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Strotkötter V, Li Y, Kostka A, Lourens F, Löffler T, Schuhmann W, Ludwig A. Self-formation of compositionally complex surface oxides on high entropy alloys observed by accelerated atom probe tomography: a route to sustainable catalysts. MATERIALS HORIZONS 2024; 11:4932-4941. [PMID: 39045620 DOI: 10.1039/d4mh00245h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/25/2024]
Abstract
Sustainable catalysts rely on abundant elements which are prone to oxidation. A route to non-noble electrocatalysts is opened by directing the formation of unavoidable surface oxides towards creating a few atomic layers of an active and stable electrocatalyst, which is in direct contact with its metallic, conducting support. This is enabled by combining possibilities of compositionally complex solid solutions with accelerated atomic-scale surface characterization. Surface composition changes from the as-synthesized state to states after exposure to the oxygen evolution reaction (OER) are investigated using a Cantor-alloy-catalyst-coated tip array for atom probe tomography (APT): The film on top of the tip forms a nanoreactor which enables acquisition of intrinsic properties. The as-deposited film has an around 3 nm thick native oxide; short and prolonged OER exposures result in an oxygen-influenced surface layer with lower oxidation depth and altered metal composition. This shows that as-synthesized complex compositions can be used to obtain active and stable surface oxides under electrochemical load, while their surface evolution is observed by accelerated APT.
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Affiliation(s)
- Valerie Strotkötter
- Materials Discovery and Interfaces (MDI) Institute for Materials, Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany.
| | - Yujiao Li
- Center for Interface-Dominated High Performance Materials (ZGH) Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany
| | - Aleksander Kostka
- Center for Interface-Dominated High Performance Materials (ZGH) Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany
| | - Florian Lourens
- Materials Discovery and Interfaces (MDI) Institute for Materials, Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany.
| | - Tobias Löffler
- Center for Interface-Dominated High Performance Materials (ZGH) Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany
- Analytical Chemistry - Center for Electrochemical Sciences (CES) Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany
| | - Wolfgang Schuhmann
- Analytical Chemistry - Center for Electrochemical Sciences (CES) Faculty of Chemistry and Biochemistry, Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany
| | - Alfred Ludwig
- Materials Discovery and Interfaces (MDI) Institute for Materials, Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany.
- Center for Interface-Dominated High Performance Materials (ZGH) Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany
- Research Center Future Energy Materials and Systems (RC FEMS), Ruhr University Bochum, Universitätsstraße 150, D-44801 Bochum, Germany
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Mughal A, Cox SJ, Schröder-Turk GE. Curvature driven motion of a bubble in a toroidal Hele-Shaw cell. Interface Focus 2017. [PMID: 28630666 DOI: 10.1098/rsfs.2016.0106] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
We investigate the equilibrium properties of a single area-minimizing bubble trapped between two narrowly separated parallel curved plates. We begin with the case of a bubble trapped between concentric spherical plates. We develop a model which shows that the surface energy of the bubble is lower when confined between spherical plates than between flat plates. We confirm our findings by comparing against Surface Evolver simulations. We then derive a simple model for a bubble between arbitrarily curved parallel plates. The energy is found to be higher when the local Gaussian curvature of the plates is negative and lower when the curvature is positive. To check the validity of the model, we consider a bubble trapped between concentric tori. In the toroidal case, we find that the sensitivity of the bubble's energy to the local curvature acts as a geometric potential capable of driving bubbles from regions with negative to positive curvature.
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Affiliation(s)
- A Mughal
- Department of Mathematics, Aberystwyth University, Aberystwyth, Ceredigion SY23 3BZ, UK.,Theoretische Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg - Staudtstr. 7, 91058 Erlangen, Germany
| | - S J Cox
- Department of Mathematics, Aberystwyth University, Aberystwyth, Ceredigion SY23 3BZ, UK
| | - G E Schröder-Turk
- Theoretische Physik, Friedrich-Alexander-Universität Erlangen-Nürnberg - Staudtstr. 7, 91058 Erlangen, Germany.,Murdoch University, School of Engineering and IT, Murdoch, Perth, WA6162, Australia
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Gera P, Salac D. Stochastic phase segregation on surfaces. ROYAL SOCIETY OPEN SCIENCE 2017; 4:170472. [PMID: 28878994 PMCID: PMC5579110 DOI: 10.1098/rsos.170472] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 05/09/2017] [Accepted: 07/17/2017] [Indexed: 06/07/2023]
Abstract
Phase separation and coarsening is a phenomenon commonly seen in binary physical and chemical systems that occur in nature. Often, thermal fluctuations, modelled as stochastic noise, are present in the system and the phase segregation process occurs on a surface. In this work, the segregation process is modelled via the Cahn-Hilliard-Cook model, which is a fourth-order parabolic stochastic system. Coarsening is analysed on two sample surfaces: a unit sphere and a dumbbell. On both surfaces, a statistical analysis of the growth rate is performed, and the influence of noise level and mobility is also investigated. For the spherical interface, it is also shown that a lognormal distribution fits the growth rate well.
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Affiliation(s)
| | - David Salac
- Author for correspondence: David Salac e-mail:
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Ryan SD, Zheng X, Palffy-Muhoray P. Curvature-driven foam coarsening on a sphere: A computer simulation. Phys Rev E 2016; 93:053301. [PMID: 27300999 DOI: 10.1103/physreve.93.053301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2015] [Indexed: 06/06/2023]
Abstract
The von Neumann-Mullins law for the area evolution of a cell in the plane describes how a dry foam coarsens in time. Recent theory and experiment suggest that the dynamics are different on the surface of a three-dimensional object such as a sphere. This work considers the dynamics of dry foams on the surface of a sphere. Starting from first principles, we use computer simulation to show that curvature-driven motion of the cell boundaries leads to exponential growth and decay of the areas of cells, in contrast to the planar case where the growth is linear. We describe the evolution and distribution of cells to the final stationary state.
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Affiliation(s)
- Shawn D Ryan
- Department of Mathematical Sciences, Kent State University, Kent, Ohio 44240, USA
- Liquid Crystal Institute, Kent State University, Kent, Ohio 44240, USA
| | - Xiaoyu Zheng
- Department of Mathematical Sciences, Kent State University, Kent, Ohio 44240, USA
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Roth AE, Jones CD, Durian DJ. Coarsening of a two-dimensional foam on a dome. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2012; 86:021402. [PMID: 23005758 DOI: 10.1103/physreve.86.021402] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2012] [Indexed: 06/01/2023]
Abstract
In this paper we report on bubble growth rates and on the statistics of bubble topology for the coarsening of a dry foam contained in the narrow gap between two hemispheres. By contrast with coarsening in flat space, where six-sided bubbles neither grow nor shrink, we observe that six-sided bubbles grow with time at a rate that depends on their size. This result agrees with the modification to von Neumann's law predicted by J. E. Avron and D. Levine [Phys. Rev. Lett. 69, 208 (1992)]. For bubbles with a different number of sides, except possibly seven, there is too much noise in the growth rate data to demonstrate a difference with coarsening in flat space. In terms of the statistics of bubble topology, we find fewer three-, four-, and five-sided bubbles, and more bubbles with six or more sides, in comparison with the stationary distribution for coarsening in flat space. We also find good general agreement with the Aboav-Weaire law for the average number of sides of the neighbors of an n-sided bubble.
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Affiliation(s)
- A E Roth
- Department of Physics & Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6396, USA
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Gautier C, Lopez PJ, Livage J, Coradin T. Influence of poly-l-lysine on the biomimetic growth of silica tubes in confined media. J Colloid Interface Sci 2007; 309:44-8. [PMID: 17258760 DOI: 10.1016/j.jcis.2006.12.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2006] [Revised: 11/29/2006] [Accepted: 12/01/2006] [Indexed: 11/19/2022]
Abstract
Pore channels of polycarbonate membranes were recently used as biomimetic models to study the effect of confinement on silicate condensation, leading to the formation of silica tubes exhibiting a core-shell structure. In this work, we preimmobilized poly-L-lysine on the membrane pores, leading to modification of the tube shell formation process and variation in core particle size. These data strengthen previous assumptions on the role of confinement on silica growth, i.e., interfacial interactions and perturbation of the diffusion coefficient. They also suggest that this approach is suitable to investigate in more detail the contribution of confinement effects on silica biomineralization.
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Affiliation(s)
- Clémentine Gautier
- Chimie de la Matière Condensée de Paris, CNRS-UMR 7574, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France
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Gautier C, Lopez PJ, Hemadi M, Livage J, Coradin T. Biomimetic growth of silica tubes in confined media. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:9092-5. [PMID: 17042515 DOI: 10.1021/la061674b] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Polymer membranes were used as biomimetic environments to study the effect of confinement on silica formation. Within membrane pores, silica tubes were formed, consisting of a dense silica shell incorporating nanoparticle aggregates. The shell structure does not depend on the membrane pore size, suggesting that its formation proceeds via interfacial interactions with the pore surface. In contrast, the size of primary nanoparticles within core aggregates is influenced by pore dimensions, indicating an effect of confinement on the diffusion-limited growth of silica. A parallel can be drawn with reported roles of confinement in biomineralization processes, providing a basis for future developments in biosilicification mimetic approaches and biofunctional nanomaterials design.
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Affiliation(s)
- Clémentine Gautier
- Chimie de la Matière Condensée de Paris, UMR CNRS-7574, Université Pierre et Marie Curie Paris VI, 4 place Jussieu (T54-E5), 75252 Paris Cedex 05, France
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Equilibrium conditions and symmetries for foams in contact with solid surfaces. Colloids Surf A Physicochem Eng Asp 2005. [DOI: 10.1016/j.colsurfa.2005.01.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Gadomski A, Rubı́ J. On the two principal curvatures as potential barriers in a model of complex matter agglomeration. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00295-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Parisio F, Moraes F, Miranda JA, Widom M. Saffman-Taylor problem on a sphere. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2001; 63:036307. [PMID: 11308768 DOI: 10.1103/physreve.63.036307] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2000] [Indexed: 05/23/2023]
Abstract
The Saffman-Taylor problem addresses the morphological instability of an interface separating two immiscible, viscous fluids when they move in a narrow gap between two flat parallel plates (Hele-Shaw cell). In this work, we extend the classic Saffman-Taylor situation, by considering the flow between two curved, closely spaced, concentric spheres (spherical Hele-Shaw cell). We derive the mode-coupling differential equation for the interface perturbation amplitudes and study both linear and nonlinear flow regimes. The effect of the spherical cell (positive) spatial curvature on the shape of the interfacial patterns is investigated. We show that stability properties of the fluid-fluid interface are sensitive to the curvature of the surface. In particular, it is found that positive spatial curvature inhibits finger tip-splitting. Hele-Shaw flow on weakly negative, curved surfaces is briefly discussed.
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Affiliation(s)
- F Parisio
- Laboratório de Física Teórica e Computacional, Departamento de Física, Universidade Federal de Pernambuco, Recife, PE 50670-901, Brazil
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