bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effect of Compression on Water Uptake and Predicted Performance of a High Pressure PEM Electrolysis Cell Model
Authors: Olesen Anders Christian , Kær Soren Knudsen 
Published: February 2020

In the electrolysis of water it is convenient and advantageous to directly compress hydrogen at the cathode. This reduces system requirements and energy consumption associated with subsequent mechanical compression [1–3]. The simplest and most energy efficient system configuration is the so-called asymmetric setup, where only the cathode is operated at elevated pressures [2]. Under these conditions a large pressure difference forms across the polymer electrolyte membrane which mechanically compresses the polymer backbone and the anode electrode. While titanium felt has to be used as a gas diffusion layer at the anode, to withstand the mechanical compression, a conventional perfluorinated sulfonic acid (PFSA) membrane can be used as the electrolyte. Although PFSA membranes like Nafion exhibit high thermo-mechanical stability, water uptake and transport properties are significantly affected by mechanical compression depending on the temperature, relative humidity and the amount of liquid water present [4]. Consequently, it is of great importance to accurately account for the physiochemical relationship between mechanical compression and equilibrium water uptake, when attempting to predict the electrochemical behavior of an asymmetric pressurized PEM electrolysis cell
In this work, a non-equilibrium formulation of the water uptake model by Kusoglu et al. [4] has been implemented in a two-dimensional, two-phase, multi-component and non-isothermal PEM electrolysis model. The non-equilibrium formulation of the water uptake model was chosen in order to account for interfacial transport kinetics between each fluid phase and the PFSA membrane. Besides modeling water uptake, the devised membrane model accounts for water transport through diffusion and electro-osmotic drag in the polymer phase, and hydraulic permeation in the liquid phase. Charge transport and Butler-Volmer electrochemistry are likewise included.
In order to investigate the effect of accounting for membrane compression, a parametric study is carried out with and without the compression corrected water uptake model by Kusoglu et al. [4]. The obtained simulation results confirm and underline that the predicted water uptake and cell voltage are highly dependent on the applied water uptake model.
References:
[1] Todd D, Schwager M, Mérida W. Thermodynamics of high-temperature, high-pressure water electrolysis. J Power Sources 2014;269:424–9.
[2] Bensmann B, Hanke-Rauschenbach R, Peña Arias IK, Sundmacher K. Energetic evaluation of high pressure PEM electrolyzer systems for intermediate storage of renewable energies. Electrochim Acta 2013;110:570–80.
[3] Onda K, Kyakuno T, Hattori K, Ito K. Prediction of production power for high-pressure hydrogen by high-pressure water electrolysis. J Power Sources 2004;132:64–70.
[4] Kusoglu A, Kienitz BL, Weber AZ. Understanding the Effects of Compression and Constraints on Water Uptake of Fuel-Cell Membranes. J Electrochem Soc 2011;158:B1504.
Effect of Composition, Particle Size and Structural Ordering on Stability of PtCu Electrocatalysts for Oxygen Reduction Reaction
Authors: Hodnik Nejc , Mayrhofer Karl J.J. 
Published: February 2020

The polymer exchange membranes fuel cells cathode electrocatalyst activity and durability are still a major challenge hindering the commercialization of these devices, despite the use of noble materials like platinum alloys. Dealloying, that is removal of less noble metals, has become one promising strategy for producing Pt-based catalysts in all design categories (skeletal surface, nanoporous, core–shell nanoparticle configuration) (1). Generally, dealloying can be triggered either chemically by acid leaching, or electrochemically by potential hold or cycling above critical potential (2-4). In this presentation I will discuss on the impact of Pt-alloy composition (5), size (6), structural ordering (4), and also the dealloying conditions on the formation of different morphologies, as well as the resulting ORR performance. By utilizing advanced characterization techniques (electrochemical scanning flow cell coupled with ICP-MS, identical location TEM and SEM – see Figure 1 and electrochemical in-situ TEM) together with conventional thin film rotating disc electrode I will provide new insights in to dealloying phenomena of PtCu alloy.
Figure 1: SEM sequential images of a dealloying and degradation of PtCu3 electrocatalyst: a) as-synthesized, b) after 500 cycles between 0 and 1.2 V with 0.5 V/s, c) after 5k cycles between 0.6 and 1.2 V z 1 V/s in d) after 50k cycles between 0.6 and 1.2 V z 1 V/s in 0.1 M HClO4; (scale bar is 20 nm)
Acknowledgements
Nejc Hodnik would like to acknowledge the FP7-PEOPLE-2013-IEF Marie Curie Intra-European Fellowship (project 625462 - ElWBinsTEM).
References:
1. M. K. Debe, Nature, 486, 43 (2012).
2. L. Gan, M. Heggen, R. O’Malley, B. Theobald and P. Strasser, Nano Letters, 13, 1131 (2013).
3. D. Wang, Y. Yu, J. Zhu, S. Liu, D. A. Muller and H. D. Abruña, Nano Letters, 15, 1343 (2015).
4. N. Hodnik, C. Jeyabharathi, J. C. Meier, A. Kostka, K. L. Phani, A. Recnik, M. Bele, S. Hocevar, M. Gaberscek and K. J. J. Mayrhofer, Physical Chemistry Chemical Physics, 16, 13610 (2014).
5. A. K. Schuppert, A. A. Topalov, A. Savan, A. Ludwig and K. J. J. Mayrhofer, ChemElectroChem, 1, 358 (2014).
6. N. Hodnik, M. Zorko, M. Bele, S. Hočevar and M. Gaberšček, The Journal of Physical Chemistry C, 116, 21326 (2012).

Figure 1
A Graphene Oxide Membrane Fuel Cell for Room Temperature Operation
Authors: Bayer Thomas , Sasaki Kazunari , Lyth Stephen Matthew 
Published: February 2020

Fuel cells for portable consumer electronics such as smartphones or optical head-mounted displays should be operated at relatively low temperatures for user comfort. However they are generally operated at over 80˚C. Recently our group reported the characterization of a graphene oxide membrane fuel cell (GOMFC) with a power density of 35 mW/cm2 measured at 30°C, showing the potential of graphene oxide to be used as a fuel cell electrolyte at low temperature.1

Graphene oxide (GO) is a sp2/sp3-hybridized carbon material with carboxyl, hydroxyl and epoxy oxygen functional groups on the surface and edges, which promote water uptake and make it insulating to electrons.2 This is in contrast to graphene, which is highly electronically conductive and therefore suitable as e.g. a catalyst support.3,4 GO is an excellent gas barrier and displays significant proton conduction,5,6making it suitable as a fuel cell electrolyte.
Free-standing flexible GO membranes were prepared from GO dispersion in water by vacuum-filtration. These were characterized as a fuel cell electrolyte (Figure 1). GO was found to have improved gas barrier properties compared to Nafion, as well as higher tensile strength and water uptake. Despite the relatively low proton conductivity (around 1% that of Nafion), graphene oxide membrane fuel cells (GOMFCs) displayed reasonable power densities up to 35 mW/cm2 at room temperature, approaching the performance of Nafion-based fuel cells at this temperature. By further reducing the thickness of the graphene oxide membrane and taking advantage of the high gas barrier properties an improved power density of up to 80 mW/cm2was achieved.
References:
1. T. Bayer, S. R. Bishop, M. Nishihara, K. Sasaki, and S. M. Lyth, J. Power Sources, 272, 239–247 (2014).
2. D. R. Dreyer, S. Park, C. W. Bielawski, and R. S. Ruoff, Chem. Soc. Rev., 39, 228–240 (2010).
3. L. Jianfeng, K. Sasaki, and S. M. Lyth, ECS Trans., 58, 1751–1762 (2013).
4. S. M. Lyth, L. Jianfeng, and K. Sasaki, ECS Trans., 58, 1529–1540 (2013).
5. R. R. Nair, H. A. Wu, P. N. Jayaram, I. V. Grigorieva, and A. K. Geim, Science, 335, 442–444 (2012).
6. K. Hatakeyama et al., Angew. Chemie, 53, 6997–7000 (2014).

Figure 1
Organic Active Species for Nonaqueous Redox Flow Batteries
Authors: Saraidaridis James Demetrios , Suttil James A. , Sevov Christo S , Sanford Melanie , Monroe Charles W 
Published: February 2020

Despite decades of research on redox flow batteries (RFBs), their widespread implementation for grid electricity storage has not manifested. In the U.S., the grid penetration of intermittent renewable power is currently too low to necessitate widespread storage, and alternatives less expensive than RFBs are available to utilities pursuing efficiency improvements. RFB development should focus both on improved performance and cost reduction. Most RFBs depend on high concentrations of expensive, environmentally impactful transition-metal-based active species to achieve viable energy densities [1]. One notable exception is the aqueous anthraquinone chemistry, based on an organic active species [2].
Polycyclic aromatic hydrocarbons (pAHs) have highly conjugated molecular structures, which offer redox activity that could be promising for all-organic RFBs. Byproducts of coal extraction and petroleum refining, pAHs are abundant and offer an inexpensive alternative to transition-metal complexes. Since they tend to offer widely separated, stable redox states, pAHs necessitate the wide electrochemical stability windows provided by polar, aprotic, nonaqueous solvents. Researchers previously attempted using the pAH rubrene in nonaqueous RFBs, but were discouraged by its extremely low solubility in conventional nonaqueous solvents.[3] Others have functionalized pAHs to form water-soluble quinone structures at the expense of large RFB operating potentials.[2]
We will focus on 9,10-diphenylanthracene(DPA)[4], a promising pAH for symmetric, nonaqueous RFBs. Figure 1 demonstrates the redox activity of DPA in acetonitrile, exhibiting couples at -2.2 V and 0.9 V vs. Ag/Ag+. A symmetric RFB based on DPA could, in principle, achieve a cell potential above 3V. As with rubrene, however, DPA suffers from solubility concerns: concentrations necessary for persuasive cell demonstration are unattainable. We modified DPA by appending various organic functional groups, examining the effects on solubility and redox activity. We functionalized the phenyl groups of DPA with both electron-withdrawing and electron-donating groups: methyl, methoxy, methoxycarbonyl, and more complicated ethylene-glycol based functionalities were investigated. Various nonaqueous solvents and supporting electrolytes are considered to optimize solubility.
[1] S. Eckroad. EPRI Report 1014836. 2007.
[2] Q. Liu et al. Electrochem. Comm. 12(2010): 1634.
[3] M. Chakrabarti, et al.
Electrochimica Acta.
52(2007): 2189.
[4] K. Santhanam, A. Bard. JACS.
88(1966): 2669.

Figure 1: Cyclic voltammogram of 0.001 M DPA/0.05 M TEABF4 in acetonitrile, glassy carbon WE (1mm diameter), Pt CE, 500 mVs-1, Argon atmosphere with <1ppm O2,H2O

Figure 1
CFD Modeling to Investigate the Performance of PEM Fuel Cells Affected By Cathodic Pressure
Authors: Wang Jiatang , Yuan Jinliang , Sundén Bengt 
Published: February 2020

The proton exchange membrane (PEM) fuel cell is a promising energy conversion device. However, the cost and durability of a PEM fuel cell are major challenges needed to be overcome before it will be widely used. The simulation is crucial for the design and optimization of practical devices based on deep understanding of coupled transport phenomena inside the fuel cell. It is widely known that the slower reaction in the cathode is a limiting factor and the cathodic operating pressure has a strong influence on the cell performance. In this paper, an open-source code OpenFOAM is employed to simulate the transport phenomena and electrochemical reactions in PEM fuel cells. The basic governing equations for continuity, momentum, mass and energy transfer are solved with appropriate source terms using a computational fluid dynamics (CFD) method. A steady state and three-dimensional (3D) model is applied for single flow channels and multi-functional layers, i.e., bipolar plates, gas diffusion layers (GDLs), catalyst layers (CLs) and electrolyte. The distributions of gas compositions, pressure, temperature, activation loss, cell voltage and current density are captured and presented. The O2 partial pressure on the reaction sites resulting from transport and inlet pressure suggests an influence on the cell performance. The influence of removal of the inert gas N2 and production of H2O vapor on the O2 partial pressure is considered based on the multi-species transport model. To verify the accuracy of the simulation approach, comparisons between the computed results and literature data have been conducted.
New Upscaled Equations for the Reliable and Efficient Catalyst Layer Modelling in PEM Fuel Cells
Authors: Schmuck Markus , Berg Peter 
Published: February 2020

Recently, we derived a rigorous macroscopic model for a porous catalyst layer in a PEM fuel cell [1,2]. Starting from a microscopic description, it accounts for the oxygen reduction reaction in periodically distributed pores, filled with liquid water. We now present first computational investigations of the newly derived macroscopic transport equations, which rely on characteristic porous media (corrector) tensors, Darcy's law and an effective Butler-Volmer equation. This macroscopic formulation is inherently linked to the dynamics at the microscale and it can be computed in a fairly straightforward manner under the assumption of local thermodynamic equilibrium. Our computational results demonstrate that this upscaling provides a convenient and efficient computational framework for the numerical investigation of optimal catalyst layer designs.
[1] M. Schmuck and P. Berg, Homogenization of a catalyst layer model for periodically distributed pore geometries in PEM fuel cells, Appl. Math. Res. Express. 2013(1):57-78 (2013).
[2] M. Schmuck and P. Berg, Effective macroscopic equations for species transport and reactions in porous catalyst layers, J. Electrochem. Soc. 161(8): E3323-E3327 (2014).
IrxRu1-XO2 Electrocatalysts for PEM Water Electrolysis
Authors: Banti Angeliki , Papazisi Kalliopi-Maria , Balomenou Stella , Tsiplakides Dimitrios 
Published: February 2020

A potential method for storing energy from renewable energy sources into hydrogen is water electrolysis [1]. Direct electrochemical splitting of water is a non-polluting way to produce pure hydrogen and oxygen. Proton Exchange Membrane Electrolysis Systems have attracted great interest as a hydrogen production method. The combination of water electrolysers and fuel cells in coupled with renewable sources could provide an ideal green and efficient mode for future energy utilization systems. PEM water electrolysers offer various advantages [2] but the major disadvantage is the relatively high anodic overpotential for the oxygen evolution reaction (OER). Oxygen evolution occurs on noble metal electrodes but metal oxides like IrO2, RuO2, etc. are generally more active for oxygen evolution than metal electrodes [3]. However, issues like electrocatalyst stability and reduction of the catalyst loading are of great and continuous research interest. In this work, unsupported IrxRu1-xO2electrocatalysts, synthesized by the modified Adams fusion method, were evaluated as potential electrodes for water splitting.
Complete physicochemical characterisation of the synthesised materials was performed regarding their structure, morphology, specific surface area as well as surface composition using X-ray Diffraction (XRD), BET analysis, High Resolution Transmission Electron Microscopy (HTTEM) and X-ray Photoelectron Spectroscopy (XPS). The electrochemical performance and stability of the prepared electrocatalysts, casted on glassy carbon (GC), were evaluated with repetitive cyclic voltammetry in a typical three-cell electrode configuration using 0.5 M H2SO4solution. Furthermore, the mixed oxides have been used as anodes in Nafion® based MEAs and evaluated in a PEM electrolysis cell.
The results have shown that the synthesis method leads to the formation of rutile structure oxides with high surface area (90-127 m2/g) and nano-level particle size (5-7 nm). The stability of the mixed oxides during potentiostatic cycling has been proven remarkable, while the best performing MEA with an anode of Ir0.4Ru0.6O2 reached a current density of 320 mA/cm2at 1.7 V.
The work is supported by the European Space Agency (ESA).
References:

F. Barbir, Solar Energy 78 (2005) 661-669.

A. Deschamps, C. Etievant, V. Fateev, S. Grigoriev, A. Kalinnikov, P. Millet, V. Porembsky and C. Puyenchet, WHEC 16, Lyon France (2006).

V. Baglio, A. Di Blasi, T. Denaro, V. Antonucci, A.S. Aricò, R. Ornelas, F. Matteucci, G. Alonso, L. Morales, G. Orozco and L.G. Arriaga, J. New Mat. Electr. Sys. 11 (2008) 105-108.
Electronic Structure of Pt and Pt-Co Nano-Particles with O2 and O2/H2o Adsorption Revealed By in Situ xafs and Hard X-Ray Photoelectron Spectroscopy
Authors: Cui Yi-Tao , Harada Yoshihisa , Hatanaka Tatsuya , Nakamura Naoki , Ando Masaki , Yoshida Toshihiko , Ikenaga Eiji , Ishii Kenji , Matsumura Daiju , Li Rui , Oshima Masaharu 
Published: February 2020

In order to clarify the effect of water adsorption on fuel cell cathode catalysis surface, we have investigated electronic structure of Pt and Pt-Co nano-particles with O2 adsorption and O2/H2O co-adsorption by in situ XAFS and in situ hard X-ray photoelectron spectroscopy (HAXPES).
First, the electronic structure change under dry and humidified oxygen conditions at room temperature was measured by in situ HAXPES equipped with an ambient cell. The valence band (mainly Pt 5d) and Pt 4f spectra were successfully obtained under up to 1 mbar for the first time. Both valence band and Pt 4f spectra show that O2/H2O co-adsorption hindered oxygen adsorption. Based on our first principles calculation of valence band density-of-states (DOS) we have found that DOS just below Fermi level strongly decreases upon oxygen adsorption, while valence band spectra remain almost unchanged upon H2O adsorption. These results suggest that H2O molecules may occupy the oxygen adsorption sites on Pt surface more easily than oxygen, resulting in hindering the successive oxygen adsorption.
However, under the more realistic condition at atmospheric pressure (1 bar) quite different results that the formation of higher oxidation states of Pt in Pt Pt L
3-edge absorption spectra was enhanced by water adsorption were obtained by high resolution (FWHM of about 2.5 eV) in situ XAFS, taking advantage of life-time free measurements1). It is difficult to observe these changes by conventional XAFS spectra with poor energy resolution (FWHM of about 5.2 eV). At the atmospheric pressure more frequent attack by oxygen molecules onto water-adsorbed Pt surface may replace water molecules by oxygen, resulting in the formation of hydrated hydroxyl intermediates and higher oxidation states which hinder oxygen reduction reaction. The molecular dynamics simulation2) also confirms the oxygen replacement on water-adsorbed Pt surfaces. This enhanced oxygen adsorption is more clearly observed for Pt nano-particles, probably because Pt nano-particles with stronger Pt-O bonding than Pt-Co nano-particles may further stabilize Pt-O bonding by additional adsorbed water. On the other hand, oxygen molecules on Pt-Co nano-particles may be difficult to form hydrated hydroxyl intermediates with adsorbed water, leading to less water effect on oxygen adsorption on Pt-Co.
These results would be much helpful to understand why Pt-Co nano particles show higher ORR activity than Pt nano particles.
References:
1) K. Hamalainen et al., Phys. Rev. Lett. 67, 2850 (1991).
2) R. Li, et al., New J. Chem.,
38, 683 (2014).
Mechanism of Enhanced Pt ORR Catalyst By Atomic Layer Deposition-Based Oxide Functionalization
Authors: Karimaghaloo Alireza , Peev Thomas , Macedo Andrade Angela , Lee Min Hwan 
Published: February 2020

In a recent study, ultrathin oxide overcoat was proven to have significant impact on the ORR kinetics of nanoporous Pt catalyst on yttria-doped zirconia (YSZ).1 In the report, a few nm thick ultrathin yttria-stabilized zirconia (uYSZ) was coated on the porous Pt cathode by atomic layer deposition (ALD). The coating was found not only to preserve the overall Pt morphology but also to improve the electrode reaction. The uniform and conformal geometry of the as-deposited overcoat became percolated at the operational temperature (~500°C), which is conjectured beneficial to the catalytic activity due to enlarged Pt/YSZ interfaces.
In this presentation, we present our revised understanding of how the ultrathin oxide overcoat improved the ORR catalysis through a parametric study. Geometrically well-defined Pt/uYSZ electrode structures were prepared by accumulating Pt nanoparticles through a colloidal process. We controlled the Pt nanoparticle size, dominant surface facets, overall electrode thickness, YSZ overcoat thickness and stoichiometry of overcoat. Pt nanocrystals with different sizes and controlled surface facets were prepared through wet chemical and electrochemical processes. We then performed electrochemical analysis at various temperature (400 – 700 °C) and oxygen partial pressure (0.01 – 1 atm). A series of characterization indicated that the enhanced ORR activity is most likely originated from the enhanced ‘chemical’ processes such as dissociation and transport. However, in samples with thin Pt electrode layer, the enhancement is largely ascribed to increased triple phase boundary areas.
This project is funded by the NASA MUREP Institutional Research Opportunity (MIRO) Program (Grant No. NNX15AQ01A).

1 I. Chang, S. Ji, J. Park, M.H. Lee, and S.W. Cha, Adv. Energy Mater. 5, 1402251 (2015).