Electrochemical Science Research Articles

Detection of corrosion degradation using electrochemical noise (EN): review of signal processing methods for identifying corrosion forms

Electrochemical noise (EN), as one of the most promising in situ electrochemical methods in corrosion and electrochemical science, has been developing rapidly in recent years with the advancements in instrumentation and signal processing methods. One advantage of EN is its application in long-term or early stage corrosion process monitoring because it instantly detects corrosion rate and corrosion forms. Investigators have applied various mathematical methods to extract characteristic parameters from EN. In this paper, identifying corrosion forms using parameters obtained from time domain, frequency domain and time–frequency domain is reviewed, and the correlation between parameters and corrosion forms is discussed. Finally, other in situ techniques are recommended to be employed synchronously with EN measurement in order to obtain reliable analyses.

The electrochemical impedance spectroscopy behavior of poly(aniline) nanocomposite electrodes modified by Layer-by-Layer deposition

In this manuscript we describe the EIS characterization of electrodes modified by poly(aniline) nanocomposites using the layer-by-layer technique. Important effects such as layer growth, electric connectivity, surface roughness, electrode durability and most importantly the interfacial Faradaic process dependence on the number of bilayers were thoroughly studied by electrochemical techniques. FTIR and EDS experiments corroborated the incorporation of both anionic and cationic species within the layered modified electrode. The EIS experiments showed that the low frequency capacitance can be directly correlated with the charge distribution depending on the number of bilayers onto the modified electrode and as a function of applied potential as well. Although widely described along the past few years in the electrochemical sciences aiming the construction of high performance electrodes for many different applications, there are very few detailed EIS studies that in fact describe the electrochemical activity of the layered electrodes.

The Importance of Surface OXIDE FILMS in Metal Dissolution Processes - a 20-Year Update

The presenter will update his 1995 presentation [ECS Vol. 95-19], which he presented in accepting the 1995 Carl Wagner Award of the ECS. A lot has happened since 1995, but the basics of high-rate EC dissolution processes are still there. As in 1995, I will try to show that these fundamental processes are not only important for High Rate Dissolution, but to many other areas of electrochemical science and technology as well [corrosion, semiconductors, electro-deposition, electro-synthesis and industrial elecrolytics, organic-electrochemistry, etc.]. I will draw upon my 45+ years in the field to highlight what I think are the parallels between the different areas, and how the potentially significant benefits of "cross-fertilization of knowledge" from different EC disciplines needs to be considered at least a bit seriously for maximum benefit.

The Subtleties of the Reversible Hydrogen Evolution Reaction Arising from the Nonunity Stoichiometry

The proton/hydrogen redox couple underpins the electrochemical sciences; however, the nonunity stoichiometry of the reaction leads to distinct voltammetric complications. This Article provides a joint analytical, numerical, and experimental investigation into the reversible hydrogen evolution reaction at a platinum microelectrode. Literature obscurities and nuances are highlighted and corrected, allowing the presentation of an holistic overview of the electrochemical reaction at the reversible limit. Under such conditions, it is demonstrated, first, how the reaction may be misinterpreted as being irreversible and, second, that the transfer coefficient for the reversible (Nernstian) hydrogen evolution reaction is equal to 2. Importantly, the use of the reversible hydrogen electrode (RHE) as a reference potential in voltammetric experiments is critically evaluated.

Mesoporous Materials‐Based Electrochemical Sensors

AbstractA review (350 references) is given to the interest of mesoporous materials for designing electrochemical sensors. After a brief summary of the implication of template‐based ordered mesoporous materials in electrochemical science, the various types of inorganic and organic‐inorganic hybrid mesostructures used to date in electroanalysis and the corresponding electrode configurations are described. The various sensor applications are then discussed on the basis of comprehensive tables and some representative illustrations. The main detection schemes developed in the field are (volt)amperometric sensing subsequent to preconcentration and electrocatalytic detection.

Vertically Aligned Carbon Nanotubes/Carbon Fiber Composites for Electrochemical Applications

Carbon fibers have been studied for electrochemical applications. Recently, carbon nanotubes present a wide potential uses in electric, mechanic, electrochemical and materials science field. At present study, vertically aligned carbon nanotubes were produced over carbon fibers. The process occurs catalytically by chemical vapor deposition (CVD) using mixture with camphor and ferrocene. After that, the VACNT/CF composite are treated by oxygen plasma for oxygen functionalization. Prior the electrochemical analysis, CNT/Carbon fibers are treated by hydrochloric acid to remove residual catalyst. The electrodes were tested in a usual electrolyte (with H2SO4 0.5M) in a conventional electrochemical cell. The specific capacitance was tested in a separate device. The configuration of carbon fibers and VACNT presents a high potential application for electro analytical application and energy storage.

Preparation of LaMnO3-CNF and Its Activity for Oxygen Electrode Reaction in Alkaline Electrolyte Solution

Cathode catalysts with low overpotential for oxygen electrode reaction including oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are required for the batteries that air and an alkaline electrolyte are used. For this purpose, a kind of perovskite metal oxides is promised. Although the electric conductivity is low, LaMnO3shows relatively high activity for both ORR and OER [1, 2]. To support the electric conductivity, some kinds of carbon must be required to practical use. Among the carbon materials, carbon nano fiber, which is partially used in lithium battery, is considered to be favorable because of adequate electric conductivity, high hydrophobicity, low surface area and quite low amount of surface functional groups.In this study, we attempted to prepare a new composite catalyst, that LaMnO3particles are supported on carbon nano fiber, and evaluated catalyst activity for ORR and OER. La(NO3)3 and Mn(NO3)2 aqueous solutions were respectively prepared at desired concentration and well mixed. Then, the solution was poured into (CH3)4NOH aqueous solution. After that, CNF (VGCF, SHOWA DENKO K.K.) was immediately added to the solution and stirred for 1 hour at room temperature. The product was washed with pure water and dried at 120oC for 12 hour. Finally, it was calcined under Ar atmosphere at 600oC for 5, 10 and 20 hour, 800 and 1000oC for 5 hour (600-5, 600-10, 600-20, 800-5 and 1000-5) to obtain LaMnO3 and CNF composites (LaMnO3-CNT).X-ray diffraction (XRD) was used to identify the product. The product was observed by field emission scanning electron microscope (FE-SEM). ORR and OER activity were evaluated in 0.1 mol dm-3 and 6.0 mol dm-3KOH solution by using glassy carbon or Ti substrate. Figure 1 shows FE-SEM image of 800-5. As indicated by allows in this figure, CNF is covered with particles of LaMnO3. In addition, the product that only edge parts were covered with particles and the product that was not covered with particles occasionally.Figure 2 shows XRD patterns of 800-5 and 1000-5. The patterns of 600-5, 600-10, 600-20 and 800-5 show the formation of LaMnO3 and the different crystallite size. In the case of 1000-5, La2O3and MnO are confirmed, suggesting that oxygen in the products should be consumed by CNF oxidation.Figure 3 shows hydrodynamic voltammograms of the samples in 0.1 mol dm-3KOH solution. Reduction current originated from ORR is shown below 0.85 V. From this point of view, 600-10 shows the highest on-set potential (lowest overpotential) among the samples. The detail including OER activity of the samples will be also presented. This work was supported by “Advanced Low Carbon Technology Research and Development Program (ALCA)” of Japan Science and Technology Agency (JST). [1] J Suntivich, H A. Gasteiger, N Yabuuchi, H Nakanishi, J B. Goodenough and Y Shao-Horn, DOI: 10.1038/NCHEM.1069.[2]J O’M. Bockris and Takaaki Otagawa,J Electronchem.Soc. :ELECTROCHEMICAL SCIENCE AND TECHNOLOGY p.290-302 Vol. 131,No. 2.(1984)

Development of Anodic Materials with Elevated Hydrogen Sulfide Tolerance for HT-PEMFCs Using Reformat

Proton exchange membrane fuel cells (PEMFCs) became attractive for mobile and portable applications. Even though, there are many aspects that should be optimize to have a better performance and durability [1]. One of these is the resilience of the electrode materials to contaminants generally present in the fuel. In this sense, the fuel for the PEMFC is produced by hydrocarbon reforming in a “hydrogen challenged” economy [2]. Therefore, the presence of contaminants such as CO and H2S in small amounts (ppm) is unavoidable. Unfortunately platinum (considered the best electrocatalytic material for the hydrogen oxidation reaction -hor-, occurring at the anode of the FC) has a large capability to adsorb these species. Consequently, low quantities of contaminant in the fuel can notably diminish the performance of the FC electrodes.In contrast to the CO poisoning, there is not so much information regarding to the contamination of the PEMFC electrodes by H2S. Similarly to CO, bimetallic materials represent a good alternative to investigate in order to increase the tolerance of the fuel cell to the presence of H2S in the hydrogen used as fuel. In the case of the sulfur species the authors suggest the use of Pt-M electrodes, where M could be: Pd, Cu, Ru, Rh, Ir, Co, etc. [3]. Taking this into account, this work is going to focus on the development of anodic materials with high tolerance to H2S. For this purpose the electrocatalytic activities of the materials for the hor in presence of H2S under HT-PEMFC conditions were evaluated.The working electrodes tested consist of homemade Pt, MB (base metal) and Pt-MB supported on carbon and deposited on a GDL H2315 (FREUDENBERG FCCT SE & CO.KG9). A three electrode cell working under HT-PEMFC conditions and connected to a DEMS (to analyze the released gases) was used to evaluate the inhibition of the material by H2S. H3PO4 85% (Carl Roth) was used as electrolyte. A RHE in the same medium was used as a reference electrode, and a large area Pt electrode as counterelectrode. The measurements were carried out at 145°C and ambient pressure. Phosphoric-acid-doped polybenzimidazole (PBI) membranes were used as separators.Dependences of the steady state current on the potential for the tested materials are presented in Figure 1. There is appreciable that MB is electrochemically inactive for the hor. Even though, at lower overpotentials (where the hor occurred) Pt-MB shows higher electrocatalytic activity than Pt (more considering that in Pt-MB the Pt active area expose is smaller). Besides that, by DEMS was verified that the ratio of SO2 to H2S in the exhaust is higher for Pt-MB than for Pt, indicating an increased conversion of H2S. Also it is observed in Figure 1 that at higher potentials (of interest in the cathodic side of the FC), the Pt-MB shows higher activity relatively close to Pt. Even more, in Figure 2 is shown that the formation of SO2 as product of reaction is also very high.Considering all this experimental evidence it is possible to conceive the implementation of this kind of materials as electrodes in the HT-PEMFCs in order to improve the tolerance to H2S. References S. Gottesfeld, T.A. Zawodzinski, in: R.C. Alkire, H. Gerischer, D.M. Kolb, C.W. Tobias (Eds.), Advances in Electrochemical Science and Engineering, vol. 5, John Wiley, 1998, p. 195.B.M. Besancon, V. Hasanov, R. Imbault-Lastapis, R. Benesch, M. Barrio, M.J. Mølnvik, Int. J. Hydrogen Energy, 2009, 34, p. 2350.T. Lopes, V. A. Paganin, E. R. Gonzalez, Int. J. of Hydrogen, 2011, 36, p. 13703.

Keynote: Product Development Based on Electrochemical Science and Engineering

Two examples, one of a successfully developed process and the other of a successfully developed product, are presented with a focus on the engineering approach used in the development process. The process is for mediated electrosynthesis and the product is a multi-layer battery separator for use in lithium-ion batteries. Each example is used to highlight the following steps in product development:1) Identify a need.Recognize long-term trendsDo good and people will help you 2) Establish in-house tests to validate that the need is met and to benchmark.Ask customers for help 3) Develop a product to address the need.Ask the best and brightest for helpUse the best tools you can – rent, borrowBe precise about what you know – don’t let prior work blind you to new opportunitiesDon’t give up to chase another product (enthusiasm is inversely proportional to knowledge), development often takes a decadeUse modeling, especially financial, whenever possible to provide directionPromptly protect your know-how as generally as possibleTry to improve on what works, don’t keep doing what doesn’t work, recognize statistical nature of testing 4) Validate through customer evaluation that the need is met. A novel process for mediated electrosynthesis was successfully developed [1-4]. The long term trend which encouraged this development is electrification [5]. The historical trajectory toward lower cost and higher efficiency of electricity encouraged its use for chemical production. However, a financial analysis revealed that electrochemical synthesis is a relatively expensive, capital-intensive means of producing chemicals. So high-value chemicals which are difficult to produce by conventional processes were targeted. Mediated electrosynthesis of aldehydes was identified as a commercially attractive process. A team including an inorganic chemist and chemical engineer was directed to develop a process. The poor solubility of mediators emerged as a critical problem and was solved by use of methanesulfonate as a counter-ion. Process modeling, following the work of Alkire et al. [6], helped identify optimize the process and small-scale lab testing of a continuous process proved feasibility of the process design. The process was transferred to a customer who carried out pilot-scale testing to validate the process.A multi-layer battery separator [7-8] was successfully developed. The growth of consumer electronics and accompanying need for batteries and battery separators was the long-term trend that drove this effort. Customers were instrumental in defining requirements for thermal stability and tensile strength. The original approach of uniaxial orientation of a membrane prepared by thermally induced phase separation was dropped when testing revealed the tensile strength requirement could not be met without an expensive biaxial orientation. Based on customer feedback, some iterations on the product were necessary before sales were made.References1) US 4,639,298 “Oxidation of Organic Compounds Using Ceric Ions in Aqueous Methanesulfonic Acid,” 27Jan1987.2) US 4,692,227 “Oxidation of Organic Compounds Using Thallium Ions,” 8Sep19873) US 4,647,349 “Oxidation of Organic Compounds Using Ceric Ions in Aqueous Trifluoromethanesulfonic Acid,” 3Mar19874) US 4,670,108 “Oxidation of Organic Compounds Using Ceric Methanesulfonate in an Aqueous Organic Solution,” 2Jun19875) J. Bockris ” Electrochemistry of Cleaner Environments” Springer 1972.6) R. Alkire, R. La Roche, G. Cera, M. Stadtherr “Computer-Aided Simulation of Electrochemical Process Flowsheets”, J. Electrochemc. Soc. 133(2) (1986) 290-295.7) US 5,240,655 “Process of Making a Battery Separator,” 31Aug19938) US 5,281,491, “Battery Separator”, 25Jan1994

Determination of the Corrosion Probability in Reinforced Concrete Structures by Design in Situ Monitoring System

Introduction Corrosion of concrete rebar has been established as the main factor of the premature deterioration of reinforced concrete structures. The occurrence of such phenomena represents mostly the durability problems of the material, especially when the structure is subjected to the chloride ions presence (in marine or high salinity enviroment) and large amounts of carbon dioxide (CO2 ), processes known as chloride penetration and carbonation respectively[1,2,3]. Once the corrosión process has appeared in rebar, these begin to generate large stresses on the layer of concrete around them (due to the iron oxides that accumulate around the transversal area) which over time can generate microcracks, cracks and failure on the general structure[4].Given the importance of preserving civil structures, is evident the strong necessity of obtaining a system with great flexibility to perform the estimation in situ of the corrosive state, capable to dispose the information for immediate consultation anywhere with minimum internet access. Therefore, the present work shows the development and implementation of a system for in situ monitoring of corrosion, for any reinforced concrete structure based on ASTM C876-91[5] standard for measuring half-cell potential, with which it is possible to determine the corrosion probability of rebar in reinforced concrete structures. Also, the equipment performance is presented by using different reference electrodes as Copper / Copper Sulfate (Cu -CuSO4 ), silver / silver chloride (Ag / AgCl) and Zinc / Zinc Sulfate (Zn -ZnSO4 ). Experiments and Results It was obtained a system for in situ monitoring of corrosion for reinforced concrete, that allows to estimate the corrosion probability on rebar, where the user send a text message, to start the test in the system and in return, via GPRS (General Packet Radio Service), the equipment disposes the data trend on a graphic trough a web server on an internet domain (figure 1). The system was tested on a building of the University complex, where its performance was evaluated using three different reference electrodes, obtaining an error over the measurement, between the standard and the system, of 6.62% (figure 2). References (1) ROA-RODRIGUEZ, G., APERADOR, W., DELGADO, A. Calculation of Chloride Penetration Profile in Concrete Structures. International Journal of Electrochemical Science. v. 8, p. 5022-5035, Apr. 2013 (2) HA WONG, S., VELI, S. Corrosion Monitoring of Reinforced Concrete Structures - A Review. International Journal of Electrochemistry Science, v. 2, p. 1 – 28, Jan. 2007. (3) SATHIYANARAYANAN, S., PANJALI NATARAJAN, K., SARAVANAN, S., SRINIVASAN, G. Corrosion monitoring of steel in concrete by galvanostatic pulse technique. Cement & Concrete Composites, v. 28, p. 630-637, May. 2006. (4) SHAMSAD, A., Reinforcement corrosion in concrete structures, its monitoring and service life prediction––a review. Cement & Concrete Composites, v. 25, p. 459 – 471, May. 2003 (5) ASTM Standard C876-09, 1991, Standard Test Method for Corrosion Potentials of Uncoated Reinforcing Steel in Concrete. ASTM International, West Conshohocken, PA, 2003, DOI: 10.1520/C0876-09.

A Comprehensive Electrochemical Solution to Climate Change: STEP, the Solar Thermal Electrochemical Pressure Process for the Production of Societal Staples

The solar thermal electrochemical pressure process is capable of the production of societal staples with little or no carbon footprint, and can directly capture & convert carbon dioxide from the air that can be stored as useful graphite.In STEP the efficient formation of metals, fuels, cement, chlorine, and carbon capture is driven by solar thermal heated endothermic electrolyses of concentrated reactants occurring at voltage below that of the room temperature energy stored in the products. As one example, CO2 is reduced to either fuels, or storable carbon, at solar efficiency higher than the best photovoltaics. This is due to a synergy of efficient solar thermal absorption and electrochemical conversion at high temperature and reactant concentration. CO2-free STEP iron production, from iron ore, occurs via Fe(III) in molten carbonate. Water is efficiently split to H2 by molten hydroxide electrolysis, and chlorine, sodium and magnesium from molten chlorides. STEP cement uses a novel molten electrochemistry for the production of calcium oxide (lime from limestone).1-7 The solar electrochemical generation of societal staples and fuels decreases society's dependence on grid-based electricity. A pathway is provided for the STEP decrease of atmospheric carbon dioxide levels to pre-industrial age levels in 10 years.Selected STEP references:(1) S. Licht, "STEP generation of energetic molecules: A solar chemical process to end anthropogenic global warming," J. Phys. Chem., C, 2009, 113, 16283-16292.(2) S. Licht, B. Wang, S. Ghosh, H. Ayub, D. Jiang, J. Ganley, "A New Solar Carbon Capture Process: STEP Carbon Capture," J. Phys. Chem. Lett., 2010, 1, 2363-2368, with online 2 page supplement.(3) S. Licht, "Efficient Solar-Driven Synthesis, Carbon Capture, and Desalinization, STEP: Electrochemical Production of Fuels, Metals, Bleach," Advanced Materials, 2011, 47, 5592-5612.(4) S. Licht, H. Wu, C. Hettige, B. Wang, J. Lau, J. Asercion, J. Stuart, " STEP Cement: solar thermal electrochemical production of CaO without CO2 emission " Chem. Comm., 2012, 48, 6019-6021, with online 20 page supplement.(5) B. Wang, Y. Hu, H. Wu, S. Licht, "STEP Pollutant to Solar Hydrogen: Solar driven thermal electrochemical wastewater treatment with synergetic production of hydrogen," Electrochemical Science Letters, 2013, 2, H34-H36.(6) B. Cui, S. Licht, ”Critical STEP advances for sustainable iron production,” Green Chemistry , 2013, 15(4), 881-884, with 16 page online supplementary information(7) S. Licht, B. Cui, B. Wang, ”STEP Carbon Capture: the barium advantage,” Journal of CO2 Utilization, 2013, 2, 58-63.

Determination of the Mechanisms of Electrocatalytic Reactions by Combining Electrochemical Methods and In Situ Spectroscopy

Many electrochemical reactions of technical interest (fuel cells, electrolyzers, etc.) need the development of efficient catalysts to increase the reaction rate and selectivity. In order to find new electrocatalysts it is of prime importance to elucidate the reaction mechanisms by identifying the different intermediates involved and elucidating their role in the rate determining step (r.d.s.).Apart from the hydrogen oxidation and evolution reactions, the mechanisms of which are thoroughly established, the oxygen reduction (ORR) and evolution reactions (OER), or the oxidation of low weight alcohols in a Direct Alcohol Fuel Cell (DAFC), are relatively complex since they involve multi electron transfer with the formation of several adsorbed intermediates and reaction by-products. The reaction rate of ORR is very low and it is the main cause of energy efficiency limitation in a Polymer Electrolyte Fuel Cell (PEFC) [1-3]. Alcohols (particularly methanol and ethanol) are of great interest as liquid fuels in a DAFC [4–10], but a rather poor kinetics of their electroxidation is observed with platinum, the only catalyst activating the C–H bond cleavage at ambient temperatures. The adsorption and oxidation of methanol and ethanol on a Pt electrode lead to the formation of poisoning species (mainly adsorbed CO), as observed by in situinfrared reflectance spectroscopy [11-12]. In both cases, the formation of such poisoning species leads to a poor electrocatalytic activity, and the challenge is to enhance the activity of platinum by avoiding the formation of poisoning species through the development of bimetallic or multi-metallic platinum-based electrocatalysts.The elucidation of the reaction mechanisms needs the use of different spectroscopic and analytical techniques under electrochemical control, i.e. the combination of electrochemical methods with other physicochemical techniques. This allows identifying the nature of adsorbed intermediates, the structure of adsorbed layers, the nature of the reaction products and by-products, etc., and determining the amount of these species, as a function of the electrode potential and experimental conditions. This will lead to a deep understanding of the reaction mechanisms, which are depending on the nature of the catalyst, the composition and structure of the electrode.In this communication we will present spectro-electrochemical methods (Infrared Reflectance Spectroscopy [13], Electron Spin Resonance Spectroscopy [14] and UV-visible Reflectance Spectroscopy [15]) able to identify in situthe adsorbed species and reaction products involved in electrochemical reactions of great interest for energy conversion. For the ORR, the comparison of electrochemical data from rotating disc electrodes with results from spectroscopic methods gives information on the reaction mechanism. For alcohol electroxidation reactions, the coupling of electrochemical measurements with Infrared Reflectance Spectroscopy allows the identification of the intermediate species and reaction products as a function of the electrode potential and of its structure. This allowed proposing mechanisms for the reactions involved in electrochemical reactions encountered in the development of Fuel Cells or Electrolyzers: the Oxygen Reduction Reaction and the electroxidation of some alcohols (methanol, ethanol, ethylene glycol, and glycerol). References[[1] G. J. K. Acres, J. C. Frost, G. A. Hards, R. J. Potter, T. R. Ralph, D. Thompsett, G. T. Burstein, G. J. Hutchings, Catal. Today, 38 (1997) 393-400.[2] T.R. Ralph, M.P. Hogarth, Platinum Metals Rev., 46 (2002) 3-14.[3] C.-C. Yang, Int. J. Hydrogen Energy, 29 (2004) 135-143.[4] C. Lamy, A. Lima, V. Le Rhun, F. Delime, C. Coutanceau, J.-M. Léger, J. Power Source,s 105 (2002) 283-296.[5] E. Peled, T. Duvdevani, A. Aharon, A. Melman, Electrochem. Solid State Lett., 4 (2001) A38-A41.[6] C. Lamy, J.-M. Léger, S. Srinivasan, Direct Methanol Fuel Cells: From a twentieth century electrochemist’s dream to twenty-first century emerging technology, in "Modern Aspects of Electrochemistry", J.O’M. Bockris and B.E. Conway (Eds.), Vol. 34, Plenum Press, New York, 2000, Chapter 3, pp.53-118.[7] C. Lamy, E.M. Belgsir, J.-M. Léger, J. Appl. Electrochem., 31 (2001) 799-809.[8] T. Iwasita-Vielstich, in Advances in "Electrochemical Science and Engineering", H. Gerischer and C.W. Tobias (Eds.), Vol.1, VCH Verlag, Weinheim, 1990, p. 127.[9] A. Hamnett, Catal. Today 38 (1997) 445-457.[10] K. Y. Chan, J. Ding, J. W. Ren, S. A. Cheng, K.Y. Tsang, J. Mater. Chem., 14 (2004) 505-516.[11] B. Beden, F. Hahn, S. Juanto, J.M. Léger, C. Lamy J. Electroanal. Chem., 225 (1987) 215.[12} J.M. Perez, B. Beden, F. Hahn, A. Aldaz, C. Lamy, J. Electroanal. Chem., 262 (1989) 251.[13] B. Beden, C. Lamy, Infrared reflectance spectroscopy, in "Spectroelectrochemistry - Theory and Practice", R.J. Gale (Ed.), Plenum Press, New York, 1988, Chapter 5, pp. 189-261[14] P. He, C. Cha, P. Crouigneau, J.M. Léger, C. Lamy, J. Electroanal. Chem., 290 (1990) 203.[15] O. El Mouahid, A. Rakotondrainibe, P. Crouigneau, J.M. Léger, C. Lamy, J. Electroanal. Chem., 455 (1998) 209.

Phase Field Modeling of SEI layer morphology in Li-Ion Batteries

Lithium-ion batteries (LIBs) suffer severe performance degradation during their lifetime application because of the undesired chemical reactions, ageing, corrosion, structural integrity compromise, and the threat of thermal runaway. Among those degradation mechanisms, much attention has been focused on LIBs materials decomposition, new components formation and growth due to undesired side reactions. The electrode is covered by a passivation layer named as the solid electrolyte interface (SEI), which is one of dominant LIBs degradation mechanisms. The SEI layer affect the LIBs cyclability, life time, power and rate capability, and even their safety. Growth of the SEI reduces the lifetime of LIBs and increases cell internal resistance.Many researchers have investigated the SEI layer in term of structure, formation and compositions, thickness growth prediction and measurement. The SEI is believed to have multilayered structure, a thin layer of inorganic components close to the anode, and followed by a thick porous organic or polymeric layer close to the electrolyte phase. The composition of SEI layer can be distinguished to include Li2CO3, LiOH, LiF, Li2O, ROCO2Li and RCOLi (1). The SEI on the cross-section is dominated by Li and F and on the basal plane is dominated by organic materials. Heavy organic fragments were found mainly at the surface of the basal SEI. The thickness of the SEI on the basal plane was found to be three to five times smaller than that on the cross-section (2). Compare to the experiment, the simulation work will be more flexible. Yan et al phenomenologically modeled the formation and evolution of the SEI on the graphite electrode. Within the framework of classical nucleation theory (CNT), they qualitatively explained the origin of the two-layer structure of SEI films (3). Broussely et al. proposed their diffusion-limited SEI growth model, then tried to explain the mechanism of lithium loss for LIBs during storage and gave us the rate of lithium loss is proportional to the SEI electronic conductance(4). Kim et al. simulated the effect of electrolytes on the structure and evolution of the SEI (5).Although much work has already been done with the SEI study, the morphology of SEI layer is still not fully understood, especially in term of SEI structure prediction. In this work, we will predict the morphologies of the SEI using the phase field (6-8). The phase field model has been applied in many electrochemical studies to simulation the electrochemical reactions and to model the phenomena as roughness formation and electronically mediated reactions between interfaces in electronic contact. Also the phase field model is more accurate in regions with sharp composition gradients and can treat phase boundaries without the need to explicitly track interfaces. Phase field model can be used as a potentially powerful tool for modeling the structure of the SEI in LIBs.1. F. M. Wang, M. H. Yu, Y. J. Hsiao, Y. Tsai, B. J. Hwang, Y. Y. Wang and C. C. Wan, International Journal of Electrochemical Science, 6, 1014 (2011).2. E. Peled, D. Bar Tow, A. Merson, A. Gladkich, L. Burstein and D. Golodnitsky, Journal of Power Sources, 97–98, 52 (2001).3. J. Yan, B.-J. Xia, Y.-C. Su, X.-Z. Zhou, J. Zhang and X.-G. Zhang, Electrochimica Acta, 53, 7069 (2008).4. M. Broussely, S. Herreyre, P. Biensan, P. Kasztejna, K. Nechev and R. J. Staniewicz, Journal of Power Sources, 97–98, 13 (2001).5. S.-P. Kim, A. C. T. v. Duin and V. B. Shenoy, Journal of Power Sources, 196, 8590 (2011).6. B. C. Han, A. Van der Ven, D. Morgan and G. Ceder, Electrochimica Acta, 49, 4691 (2004).7. J. E. Guyer, W. J. Boettinger, J. A. Warren and G. B. McFadden, Physical Review E, 69, 12 (2004).8. J. E. Guyer, W. J. Boettinger, J. A. Warren and G. B. McFadden, Physical Review E, 69, 13 (2004).

Advanced Diagnoses on Dead Ended Anode Operations for Proton Exchange Membrane Fuel Cell Stacks

Proton Exchange Membrane Fuel Cells (PEMFCs) offer the possibility of zero-emission electricity generation. The technology has shown tremendous advances in terms of performance and durability and wide-scale commercialization in a range of applications is imminent. In order to make further improvements to the key performance metrics, it is important that we know as much as possible about the way the fuel cell is working in space and time. Electrochemical impedance spectroscopy (EIS) is a powerful in situ diagnostic technique for monitoring fuel cell performance; however, its use is limited to steady state conditions and typically requires costly hardware. A low-cost multichannel impedance analyzer developed during this project using a commercial data acquisition National Instrument hardware and LabVIEW in house software[1]. This novel diagnostic system is applied to a commercial Intelligent Energy air-cooled open-cathode 5-cell PEMFC stack.Fig. 1. (a) Voltage loss at 0.75A cm-2 in Through flow and Dead ended conditions. (b) Reconstructed Nyquist plots at 0.75A cm-2 in Through flow and Dead ended conditions.This system was used to distinguish the causes of the voltage loss in dead ended anode conditions. A novel reconstructive impedance strategy was developed. The same frequency of interest was measured every 20 seconds in through-flow and dead-ended conditions. The events were repeated, but changing the frequency of interest (1 kHz to 1 Hz) at each repeat. It was found possible to associate Nyquist plots with different stages of the voltage loss over time (Fig 1 a). These results (Fig 1 b) highlight an increase of the resistance in the low frequency region during dead-ended operation, an indication of flooding. Thus the reconstructive impedance technique enables the study of dynamic processes, unsuitable for investigation using steady-state EIS. The influence of the current density on the voltage loss during a purge was also investigated (Fig 2). This result highlights the role of water in causing the voltage drop, since the amount of accumulating water is proportional to the current density. However, off gas analysis, inserting the probe between the hydrogen exhaust and the purge valve, also highlighted that the nitrogen accumulation is also proportional to the current density. This result suggests that the accumulation of nitrogen does not only come from permeation from the air through the membrane, but also from the small quantity contained in the hydrogen (50 ppm at BOC zero grade), with an accumulation rate proportional to the hydrogen consumption rate and to the volume of the anodic compartment.Fig. 2. Evolution of the voltage losses (a) and nitrogen accumulation (b) from 0.4 to 1 A cm-2in dead ended anode.In addition, a 16-segment S++ plate, capable of current, temperature and impedance mapping enabled to move from global to localized in situ measurements. The local and temporal evolution of the ohmic resistance, current density and temperature was studied as the current density was increased in order to provide more information on the process described Fig.2. Also, the heat distribution profile, obtained simultaneously from the S++plate and the thermal imaging camera provided a grid of the temperature distribution inside the stack and at its edges.Reference:[1] Q. Meyer, S. Barass, O. Curnick, T. Reisch, and D. J. L. Brett, “A multichannel frequency response analyser for impedance spectroscopy on power sources,” Journal of Electrochemical Science and Engineering, vol. 3, no. 3, pp. 107–114, 2013.

Synthesis, characterization and electrochemical recognition of metal ions of three new ferrocenyl derivatives containing pyridyl moiety

Three new ferrocene (Fc) based receptors with pyridyl moiety, named methyl-6-ferrocenoylacetyl-2-pyridine carboxylate (FcL1), 1,1′-(2,6-bispyridyl)bis-3-ferrocenyl-1,3-propanedione (FcL2), ferrocenecarboxaldehyde-2,6-dipicolinoyhydrazone (FcL3) were synthesized, and further characterized by elemental analysis, IR spectra, UV-Vis spectra, 1H and 13C NMR. The electrochemical properties and ion sensing properties of FcL1, FcL2 and FcL3 were also investigated by means of cyclic voltammetry in ethanol solution with 0.1 mol/L LiClO4 as the supporting electrolyte. The E0 values of the receptors increase with the scanning rate increasing at high scanning rate, and Ipa/Ipc approaches unity, indicating that the redox reaction is basically reversible. Their recognition performances to different metal cations such as Cd(II), Co(II), Cu(II), Hg(II), Mn(II), Ni(II), Zn(II) show that the FcL1 is responsive to Cu(II) with the maximum electrochemical shift of the FcL1 for Cu(II) of about 72.0 mV, whereas the FcL2 is responsive to Cu(II) and Mn(II) with shift of 102 mV and 109 mV, respectively, and the FcL3 is responsive to Hg(II) and Mn(II) with the shift of 53.0 mV and 54.0 mV, respectively. All the results show that these receptors may have potential applications in electrochemical sensor technology, material science, and molecular devices.

Keith B. Oldham, Jan C. Myland and Alan M. Bond: Electrochemical Science and Technology. Fundamentals and Applications

Keith B. Oldham, Jan C. Myland and Alan M. Bond: Electrochemical Science and Technology. Fundamentals and Applications

Visualization of Oxygen Consumption of Single Living Cells by Scanning Electrochemical Microscopy: The Influence of the Faradaic Tip Reaction

The respiration activity of an individual living cell is an indicator of its metabolic vitality. Closely positioned microelectrodes have been suggested for determination of the respiration activity by monitoring the local oxygen concentration. Although first attempts for visualization of the oxygen consumption rate of single living cells by means of scanning electrochemical microscopy (SECM) were already described in 1998, evaluation of the respiratory activity of individual cells remains challenging and the complexity is often underestimated. In particular, the dimensions of the cell itself lead to limitations of conventionally used constant-height mode SECM investigations. Apart from convolution of the oxygen reduction current at the SECM tip with topographic effects, constant-height mode experiments require working distances comparable or below the height of the cell body, thus increasing the risk of tip crash. Attempts to overcome these restrictions include among others positioning of the tip to distances outside the feedback range, embedding of the cells into cavities, or efforts to subtract topographic contributions after cell death. Moreover, as living cells are irregular in dimension, the tip-to-cell distance varies with the tip position. Therefore, constant-distance mode (cd-mode) SECM techniques are inherently advantageous for this purpose. In particular, coupling SECM with scanning probe techniques, such as atomic force microscopy (AFM) and scanning ion conductance microscopy (SICM) as well as shearforce and impedance-based techniques, led to efficient strategies to control the tip-to-sample separation. Recently, we described a shearforce-based cd method (4D SF/ CD-SECM) that is able to work at various tip-to-sample separations. It can hence detect complete diffusion profiles in the surroundings of sources or sinks of redox-active species. Although SECM distance control systems are available, the detection of the respiration activity of single living cells remains challenging. Owing to the small rate of oxygen consumption by a single cell, only small current variations ontop of a high background current are measured. Even more importantly, a biological cell acts as an immiscible liquid– liquid interface in a SECM experiment. Lipophilic redox mediators are known to undergo transmembrane diffusion processes and can be utilized to investigate intracellular redox activity. However, concentration changes in the vicinity of the cellular membrane, for example by the tip reaction, may induce local concentration gradients and cause a diffusional exchange of redox species over the lipid bilayer in a socalled SECM-induced transfer (SECM-IT) mode. The high solubility of oxygen in lipids promotes this transmembrane diffusion and oxygen can easily cross the cell membrane. This diffusion process superimposes the detection of cell respiration. As a result, in most reports addressing detection of cell metabolism based on the detection of variations in the local oxygen concentration, the positioned microelectrode does not act as a passive observer but actively influences the oxygen concentration inside the gap between tip and cell, resulting in imaging artifacts that have not previously been addressed. Even though mentioned occasionally, this effect was neglected in SECM investigations of respiration activity at living cells. Herein, we address the influence of the oxygen reduction rate at the SECM tip on imaging the respiration activity at living cells. We provide strategies to avoid limitations resulting from a strong tip reaction using a potential pulse profile at the tip with a time dependent data acquisition in the shearforce-based cd-mode of SECM. Commonly, the detection of the local oxygen concentration in close proximity to the cell body is performed by means of a variation of the generator-collector mode of SECM with the tip being continuously polarized at oxygen reduction potential. The tip competes with the respiring living cell for the available oxygen inside the gap between SECM tip and cell surface. Crossing the cell body during a SECM line scan should therefore lead to a decrease of the tip current owing to a locally lowered oxygen concentration caused by cell [*] Dr. M. Nebel, S. Gr tzke, Prof. Dr. W. Schuhmann Lehrstuhl f r Analytische Chemie, Elektroanalytik & Sensorik and Center for Electrochemical Sciences, CES Ruhr-Universit t Bochum Universit tsstrasse 150, 44780 Bochum (Germany) E-mail: wolfgang.schuhmann@rub.de

Electrochemical Science and Technology

Electrochemical Science and Technology

Multiphysics Design and Development of Heterogeneous Functional Materials for Renewable Energy Devices: The HeteroFoaM Story

The electrochemical science that makes many energy conversion and storage technologies work rests on our knowledge and understanding of heterogeneous materials and material systems. The function and functionality of those systems share many common features across a wide range of technologies including fuel cells, batteries, capacitors, and membranes. The science that controls that functionality for these complex material systems is typically summoned in fragments to design a specific device. The present paper discusses an attempt to create a codified multiphysics approach to that general subject, across multiple scales in space and time, for heterogeneous functional materials, or “HeteroFoaM” as we call it. The scope of the paper will be necessarily limited to a general definition of the problem focused on a few specific examples of the progress made for directions that support technologies such as conversion of chemical energy to electricity, membranes for selective transport, and charge storage devices. The principal motivation for this approach is to establish the science that controls emergent properties in heterogeneous functional materials as a foundation for design of functional material systems with performance not bounded by constituent properties.

Preface to the Focus Issue on Nanocarbons for Energy Harvesting and Storage

We are pleased to present a Focus Issue of the ECS Journal of Solid State Science and Technology (JSS) on nanocarbons for energy harvesting and storage. Fullerenes, carbon nanotubes and graphene have taken a solid place in modern science and technology, as demonstrated by the awarding of two Nobel Prizes – the first, in Chemistry, was given in 1996 to Robert F. Curl Jr., Sir Harold Kroto and Richard E. Smalley for the discovery of fullerenes. The second, in Physics, was awarded in 2010 to Andre Geim and Konstantin Novoselov for the isolation of graphene. Since 1985, more than 115,000 scientific papers have been published on topics devoted to fullerenes, carbon nanotubes, graphene and related materials and there is no doubt that these types of carbon nanomaterials, with their unique structures and properties, will continue to find many new applications in all areas of science, medicine and technology, including electrochemical science and technology.