Publications
136 results found
Nitopi S, Bertheussen E, Scott SB, et al., 2019, Progress and Perspectives of Electrochemical CO2 Reduction on Copper in Aqueous Electrolyte, CHEMICAL REVIEWS, Vol: 119, Pages: 7610-7672, ISSN: 0009-2665
Chan AK, Tatara R, Feng S, et al., 2019, Concentrated Electrolytes for Enhanced Stability of Al-Alloy Negative Electrodes in Li-Ion Batteries, JOURNAL OF THE ELECTROCHEMICAL SOCIETY, Vol: 166, Pages: A1867-A1874, ISSN: 0013-4651
Mezzavilla S, Horch S, Stephens IEL, et al., 2019, Structure Sensitivity in the Electrocatalytic Reduction of CO2 with Gold Catalysts., Angew Chem Int Ed Engl
An understanding of the influence of structural surface features on electrocatalytic reactions is vital for the development of efficient nanostructured catalysts. Gold is the most active and selective known electrocatalyst for the reduction of CO2 to CO in aqueous electrolytes. Numerous strategies have been proposed to improve its intrinsic activity. Nonetheless, the atomistic knowledge of the nature of the active sites remains elusive. We systematically investigated the structure sensitivity of Au single crystals for electrocatalytic CO2 reduction. Reaction kinetics for the formation of CO are strongly dependent on the surface structure. Under-coordinated sites, such as those present in Au(110) and at the steps of Au(211), show at least 20-fold higher activity than more coordinated configurations (for example, Au(100)). By selectively poisoning under-coordinated sites with Pb, we have confirmed that these are the active sites for CO2 reduction.
Mezzavilla S, Horch S, Stephens IEL, et al., 2019, Structure Sensitivity in the Electrocatalytic Reduction of CO<sub>2</sub> with Gold Catalysts, Angewandte Chemie, Vol: 131, Pages: 3814-3818, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>An understanding of the influence of structural surface features on electrocatalytic reactions is vital for the development of efficient nanostructured catalysts. Gold is the most active and selective known electrocatalyst for the reduction of CO<jats:sub>2</jats:sub> to CO in aqueous electrolytes. Numerous strategies have been proposed to improve its intrinsic activity. Nonetheless, the atomistic knowledge of the nature of the active sites remains elusive. We systematically investigated the structure sensitivity of Au single crystals for electrocatalytic CO<jats:sub>2</jats:sub> reduction. Reaction kinetics for the formation of CO are strongly dependent on the surface structure. Under‐coordinated sites, such as those present in Au(110) and at the steps of Au(211), show at least 20‐fold higher activity than more coordinated configurations (for example, Au(100)). By selectively poisoning under‐coordinated sites with Pb, we have confirmed that these are the active sites for CO<jats:sub>2</jats:sub> reduction.</jats:p>
Winiwarter A, Silvioli L, Scott SB, et al., 2019, Towards an atomistic understanding of electrocatalytic partial hydrocarbon oxidation: propene on palladium, ENERGY & ENVIRONMENTAL SCIENCE, Vol: 12, Pages: 1055-1067, ISSN: 1754-5692
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Wei C, Rao RR, Peng J, et al., 2019, Recommended Practices and Benchmark Activity for Hydrogen and Oxygen Electrocatalysis in Water Splitting and Fuel Cells, Advanced Materials, ISSN: 0935-9648
© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Electrochemical energy storage by making H 2 an energy carrier from water splitting relies on four elementary reactions, i.e., the hydrogen evolution reaction (HER), hydrogen oxidation reaction (HOR), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR). Herein, the central objective is to recommend systematic protocols for activity measurements of these four reactions and benchmark activities for comparison, which is critical to facilitate the research and development of catalysts with high activity and stability. Details for the electrochemical cell setup, measurements, and data analysis used to quantify the kinetics of the HER, HOR, OER, and ORR in acidic and basic solutions are provided, and examples of state-of-the-art specific and mass activity of catalysts to date are given. First, the experimental setup is discussed to provide common guidelines for these reactions, including the cell design, reference electrode selection, counter electrode concerns, and working electrode preparation. Second, experimental protocols, including data collection and processing such as ohmic- and background-correction and catalyst surface area estimation, and practice for testing and comparing different classes of catalysts are recommended. Lastly, the specific and mass activity activities of some state-of-the-art catalysts are benchmarked to facilitate the comparison of catalyst activity for these four reactions across different laboratories.
Engstfeld AK, Maagaard T, Horch S, et al., 2018, Polycrystalline and Single-Crystal Cu Electrodes: Influence of Experimental Conditions on the Electrochemical Properties in Alkaline Media, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 24, Pages: 17743-17755, ISSN: 0947-6539
Roy C, Sebok B, Scott SB, et al., 2018, Impact of nanoparticle size and lattice oxygen on water oxidation on NiFeO<inf>x</inf>H<inf>y</inf>, Nature Catalysis, Vol: 1, Pages: 820-829, ISSN: 2520-1158
NiFeOxHy are the most active catalysts for oxygen evolution in a base. For this reason, they are used widely in alkaline electrolysers. Several open questions remain as to the reason for their exceptionally high catalytic activity. Here we use a model system of mass-selected NiFe nanoparticles and isotope labelling experiments to show that oxygen evolution in 1 M KOH does not proceed via lattice exchange. We complement our activity measurements with electrochemistry–mass spectrometry, taken under operando conditions, and transmission electron microscopy and low-energy ion-scattering spectroscopy, taken ex situ. Together with the trends in particle size, the isotope results indicate that oxygen evolution is limited to the near-surface region. Using the surface area of the particles, we determined that the turnover frequency was 6.2 ± 1.6 s−1 at an overpotential of 0.3 V, which is, to the best of our knowledge, the highest reported for oxygen evolution in alkaline solution.
Escudero-Escribano M, Pedersen AF, Ulrikkeholm ET, et al., 2018, Active-Phase Formation and Stability of Gd/Pt(111) Electrocatalysts for Oxygen Reduction: An In Situ Grazing Incidence X-Ray Diffraction Study, CHEMISTRY-A EUROPEAN JOURNAL, Vol: 24, Pages: 12280-12290, ISSN: 0947-6539
Rao RR, Kolb MJ, Hwang J, et al., 2018, Surface Orientation Dependent Water Dissociation on Rutile Ruthenium Dioxide, JOURNAL OF PHYSICAL CHEMISTRY C, Vol: 122, Pages: 17802-17811, ISSN: 1932-7447
Roy C, Rao RR, Stoerzinger KA, et al., 2018, Trends in activity and dissolution on RuO2 under oxygen evolution conditions: particles versus well-defined extended surfaces, ACS Energy Letters, Vol: 3, Pages: 2045-2051, ISSN: 2380-8195
Rutile RuO2 catalysts are the most active pure metal oxides for oxygen evolution; however, they are also unstable toward dissolution. Herein, we study the catalytic activity and stability of oriented thin films of RuO2 with (111), (101), and (001) orientations, in comparison to a (110) single crystal and commercial nanoparticles. These surfaces were all tested in aqueous solutions of 0.05 M H2SO4. The initial catalyst activity ranked as follows: (001) > (101) > (111) ≈ (110). We complemented our activity data with inductively coupled plasma mass spectroscopy, to measure Ru dissolution products occurring in parallel to oxygen evolution. In contrast to earlier reports, we find that, under our experimental conditions, there is no correlation between the activity and stability.
Colic V, Yang S, Revay Z, et al., 2018, Carbon catalysts for electrochemical hydrogen peroxide production in acidic media, ELECTROCHIMICA ACTA, Vol: 272, Pages: 192-202, ISSN: 0013-4686
Yang S, Verdaguer-Casadevall A, Arnarson L, et al., 2018, Toward the decentralized electrochemical production of H2O2: A focus on the catalysis, ACS Catalysis, Vol: 8, Pages: 4064-4081, ISSN: 2155-5435
H2O2 is a valuable, environmentally friendly oxidizing agent with a wide range of uses from the provision of clean water to the synthesis of valuable chemicals. The on-site electrolytic production of H2O2 would bring the chemical to applications beyond its present reach. The successful commercialization of electrochemical H2O2 production requires cathode catalysts with high activity, selectivity, and stability. In this Perspective, we highlight our current understanding of the factors that control the cathode performance. We review the influence of catalyst material, electrolyte, and the structure of the interface at the mesoscopic scale. We provide original theoretical data on the role of the geometry of the active site and its influence on activity and selectivity. We have also conducted a series of original experiments on (i) the effect of pH on H2O2 production on glassy carbon, pure metals, and metal–mercury alloys, and (ii) the influence of cell geometry and mass transport in liquid half-cells in comparison to membrane electrode assemblies.
Arnarson L, Schmidt PS, Pandey M, et al., 2018, Fundamental limitation of electrocatalytic methane conversion to methanol, PHYSICAL CHEMISTRY CHEMICAL PHYSICS, Vol: 20, Pages: 11152-11159, ISSN: 1463-9076
Jensen KD, Tymoczko J, Rossmeisl J, et al., 2018, Frontispiece: Elucidation of the Oxygen Reduction Volcano in Alkaline Media using a Copper–Platinum(111) Alloy, Angewandte Chemie International Edition, Vol: 57, ISSN: 1433-7851
Jensen KD, Tymoczko J, Rossmeisl J, et al., 2018, Elucidation of the Oxygen Reduction Volcano in Alkaline Media using a Copper–Platinum(111) Alloy, Angewandte Chemie, Vol: 130, Pages: 2850-2855, ISSN: 0044-8249
<jats:title>Abstract</jats:title><jats:p>The relationship between the binding of the reaction intermediates and oxygen reduction activity in alkaline media was experimentally explored. By introducing Cu into the 2nd surface layer of a Pt(111) single crystal, the surface reactivity was tuned. In both 0.1 <jats:sc>m</jats:sc> NaOH and 0.1 <jats:sc>m</jats:sc> KOH, the optimal catalyst should exhibit OH binding circa 0.1 eV weaker than Pt(111), via a Sabatier volcano; this observation suggests that the reaction is mediated via the same surface bound intermediates as in acid, in contrast to previous reports. In 0.1 <jats:sc>m</jats:sc> KOH, the alloy catalyst at the peak of the volcano exhibits a maximum activity of 101±8 mA cm<jats:sup>−2</jats:sup> at 0.9 V vs. a reversible hydrogen electrode (RHE). This activity constitutes a circa 60‐fold increase over Pt(111) in 0.1 <jats:sc>m</jats:sc> HClO<jats:sub>4</jats:sub>.</jats:p>
Jensen KD, Tymoczko J, Rossmeisl J, et al., 2018, Frontispiz: Elucidation of the Oxygen Reduction Volcano in Alkaline Media using a Copper–Platinum(111) Alloy, Angewandte Chemie, Vol: 130, ISSN: 0044-8249
Jensen KD, Tymoczko J, Rossmeisl J, et al., 2018, Elucidation of the oxygen reduction volcano in alkaline media using a copper–platinum(111) alloy, Angewandte Chemie International Edition, Vol: 57, Pages: 2800-2805, ISSN: 1433-7851
The relationship between the binding of the reaction intermediates and oxygen reduction activity in alkaline media was experimentally explored. By introducing Cu into the 2nd surface layer of a Pt(111) single crystal, the surface reactivity was tuned. In both 0.1 m NaOH and 0.1 m KOH, the optimal catalyst should exhibit OH binding circa 0.1 eV weaker than Pt(111), via a Sabatier volcano; this observation suggests that the reaction is mediated via the same surface bound intermediates as in acid, in contrast to previous reports. In 0.1 m KOH, the alloy catalyst at the peak of the volcano exhibits a maximum activity of 101±8 mA cm−2 at 0.9 V vs. a reversible hydrogen electrode (RHE). This activity constitutes a circa 60‐fold increase over Pt(111) in 0.1 m HClO4.
Roy C, Knudsen BP, Pedersen CM, et al., 2018, Scalable Synthesis of Carbon-Supported Platinum-Lanthanide and -Rare-Earth Alloys for Oxygen Reduction, ACS CATALYSIS, Vol: 8, Pages: 2071-2080, ISSN: 2155-5435
Stephens IEL, Bertheussen E, Hogg TV, et al., 2018, Electroreduction of CO on Polycrystalline Copper at Low Overpotentials, ACS Energy Letters
Pedersen AF, Escudero-Escribano M, Sebok B, et al., 2018, Operando XAS Study of the Surface Oxidation State on a Monolayer IrOx, on RuOx and Ru Oxide Based Nanoparticles for Oxygen Evolution in Acidic Media, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 122, Pages: 878-887, ISSN: 1520-6106
Escudero-Escribano M, Pedersen AF, Paoli EA, et al., 2018, Importance of Surface IrOx in Stabilizing RuO2 for Oxygen Evolution, JOURNAL OF PHYSICAL CHEMISTRY B, Vol: 122, Pages: 947-955, ISSN: 1520-6106
Rao RM, Kolb MJ, Halck NB, et al., 2017, Towards identifying the active sites on RuO2 (110) in catalyzing oxygen evolution, Energy and Environmental Science, Vol: 10, Pages: 2626-2637, ISSN: 1754-5692
While the surface atomic structure of RuO2 has been well studied in ultra high vacuum, much less is known about theinteraction between water and RuO2 in aqueous solution. In this work, in situ surface X-ray scattering measurementscombined with density functional theory (DFT) was used to determine the surface structural changes on single-crystalRuO2 (110) as a function of potential in acidic electrolyte. The redox peaks at 0.7, 1.1 and 1.4 V vs. reversible hydrogenelectrode (RHE) could be attributed to surface transitions associated with the successive deprotonation of -H2O on thecoordinatively unsaturated Ru sites (CUS) and hydrogen adsorbed to the bridging oxygen sites. At potentials relevant tothe oxygen evolution reaction (OER), an –OO species on the Ru CUS sites was detected, which was stabilized by aneighboring -OH group on the Ru CUS or bridge site. Combining potential-dependent surface structures with theirenergetics from DFT led to a new OER pathway, where the deprotonation of the -OH group used to stabilize –OO wasfound to be rate-limiting.
Vej-Hansen UG, Escudero-Escribano M, Velazquez-Palenzuela A, et al., 2017, New Platinum Alloy Catalysts for Oxygen Electroreduction Based on Alkaline Earth Metals, ELECTROCATALYSIS, Vol: 8, Pages: 594-604, ISSN: 1868-2529
Zamburlini E, Jensen KD, Stephens IEL, et al., 2017, Benchmarking Pt and Pt-lanthanide sputtered thin films for oxygen electroreduction: fabrication and rotating disk electrode measurements, 15th International Symposium on Polymer Electrolytes (ISPE), Publisher: PERGAMON-ELSEVIER SCIENCE LTD, Pages: 708-721, ISSN: 0013-4686
Lindahl N, Zamburlini E, Feng L, et al., 2017, High Specific and Mass Activity for the Oxygen Reduction Reaction for Thin Film Catalysts of Sputtered Pt3Y, ADVANCED MATERIALS INTERFACES, Vol: 4, ISSN: 2196-7350
Bertheussen E, Abghoui Y, Jovanov ZP, et al., 2017, Quantification of liquid products from the electroreduction of CO2 and CO using static headspace-gas chromatography and nuclear magnetic resonance spectroscopy, CATALYSIS TODAY, Vol: 288, Pages: 54-62, ISSN: 0920-5861
Stoerzinger KA, Diaz-Morales O, Kolb M, et al., 2017, Orientation-Dependent Oxygen Evolution on RuO2 without Lattice Exchange, ACS ENERGY LETTERS, Vol: 2, Pages: 876-881, ISSN: 2380-8195
Frydendal R, Seitz LC, Sokaras D, et al., 2017, Operando investigation of Au-MnOx thin films with improved activity for the oxygen evolution reaction, ELECTROCHIMICA ACTA, Vol: 230, Pages: 22-28, ISSN: 0013-4686
Stephens IEL, Rossmeisl J, Chorkendorff I, 2016, Toward sustainable fuel cells, SCIENCE, Vol: 354, Pages: 1378-1379, ISSN: 0036-8075
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