bluuebunny/crossref_metadata_2025_split huggingface dataset:
Structural and Chemical Analysis By Transmission Electron Microscopy of Pt-Ru Membrane Precipitates in Proton Exchange Membrane Fuel Cell Aged Under Reformate
Authors: Escribano Sylvie , Guetaz Laure , Henry Philemon A. , Jacques Pierre-André 
Published: February 2020

Carbon supported platinum-ruthenium (Pt-Ru/C) nanoparticles are used as anode catalysts in PEMFCs operated under reformate owing to their good carbon monoxide tolerance. The stability of these catalysts during fuel cell operation is still not well known. In this work, we have studied by transmission electron microscopy (TEM) the microstructural evolution of a membrane/electrode assembly after a 1,000 h ageing test under reformate (26 ppm of CO) representative of a stationary application. The analyses clearly show evidence of Ru dissolution from the anode with the observation of Pt-Ru precipitates in the membrane and of small Ru precipitates in some areas of the microporous layer near the anode. This Ru dissolution happens despite a rather low estimated anode overpotential (around 0.2V). The distribution of the Pt-Ru membrane precipitates was found to be similar to that observed in aged MEAs with pure Pt catalysts, i.e. a precipitation band several micrometres away from the cathode catalyst layer made of the largest precipitates along with smaller precipitates between the band and the anode catalyst layer. The structure and the chemistry of the membrane precipitates were accurately analysed 1. The high resolution TEM images and EDS (Energy Dispersive X-Ray Spectroscopy) Pt, Ru elemental maps show that the largest precipitates display a singular flower shape consisting of a Pt-rich face-centred cubic ( fcc) crystallographic structure core surrounded by a Ru-rich hcp (hexagonal close-packed) crystallographic structure shell (Fig. 1 a and b). These results suggest a precipitate formation mechanism (Fig. 1c) where the Ru reduction is catalysed by Pt within the membrane. Moreover, the localization of the precipitation band near the cathode seems to indicate that the Pt in the precipitates comes from the dissolution of cathodic Pt/C and that both Pt and Ru ions are reduced by the hydrogen crossover.
In addition, the degradation of a MEA aged in a stack under 10 ppm of CO was studied. The MEA degradation was analysed in different zones of the MEA surface area; near the gas inlet, outlet and in the middle. As the durability tests were applied with continuous registration of current density maps thanks to a S++ ® current scan line device, the observed degradation heterogeneities has been correlated to the local conditions.

1 P. A. Henry, L. Guétaz, N. Pelissier, P.-A. André, S. Escribano, J. Power Sources 275 (2015) 312-321

Aknowledgement : This work was supported by the European Union’s Seventh Framework Program (FP7/2007-2013) for the Fuel Cells and Hydrogen Joint Technology Initiative under grant agreement n°256776 (FCH-JU project Premium Act).

Figure 1
Activity and Durability of Iridium Nanoparticles in Oxygen Evolution
Authors: Alia Shaun M , Kocha Shyam S , Pivovar Bryan S 
Published: February 2020

Electrolysis is near parity as an energy storage process when compared to the cost of competing technologies, including batteries, pumped hydro, and compressed air.[1] When coupled with renewable energy sources, such as wind and solar, electrochemical water splitting can also produce hydrogen using a nearly carbon free pathway.[2] Iridium nanoparticles are commonly used as electrocatalysts in acidic electrolyzers due to moderate stability and activity in the oxygen evolution reaction. The activity and durability of iridium nanoparticles has been studied in rotating disk electrode half-cells to develop methods for establishing electrochemical baselines.
Mercury underpotential deposition has been used to determine the surface areas and specific activities of iridium catalysts.[3] This evaluation method has proved beneficial to those used previously since similar surface areas are obtained prior to and following exposure to high potential and the irreversible oxidation of surface iridium. Through mercury adsorption, the intrinsic activities of oxygen evolution catalysts can be evaluated and used to direct future electrocatalyst development.
The activities of iridium nanoparticle have been evaluated over a wide range of potentials in the kinetic region and transport limitations generally become a factor at potentials greater than 1.5 V vs a reversible hydrogen electrode. Initial optimization of electrode coating processes has further provided a robust benchmark in oxygen evolution. Accelerated stress tests have been applied in rotating disk electrode half-cells using potential cycling and potential holds. At moderate potential, activity losses are generally attributed to losses in surface area by nanoparticle agglomeration. Although bubble formation may destabilize the catalyst layer, similar experiments in hydrogen peroxide and formic acid oxidation have suggested that this loss is unique to the higher potentials in oxygen evolution. At elevated potential, heavy activity losses are observed and are increasingly due to iridium dissolution into the electrolyte.
This study establishes rotating disk electrode testing protocols for iridium in oxygen evolution. The observed losses in accelerated stress tests have significant implications on acidic electrolyzers, particularly at low iridium loadings.
[1] K. Harrison, M. Peters, in: U.S. Department of Energy (Ed.), http://www.hydrogen.energy.gov/pdfs/review13/pd031_harrison_2013_o.pdf, 2013.
[2] K. Harrison, M. Peters, C. Ainscough, in: U.S. Department of Energy (Ed.), http://www.hydrogen.energy.gov/pdfs/progress13/ii_a_2_harrison_2013.pdf, 2013.
[3] S.P. Kounaves, J. Buffle, Journal of The Electrochemical Society, 133 (1986) 2495-2498.
Fundamental Studies of Ion Sorption, Diffusion and Transport in Polyelectrolyte Membranes
Authors: Kamcev Jovan , Paul Donald R. , Freeman Benny D. 
Published: February 2020

Charged polymer membranes are widely used for water purification applications involving control of water and ion transport, such as reverse osmosis and electrodialysis, as well as applications such as fuel cell membranes. Efforts are also underway worldwide to harness separation properties of such materials for energy generation in related applications such as reverse electrodialysis and pressure retarded osmosis. Improving membranes for such processes would benefit from more complete fundamental understanding of the relation between membrane structure and ion sorption, diffusion and transport properties in both cation and anion exchange membrane materials. Ion-exchange membranes often contain strongly acidic or basic functional groups that render the materials hydrophilic, but the presence of such charged groups has a substantial impact on ion (and water) transport properties. This presentation will discuss aspects of chemistry, thermodynamics, and transport that are or may be at play in such membrane processes. Our long-term goal is to develop and validate a common framework to interpret data from both electrically driven and concentration gradient driven mass transport in such polymers and to use it to establish structure/property relations leading to rational design of membranes with improved performance. Questions of interest include how to properly formulate sorption and transport relationships, how to decouple effects of fixed charge density and water content on sorption and transport properties, how fixed charges affect mobility of counterions and coions, etc. Ion sorption and permeability data were used to extract information about salt diffusion coefficients in charged membranes. Techniques have been developed to determine concentrations of both counter-ions and co-ions in polymers. Salt permeability, sorption and ionic conductivity data have been combined to determine individual ion diffusion coefficients in neutral, cation exchange and anion exchange polymers. The use of models to correlate and, in many cases, predict the experimental data is discussed.
Autostack - CORE - Industry Led European Consortium to Develop Next Generation Automotive Stack Hardware
Authors: Martin André , Jörissen Ludwig 
Published: February 2020

Most of international automotive OEMs have announced plans for the commercialization of fuel cell vehicles in the next years. While this is a clear signal for the functional readiness of fuel cell technology in automotive application, durability, efficiency, power density and cost of the fuel cell stack need further advancements in years to come.
“Auto-Stack Core” is a European funded collaborative project establishing a coalition with the objective to develop best-of-its-class automotive stack hardware with superior power density and performance while using components manufactured in an industrial scale and meeting commercial target cost. The project consortium combines the collective expertise of European automotive OEMs, component suppliers, system integrators and research institutes thus removing critical disconnects between stakeholders.
The technical concept is based on the Auto-Stack assessments carried out under an FCH JU Grant from 2010 to 2012 andreflects the system requirements of major OEMs. It suggests a stack platform concept with the aim to substantially improve economies of scale and reduce critical investment cost for individual OEMs by sharing the same stack hardware for different vehicles and vehicle categories.
Technical stack development is set up in 3 evolutions. So far stack evolution 1 has been designed, built and tested. The stack is based on components ready for manufacturing on an industrial scale. Metallic bipolar plates have been used to fulfill volume and cost targets. The following results have been achieved in evolution 1:

Achievements

Evolution 1

Final Specification

Evolution 3

Power
94 kW (continuous) 99 kW peak for 30 sec
98 KW (continuous) 118 kW peak 30 sec

Power density
2.7 kW×l-1 (continuous) 2.9 kW×l-1 peak for 30 sec
2.8 kW×l-1 (Continuous) 3.4 kW×l-1 peak for 30 sec

Freeze-start capability
Demonstrated from -20 °C
From -25 °C

Specific stack cost
47.32 €×kW-1 @ 30 000 p.a.
< 40.00 €×kW-1 @ 120 000 p.a.

According to a benchmark study of state-of-the-art stack development including innovative material and component solutions, the stack specifications for evolution 3 are within the most demanding in the industry.
Industrial participation in the project and lead of critical work packages by industrial partners will ensure compliance of project objectives with industrial needs and allow direct implementation and utilization of the results. The project is of strategic importance for the competitiveness of the European supply industry and provides a critical contribution to supporting the commercialization of fuel cell and hydrogen technologies in Europe.
The work reported has been supported by the Fuel Cell and Hydrogen Joint Undertaking under Grant Agreement 325335.

Figure 1
Engineering Modeling of PEM Water Electrolysis
Authors: Hanke-Rauschenbach Richard , Bensmann Boris 
Published: February 2020

The conversion of electric energy into pressurized hydrogen by means of water electrolysis is currently discussed as promising option to handle intermittent electricity supply that occurs with the increasing use of renewable energy sources. Subsequently, this hydrogen could be (1) either reconverted into electricity, or (2) converted into other energetic molecules, such as methane (power to gas) or liquid fuels, or (3) utilized as a feed stock for the chemical industry.
Besides conventional alkaline water electrolysis, a water electrolysis technology based on a Polymer Electrolyte Membrane (PEM) is discussed since several years, which is the focus of the present contribution. The particular advantages of PEM water electrolysis are higher attainable current densities, higher voltage efficiency, and higher load flexibility. Current disadvantages include far lower technical maturity, shorter life time, and higher specific costs compared to alkaline water electrolysis.
The formulation of appropriate physico-chemical models for solid polymer electrolysis can help to contribute to the solution of the above mentioned problems. In the present contribution state of the art of modelling of solid polymer electrolyzers is summarized and discussed.
Influence of MPL Structure Modification on Fuel Cell Oxygen Transport Resistance
Authors: Lu Zijie , Waldecker James , Tam Mickey , Cimenti Max 
Published: February 2020

Proton exchange membrane fuel cell (PEMFC)) technology is the basis for a promising future automotive powertrain. However, PEMFC cost must be reduced and durability must be improved. The greatest opportunity to reduce cost is to run the fuel cell at high current density while not considerably lowering the cell voltage [1], which requires excellent mass (both oxygen and water) transport in the fuel cell electrode, as well as low ohmic loss. In this work we report the measurement of the resistances to oxygen transport in the fuel cell cathode electrode and the impact of microporous layer (MPL) structure modification on the oxygen transport.
The oxygen transport resistance is measured by the limiting current density method [2-4] in a specially designed 5 cm2 cell using a variety of O2 concentrations. The total oxygen transport resistance in a fuel cell cathode sums the resistance from the diffusion media and that from the catalyst layer (CL). The CL resistance includes the Knudsen diffusion resistance and the ionomer permeation resistance: Rtot = RDM + RCL = RDM + RCL,Knud + RCL,ion, where RDM is quantified by varying the cathode gas pressure [2], and RCL,Knud and RCL,ion can be differentiated by varying the temperature [4].
The effect of MPL modification on the oxygen transport resistance has been studied. Straight holes of 20 mm diameter through the MPL, but not through the carbon fiber substrate, were made by a laser perforation technique. The oxygen transport resistances in the cell with the perforated MPL on the cathode were measured and compared to those in the cell with the baseline MPL.
The total oxygen transport resistance depended on the water production rate, revealing a dry region and a dry-to-wet transition for both MPLs in response to the oxygen concentration increase. The MPL modification had little influence on the total transport resistance in the dry region, while the perforated MPL significantly reduced the transport resistance in the dry-to-wet transition region, indicating the perforated MPL improved the cathode water management. It is not clear at this moment whether the increased transport resistance under the wet condition occurs in the diffusion medium or in the catalyst layer. The transport resistance in the CL can only be obtained for the dry conditions and the MPL modification shows little influence on the CL resistance. A trend of decreasing CL resistance with increasing temperature was observed. This temperature effect is mainly attributable to the oxygen permeation in CL ionomer, while the Knudsen diffusion in CL secondary pores is only weakly dependent on temperature.
References:

DOE Roadmap, 2014.

D.R. Baker, D.A. Caulk, K.C. Neyerlin, M.W. Murphy, J. Electrochem. Soc., 156, B991 (2009).

D.A. Caulk and D.R. Baker, J. Electrochem. Soc., 157, B1237 (2010).

N. Nonoyama, S. Okazaki, A.Z. Weber, Y. Ikogi, T. Yoshida, J. Electrochem. Soc., 158, B416 (2011).
Determination of Permeability of the Gas Diffusion Layer of Proton Exchange Membrane Fuel Cells (PEMFCs)
Authors: Hasanpour Sadegh , Hoorfar Mina , Phillion Andre 
Published: February 2020

One vital component in the Proton Exchange Membrane Fuel Cells (PEMFCs) is the Gas Diffusion Layer (GDL). This layer is a pathway for the reactants to reach the reaction site and for the by-products to be removed. Due to this application, the permeability of this layer has been investigated experimentally and numerically [1]. This layer has a highly porous structure, and hence identifying a geometry that resembles best the GDL for modeling flow through this layer is very important. In this study, the 3D image of a GDL sample has been obtained with high resolution imaging, X-ray microtomography, and is used as a model to simulate flow through this layer. This layer typically treated with micro-porous layer (MPL). In this paper, MPL was separated and permeability through the MPL is investigated separately using an image-processing method developed in-house. The results indicate that MPL reduces the permeability of GDL considerably. This work facilitates the study of the effect of MPL on the permeability of the GDL, which is impossible to be determined in experimental approaches [2].
[1] J. Pharoah, "On the permeability of gas diffusion media used in PEM fuel cells," J. Power Sources, vol. 144, pp. 77-82, 2005.
[2] J. Ihonen, M. Mikkola and G. Lindbergh, "Flooding of gas diffusion backing in PEFCs physical and electrochemical characterization," J. Electrochem. Soc., vol. 151, pp. A1152-A1161, 2004.
Photoelectrochemical Characterization of Spin-Coated CuBi2O4 Thin Films for Water Splitting
Authors: Rodríguez Gutiérrez Ingrid Guadalupe , Flores Pinto Maricarmen , Rodríguez Pérez Manuel Jesús , Rodriguez-Gattorno Geonel , Oskam Gerko 
Published: February 2020

Complex oxides containing multiple cations or in some cases multivalent cations such as Bi3+,5+, Co2+,3+, Sn2+,4+, have attracted much attention for photoelectrochemical applications due to their unique properties. Bismuth has a multivalent nature (Bi3+, Bi5+) that can be present at the same time in the same crystal structure in the Bi site, improving the conductivity of the material. An interesting new p-type semiconductor, which has shown high photocurrent under visible light conditions, is CuBi2O4 [1]. In this work, we present the growth of CuBi2O4 thin films prepared by spin coating method on FTO glass substrate. The precursor solution was prepared using bismuth nitrate, copper nitrate and dilute aqueous acetic acid as a solvent. The films were spin coated and annealed at 650°C.

The influence of parameters such as the heating rate during sintering and the substrate’s etching treatment on the films quality was studied. The films were characterized by X-ray diffraction, SEM, and UV-Vis spectrophotometry. We observed that the heating rate is an essential parameter to obtain a homogeneous layer. The optical response and photoelectrochemical behavior were studied as function of the film thickness. We show that the material is capable of reducing water under sunlight.
[1] L. Wei, C. Shifu, Z. Sujuan, Z. Wei, Z. Huaye, Y. Xiaoling, Journal of Nanoparticle Research 2010, 12, 1355-1366.
Electronic Structure and Optical Properties of Nb2O5 Photo-Catalyst Calculated By Density Functional Method
Authors: Shirvanian Pezhman , Hao Michael 
Published: February 2020

Recently, there has been attempts to increase the photo-catalytic activities of Nb2O5 with the addition of carbon modifications [1-4]. It has been proposed that carbonate species on the modified Nb2O5 act as surface sensitizer, which extends the photo-catalytically active region of Nb2O5 into the visible range [1-3]. Experiments have shown the photo-catalytic activity of these carbon-modified Nb2O5 structures are higher than of non-carbon-modified Nb2O5 and carbon-modified meso-porous TiO2 [1]. These carbon-modified Nb2O5 structures are promising candidates for photo-catalytic water splitting and more research is needed to understand these materials at the atomic scale. Here, we propose a DFT study of carbon-modified Nb2O5 (001) plane. The aim of this study is to determine the source of activity gain through electronic structure calculations. First, ground state, density of states, energy band structures, and optical properties of carbon-modified Nb2O5 are calculated. The electronic interaction between carbon and Nb2O5 will also be examined to determine its contribution to modify adsorption of intermediate species such as O2, H2, and OH. Band edge potentials and band gaps as calculated indicate the potential for driving the water cleavage reaction using solar energy. These results as presented point to a set of design guidelines for optimizations of photo-catalytic activity of Nb2O5.
References

1. Ge, S., Jia, H., Zhao, H., Zheng, Z., & Zhang, L. (2010). First observation of visible light photo-catalytic activity of carbon modified Nb2O5 nanostructures. Journal of Materials Chemistry, Journal of Materials Chemistry, 20, 3052-3058.
2.Ma, Chen, Li, Cui, & Lin. (2015). Annealing-free synthesis of carbonaceous Nb2O5 microspheres by flame thermal method and enhanced photo-catalytic activity for hydrogen evolution. Materials Research Bulletin, 66, 51-58.
3. Qi, S., Fei, L., Zuo, R., Wang, Y., & Wu, Y. (2014). Graphene nano-cluster decorated niobium oxide nanofibers for visible light photo-catalytic applications. Journal of Materials Chemistry A, 2(22), 8190-8195.
4. Li, L., Deng, J., Yu, R., Chen, J., Wang, Z., & Xing, X. (2013). Niobium pentoxide hollow nanospheres with enhanced visible light photo-catalytic activity. Journal of Materials Chemistry A, 1(38), 11894-11900.
(Invited) Personalized Breath-Based Health Monitors
Authors: Gouma Pelagia 
Published: February 2020

This talk will highlight the research and development efforts of my team towards
the personalized diagnostic breathalyzer to be used for the detection and monitoring
of diseases or metabolic malfunctions, both in humans and in livestock. Based on the
principle of selective chemosensing, nanostructured, gas-selective probes have been
developed which detect disease-signaling biomarkers in a single exhale. Such probes include:
NO sensor for asthma monitoring; acetone sensor for the control of treatment in diabetics;
ammonia for determining the end-point in hemodialysis, etc. These sensing probes, whether
individually or in arrays, constitute components of sensory systems that are inexpensive,
handheld, wireless, and low power. The pathway and timeline from lab-based prototyping
to industrial scale manufacturing of this technology are also discussed here.
Preparation of Glucose Oxidase-Immobilized Electrodes Using Cellulose Aqueous Solution
Authors: Yasuzawa Mikito , Omura Yuya , Hiura Kentaro , Li Jiang , Fuchiwaki Yusuke , Tanaka Masato 
Published: February 2020

Nearly transparent cellulose aqueous solution was prepared using the clear layer of diluted cellulose dispersion solution produced by wet jet milling. Glucose oxidase (GOx) was immobilized on platinum-iridium electrode by applying certain amount of cellulose aqueous solution containing GOx and dried for at least two days in room temperature. The obtained GOx-immobilized electrodes provided good response current up to 22.4 mM. Good linear relationship between glucose concentration and response current was observed. Correlation coefficient of 0.994 was obtained ranging from 0 to 11 mM on the electrode prepared using 500 mg/L cellulose and 250 mg/L GOx mixture solution. The sensor response was significantly fast and steady state current was obtained within one second. The stability of GOx-immobilized electrode response was measured for 30 days. After initial decrease of response current for the first few days, relatively constant responses were obtained for twenty days.