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Hoydoo You

Bio: Hoydoo You is an academic researcher from Argonne National Laboratory. The author has contributed to research in topics: Scattering & Thin film. The author has an hindex of 34, co-authored 144 publications receiving 3887 citations. Previous affiliations of Hoydoo You include University of Illinois at Urbana–Champaign & University of Illinois at Chicago.


Papers
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Journal ArticleDOI
TL;DR: In this article, the authors show that the strong interaction of Fe with the MOxHy host is the key to controlling the average number of Fe active sites present at the solid/liquid interface.
Abstract: The poor activity and stability of electrode materials for the oxygen evolution reaction are the main bottlenecks in the water-splitting reaction for H2 production. Here, by studying the activity–stability trends for the oxygen evolution reaction on conductive M1OxHy, Fe–M1OxHy and Fe–M1M2OxHy hydr(oxy)oxide clusters (M1 = Ni, Co, Fe; M2 = Mn, Co, Cu), we show that balancing the rates of Fe dissolution and redeposition over a MOxHy host establishes dynamically stable Fe active sites. Together with tuning the Fe content of the electrolyte, the strong interaction of Fe with the MOxHy host is the key to controlling the average number of Fe active sites present at the solid/liquid interface. We suggest that the Fe–M adsorption energy can therefore serve as a reaction descriptor that unifies oxygen evolution reaction catalysis on 3d transition-metal hydr(oxy)oxides in alkaline media. Thus, the introduction of dynamically stable active sites extends the design rules for creating active and stable interfaces. Understanding what underpins the activity and stability of oxygen evolution catalysts is an ongoing issue in the field of water splitting. Now, researchers show that balancing the rate of Fe dissolution and deposition over a metal hydr(oxy)oxide host yields dynamically stable Fe active sites, with the Fe–host interaction key to the performance.

423 citations

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TL;DR: In this paper, in situ surface X-ray scattering measurements combined with density functional theory (DFT) were used to determine the surface structural changes on single-crystal RuO2(110) as a function of potential in acidic electrolyte.
Abstract: While the surface atomic structure of RuO2 has been well studied in ultra high vacuum, much less is known about the interaction between water and RuO2 in aqueous solution. In this work, in situ surface X-ray scattering measurements combined with density functional theory (DFT) were used to determine the surface structural changes on single-crystal RuO2(110) as a function of potential in acidic electrolyte. The redox peaks at 0.7, 1.1 and 1.4 V vs. reversible hydrogen electrode (RHE) could be attributed to surface transitions associated with the successive deprotonation of –H2O on the coordinatively unsaturated Ru sites (CUS) and hydrogen adsorbed to the bridging oxygen sites. At potentials relevant to the oxygen evolution reaction (OER), an –OO species on the Ru CUS sites was detected, which was stabilized by a neighboring –OH group on the Ru CUS or bridge site. Combining potential-dependent surface structures with their energetics from DFT led to a new OER pathway, where the deprotonation of the –OH group used to stabilize –OO was found to be rate-limiting.

247 citations

Journal ArticleDOI
TL;DR: In this paper, annealing effects in both single-crystal and ceramic samples of oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} that occur at temperatures as low as 0.
Abstract: We have observed annealing effects in both single-crystal and ceramic samples of oxygen-deficient YBa{sub 2}Cu{sub 3}O{sub 7-{delta}} that occur at temperatures as low as 0 {degree}C. Oxygen stoichiometries were controlled by quenching, from 520 {degree}C, samples equilibrated in a controlled O{sub 2}-N{sub 2} atmosphere. For single crystals, transition temperatures with any desired value between 0 and 92 K, and transition widths less than 2 K, were readily obtained with appropriate variation of {delta}. After quenching, superconducting transition temperatures of the reduced samples rise, as much as 15 K, when aged in ambient atmosphere for several days; the sample composition does not change with aging. With low-temperature aging, structural changes also occur; e.g., orthorhombicity increases. These effects are attributed to oxygen-vacancy ordering that occurs in the chain region of the structure. The rise in {Tc} with aging (ordering) is attributed to increased hole doping in the planes that results from an increased population of two-coordinated (monovalent) copper atoms. For samples with reduced stoichiometries, the degree of disorder can be reversibly controlled with secondary quenches in the temperature range 0--120 {degree}C. For stoichiometries 7{minus}{delta}{approx equal}6.5, an approximate activation energy of 0.96 eV was obtained for the annealing process. This low-temperature annealing behavior,more » occurring in samples of constant composition, provides a remarkably simple and effective way to study the relationship between superconductivity, structure, and associated electronic properties.« less

241 citations

Journal ArticleDOI
TL;DR: In this article, the Pt3Co nanoparticles with size controlled from 3 to 9 nm have been synthesized through an organic solvothermal approach and applied as electrocatalysts for the oxygen reduction reaction.
Abstract: Monodisperse Pt3Co nanoparticles with size controlled from 3 to 9 nm have been synthesized through an organic solvothermal approach and applied as electrocatalysts for the oxygen reduction reaction. Electrochemical study shows that the Pt3Co nanoparticles are highly active for the oxygen reduction reaction and the activity is size-dependent. The optimal size for maximal mass activity was established to be around 4.5 nm by balancing the electrochemically active surface area and specific activity.

191 citations

Journal ArticleDOI
TL;DR: Oxygen stoichiometries in single crystals of YBa{sub 2}Cu{sub 3}O{sub {ital x}} are controlled by quenching from an O-N-N atmosphere at 520 C to liquid nitrogen and the superconducting behavior and lattice parameters are found to be time dependent.
Abstract: Oxygen stoichiometries in single crystals of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{\mathit{x}}$ are controlled by quenching from an ${\mathrm{O}}_{2}$-${\mathrm{N}}_{2}$ atmosphere at 520 \ifmmode^\circ\else\textdegree\fi{}C to liquid nitrogen. After quenching, the superconducting behavior and lattice parameters are found to be time dependent. ${\mathit{T}}_{\mathit{c}}$ increases as much as 15 K in a period of several days. Apparently, annealing, with increasing oxygen vacancy order, occurs at room temperature.

159 citations


Cited by
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TL;DR: The field of photocatalysis can be traced back more than 80 years to early observations of the chalking of titania-based paints and to studies of the darkening of metal oxides in contact with organic compounds in sunlight as discussed by the authors.

5,729 citations

Journal ArticleDOI
07 Jun 2012-Nature
TL;DR: Taking the step towards successful commercialization requires oxygen reduction electrocatalysts that meet exacting performance targets, and these catalyst systems will need to be highly durable, fault-tolerant and amenable to high-volume production with high yields and exceptional quality.
Abstract: Fuel cells powered by hydrogen from secure and renewable sources are the ideal solution for non-polluting vehicles, and extensive research and development on all aspects of this technology over the past fifteen years has delivered prototype cars with impressive performances. But taking the step towards successful commercialization requires oxygen reduction electrocatalysts--crucial components at the heart of fuel cells--that meet exacting performance targets. In addition, these catalyst systems will need to be highly durable, fault-tolerant and amenable to high-volume production with high yields and exceptional quality. Not all the catalyst approaches currently being pursued will meet those demands.

4,538 citations

Journal ArticleDOI
TL;DR: This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core-shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts and metal-free catalysts.
Abstract: The recent advances in electrocatalysis for oxygen reduction reaction (ORR) for proton exchange membrane fuel cells (PEMFCs) are thoroughly reviewed. This comprehensive Review focuses on the low- and non-platinum electrocatalysts including advanced platinum alloys, core–shell structures, palladium-based catalysts, metal oxides and chalcogenides, carbon-based non-noble metal catalysts, and metal-free catalysts. The recent development of ORR electrocatalysts with novel structures and compositions is highlighted. The understandings of the correlation between the activity and the shape, size, composition, and synthesis method are summarized. For the carbon-based materials, their performance and stability in fuel cells and comparisons with those of platinum are documented. The research directions as well as perspectives on the further development of more active and less expensive electrocatalysts are provided.

2,964 citations

Journal ArticleDOI
TL;DR: In this paper, a large variety of experiments reviewed in detail here contain results compatible with the theoretical predictions, including phase diagrams of manganite models, the stabilization of the charge/orbital/spin ordered half-doped correlated electronics (CE)-states, the importance of the naively small Heisenberg coupling among localized spins, the setup of accurate mean-field approximations, and the existence of a new temperature scale T∗ where clusters start forming above the Curie temperature, the presence of stripes in the system, and many others.

2,927 citations

Journal ArticleDOI
TL;DR: The research focuses on the durability of polymer electrolyte fuel cells (PEFCs), in particular, membrane degradation, and he has been involved in NEDO R&D research projects on PEFC durability since 2001.
Abstract: Rod Borup is a Team Leader in the fuel cell program at Los Alamos National Lab in Los Alamos, New Mexico. He received his B.S.E. in Chemical Engineering from the University of Iowa in 1988 and his Ph.D. from the University of Washington in 1993. He has worked on fuel cell technology since 1994, working in the areas of hydrogen production and PEM fuel cell stack components. He has been awarded 12 U.S. patents, authored over 40 papers related to fuel cell technology, and presented over 50 oral papers at national meetings. His current main research area is related to water transport in PEM fuel cells and PEM fuel cell durability. Recently, he was awarded the 2005 DOE Hydrogen Program R&D Award for the most significant R&D contribution of the year for his team's work in fuel cell durability and was the Principal Investigator for the 2004 Fuel Cell Seminar (San Antonio, TX, USA) Best Poster Award. Jeremy Meyers is an Assistant Professor of materials science and engineering and mechanical engineering at the University of Texas at Austin, where his research focuses on the development of electrochemical energy systems and materials. Prior to joining the faculty at Texas, Jeremy workedmore » as manager of the advanced transportation technology group at UTC Power, where he was responsible for developing new system designs and components for automotive PEM fuel cell power plants. While at UTC Power, Jeremy led several customer development projects and a DOE-sponsored investigation into novel catalysts and membranes for PEM fuel cells. Jeremy has coauthored several papers on key mechanisms of fuel cell degradation and is a co-inventor of several patents. In 2006, Jeremy and several colleagues received the George Mead Medal, UTC's highest award for engineering achievement, and he served as the co-chair of the Gordon Research Conference on fuel cells. Jeremy received his Ph.D. in Chemical Engineering from the University of California at Berkeley and holds a Bachelor's Degree in Chemical Engineering from Stanford University. Bryan Pivovar received his B.S. in Chemical Engineering from the University of Wisconsin in 1994. He completed his Ph.D. in Chemical Engineering at the University of Minnesota in 2000 under the direction of Profs. Ed Cussler and Bill Smyrl, studying transport properties in fuel cell electrolytes. He continued working in the area of polymer electrolyte fuel cells at Los Alamos National Laboratory as a post-doc (2000-2001), as a technical staff member (2001-2005), and in his current position as a team leader (2005-present). In this time, Bryan's research has expanded to include further aspects of fuel cell operation, including electrodes, subfreezing effects, alternative polymers, hydroxide conductors, fuel cell interfaces, impurities, water transport, and high-temperature membranes. Bryan has served at various levels in national and international conferences and workshops, including organizing a DOE sponsored workshop on freezing effects in fuel cells and an ARO sponsored workshop on alkaline membrane fuel cells, and he was co-chair of the 2007 Gordon Research Conference on Fuel Cells. Minoru Inaba is a Professor at the Department of Molecular Science and Technology, Faculty of Engineering, Doshisha University, Japan. He received his B.Sc. from the Faculty of Engineering, Kyoto University, in 1984 and his M.Sc. in 1986 and his Dr. Eng. in 1995 from the Graduate School of Engineering, Kyoto University. He has worked on electrochemical energy conversion systems including fuel cells and lithium-ion batteries at Kyoto University (1992-2002) and at Doshisha University (2002-present). His primary research interest is the durability of polymer electrolyte fuel cells (PEFCs), in particular, membrane degradation, and he has been involved in NEDO R&D research projects on PEFC durability since 2001. He has authored over 140 technical papers and 30 review articles. Kenichiro Ota is a Professor of the Chemical Energy Laboratory at the Graduate School of Engineering, Yokohama National University, Japan. He received his B.S.E. in Applied Chemistry from the University of Tokyo in 1968 and his Ph.D. from the University of Tokyo in 1973. He has worked on hydrogen energy and fuel cells since 1974, working on materials science for fuel cells and water electrolysis. He has published more than 150 original papers, 70 review papers, and 50 scientific books. He is now the president of the Hydrogen Energy Systems Society of Japan, the chairman of the Fuel Cell Research Group of the Electrochemical Society of Japan, and the chairman of the National Committee for the Standardization of the Stationary Fuel Cells. ABSTRACT TRUNCATED« less

2,921 citations