In Situ Spectroscopic Studies of Metal Oxide Electrodes During Water Oxidation

Meeting Program – April 2013

John Kitchin
Department of Chemical Engineering,
Carnegie Mellon University

Abstract – Electrochemical water splitting may be in integral part of future energy storage strategies by enabling energy storage in chemical bonds. One of the primary sources of inefficiency in the water splitting reaction is the oxygen evolution reaction, which has high reaction barriers that require additional applied electric potential to drive the reactions at practical rates. The most active electrode materials in acid electrolytes include ruthenium and iridium oxides, which are expensive but necessary for stability. In alkaline environments, many base metal oxides become stable, although they are still less active than Ru and Ir oxides. It has been known that small amounts of Fe can promote the electrochemical activity of nickel oxides, making it almost as active as cobalt oxide. We have investigated the mechanisms behind the promotion using in situ Raman and synchrotron spectroscopies as well as ex situ characterization techniques. Interestingly, we found the electrode changes under oxygen evolution conditions, turning from an oxide to an oxyhydroxide phase. Furthermore, the composition of the electrolyte has a significant effect on the oxygen evolution activity. We will discuss these results and their implications in finding better oxygen evolution electrocatalysts.

John Kitchin

John Kitchin

Biography – John Kitchin completed his B.S. in Chemistry at North Carolina State University. He completed a M.S. in Materials Science and a PhD in Chemical Engineering at the University of Delaware in 2004 under the advisement of Dr. Jingguang Chen and Dr. Mark Barteau. He received an Alexander von Humboldt postdoctoral fellowship and lived in Berlin, Germany for 1 ½ years studying alloy segregation with Karsten Reuter and Matthias Scheffler in the Theory Department at the Fritz Haber Institut. Professor Kitchin began a tenure-track faculty position in the Chemical Engineering Department at Carnegie Mellon University in January of 2006. He is currently an Associate Professor. At CMU, Professor Kitchin is active in a major research effort within the National Energy Technology Laboratory Regional University Alliance in CO2 capture, chemical looping and superalloy oxidation. Professor Kitchin also uses computational methods to study adsorbate-adsorbate interactions on transition metal surfaces for applications in catalysis. He was awarded a DOE Early Career award in 2010 to investigate multifunctional oxide electrocatalysts for the oxygen evolution reaction in water splitting using experimental and computational methods. He received a Presidential Early Career Award for Scientists and Engineers in 2011.
Recent Publications
  1. Sneha A. Akhade and John R. Kitchin*, “Effects of strain, d-band filling and oxidation state on the surface electronic structure and reactivity of 3d perovskite surface”, J. Chem. Phys. 137, 084703 (2012).
  2. James Landon, Ethan Demeter, Nilay İnoğlu, Chris Keturakis, Israel E. Wachs, Relja Vasić, Anatoly I. Frenkel, John R. Kitchin, “Spectroscopic characterization of mixed Fe-Ni oxide electrocatalysts for the oxygen evolution reaction in alkaline electrolytes”, ACS Catalysis, 2, 1793-1801 (2012).
  3. Sneha A. Akhade and John R. Kitchin*, Effects of strain, d-band filling and oxidation state on the bulk electronic structure of cubic 3d perovskites, J. Chem. Phys. 135, 104702 (2011).
  4. N. Inoglu, and J.R. Kitchin, Identification of sulfur tolerant bimetallic surfaces using DFT parameterized models and atomistic thermodynamics, ACS Catalysis, 1, 399-407 (2011).
  5. Isabela C. Man, Hai-Yan Su, Federico Calle-Vallejo, Heine A. Hansen, José I. Martínez, Nilay G. Inoglu, John Kitchin, Thomas F. Jaramillo, Jens K. Nørskov, Jan Rossmeisl, Universality in Oxygen Evolution Electro-Catalysis on Oxide Surfaces, ChemCatChem, 3, (2011).
  6. Spencer D. Miller, Nilay İnoğlu, and John R. Kitchin, Configurational correlations in the coverage dependent adsorption energies of oxygen atoms on late transition metal fcc (111) surfaces, J. Chemical Physics, 134, 104709 (2011).
  7. R. Chao, J. R. Kitchin, K. Gerdes, E. M. Sabolsky, and P. A. Salvador, Preparation of Mesoporous La0.8Sr0.2MnO3 Infiltrated Coatings in Porous SOFC Cathodes Using Evaporation-Induced Self-Assembly Methods, ECS Transactions, 35 (1) 2387-2399 (2011).
  8. W. Richard Alesi Jr., McMahan Gray, John R. Kitchin, CO2 Adsorption on Supported Molecular Amidine Systems on Activated Carbon, ChemSusChem, 3(8), 948-956 (2010) Special issue on CO2 capture and Sequestration.
  9. Nilay Inoglu, John R. Kitchin, Simple model explaining and predicting coverage-dependent atomic adsorption energies on transition metal surfaces, Physical Review B, 82, 045414 (2010).

Nature of Catalytic Active Surface Sites on Semiconductor Photocatalysts for Splitting of Water

Meeting Program – March 2013

Somphonh Peter Phivilay
Operando Molecular Spectroscopy & Catalysis Laboratory
Department of Chemical Engineering
Lehigh University
Bethlehem, PA 18015 USA
Student Speaker

Abstract – One of society’s great challenges for the 21st century is the development of alternative energy resources. Hydrogen is considered to be one of the potential candidates especially if it can be generated from the photocatalytic conversion of cheap abundant H2O into clean non-carbon H2 from solar energy resources. Development of this clean, renewable form of energy will help to address our reliance on depleted fossil fuel supplies and the environmental problems accompanying its use.

Photocatalytic splitting of waters proceeds via generation of excited electrons and holes in the semiconductor catalyst bulk lattice, the diffusion of the excitons through the semiconductor lattice to the surface, and surface reactions of the excitons with water to split H2O to H2 and O2. The photocatalysis literature, however, has almost completely neglected the surface nature of photocatalysts and focused on the semiconductor catalyst bulk lattice that is only responsible for generation of the excited holes and electrons.

This presentation will examine the anatomy of the supported (Rh2-yCryO3)/(Ga1-xZnx)(N1-xOx) photocatalysts that are able to split water with visible light excitation by determining the nature of the bulk lattice (mm), surface region (~1-3 nm) and outermost surface later (~0.3 nm) with unique cutting edge characterization techniques.

Sulfur-Resistant Pd-Alloy Membranes for H2 Purification

Meeting Program – March 2013

James B. Miller
Department of Chemical Engineering
Carnegie Mellon University

Abstract – Separation of hydrogen from mixed gas streams is a key unit operation in the generation of carbon-neutral fuels and electricity from fossil- and bio-derived feedstocks. Dense Pd membranes have received significant attention for the separation application in advanced gasification processes. Pd’s near-perfect selectivity reflects its unique interactions with H2: molecular H2 dissociates on the catalytic Pd surface to create H-atoms, which dissolve into and diffuse through the Pd bulk, to eventually recombine on the downstream side of the membrane. In practice, Pd suffers from several limitations, including high cost, structural instability, and deactivation by minor components of the mixed gas, most notably H2S. Alloying with minor components, such as Cu, can be an effective strategy for improving membrane performance.

In collaboration with scientists at the National Energy Technology Laboratory, we have combined membrane performance testing, computational modeling, and H2 dissociation activity characterization to provide fundamental understanding of the interactions of H2 and H2S with Pd and PdCu alloys. We have shown that H2S influences membrane performance by two distinct mechanisms: surface deactivation, which inhibits the dissociative adsorption of H2, and reaction with the metal to form a low-permeability sulfide scale. The mechanism that dominates depends on both alloy composition and operating conditions. Significantly, the surface of the sulfide scale is itself active for H2 dissociation. Atomistic modeling of the dissociation process provides context for this observation, showing that while the energetic barrier for H2 dissociation is higher on Pd4S than on Pd, there exist reaction trajectories with relatively low barriers that can sustain the separation sequence at acceptable rates. Microkinectic analysis of H2-D2 exchange conducted over Pd and a series of PdCu alloys, both in the presence and absence if H2S, confirms this finding and provides insight into the role of the Cu minor component in imparting S-tolerance to the alloy.

Finally, we have developed a high throughput capability to explore alloy properties over broad, continuous composition space, based on Composition Spread Alloy Film (CSAF) libraries of model separation alloys. CSAFs are thin (~100 nm) films with compositions that vary continuously across the surface of a compact (~1cm2) substrate. Using a unique multichannel microreactor for spatially resolved measurement of reaction kinetics across CSAF surfaces, we have characterized the kinetics of H2-D2 exchange across continuous Pd1-xCux and Pd1-x-yCuxAuy composition space.

James B. Miller

James B. Miller

Biography – Jim Miller is Associate Research Professor of Chemical Engineering at Carnegie Mellon University, where he studies advanced materials for energy-related applications in separations, catalysis and chemical sensing. Jim earned BS, MS and PhD degrees at Carnegie Mellon and an MS at the University of Pittsburgh. Before joining the faculty in 2006, he worked in industry as a developer of catalysts, catalytic processes and chemical sensors for over 25 years. Jim is a two-time past president of the Pittsburgh-Cleveland Catalysis Society; he recently led the Society’s successful efforts to obtain tax exempt status in anticipation of NAM 2015. He is a winner of AIChE’s 2010 “Shining Star” in recognition of his volunteer work in the Pittsburgh Local Section.

Oxidative Dehydrogenation of Ethane to Ethylene

Meeting Program – February 2013

Anne M. Gaffney
AMG Catalysis and Chemistry Consulting, LLC
Abstract – This seminar will discuss a newly patented catalytic process and catalyst for the selective, oxidative dehydrogenation (ODH) of ethane to ethylene. Recent advances in shale gas technology, especially as practiced in the United States, has significantly improved the economics around producing ethylene and has revolutionized manufacturing approaches to basic chemicals, polymers and materials. Ethane is second to methane as a major hydrocarbon component of shale gas, serving as the precursor to ethylene. Ethylene is used to produce a wide variety of consumer goods, including packaging, building & automotive materials, fibers, tires and bottles. In 2012, a number of U.S. chemical companies announced plans to invest in new plant capacity, expand existing facilities, or re-open plants near shale gas supplies, primarily based on the assumption that the U.S. is entering a period of sustained low natural gas prices and growing supply.

This selective ODH process provides an alternative to ethylene production via naphtha or ethane cracking. In addition to replacing these crackers and recycle crackers, the ethylene product effluent from the ODH process may be used to feed ethyl benzene/styrene monomer and ethylene oxide plants. The synthesis, characterization and catalytic applications of the new, M1 structured, mixed metal oxide catalyst will be reviewed.

Anne M.  Gaffney

Anne M. Gaffney

Biography – Dr. Anne M. Gaffney joined INVISTA™ in 2011 as Director of R&D, Specialty Materials and is currently Program Leader for C11/C12™ R&D. She was previously VP of Technology at Lummus Technology. Other prior industrial roles include Senior Research Fellow at Rohm and Haas, Senior Research Associate at DuPont and Manager of Catalysis at ARCO Chemical Company. Anne is the inventor/co-inventor of over 100 patents and author/co-author of over 80 publications. She was selected as an ACS Fellow in 2010 and holds several other awards, including the 2013 ACS award in Industrial Chemistry and the 1999 Philadelphia Catalysis Club Award. Anne received her Ph.D. in Physical Organic Chemistry from the University of Delaware and her B.A. in Chemistry and Mathematics from Mount Holyoke College. Anne’s endeavors and interests include R&D Leadership, break -through technologies, heterogeneous catalysis, selective oxidation, catalyst synthesis and characterization. He is the recipient of the New York Catalysis Society Excellence in Catalysis Award, the North American Catalysis Society Frank Ciapetta Lectureship Award, the ACS Heroes in Chemistry Award, and the Herman Pines in Catalysis.

Supported Metal Catalysts – Issues and Opportunities

Meeting Program – Janiary 2013

Stuart Soled
ExxonMobil Research and Engineering Co
Rt. 22 East
Annandale, NJ

Abstract – Supported metal oxides, metals and sulfides form a large fraction of industrially important catalysts. Preparation of supported catalysts can involve a rich chemistry. We will detail different preparation approaches all aimed at controlling active site number and site location. Issues involving activity, transport, and deactivation come into play. Site locations are optimized on both mm and nm scale. Approaches involving electrostatic interactions and surface complex formation will be illustrated. We will describe approaches to making supported noble metal catalysts on silica as well as catalysts used in Fischer-Tropsch chemistry. The importance of nanoscale homogeneity on catalyst stability will be illustrated in several examples.
Biography – Stuart Soled received his Ph.D in chemistry from Brown University in 1973. He then did 4 year of post-doctoral work in solid state chemistry both at Brown University and in France, focusing on the synthesis and characterization of novel oxide and sulfide materials. He has been at Exxon’s Corporate Research Labs for more than 31 years. His research interests lie in the synthesis, characterization and evaluation of novel catalytic materials. He has worked extensively on Fischer-Tropsch chemistry, solid acid and metal catalysis, and hydrotreating. He is the coauthor of more than 70 publications and over 100 U.S. patents. He worked on the team discovering the Nebula catalyst and has worked on a joint ExxonMobil-Albemarle team to bring it to commercial reality. Nebula has been producing low sulfur diesel fuels in over 15 refinery units worldwide.

He is the recipient of the New York Catalysis Society Excellence in Catalysis Award, the North American Catalysis Society Frank Ciapetta Lectureship Award, the ACS Heroes in Chemistry Award, and the Herman Pines in Catalysis.

A DFT study of the acid-catalyzed conversion of 2,5-dimethylfuran and ethylene to p-xylene

Meeting Program – November 2012

Nima Nikbin
Department of Chemical and Biomolecular Engineering
University of Delaware
Newark, DE
Student Presentation

Abstract – In this paper we present the detailed mechanism for the conversion of DMF and ethylene to p-xylene. The mechanism was calculated by gas-phase DFT (Density-Functional Theory) for the uncatalyzed, the Brønsted acid-catalyzed and the Lewis acid-catalyzed reaction. The conversion consists of Diels-Alder cycloaddition and subsequent dehydration of the cycloadduct, an oxa-norbornene derivative. Even though the DMF-ethylene cycloaddition is thermally feasible, we find that Lewis acids can further lower the activation barriers by decreasing the HOMO-LUMO gap of the addends. The catalytic effect may be significant or negligible depending on whether the Diels-Alder reaction proceeds in the normal or the inverse electron-demand direction. We find that Brønsted acids are extremely effective at catalyzing the dehydration of the oxa-norbornene derivative, which, according to our calculations, cannot proceed uncatalyzed. On the other hand, we find that Brønsted acids do not catalyze the cycloaddition. Although strong Lewis acids like Li+ can catalyze the dehydration, our calculations indicate that relatively elevated temperatures would be required as they are not as effective as Brønsted acids. We argue that the specific synthetic route to p-xylene is kinetically limited by the Diels-Alder reaction when Brønsted acids are used and by the dehydration when a Lewis acid is used, with the latter being slower than the former. Finally, we adduce experimental data that corroborate the theoretical predictions: we observe no activity in the absence of a catalyst and a higher turnover frequency to p-xylene in the Brønsted acidic zeolite HY than in the Lewis acidic zeolite NaY.

Designing and Probing Photovoltaic and Photocatalytic Materials

Meeting Program – November 2012

Jason B. Baxter
Department of Chemical and Biological Engineering
Drexel University
Philadelphia, PA

Abstract – The sunlight incident on the earth provides 10,000 times more power than is needed to meet global demand. However, converting this energy into electricity or fuels efficiently and cost effectively remains a great challenge. Nanostructured solar cells present opportunities to inexpensively convert sunlight to electricity through the use of architectures tailored on the nanometer to micrometer length scale. Planar solar cells are subject to opposing constraints where thick films are required for light absorption while thinner films are desirable for efficient charge separation. Extremely thin absorber (ETA) solar cells can decouple these constraints by using a thin absorber at the interface between highly structured p- and n-type layers. In this talk, I will describe our work on ETA solar cells that use a thin CdSe coating on a ZnO nanowire array to absorb light and inject electrons into the oxide. Rational design of these architectures requires control over morphology and microstructure of the materials, as well as knowledge of material properties such as photoexcited carrier lifetimes and mobilities. Our approach utilizes a combination of solar cell measurements and ultrafast transient absorption spectroscopy to understand the effects of CdSe thickness, annealing conditions, and interfacial treatments on the dynamics and efficiency of charge carrier separation, and ultimately on the solar-to-electric energy conversion efficiency. These studies provide guidelines for architecture design and materials selection for ETA solar cells.

Jason B. Baxter

Jason B. Baxter

Biography – Dr. Jason B. Baxter is an Assistant Professor in the Department of Chemical and Biological Engineering at Drexel University in Philadelphia, PA, where he began in 2007. He received his B.Ch.E. from the University of Delaware in 2000, where he did undergraduate research on dye sensitized solar cells at the Institute of Energy Conversion under the guidance of Prof. T.W. Fraser Russell. He earned his Ph.D. in chemical engineering from the University of California Santa Barbara in 2005. Advised by Prof. Eray S. Aydil and funded by an NSF Graduate Research Fellowship, he investigated growth and characterization of ZnO nanowires and their application in dye sensitized solar cells. From 2005-2007, Dr. Baxter was an ACS Petroleum Research Fund Alternative Energy Postdoctoral Fellow at Yale University. There he worked with Prof. Charles A. Schmuttenmaer in the Chemistry Department on the application of time-resolved terahertz spectroscopy to probe transient photoconductivity in oxide thin films, nanoparticles, nanowires, and bulk crystals.

Dr. Baxter’s current research interests are in designing, fabricating, and probing semiconductor nanomaterials and thin films for solar energy conversion. Most current efforts focus on solar-to-electric energy conversion, but the group has growing interest in photocatalytic water splitting for clean and renewable hydrogen production. Various projects in the group include extremely thin absorber solar cells, organic solar cells, microreactor deposition of graded thin films for high-throughput characterization, and ultrafast pump-probe spectroscopy to measure charge carrier dynamics. The general focus of the group is on striving to understand how materials and interfaces affect device performance, and how these materials and interfaces can be controlled during the fabrication process. Low-temperature solution processing methods are used whenever possible to provide a pathway to low-cost, scalable manufacturing.
Dr. Baxter advises a group of 4 PhD students, 2 MS students, and 8 BS students. He has published nearly 25 papers, which have collectively garnered well over 1000 citations. He has been awarded over $1 million in funding as lead investigator and another $3 million as co-investigator. He received the NSF CAREER Award in 2009.