ELC - Electrochemistry at surfaces€¦ · ABSTRACT BOOK 71/499 O1-ELC_426 THE GITSAXS-BASED STUDY OF OPERANDO AL ANODIZATION ELC - Electrochemistry at surfaces N. Vinogradov 1,*,

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ELC - Electrochemistry at surfaces

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O1-ELC_426

THE GITSAXS-BASED STUDY OF OPERANDO AL ANODIZATION


N. Vinogradov 1,*, F. Carlà 2, J. Evertsson 1, L. Rullik 1, R. Felici 3, E. Lundgren 1 1Lund University - Lund (Sweden), 2ESRF - Grenoble (France), 3SPIN-CNR - Rome (Italy)

For their fascinating properties, nanoporous materials are of high demand in the various industrial processes and academic research. Nanoporous anodic aluminium oxide (NP-AAO) is a very special case of such materials, due to the remarkably narrow pore size distribution, self-ordering of the pores and giant aspect ratios of those, developed under certain anodization conditions. For these properties NP-AAO are vastly used as templates and supports/carriers in engineering various types of hierarchical materials.

As of now, a general understanding of Al anodization process has been developed. This resulted in a number of empirically-derived formulae relating the anodization parameters, such as anodization time, voltage, electrolyte type, etc. to the structure and properties of the anodic oxide. However, this knowledge has been based mostly on the scanning electron microscopy (SEM) studies of the NP-AAO performed ex-situ. However, using this approach the changes in sample structure can only be related post-factum to the variation of the anodization conditions. This significantly complicates studying of dynamical processes in NP-AAO and may lead to uncertainties in results interpretation.

Here we present a different approach to the problem. Making use of high penetration ability of hard X-rays, we were able to observe a striking evolution of the X-ray scattering pattern, generated by growing NP-AAO film, in operando. The clear changes in this pattern arise from the changes in the NP-AAO, and the structural parameters of the latter can be easily calculated at any stage of anodization, with high precision. Using this approach we have performed a comparative study of NP-AAO structural parameters evolution upon anodization with three most common electrolytes. Our approach is neither limited to aluminum only, nor to studying porous structures solely, but can be applied to a number of other elements and materials.

Fig.1 Experiment schematics and typical scattering pattern. X-rays that impinge on the sample surface at a grazing incidence (>0.5 deg), are scattered by the electron density variation (pore-electrolyte interfaces) and captured by the detector. Analysis of the scattering pattern allows for determination of the structural parameters of the pores: pore separation L, pore diameter D, and pore height H.

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O2-ELC_74

ACTIVE SITES OF NITROGEN-DOPED CARBON MATERIALS FOR OXYGEN

REDUCTION REACTION


J. Nakamura *, D. Guo *, T. Kondo

University of Tsukuba - Tsukuba (Japan)

Nitrogen-doped carbon materials exhibit high electrocatalytic activity for the oxygen reduction reaction (ORR), which is essential for several renewable energy systems. However, the ORR active site(s) is unclear, which retards further developments of high-performance catalysts. We have conclusively characterized the ORR active site by using newly designed graphite (HOPG) model catalysts with well-defined π-conjugation and well-controlled doping of nitrogen species [1]. As shown in Fig.1, the ORR active site is created by pyridinic N, while graphitic N-doped HOPG surfaces show no catalytic activity for ORR. CO2 adsorption experiments indicated that pyridinic N also creates Lewis basic sites. The specific activities per pyridinic N in the HOPG model catalysts are comparable with those of N-doped graphene powder catalysts. It is thus concluded that the ORR active sites in nitrogen-doped carbon materials are carbon atoms with Lewis basicity next to pyridinic N. We have further examined the local electronic structure of the pyridinic N-doped HOPG surface by scanning tunneling spectroscopy (STS). As a result, a non-bonding pz state or edge state was observed by STS in the vicinity of the nitrogen atom, which is ascribed to the origin of the ORR activity.

Thanks

This study is partially supported by JST PRESTO and NEDO projects.

References

[1] D. Guo, R. Shibuyaa, C. Akiba, S. Saji, T. Kondo, J. Nakamura, Science , 351 (2016)1,361.

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I02_ELC_435

ELECTROCATALYSTS AND "ANTI-ELECTROCATALYSTS" FOR ENERGY

APPLICATIONS


A. Bandarenka *

Physics of Energy Conversion and Storage - ECS, Physik-Department, Technische Universität München - Garching (Germany)

Electrocatalysis will play an increasingly important role to overcome challenges associated with efficient generation and conversion of so-called “solar fuels”. The catalytic properties of the electrode surface are primarily determined by its electronic structure, which, in turn, influences adsorption and desorption of reaction intermediates. It is well known through the Sabatier principle that the ideal catalytic surface sites should neither bind them too strongly nor too weakly. Indeed, the strength of the binding of an adsorbed species to the catalytic centers has been shown to play a key role in the activity of electrocatalysts, as activation energies for elementary surface reactions are strongly correlated with the adsorption energies. In many cases it is possible to optimize the binding energies of the adsorbed intermediates by changing the atomic composition and/or structure at the catalytic sites. For instance, the common way of improving the activity of metal electrodes is a modification of the electronic properties of the surface through alloying it with other metals. One can distinguish approaches which are based on “bulk”, “sub-surface” and “surface” alloying. Additionally, introduction of specific (often quasi-periodic) defects can also result in a drastic increase in the catalyst activity. In the presentation, examples will be given of how the above-mentioned approaches can be used to design active surfaces rationally; and how the model electrodes can help in better understanding of the performance of electrocatalytic systems.

While for the fuel cells, electrolysers, metal air batteries and many other energy conversion and storage devices the design of the most active electrocatalysts is one of the primary tasks, many batteries (which use the phenomenon of intercalation) and supercapacitors require the electrode surfaces and systems in which no catalytic reactions should take place. For instance, in aqueous Na-ion batteries in order to extend the operational potential window, the oxygen evolution reaction and hydrogen evolution reactions at the electrode surfaces must be prohibited. It can be done by several ways. One can optimize the electrolyte composition. Namely, it is important to identify inhibitors (molecules or ions), which adsorb at the surface and selectively poison the catalytic centers, but do not interrupt intercalation and de-intercalation of cations. Another approach would involve the development of the thinnest possible layers of a non-active material which can still conduct cations. Finally, one can identify an electrode material which is both inactive towards the side reactions and good in terms of intercalation properties. A set of various approaches aiming to suppress side electrocatalytic reactions in many energy storage devices can be arbitrarily called “anti-electrocatalysis”. In the presentation, several examples involving electrode materials for Na-ion batteries operating in aqueous media will be presented.

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I25_ELC_436

ADVANCING OXYGEN ELECTROREDUCTION ON THE BASIS OF MODEL

INVESTIGATIONS OF PT-ALLOY SURFACES


I.E.L. Stephens *

Technical University of Denmark (DTU), Department of Physics (Denmark)

Low temperature fuel cells, could provide a potentially zero emission source of power for automotive vehicles. However, they are limited by the slow kinetics of oxygen reduction. High loadings of platinum are required to catalyse the reaction; its short supply limits the extent to which fuel cell technology could be scaled up. The most widely used strategy to decrease the Pt loading is to enhance the catalytic activity of Pt by alloying it with late transition metals, in particular Ni or Co. However, these materials typically degrade via dealloying. At our laboratory, we have developed a different class of oxygen reduction catalyst: alloys of Pt with rare earths, including Y and Gd. The strong interaction between Pt and the rare earth elements should make these compounds inherently less prone towards dealloying. These catalysts exhibit high activity, both on extended surfaces and in the nanoparticulate form.[1-3] Our efforts are now aimed towards the large scale synthesis of these catalysts, so that they can be implemented in fuel cells and tested for their long term stability.

It turns out that that both the activity and stability are a function of the bulk Pt-Pt distance. Bulk compression brings about a strain onto the pure Pt overlayer. Thus changing the rare earth element provides us with a lever to control the catalytic performance, via the “lanthanide contraction”. [4] We have investigated well defined Pt-rare earth alloy catalysts in the form of mass-selected nanoparticles,[3] smooth polycrystalline surfaces[1,2,4] and single crystals.[5] Our studies incorporate electrochemical measurements, ultra-high vacuum based surface science methods, electron microscopy, synchrotron-based X-ray spectroscopy and density functional theory calculations.

References

[1] J. Greeley, I.E.L. Stephens, A.S. Bondarenko, T.P. Johansson, H.A. Hansen, T.F. Jaramillo, J. Rossmeisl, I. Chorkendorff, J.K. Nørskov, Nature Chemistry, 1 (2009) 552-556.

[2] I.E.L. Stephens, A.S. Bondarenko, U. Gronbjerg, J. Rossmeisl, I. Chorkendorff, Energy & Environmental Science, 5 (2012) 6744-6762.

[3] P. Hernandez-Fernandez, F. Masini, D.N. McCarthy, C.E. Strebel, D. Friebel, D. Deiana, P. Malacrida, A. Nierhoff, A. Bodin, A.M. Wise, J.H. Nielsen, T.W. Hansen, A. Nilsson, I.E.L. Stephens, I. Chorkendorff Nature Chemistry, 6 (2014) 732-738.

[4] M. Escudero Escribano, P. Malacrida, M.H. Hansen, U.G. Vej-Hansen, A. Velazquez-Palenzuela, V. Tripkovic, J. Schiøtz, J. Rossmeisl, I.E.L. Stephens, I. Chorkendorff, Science, 352 (2016) 73-76.

[5] Pedersen, A. F., Ulrikkeholm, E. T., Escudero-Escribano, M., Johannson, T. P., Malacrida, P., Pedersen, C. M., Hansen, M. H., Jensen, K. D., Rossmeisl, J., Friebel, D., Nilsson, A., Chorkendorff,I., Stephens, I. E. L. Nano Energy (2016) in press.

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O3-ELC_365

COUPLING BETWEEN ELECTROCHEMISTRY AND SURFACE X-RAY DIFFRACTION

FOR A MULTISCALE ANALYSIS OF THE PD/M(111°)-H SYSTEM (M=PT,AU)


Y. Soldo-Olivier 1,*, M. De Santis 1, L. Wang 2, B. Previdello 2, E. Sibert 2 1Institut Néel - CNRS - Grenoble (France), 2LEPMI - Grenoble (France)

Palladium presents remarkable properties as a catalyst for hydrogen dissociation and is characterized by a high insertion/desorption kinetic. Compared to bulk Pd, the nanometric size of ultra-thin films is expected to induce deep modifications on the thermodynamic properties. This is the case for Pd nanoparticles, which present reduced hydrogen solubility.

In order to get a thorough comprehension of the mechanisms governing the hydrogen insertion into Pd ultra-thin films, we have studied the influence of the film nanometric size and of the substrate on the electrochemical isotherms. In our approach, the global behavior of this electrochemical system (macroscopic characterization) is elucidated by its structural characterization at the atomic scale.

For Pd/Pt(111) and Pd/Au(111) films of different equivalent thicknesses up to about 20 monolayers, the original behavior of the different thermodynamic parameters, like the maximal hydrogen insertion rate, has been pointed out. The large effect of the substrate has been revealed, as well.

Thanks to the powerful approach coupling electrochemistry with in situ Surface X-ray Diffraction, we have been able to give a deep insight into the strong relationship between the detailed description at the atomic level of the films structure and the corresponding isotherms behavior. In particular, we propose a model where the hydrogen insertion rate into the Pd deposit is deeply correlated with the film constraints induced by the substrate.

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O4-ELC_315

OPERANDO SXRD OF E-ALD DEPOSITED SULPHIDES ULTRA-THIN FILMS:

CRYSTALLITE STRAIN AND SIZE.


A. Giaccherini 1,*, F. Carlà 2, M. Giordano 3, I. Massimo 1, F. Roberto 4, D.B. Francesco 5 1Department of chemistry - Università degli Studi di Firenze (Italy), 2ESRF (Italy), 3IGG - CNR (Italy), 4SPIN - CNR (Italy), 5Department of earth sciences - Università degli Studi di Firenze (Italy)

In the last year scientific community manifested a growing interest for cheaper, more productive and greener methods of deposition for highly ordered ultra-thin films and 2D structures. Electrochemical Atomic Layer Deposition (E-ALD), exploiting surface limited electrodeposition of atomic layers, proved to be easily implemented to deposit such systems. Among the first technologically interesting materials deposited by means of E-ALD are chalcogenides such as CdSe and CdTe thin-films. On the other hand, toxicity and shortage of the involved elements, must be considered. Hence scientific community is focusing attention on new compounds based on economic and low-environmental impact elements such as Cu, Sn, Fe and Zn. In particular, quaternary semiconducting materials based on the kesterite (Cu2ZnSnS4) mineral structure are the most promising candidates to overtake the current generation of light-absorbing materials for thin-film solar cells. On this ground, an assesment of the structural ordering and growth mechanism investigation on ultra-thin films of Cu, Zn and Cd bearing sulphides has been performed by means of SXRD. The experiments were performed at ESRF (Grenoble) and focused on Cu2S, CuxZnyS and CuxZnyS/CdS ultra-thin films on the Ag(111) crystal plane. The growth of the films were monitored by following the evolution of the Bragg peaks after a certain number of E-ALD steps. Pseudo single crystal pattern emerges for each film and in some cases a powder pattern can also be obtained. Usually, after the Bragg reflections are observed for the first time, only minor changes of the structural arrangement are registered for the pseudo single crystal patterns. Breadth and profile analysis of the Bragg peaks lead to a qualitative interpretation of the growth mechanism, in the normal and in-plane directions, with respect to the Ag surface. Namely, the contribution of crystallite’s strain and size were identified in the width of the Bragg reflections. The crystal structure of the electro-deposited Cu2S phase, identified in the three films, could be related to that of chalcocite, in particular considering the layering of triangular Cu sites and octahedral Cu sites. Eventually, the influence of the applied electric potential on the stability of the electro-deposited crystal structure has been monitored by means of SXRD measurements performed during the switch off of the potential. A structural change was, in fact, registered, and correlated to the occurrence of the stable phases under conventional laboratory conditions.

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O5-ELC_202

ELECTROCHEMICAL LAYER BY LAYER DEPOSITION: AN IN-SITU SXRD STUDY


F. Carlà 1,*, A. Magrini 2, R. Felici 3 1ESRF - Grenoble (France), 2Universita degli Studi di Firenze - Firenze (Italy), 3SPIN-CNR - Roma (Italy)

The electrochemical synthesis of thin films of semiconductor materials with well defined crystalline structure and physical properties has been attempted using different approaches during the past. Among the methods developed, the Electrochemical Atomic Layer Deposition (EC-ALD) [1] seems to be an extremely promising as it allows for a strict control on film thickness and composition. The EC-ALD method is based on the alternate Under Potential Deposition (UPD) of different elements. UPD is a surface limited phenomenon and in electrochemical environment can be easily exploited for the sequential deposition of elemental layers which leads to the layer by layer growth of thin films of compounds on single crystal substrates. The method has been demonstrated very effective for the production of thin films of semiconductor compounds with high grade of crystallinity by post-growth Surface X-ray Diffraction experiments. Even if it's well established that the sequential deposition of UPD layers results in an ordered multilayer structure many aspects of the growth process are not clear yet. It appears in fact that several experimental parameters such as substrate structure, chemical environment and applied potential may affect the mechanism of the ECALE growth [2]. In this contribution we will report the results of a series of in-situ Surface X-ray Diffraction (SXRD) experiments devoted to the investigation of the ECALE deposition of CdS multilayers on Ag(111). The experiments were carried on the ID03 beamline at ESRF (Grenoble) using electrochemical flow cell specifically designed for this purpose. In-situ experiments allowed to record the structural changes of the in-plane order and details of the out-of-plane relaxation of the film during the growth. Moreover the dependency of the epitaxial order on the potential used for the UPD deposition process was also observed.

References

1. B. W. Gregory et al. , J. Electroanal. Chem. 300, 543 (1991)

2. F. Carla' et al., J. Phys. Chem. C 12, 6132 (2014)

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O6-ELC_309

ELECTROCHEMICAL MODIFICATION OF INDIUM PHOSPHIDE INDUCED BY IONIC

BOMBARDMENT


D. Aureau *, A.M. Gonçalves, A. Etcheberry

Institut Lavoisier-UMR 8180 CNRS-UVSQ - Versailles (France)

When XPS profiling of crystalline materials by ionic bombardment is performed, a peak broadening is generally observed. In case of alloys, changes in the atomic ratios may also appear. These effects can be interpreted as the appearance of disorder in a crystalline structure and a preferential etching. The purpose of this work is to study in detail the effects of monoatomic projectiles and clusters on indium phosphide. The objective here is the correlation between XPS and interfacial electrochemistry. Such approach allows to know the overall change in the properties of the electrode induced by various bombings and therefore highlights the limits of interpretations in XPS profiling study and the possible reorganizations when delivered to the air.

Deoxidized InP has typical and reproducible electrochemical signatures, both in the darkness and under illumination where a photocurrent appears at a specific potential whose intensity is directly proportional to the incident photon flux. Modifications of the electrode could be followed by its electrochemical behavior during for hydrogen evolution leading to the cathodic decomposition of the material (appearance of metallic indium). After monoatomic bombardment, indium enrichment (figure 1) and electrochemical modification are observed. The photocurrent is no longer detectable, showing formation of a film hiding the semiconductor. The Mott-Schottky plot strongly flattens over the entire potential gap of InP. Nyquist plots also show (Figure 2) an increase in the charge transfer resistance at the open circuit potential. Using cluster of thousands of atoms of argon (lower energy per atom) allows better control of the induced modifications and a regime where the characteristics of the semiconductor can be retrieved by anodic dissolution.

Figure 1: Evolution of the atomic percentage of indium and phosphorus during abrasion (argon ions, 180 s, 4 keV). inset: P2p spectra before and after bombardment. Figure 2: Nyquist plots before and after bombardment.

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O7-ELC_323

UNDERSTANDING CORROSION INHIBITION WITH DFT METHODS: THE CASE OF

BENZOTRIAZOLE


C. Gattinoni *

University College London - London (United Kingdom)

The adsorption of benzotriazole (BTAH), an effective corrosion inhibitor for copper, has been a matter of debate for more than sixty years. The use of computer simulation approaches based on density functional theory (DFT) has allowed us to establish the nature of BTAH adsorption on copper and copper oxide, and to contribute to explain its efficacy as an inhibitor.

The atomistic understanding of the processes underlying corrosion and corrosion inhibition is of paramount importance towards the treatment of this undesirable and costly process. In particular, the development of novel, improved organic molecule based inhibitors depends on understanding the corrosion reduction mechanism of current ones. Benzotriazole is the most widely used and studied corrosion inhibitor for copper, and a molecule of great industrial relevance. However, conflicting experimental results have been obtained over the years regarding its adsorption mechanism on metal and oxide surfaces.

In this work, the systems formed by intact and dissociated BTAH molecules on Cu(111) and Cu2O(111) have been determined and linked to their inhibiting properties. Moreover, simulated NEXAFS and XPS spectra directly link the proposed DFT-calculated structures to experimental data. It is found1 that hydrogen bonding, van der Waals interactions and steric repulsions all contribute in shaping how BTAH molecules adsorb, with flat-lying structures preferred at low coverage and upright configurations preferred at high coverage. The interaction of dissociated benzotriazole (BTA) with the copper and oxide surfaces is instead dominated by strong chemisorption via the azole moiety with the aid of copper adatoms. Structures of dimers or chains are found to be the most stable structures at all coverages, in good agreement with STM, NEXAFS and XPS experimental results. Benzotriazole thus shows a complex phase behaviour in which van der Waals forces play an important role, and which depends on coverage and on its protonation state and all of these factors feasibly contribute to its effectiveness as a corrosion inhibitor.

The importance of external conditions when dealing with complex oxide surfaces is also highlighted, via the use of ab initio thermodynamics. The adsorbed complexes were found to be strongly dependent on external factors, e.g. on the O2 partial pressure. Indeed, different pressure conditions lead to strikingly different adsorption structure and adsorption energies. The strong dependence of BTAH and BTA adsorption structures on environmental factors also explain the wide range of results from experiments performed under different conditions.

References

C. Gattinoni and A. Michaelides, Faraday Discuss., 180, 439 (2015)

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O8-ELC_128

A NEW PROBE OF THE ELECTROCHEMICAL INTERFACE: SURFACE MAGNETISM


F. Maroun *, N. Tournerie *, A. Engelhardt, P. Allongue

Physique de la Matière Condensée, CNRS, Ecole Polytechnique - Palaiseau (France)

In this presentation, we present a new method to probe electrode surface chemistry and double layer structure at the electrochemical interface [1]. This method is based on the high sensitivity of the magnetism to the surface chemistry of magnetic electrodes. For this purpose, we designed a new setup where the magnetic properties (magnetization amplitude and orientation) can be measured in-situ on electrodes in an electrochemical flow cell. The measurement time resolution is ~0.5 s and its sensitivity is a small fraction of chemically modified electrode surface. In this presentation, we will give several examples in the case of Co/Au(111) electrodes showing the insights into the electrochemical interface provided by this powerful probe.

In the first example, we probe the adsorption of CO on Co. Since CO adsorption induce a 90° change of the magnetization orientation of the Co electrode, the CO adsorption kinetic could be measured as shown in the plot of the Figure below. We will also show that this probe is sensitive to the initial step of Co oxidation in alkaline electrolytes [2].

In the second example, we demonstrate that the magnetic properties are strongly modified by the hydrogen evolution reaction (HER) at CO-covered Co electrodes. We exploit this correlation to study the HER reaction mechanism.

In the third example, we take advantage of the sensitivity of this probe to the electric field present at the electrochemical interface to unravel the structure of the double layer at H- and CO-covered Co electrodes (see drawing below) [3].

References

[1] N Tournerie, A Engelhardt, F Maroun, and P Allongue, Surf. Sci. 631 (2015) 88.

[2] N Di, J Kubal, Z Zeng, J Greeley, F Maroun, and P Allongue, Appl. Phys. Lett. 106 (2015) 122405.

[3] N Tournerie, A P Engelhardt, F Maroun, and P Allongue, Phys. Rev. B 86 (2012) 104434.

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O9-ELC_227

STRUCTURAL DYNAMICS OF METAL DEPOSITION ON AU(111) ELECTRODE


M. Nakamura 1,*, T. Banzai 1, Y. Maehata 1, H. Tajiri 2, O. Sakata 3, N. Hoshi 1 1Chiba University (Japan), 2Japan Synchrotron Radiation Research Institute (Japan), 3National Institute for Materials Science (Japan)

Underpotential deposition (upd) of metal cations has been investigated by using scanning tunneling microscopy, X-ray diffraction and spectroscopic techniques because the understanding of upd processes is useful for fundamental research as an initial model of metal deposition. The understanding of transient structure is also necessary to elucidate deposition/dissolution processes. In this study, deposition process of various metal cations on Au(111) was studied by using time resolved X-ray diffraction and time resolved infrared spectroscopy. Transient structures of metal cations in the electrical double layer were captured by time resolved techniques.

X-ray diffraction measurements were performed with a multi-axis diffractometer at BL13XU (SPring-8). Diffracted X-ray was counted by the multichannel scaler synchronized with the function generator [1]. The upd metal used were Ag+, Cu2+, and Bi3+. After the potential is stepped from non-upd potential to upd potential, the CTR intensity between Bragg peaks is reduced because of the interference between the Au substrate and the upd layer. However, the intensity between Bragg peaks increases within a few ms and then decreases over the next 200 - 400 ms in Cu2+ and Bi3+ containing solutions. Structural analysis was performed from time-resolved measurements at the peak positions along the CTR. Intensity increase at the initial step suggests the presence of the outer layer species in the electrical double layer, and we assigned to the hydrated metal ion. During Cu2+ and Bi3+ deposition, hydrated metal cations approach to the outer layer and then metal ions are deposited on Au(111) with the destruction of hydration shell.

References

[1] M. Nakamura, H. Kaminaga, O. Endo, H. Tajiri, O. Sakata, N. Hoshi, J. Phys. Chem. C, 118, 22136 (2014).

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P1-ELC_127

IN VITRO ELECTROCHEMICAL AND ANTIBACTERIAL PERFORMANCE OF

P(ACRYLIC ACID-CO- 2-ETHYLHEXYL ACRYLATE)/SILICA NANOHYBRIDS


M. Mohamadpour Nazarabady *, G.A. Farzi *

Department of Materials and Polymer Engineering, Faculty of Engineering, Hakim Sabzevari University - , Sabzevar (Iran, islamic republic of)

A facile one-pot synthesis for the preparation of acrylate copolymers/silica nanohybrids particles is described, see Figure 1. This can be effectively accomplished through a simultaneous radical polymerization of acrylic monomers and sol-gel process of silica precursor. Silane coupling agents, 3- methacryloxy propyltrimethoxysilane (γ-MPS) and 3-aminopropyltriethoxysilane (APTS), here also serve to enhance chemically linking as revealed by Fourier transform infrared spectroscopy, X-ray diffractometer and scanning electron microscopy and is beneficial to electrical communication, leading to the formation of well-defined nanohybrids.

The prepared nanomaterial showed the electrochemical discrimination as a result of polymer/silica rational conjunction in their nanostructures. Moreover, the result of plate-counting method reveals the effective antibacterial properties of the nanohybrids. Thus, it can be concluded that the present method is simple and holds potential for electroanalytical and antibacterial applications.

Keywords: P(acrylic acid-co- 2-ethylhexyl acrylate)/silica, Nanohybrids, One-pot synthesis, Antibacterial activity, Electrochemical analysis.

Figure 1. Schematic of the procedure for preparation of P(acrylic acid-co- 2-ethylhexyl acrylate)/silica nanohybrids.

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P2-ELC_136

IN-SITU STUDIES OF THE LITHIUM INCORPORATION INTO SILICON AS AN

LITHIUM-ION BATTERY MODEL SYSTEM


B. Seidlhofer 1,*, B. Jerliu 2, E. Hüger 2, M. Trapp 1,*, S. Risse 1, A. Ronneburg 1, H. Schmidt 2, R. Steitz 1, M. Ballauff 1 1Helmholtz-Zentrum Berlin für Materialien und Energie GmbH - Berlin (Germany), 2Technische Universität Clausthal - Clausthal-Zellerfeld (Germany)

Lithium-ion batteries are widely developed and used as rechargeable power sources for several portable devices but will also be essential in the field of automotive transportation. For the latter improvements in cycling and life time, driving range, power density, safety and costs are required. The limiting factors of these properties are the processes taking place at the electrodes during lithiation. Therefore their investigation and the determination of lithiation kinetics and pathways are essential. In situ neutron reflectivity studies are ideally suited to investigate the processes occuring during cycling directly at the electrode/electrolyte interface. With this method it is possible to monitor the concentration gradient of lithium and the volume changes inside of the working electrode and to gain important information on the lithiation/delithiation mechanisms and kinetics.1

Measurements were performed using a three electrode electrochemical cell setup with a crystalline silicon working electrode. Counter and reference electrode were composed of pure lithium. A liquid electrolyte and a housing made of high density polyethylene were used.

Crystalline silicon was chosen as negative electrode material as it provides a very simple and well suited model system. In situ investigations of the lithiation/delithiation processes of this battery model system indicate that a lithium concentration gradient is formed during cycling in an interfacial zone with total thickness of about 500 Å (Figure 1) and an amount of Li ions of about x ~ 2.5 in LixSi next to the silicon electrode. After the first cycle a rest amount of Li rich material remains adjacent to the silicon electrode (x ~ 1.1 in LixSi).The total thickness of the lithiated phase increases to about 900 Å after the second lithiation. Moreover, a solid electrolyte interface is formed and dissolved during the entire cycling. The findings indicate an irreversible degradation of the silicon electrode. Further in-operando measurements are shown and discussed in the context of lithiation mechanisms and kinetics with unprecedented spatial and temporal resolution.

References 1 B. Jerliu, L. Dörrer, E. Hüger, G. Borchardt, R. Steitz, U. Geckle, V. Oberst, M. Bruns, O. Schneider, H. Schmidt, Phys. Chem. Chem. Phys. 2013, 15, 7777.

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P3-ELC_205

ELECTROLESS DEPOSITION OF NANOSTRUCTURES ON MICROPATTERNED

SUBSTRATES: FROM NANOWIRES TO NANOPORES


A. Ellsworth 1,*, A. Walker 2,* 1University of Texas at Dallas, Department of Chemistry - Richardson (United States of America), 2University of Texas at Dallas, Department of Chemistry, Department of Materials Science & Engineering - Richardson (United States of America)

One of the most significant challenges in nanoscience is the precise placement and orientation of nano-objects in situ over the mesoscale on technologically relevant substrates. Electroless deposition on micropatterned substrates (ENDOM) allows for the simultaneous synthesis and placement of a variety of nano-objects in a fast, flexible, parallel, and highly controllable method. These nano-objects have a wide range of applications from electronics to sensing. The shape of the deposit is controlled by the substrate pattern, resulting in nanowires (width <100 nm) which can follow arbitrary shapes such as around a right angle bend or in an arc. The width of the nanowire can be precisely controlled by monitoring the deposition time, leading to the formation of mesowires (100 nm < width < ~3000 nm) at intermediate times, and at later times nanopores and nanochannels. We have observed that the nanostructure adhesion to the surface is dependent upon the reagent concentrations within the deposition bath. For example in Cu ENDOM, upon reduction of the triethanolamine (complexing agent and buffer) concentration, nanowires no longer adhere strongly to the substrate and can be transferred to other substrates, such as silicon and poly(methyl methacrylate). The ENDOM process can also be used to create more complex nanostructures. We have demonstrated the synthesis of crossbar nanowire structures over large areas (millimeters) in parallel in as few as 6 steps.

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P4-ELC_288

ELECTROCHEMICAL STUDY OF A COPPER SEED-LAYER DISSOLUTION FOR 3D

INTERCONNECTIONS


E. Delbos 1,*, H. El Belghiti 1,*, A.M. Gonçalves 2, M. Bouttemy 2, A. Etcheberry 2 1KMG Ultra Pure Chemicals - Saint-Fromond (France), 2Institut Lavoisier de Versailles - Versailles (France)

In microelectronic area, the interconnections between different microprocessor levels are currently made by 3D contacts from Damascene (nanometric scale) or Through Silicon Vias (TSV) (micrometric scale) processes. These trenches or vias are filled by copper electrodeposition to ensure a performing electrical transfer. From these processes, the substrates are constituted by a silicon wafer, where the contact cavities are etched (mainly by the Bosch process). Then, a silicon oxide is generated to create a dielectric component. A diffusion barrier is next deposited by PVC, CVD or ALD process to provide the copper diffusion throughout the silicon substrate, followed by a copper seed-layer made also classically by a physical process. Thanks to this copper seed-layer, electrochemical deposition can be used as fast method to fill the cavities.

Several parameters govern the electrodeposition [1,2], as the bath chemical composition, the applied current density or potential, the nature of the substrate… and it is necessary to well understand the nucleation-growth mechanisms to guarantee free-defect fillings. One of scientific key points is the determination of the seed-layer evolution during its immersion in the plating bath, just before the application of a current density or a potential.

Therefore the aim of this study is to determine the behaviour of the seed-layer by electrochemical methods: open circuit potential tracking and evolution of the copper content on the sample surface by quartz crystal microbalance [3]. The copper bath is mainly constituted by copper sulphate and sulphuric acid. So, experiments were done both in the copper bath (with and without the addition of organic additives) and in H2SO4 solution [4]. The sample surfaces were characterised by SEM-EDS analyses before and after immersion. To complement the study, some experiments using atomic adsorption spectroscopy were performed to determine the variation of the copper content in solution, to confirm the dissolution of the seed-layer.

References

[1] E. Delbos, L. Omnès, A. Etcheberry, Copper electrodeposition parameters optimization for through-silicon vias filling, ECS Trans., 25-38, 109, (2010)

[2] E. Delbos, L. Omnès, A. Etcheberry, Bottom-up filling optimization for efficient TSV metallization, Microelectronic Engineering, 514-516, 87(3), (2010)

[3] A.G. Zelinsky, B.Ya. Pirogov, O.A. Yurjev, Open circuit potential transients and electrochemical quartz crystal microgravimetry measurements of dissolution of copper in acidic sulfate solutions, Corrosion Science,1083-1093, 46, (2004)

[4] D.K.Y. Wong, B.A.W. Coller and D.R. MacFarlane, A kinetic model for the dissolution mechanism of copper in acidic sulfate solutions, Electrochimica Acta, Vol. 38, No. 14,2121-2127, 38 (14), (1993)

ABSTRACT BOOK

86/499

P5-ELC_307

ELECTROLEACHING PROCESS, TECHNIQUE IMPROVED BY ADDITION OF

NANOPARTICLES


N. Sabba *, M. Taleb

USTHB - Bab Ezzouar (Algeria)

This work has concerned the study of the effectiveness of electroleaching process applied in batch using selective membrane, for the treatment of five synthetic solution of pure hues of different colors and for real discharge painting water from (ENAP / Algeria). Its efficiency is evaluated by measurement of indicators of pollution, concentration and COD (for the actual discharge).

This process was developed to overcome the disadvantages of industrial water treatment technologies. Electroleaching is very efficient in the removal of heavy metals, suspended particles, and organic matter. To improve this process, we have introduced a nonopaticles into solution.

Parametric study was followed including: pH of the medium concentration of the pollutant load processing time, current density on the electrochemical treatment process.

ABSTRACT BOOK

87/499

P6-ELC_376

EFFECT OF TEMPERATURE ON THE CORROSION BEHAVIOUR OF ZN AND ZN-

0.2AL ALLOY IN 3% NACL


S. Moussaoui 1,*, A. Benchettara 2 1Laboratoire d’Electrochimie Corrosion -Métallurgie et Chimie Minérale, Faculté de Chimie BP32 El Alia Bab Ezzouar 16111 - Boumerdes (Algeria), 2Laboratoire d’Electrochimie Corrosion -Métallurgie et Chimie Minérale, Faculté de Chimie BP32 El Alia Bab Ezzouar 16111 - Bab Ezzouar (Algeria)

Iron and steel of buried pipe lines in maritime structures is exposed at a severe corrosion. To avoid this problem, cathodic protection with sacrificial anodes is generally used, in order to shift corrosion potential of the materials towards cathodic values and make them cathodically protected. Zinc remains the most widely adopted anode materiel for cathodic protection in the conductive environments [1- 3].

The behaviour of Zn and Zn-0.2Al alloy sacrificial anodes was studied, in 3% NaCl solution at different temperatures (15, 25, 35 and 45°C), by the electrochemical techniques such as potentiodynamic polarization and linear polarization resistance.

The results obtained, by potentiodynamic polarization, show that the addition of 0.2 wt % in Al to Zn pure slowed down the corrosion current value at different temperature. With the method of linear polarization resistance, it reveals a substantial improvement of the charge transfer resistance for zinc-aluminium alloy with respect to pure zinc.

These results show that Zn-0.2Al alloy shows a better corrosion resistance at different temperature.

Thanks

Thank you for allowing us to participate in this scientific pole

References

[1] Bounoughaz M., Salhi E., Benzine K. and Dalard F., J. Mater. Sci., 38 (2003) 1139.

[2] Rabiot D., Dalard F., Rameau J.-J. and Boyer S., J. Appl. Electrochem., 29 (1999) 541.

[3] Marder A.R., Prog. Mater. Sci., 45 (2000) 191.

ABSTRACT BOOK

88/499

P7-ELC_403

PHOTO-ELECTROCHEMICAL STUDY OF: ANTIMONY DOPED SNO2 FILM/

CHROMATE SOLUTION


H. Ali *, R. Outemzabet, M. Trari, R. Brahimi

University of Sciences and Technology Houari Boumediene - Algiers (Algeria)

Tin dioxide SnO2 is a widely used material in various fields of applications because of its special properties. It is found in the design of gas sensors, photovoltaic cells dye-based nanocrystalline. It has been used as electrodes in solar cells and fuel cells, liquid crystal displays, infrared reflectors, plasma display panels (PDPs), transistors, etc .... [1]. In addition, SnO2 has environmental friendly characteristics and it is chemically stable and low cost. When doped with antimony (ATO), indium (ITO) or fluorine (FTO), it behaves like a metal. The Sb doping generates free electrons, responsible of the enhanced transport properties. The main objective of this work is to correlate the structural properties with the electrochemical and photo-electrochemical behavior of pure and doped thin layers of tin dioxide. The layers were developed by the CVD method (chemical vapor deposition) in the configuration of a horizontal reactor then characterized by X-ray diffraction and SEM analysis. The results indicate a rutile phase and a growth of pyramidal grains. Firstly we show that material properties are strongly influenced by their microstructures such as texture and crystallography.

To study the phenomena of interfaces and to better understand the processes involved, we characterize the layers deposited on various substrates by electrochemical techniques such as electrochemical impedance spectroscopy (EIS) and Mott Schottky C-2 (V) [2] in the second part. In this study, we found that antimony doped tin dioxide structures / chromate solution provides variable electrochemical properties, as well as appreciable difference in the absorbance under light confirming the reduction of chromate.

We also show by using Nyquist plot (experimental measures EIS) on these structures that the values of relaxation electrical components, conductivity, dielectric constant of the system are reduced. The n type character induced by the charge compensation mechanism is confirmed by the capacitance measurements (Mott-Schottky). The photocatalytic activity was predicted from the energy diagram and the chromate removal is used as reaction test.

References

[1] Zhen Zhu, Jin Ma, Caina Luan, Lingyi Kong, Qiaoqun Yu, Applied Surface Science 257 (2011) 2516–2519.

[2] J. Ross. Mac Donald, Impedance spectroscopy; John Wiley & Sons New York (1987).

ABSTRACT BOOK

89/499

P8-ELC_330

IN-SITU X-RAY DIFFRACTION STUDY OF PT(111) OXIDATION DURING OXYGEN

REDUCTION REACTION


J. Drnec 1,*, M. Ruge 2, F. Reikowski 2, B. Rahn 2, F. Carlà 1, R. Felici 3, O.M. Magnussen 2, D.A. Harrington 4 1ESRF - Grenoble (France), 2Institute of Experimental and Applied Physics, Kiel University - Kiel (Germany), 3CNR-SPIN - Roma (Italy), 4University of Victoria - Victoria (Canada)

ORR is one of the most studied electrochemical reactions due to its tremendous fundamental and practical importance. Oxygen is a common, readily accessible oxidizing agent and, therefore, the Pt ORR cathode is part of many energy conversion devices, e.g. fuel cells. Unfortunately, the slow kinetics of ORR negatively affects the performance and is currently one of the main bottleneck in large scale fuel cell commercialization. It has been suggested that this is partly caused by the presence of surface Pt oxides, which slow the reaction rate and trap reaction intermediates on the surface. The oxide formation and dissolution is also known to cause dissolution of Pt catalyst, which further degrades the performance. Even though the electrochemical formation of surface oxides on platinum surface has been extensively studied in the past, there are still many questions unanswered, mainly regarding the detailed structure of the oxide and its growth mechanism [1 and references therein]. Most of the studies were performed in the absence of O2, the fuel cell oxidant, and therefore they are less relevant to the fuel cell operation as gaseous O2 can modify the oxidation potentials and mechanism.

Here we show the results of an in-situ surface X-ray diffraction (SXRD) study of electrochemical oxide formation on Pt(111) and how it is influenced by the presence of O2 during ORR. The place exchange process associated with the initial stages of oxidation is followed dynamically by parallel SXRD and electrochemical measurements during cyclic voltammetry (CV) and potential step experiments in the presence and absence of oxygen. Detailed analysis at two potentials shows that the structural changes are consistent with a place exchange between Pt and O atoms, in which the exchanged Pt atoms are located directly above their original positions in the Pt(111) lattice. Adding O2 to the electrolyte does not have any significant effect on the oxidation behavior, in contrast to some literature reports, and the O2 -accelerated Pt dissolution is not caused by the negative shift in the oxidation potential. Furthermore, the ORR current decreases before oxidation, implying that the presence of the surface oxide is not the limiting factor in the ORR and the high ORR overpotential is solely due to the slow ORR mechanism on an unreconstructed surface.

References

[1] Kongkanand and Ziegelbauer, J. Phys. Chem. C, 2012, 116, 3684-3693

ABSTRACT BOOK

90/499

P9-ELC_411

ONE-POT SYNTHESIZED P(ACRYLIC ACID)/SILICA NANOHYBRIDS COATINGS FOR

PROTECTIVE APPLICATIONS


M. Mohamadpour Nazarabady *, G.A. Farzi *

Hakim Sabzevary university - Sabzevar (Iran, islamic republic of)

A series of p(acrylic acid)/silica nanohybrid coatings (P(AA)/SiO2) consisting of two different silane coupling agents, i.e. 3- methacryloxy propyltrimethoxysilane (γ-MPS) and 3-aminopropyltriethoxysilane (APTS), were developed for antibacterial and corrosion protection. As it was revealed by Fourier transform infrared spectroscopy, X-ray diffractometry and transmission and scanning electron microscopy, the two coupling agents not only serve to enhance chemically linking but also play a significant role in the morphology conduction of the well-defined nanostructures. The effect of silica content and morphology of the P(AA)/SiO2 nanohybrid coatings were investigated by electrochemical and optical density at 600 nm (O.D. 600) measurements. The electrochemical potentiodynamic measurements in Harrison’s solution, which simulates aircraft conditions, suggested that the nanohybrids deposited as coatings on aluminum (Al) substrates improved the corrosion resistance of Al. Finally, the result of antibacterial test demonstrates the effective antibacterial properties of the nanohybrids. Thus, it can be concluded that the facile one-pot rout reported here is a versatile approach to develop antibacterial and anticorrosion coatings.

Keywords: P(acrylic acid) /silica nanohybrids coating, Morphology conduction, One-pot synthesis, Antibacterial protection, Corrosion resistance.

Figure 1: Schematic of the procedure for preparation of p (acrylic acid)/silica nanohybrids. Changing the coupling agents affects the morphology, anticorrosion and antibacterial properties of the nanohybrids.

ELC - Electrochemistry at surfaces€¦ · ABSTRACT BOOK 71/499 O1-ELC_426 THE GITSAXS-BASED STUDY OF OPERANDO AL ANODIZATION ELC - Electrochemistry at surfaces N. Vinogradov 1,*,

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