Andrzej Wieckowski

University of Illinois, Urbana-Champaign, Urbana, Illinois, United States

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Publications (150)534.87 Total impact

  • Andrzej Wieckowski · Carol Korzeniewski · Björn Braunschweig
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    ABSTRACT: Surface vibrational spectroscopy techniques probe the structure and composition of interfaces at the molecular level. Their versatility, coupled with their non-destructive nature, enables in-situ measurements of operating devices and the monitoring of interface-controlled processes under reactive conditions. Vibrational Spectroscopy at Electrified Interfaces explores new and emerging applications of Raman, infrared, and non-linear optical spectroscopy for the study of charged interfaces. The book draws from hundreds of findings reported in the literature over the past decade. It features an internationally respected team of authors and editors, all experts in the field of vibrational spectroscopy at surfaces and interfaces. Content is divided into three parts: Part One, Nonlinear Vibrational Spectroscopy, explores properties of interfacial water, ions, and biomolecules at charged dielectric, metal oxide, and electronically conductive metal catalyst surfaces. In addition to offering plenty of practical examples, the chapters present the latest measurement and instrumental techniques. Part Two, Raman Spectroscopy, sets forth highly sensitive approaches for the detection of biomolecules at solid-liquid interfaces as well as the use of photon depolarization strategies to elucidate molecular orientation at surfaces. Part Three, IRRAS Spectroscopy (including PM-IRRAS), reports on wide-ranging systems—from small fuel molecules at well-defined surfaces to macromolecular complexes—that serve as the building blocks for functional interfaces in devices designed for chemical sensing and electric power generation.
    No preview · Book · Oct 2013
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    Niancai Cheng · Robert Kutz · Christopher Kemna · Andrzej Wieckowski
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    ABSTRACT: a b s t r a c t We co-deposited cobalt porphyrins (CoP) and transition metal oxides on gold and carbon/graphene elec-trodes as catalysts for the oxygen reduction reaction (ORR). Porphyrins were adsorbed spontaneously, and the transition metal oxides (CoO x and NiO x) were deposited using spontaneous deposition tactics or an electrochemical deposition method. The electrodes were characterized in acidic media by cyclic vol-tammetry (CV), by broad-band sum frequency generation (BB-SFG) and – in vacuum – by the Auger elec-tron spectroscopy (AES). The ORR activity data indicate that the activity of cobalt porphyrin towards ORR is enhanced by co-deposited transition metal oxides. The detailed reasons for this behavior are being interrogated. Ó 2013 Elsevier B.V. All rights reserved.
    Full-text · Article · Sep 2013 · Journal of electroanalytical chemistry
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    Junhua Jiang · John Scott · Andrzej Wieckowski
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    ABSTRACT: Electrooxidation of formate on high-surface Pt black in alkaline media has been studied at varying temperature by means of cyclic voltammetry and stripping voltammetry. In the positive-going scans from 0.10 to 1.2 V vs RHE, the formate oxidation produces three oxidation current peaks: (i) peak I (at potentials where the coverages of both surface hydrogen and oxygen-species are very low), (ii) peak II (exhibiting obvious potential shift from 0.66 to 0.51 V upon increasing temperature from 20 to 80 °C), and (iii) peak III (at higher potentials where a considerable formation of surface oxygen species commences). Both peaks I and II are closely correlated but they are independent of peak III. Among the three peaks, the temperature dependence of peak II is well in agreement with that of the stripping peak of a CO adlayer. These results suggest a triple-path reaction mechanism. Adsorption of formate onto Pt surfaces may result in formation of precursor adsorbates with different reactivity. Analogous to the reported dual-path mechanism, active precursor adsorbate is responsible for (i) a direct path involving the formate oxidation to CO2 (leading to peak I), and (ii) an indirect path involving the formation of surface CO and its further oxidation to CO2 (leading to peak II). An independent third path via oxidation of less-active precursor adsorbate to CO2 with adsorbed HCOO as the most likely intermediate accounts for peak III. All the oxidation reactions involved in the triple paths are accelerated by increasing reaction temperature with different apparent activation energies. At elevated temperature, diffusion-limited oxidation currents are attained. It is suggested that both the activities of surface OH and precursor adsorbates play a major role in mediating the reaction mechanism as well as participating in the formate oxidation.
    Full-text · Article · Aug 2013 · Electrochimica Acta
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    ABSTRACT: This chapter focuses on the application of vibrational sum frequency generation (SFG) spectroscopy to study the molecular structure of electrode‐electrolyte and electrified liquid‐gas interfaces. Vibrational SFG is inherently interface specific because a second‐order process such as SFG is not allowed in the bulk of materials with inversion symmetry. The development of direct ethanol fuel cells demands an in‐depth understanding of ethanol's electrooxidation reactions. With recent advances in the practical design of alkaline fuel cells, a thorough understanding of the ethanol electrooxidation mechanism in alkaline media is now more important than ever. The chapter provides novel insights into this mechanism by examining new data on surface‐adsorbed reaction intermediates at fuel cell relevant conditions. Foams are materials of particular importance since they have a broad range of applications such as metal foams for light‐weight structures, polymer foams for thermal insulation, as well as in textured food products.
    No preview · Chapter · Jul 2013
  • Rui Lin · Chunhui Cao · Tiantian Zhao · Zhen Huang · Bing Li · Andrzej Wieckowski · Jianxin Ma
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    ABSTRACT: Co@Pt/C core–shell catalysts are synthesized by a two-step chemical reduction method followed by the heat treatment in H2 and N2 mixture. High Resolution (HR-TEM), EDX (Energy-dispersive X-ray spectroscopy) and in-situ X-ray diffraction (XRD) techniques are used to characterize the nano-structured catalysts. The results show that the core–shell structure of Co@Pt/C is formed and the average particle size is about 3 nm. From the result of the in-situ XRD, it is found that the heat treatment favors for the formation of crystalline structure and the proper particle size of catalyst. The in-situ XRD detection also helps find the optimized heat treatment temperature. The linear sweep voltammetry (LSV) result reveals that the Co@Pt (1:3)/C (reduced) catalyst exhibits the best catalytic activity toward oxygen reduction reaction (ORR). A 130 h life time test for the single cell, in which the membrane electrode assembly (MEA) using Co@Pt (1:3)/C (reduced) as the cathode catalyst, is operated to evaluate the durability. The results of the test show that the formation of the core–shell structure of Co@Pt/C catalyst is favorable to improve the stability and durability.
    No preview · Article · Feb 2013 · Journal of Power Sources
  • Cynthia Ann Rice · Andrzej Wieckowski
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    ABSTRACT: Direct liquid fuel cells for portable electronic devices are plagued by poor efficiency due to high overpotentials and accumulation of intermediates on the electrocatalyst surface. Direct formic acid fuel cells have a potential to maintain low overpotentials if the electrocatalyst is tailored to promote the direct electrooxidation pathway. Through the understanding of the structural and environmental impacts on preferential selection of the more active formic acid electrooxidation pathway, a higher performing and more stable electrocatalyst is sought. This chapter overviews the formic acid electrooxidation pathways, enhancement mechanisms, and fundamental electrochemical mechanistic studies.
    No preview · Chapter · Jan 2013
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    ABSTRACT: In 2007, the field of oxygen reduction reaction (ORR) by porphyrins was partially reviewed by Y. Kiros. The new development reported under the current review is the effect of surface state (composition) on porphyrin’s activity toward oxygen reduction in fuel cells, and the highlight of the analogue of fuel cell cathode activity and the oxygen reduction activity in nature. This field also needs a fresh look vs. its overall importance. The porphyrins themselves are moderate oxygen reduction catalysts, and their activity needs to be enhanced. In perspectives of fuel cells, the methods that are practiced and reviewed here are the use of carbon and gold support, pyrolysis and co-deposition with transition metal oxides. Reasons for the porphyrin enhancements and catalysis have been scrutinized. Although great progress has been achieved, there are still some challenges ahead (concerning the ORR mechanism on porphyrins and the activity and stability enhancement for porphyrins to meet practical applications). Therefore, exploring ORR mechanisms on porphyrin, the continuation of the characterization efforts and enhancing porphyrins catalytic performance (a paper in preparation from this group), as well achieving better catalyst durability, are major focuses for fuel cell research in the future.
    Full-text · Article · Dec 2012
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    ABSTRACT: Quantitative monitoring of water conditions in a field is a critical ability for environmental science studies. We report the design, fabrication and testing of a low cost, miniaturized and sensitive electrochemical based nitrate sensor for quantitative determination of nitrate concentrations in water samples. We have presented detailed analysis for the nitrate detection results using the miniaturized sensor. We have also demonstrated the integration of the sensor to a wireless network and carried out field water testing using the sensor. We envision that the field implementation of the wireless water sensor network will enable "smart farming" and "smart environmental monitoring".
    Full-text · Article · Nov 2012 · Journal of Environmental Monitoring
  • Junhua Jiang · Andrzej Wieckowski
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    ABSTRACT: To explore strategies for addressing the process of CO poisoning on Pt-based catalysts, CO electrooxidation on Pt-based electrodes in alkaline media has been studied by cyclic voltammetry in the intermediate temperature range of 80 to 130 °C. In this temperature range, CO spontaneously reacts with bulk hydroxide anion to generate soluble formate, which electrooxidation is apparently more facile than the CO electrooxidation. A pathway involving the formate intermediate therefore results in accelerated CO electrooxidation. The corresponding voltammetric behaviors are characteristic of: (i) low onset potentials falling within the hydrogen zone, (ii) maximized oxidation currents in the double-layer zone and (iii) the oxidation inhibition in the oxide zone. These observations are quite different from the literature results for the CO electrooxidation in low temperature alkaline media. This fact provides fundamentals for the development of novel fuel cell and hydrogen purification technologies since CO can be oxidized at very low potentials in the intermediate temperature alkaline media.
    No preview · Article · Jul 2012 · Electrochemistry Communications
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    ABSTRACT: The design of polymer electrolyte fuel cell electrocatalysts depends on two equally important fundamental principles: the optimization of electrocatalytic activities as well as the long-term stability under operating conditions (e.g., pH < 1 and E > 0.8 V). Pt-based alloys with transition metals (i.e., Pt–La) address both of these key issues. The oxygen reduction kinetics depends on the alloy composition which, in turn, is related to the d-band center position. The stability of the oxygen reduction reaction is predictable by correlation of the d-band fillings and vacancies of Pt–M (M = Ti, Fe, Zr and La).
    Full-text · Article · May 2012 · Energy & Environmental Science
  • Paul S. Bagus · Andrzej Wieckowski · Hajo Freund
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    ABSTRACT: Changes of the inter-atomic distances, described as lattice strain, make important, initial state, contributions to the shifts of core-level binding energies, ΔBE’s, of supported nano-particles as the size of the particles changes. In the present paper, we consider how the BE shifts due to lattice strain vary for the 3d, 4d, and 5d noble metals, Cu, Ag, and Au. We identify and discuss two important but cancelling mechanisms that contribute to the total BE shifts. We predict and explain why the ΔBE will be larger for 3d series metals than for those of the 4d and 5d series.
    No preview · Article · May 2012 · Computational and Theoretical Chemistry
  • J. Jiang · A. Wieckowski
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    ABSTRACT: CO electrooxidation at Pt-group catalysts in alkaline media has been first studied in the intermediate temperature range of 80 to 150°C by means of cyclic voltammetry and chronoamperometry. Accelerated CO electrooxidation reaction kinetics has been achieved in this intermediate temperature. A new pathway involving a formate intermediate formed through the reaction of CO and hydroxide has been proposed to account for the accelerated kinetics. This is quite different from the CO electrooxidation in alkaline media at low temperature which follows a Langmuir-Hinshelwood (L-H) mechanism. This accelerated CO electrooxidation reaction kinetics would provide fundamentals for the development of fuel cell and hydrogen purification technologies since CO adsorbed on the catalyst surfaces or in bulk solutions can be oxidized at very low potential in the intermediate temperature alkaline media.
    No preview · Article · Apr 2012 · ECS Transactions
  • Junhua Jiang · Andrzej Wieckowski
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    ABSTRACT: A direct formate fuel cell (DFFC) operated with a fuel of alkaline potassium formate has been studied using Pd anode and Ag cathode electrocatalysts in an intermediate temperature range of 80 to 120 °C by means of cyclic voltammetry and single cell measurements. Voltammetric studies clearly show that the kinetics of the formate electrooxidation on Pd in alkaline media is substantially increased with increasing temperature, leading to a high apparent activation energy of around 74.3 ± 6.2 kJ mol− 1. Preliminary single cell measurements show that increasing operating temperature and the formate concentration obviously increase the performance. A DFFC operated with 6 mol dm− 3 HCOOK and at 120 °C demonstrates a peak power density of around 160 mW cm− 2 over a current density range of 250 to 550 mA cm− 2 without Ohmic resistance correction. The DFFC is therefore a promising high performance, environmentally benign and low cost fuel cell technology.
    No preview · Article · Jan 2012 · Electrochemistry Communications
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    Andrzej Wieckowski · Matthew Neurock
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    ABSTRACT: The advances in spectroscopy and theory that have occurred over the past two decades begin to provide detailed in situ resolution of the molecular transformations that occur at both gas/metal as well as aqueous/metal interfaces. These advances begin to allow for a more direct comparison of heterogeneous catalysis and electrocatalysis. Such comparisons become important, as many of the current energy conversion strategies involve catalytic and electrocatalytic processes that occur at fluid/solid interfaces and display very similar characteristics. Herein, we compare and contrast a few different catalytic and electrocatalytic systems to elucidate the principles that cross-cut both areas and establish characteristic differences between the two with the hope of advancing both areas.
    Preview · Article · Nov 2011 · Advances in Physical Chemistry
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    ABSTRACT: The ethanol electrococidation reaction (EOR) on polycrystalline Pt catalysts in alkaline solution was studied for the first time with broadband sum-frequency generation (BB-SFG) spectroscopy. We find that C-C bond cleavage and CO formation occur as early as 0.05 V versus reversible hydrogen electrode (RHE), and that CO is oxidized at similar to 0.45 V, which is 0.2 V lower than in acidic media. In order to track the oxidation of singlecarbon intermediates, we have monitored the oxidation of isotopically labeled ethanol ((12)CH(3) (13)CH(2)OH). Surface-adsorbed (12)CO and (13)CO are observed and show very different potential-dependent behaviors. (13)CO molecules formed from preoxidized carbon species such as -CH(x)O, show the behavior expected from studies of CO-saturated alkaline media. (12)CO, however, which is indicative of the oxidation of methyl-like species (-CH(x)) on the catalyst surface, is observed at unusually high potentials. The strongly adsorbed -CH(x) is not oixdatively removed from the surface until the electrode potential is swept past 0.65 V.
    Full-text · Article · Sep 2011 · Journal of Physical Chemistry Letters
  • Stephanie N.S. Goubert-Renaudin · Andrzej Wieckowski
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    ABSTRACT: Unsuccessful attempts in using Ni and/or Co nanoparticles as catalysts for oxygen reduction reaction (ORR) are reported. Several synthetic approaches such as encapsulation of nanoparticles in dendrimers, coating by polyethylene glycol and surface modification by anthraquinone were carried out to isolate the nanoparticles from aqueous corrosive media and to prevent their agglomeration at very low and very high pH. In all the attempts described, negative results towards ORR were consistently obtained. On the contrary, in the case of cobalt incorporated in a polypyrrole matrix (Co–Ppy–C) a catalytic activity for oxygen reduction both in acidic and alkaline medium was observed. The data indicate that neither Ni nor Co surface sites, when not coordinated to the matrix nitrogen, are electroactive towards oxygen reduction, pointing out the crucial role of the heteroatom associated with (coordinating) transition metals in the ORR catalytic process. We believe that our data are in agreement with literature although the reported data scarcity does not make the full conclusion possible. All results were obtained at room temperature, the catalytic activity of the synthesized materials at elevated temperatures are unknown.
    No preview · Article · Mar 2011 · Journal of electroanalytical chemistry
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    ABSTRACT: Ethanol electrooxidation reaction (EOR) pathways on polycrystalline platinum were studied with broadband sum-frequency generation (BB-SFG) spectroscopy and electrochemistry in unprecedented detail and under working fuel cell conditions. We present the first observation of adsorbed acetate and co-adsorbed sulfuric acid anions with SFG and a discussion of their relation to the EOR. Surface-adsorbed intermediates such as CO on Pt atop sites and acetate are observed in both H2SO4 and HClO4 solutions. However, CO molecules on bridge sites and sulfuric acid anions are found in H2SO4 only. At E < 0.5 V vs. Ag/AgCl, CO is the predominantly adsorbed species. Increasing the potential to E > 0.5 V results in the oxidative removal of CO and the adsorption of acetate anions. Experiments with isotopically labeled ethanol (12CH313CH2OH) reveal information on the carbon–carbon bond cleavage and the subsequent CO formation. In particular, the methyl fragment (–12CHx) produces far less 12CO and suggests methyl electroreduction to methane and/or the persistence of –CHx on the Pt surface.Graphical abstractPotentiodynamic broadband sum-frequency generation and electrochemistry were used to elucidate the mechanism of ethanol electrooxidation on polycrystalline platinum in acidic electrolytes.View high quality image (50K)Research highlights► Electrocatalysis of ethanol on polycrystalline Pt surfaces. ► Reaction pathways revealed by sum-frequency generation (SFG) and electrochemistry. ► Surfaces-adsorbed intermediates include CO, acetate, and methyl fragment of ethanol produces –CHx. ► –CHx is difficult to oxidize. ► Electrolyte anions affect adsorption of intermediates CO and acetate.
    No preview · Article · Jan 2011 · Journal of Catalysis
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    ABSTRACT: The reversible adsorption of acetate on polycrystalline Au and Pt surfaces was investigated with broadband sum-frequency generation (SFG) and cyclic voltammetry. Specifically adsorbed acetate as well as coadsorbed sulfuric acid anions are observed for the first time with SFG and give rise to dramatically different SFG intensities on Au and Pt surfaces. While similar coverages of acetate adlayers on Au and Pt surfaces are well established by previous studies, an identification of the interfacial molecular structure has been elusive. However, we have applied the high sensitivity of SFG for interfacial polar ordering to identify different acetate structures at Au and Pt surfaces in contact with HClO(4) and H(2)SO(4) electrolytes. Acetate competes with the formation of surface oxides and shifts the oxidation threshold of both Au and Pt electrodes anodically. Effects of the supporting electrolyte on the formation of acetate adlayers are revealed by comparing SFG spectra in HClO(4) and H(2)SO(4) solutions: Sulfuric acid anions modify the potential-dependent acetate adsorption, compete with adsorbed acetate on Au and coadsorb with acetate on Pt surfaces.
    Full-text · Article · Dec 2010 · The Journal of Chemical Physics
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    Rachel L. Behrens · Alexei Lagutchev · Dana D. Dlott · Andrzej Wieckowski
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    ABSTRACT: Broad-band sum frequency generation spectroscopy (BB-SFG) was used to obtain vibrational spectra of CO adsorbates produced from formic acid oxidation on a Pt (1 0 0) electrode in sulfuric acid media. The BB-SFG simultaneously monitored all forms of the CO intermediates, including steady-state, as the potential was scanned at 5 mV/s. Spectra were compared to those obtained from CO adsorbed from a CO-saturated electrolyte. While adsorbed from HCOOH, the CO had a sharp atop transition near 2050 cm−1 and a broader multiply-bonded transitions in the 1700–1900 cm−1 range, which appear to result from bridge-like and higher-coordinated (possibly fourfold) CO. As the potential scanned from −0.2 to 0.3 V (vs. Ag/AgCl), the bridge-like CO disappeared, and the amount of atop CO increased. At potentials above 0.5 V, the CO was in steady-state, being oxidized on the surface to CO2 and replenished by CO from HCOOH. These measurements show that BB-SFG can observe potential-dependent interconversion of different CO forms on the electrode surface and can measure steady-state reaction intermediates on a surface in real time.
    Full-text · Article · Nov 2010 · Journal of electroanalytical chemistry
  • Andrzej Wieckowski

    No preview · Article · Nov 2010 · Journal of electroanalytical chemistry

Publication Stats

6k Citations
534.87 Total Impact Points


  • 1986-2013
    • University of Illinois, Urbana-Champaign
      • Department of Chemistry
      Urbana, Illinois, United States
  • 2008
    • Urbana University
      Urbana, Illinois, United States
  • 2001
    • University of Guelph
      • Department of Chemistry
      XIA, Ontario, Canada
  • 1988
    • Purdue University
      ウェストラファイエット, Indiana, United States
  • 1985-1987
    • University of California, Santa Barbara
      • Department of Chemistry and Biochemistry
      Santa Barbara, California, United States
  • 1985-1986
    • Laval University
      Quebec City, Quebec, Canada
  • 1974-1982
    • University of Warsaw
      • Faculty of Chemistry
      Warszawa, Masovian Voivodeship, Poland