 11/2013; · 20.83 Impact Factor
  • 224th ECS Meeting; 10/2013
  • [Show abstract] [Hide abstract]
    ABSTRACT: Active catalytic sites have traditionally been analyzed based on static representations of surface structures and characterization of materials before or after reactions. We show here by a combination of in situ microscopy and spectroscopy techniques that in the presence of reactants, an oxide catalyst's chemical state and morphology are dynamically modified. The reduction of Cu2O films is studied under ambient pressures (AP) of CO. The use of complementary techniques allow us to identify intermediate surface oxide phases and determine how reaction fronts propagate across the surface by massive mass transfer of Cu atoms released during the reduction of the oxide phase in the presence of CO. High resolution in situ imaging by AP scanning tunneling microscopy (AP-STM) shows that the reduction of the oxide films is initiated at defects both on step edges and the center of oxide terraces.
    Journal of the American Chemical Society 10/2013; · 10.68 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Ceria based catalysts show remarkable activity for CO conversion reactions such as CO oxidation and the water-gas shift reaction. The identification of adsorption sites on the catalyst surfaces is essential to understand the reaction mechanisms of these reactions, but the complexity of heterogeneous powder catalysts and the propensity of ceria to easily change oxidation states in the presence of small concentrations of either oxidizing or reducing agents make the process difficult. In this study, the adsorption of CO on CuOx/Cu(111) and CeOx/Cu(111) systems has been studied using infrared reflection absorption spectroscopy (IRRAS), X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations. IR peaks for the adsorbed CO on O/Cu(111) with only chemisorbed oxygen, well-ordered Cu2O/Cu(111) and disordered copper oxide [CuOx/Cu(111)] were observed at 2070-2072, 2097-2098 and 2101-2111 cm(-1), respectively. On CeOx/Cu(111) systems CO chemisorbs at 90 K only on Cu sites under ultra-high vacuum (UHV) conditions, whereas at elevated CO pressures and low temperatures adsorption of CO on Ce(3+) is observed, with a corresponding IR peak at 2162 cm(-1). These experimental results are further supported by DFT calculations, and help to unequivocally distinguish the presence of Ce(3+) cations on catalyst samples by using CO as a probe molecule.
    Physical Chemistry Chemical Physics 08/2013; · 4.20 Impact Factor
  • ChemInform 08/2013; 44(33).
  • Hui Wang, Kai Sun, Franklin Tao, Dario J Stacchiola, Yun Hang Hu
    [Show abstract] [Hide abstract]
    ABSTRACT: A useful Li: A simple reaction between Li2 O and CO, gives a new type of three-dimensional graphene sheets-honeycomb structured graphene. A dye-sensitized solar cell (DSSC) with the new graphene counter electrode has an energy conversion efficiency as high as 7.8 %, which is comparable to that of DSSCs with an expensive Pt counter electrode.
    Angewandte Chemie International Edition 07/2013; · 11.34 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The interaction of atomic hydrogen with the Cu(111) surface was studied by a combined experimental-theoretical approach, using infrared reflection absorption spectroscopy, temperature programmed desorption, and density functional theory (DFT). Adsorption of atomic hydrogen at 160 K is characterized by an anti-absorption mode at 754 cm(-1) and a broadband absorption in the IRRA spectra, related to adsorption of hydrogen on three-fold hollow surface sites and sub-surface sites, and the appearance of a sharp vibrational band at 1151 cm(-1) at high coverage, which is also associated with hydrogen adsorption on the surface. Annealing the hydrogen covered surface up to 200 K results in the disappearance of this vibrational band. Thermal desorption is characterized by a single feature at ∼295 K, with the leading edge at ∼250 K. The disappearance of the sharp Cu-H vibrational band suggests that with increasing temperature the surface hydrogen migrates to sub-surface sites prior to desorption from the surface. The presence of sub-surface hydrogen after annealing to 200 K is further demonstrated by using CO as a surface probe. Changes in the Cu-H vibration intensity are observed when cooling the adsorbed hydrogen at 180 K to 110 K, implying the migration of hydrogen. DFT calculations show that the most stable position for hydrogen adsorption on Cu(111) is on hollow surface sites, but that hydrogen can be trapped in the second sub-surface layer.
    The Journal of Chemical Physics 07/2013; 139(4):044712. · 3.12 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Formic acid (HCOOH) deprotonates on the open surfaces of Cu(110) and Cu(100) when exposed at 300 K. However, this does not occur on the close-packed surface of clean Cu(111). In this study, we show that the deprotonation of formic acid on atomically flat Cu(111) surfaces can be induced by pre-adsorbing polymeric formic acid clusters at low temperatures, and then annealing the system to break the acidic O-H bond of HCOOH adsorbed on the edges of the polymeric clusters. The thermal activation of HCOOH to bidentate formate was studied using a combination of infrared reflection absorption spectroscopy, scanning tunneling microscopy, X-ray photoelectron spectroscopy, and near edge X-ray absorption fine structure spectroscopy. Extended 1D formate structures self-assemble due to a templating effect introduced by the formation of long α-polymeric formic acid chains commensurate with the substrate.
    Physical Chemistry Chemical Physics 06/2013; · 4.20 Impact Factor
  • Kumudu Mudiyanselage, Wei An, Fan Yang, Ping Liu, Darío J Stacchiola
    [Show abstract] [Hide abstract]
    ABSTRACT: In this study the identity of diverse adsorption sites on a 5-7 Cu2O/Cu(111) surface oxide structure has been identified. The 5-7 membered rings formed by a topological defect on stoichiometric Cu2O present different electronic structures from the originating hexagonal rings, as shown by combined bias dependent scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. The adsorption of CO as a probe molecule on the 5-7 structure, studied using infrared reflection-absorption spectroscopy (IRRAS), shows the existence of special adsorption sites. By combining experimental and theoretical results, it is determined that CO molecules can be selectively confined inside the 7-membered oxide rings with internal dimensions of ∼0.85 nm, leading to a marked different adsorbate-substrate interaction than in either clean Cu(111) or Cu2O. The implication of these newly discovered sites on the chemistry of copper for catalytic reactions is discussed.
    Physical Chemistry Chemical Physics 05/2013; · 4.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this perspective article, we show how a series of in situ techniques {X-ray diffraction (XRD), pair-distribution-function analysis (PDF), X-ray absorption fine structure (XAFS), environmental transmission electron microscopy (ETEM), infrared spectroscopy (IR), ambient-pressure X-ray photoelectron spectroscopy (AP-XPS)} can be combined to perform detailed studies of the structural, electronic and chemical properties of metal oxide catalysts used for the production of hydrogen through the water-gas shift reaction (WGS, CO + H2O → H2 + CO2). Under reaction conditions most WGS catalysts undergo chemical transformations that drastically modify their composition with respect to that obtained during the synthesis process. Experiments of time-resolved in situ XRD, XAFS, and PDF indicate that the active phase of catalysts which combine Cu, Au or Pt with oxides such as ZnO, CeO2, TiO2, CeOx/TiO2 and Fe2O3 essentially involves nanoparticles of the reduced noble metals. The oxide support undergoes partial reduction and is not a simple spectator, facilitating the dissociation of water and in some cases modifying the chemical properties of the supported metal. Therefore, to optimize the performance of these catalysts one must take into consideration the properties of the metal and oxide phases. IR and AP-XPS have been used to study the reaction mechanism for the WGS on metal oxide catalysts. Data of IR spectroscopy indicate that formate species are not necessarily involved in the main reaction path for the water-gas shift on Cu-, Au- and Pt-based catalysts. Thus, a pure redox mechanism or associative mechanisms that involve either carbonate-like (CO3, HCO3) or carboxyl (HOCO) species should be considered. In the last two decades, there have been tremendous advances in our ability to study catalytic materials under reaction conditions and we are moving towards the major goal of fully understanding how the active sites for the production of hydrogen through the WGS actually work.
    Physical Chemistry Chemical Physics 05/2013; · 4.20 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: doi: 10.1021/jp4015367
    The Journal of Physical Chemistry C 05/2013; 117(21):11149–11158. · 4.84 Impact Factor

Publication Stats

545 Citations
514.06 Total Impact Points

Institutions

  • 2010–2014
    • Brookhaven National Laboratory
      • Chemistry Department
      New York City, New York, United States
  • 2009–2010
    • Michigan Technological University
      • Department of Chemistry
      Houghton, Michigan, United States
  • 1999–2010
    • University of Wisconsin - Milwaukee
      • Department of Chemistry and Biochemistry
      Milwaukee, WI, United States
  • 2006–2009
    • Fritz Haber Institute of the Max Planck Society
      • Department of Physical Chemistry
      Berlin, Land Berlin, Germany
  • 2008
    • Humboldt-Universität zu Berlin
      • Department of Chemistry
      Berlin, Land Berlin, Germany
  • 2006–2008
    • Max Planck Society
      München, Bavaria, Germany
  • 2000
    • Universidad Nacional de San Luis
      • Department of Physics
      San Luis, Provincia de San Luis, Argentina