bluuebunny/crossref_metadata_2025_split huggingface dataset:
Bing Energy Reduced Pt Membrane Electrode Assemblies
Authors: Zheng Jim P. , Zhu Wei 
Published: February 2020

We have explored and demonstrated a novel nano-engineered electrode technology to meet the DOE’s targets for platinum group metal utilization and electrode durability for proton exchange membrane fuel cells. Our new electrode technology has made three major technical improvements of (1) the intrinsic electrocatalytic activity and stability of the catalystic electrodes; (2) the utilization of these materials using nano-structured and functionalized supports; and (3) the stability of the electrocatalyst/support system by strengthening the electrocatalyst-support interaction and by using corrosion resistant supports.
A double-layered buckypaper (DLBP) was prepared by filtering the carbon nanotube (CNT)/carbon nanofiber (CNF) mixture and the CNF suspension sequentially under full vacuum. CNTs of ~10 nm in diameter and 10 mm in length and CNFs of 100-200 nm in diameter and 30-100 μm long. Platinum (Pt) nanoparticles were deposited onto the buckypaper using a pulse electrodeposition technique.
As shown in Fig. 1(a), large-sized CNFs entangled randomly forming a highly porous sublayer with a porosity of 90.8% and an average pore size of 85 nm, while fewer and smaller pores were formed in the CNT/CNF sublayer by adding 25 wt.% smaller CNTs. After depositing Pt on the buckypaper by electrochemical deposition, an energy-dispersive X-ray spectrometer analysis showed an obvious gradient distribution of Pt (Fig. 1(b)); over 70% Pt was distributed in the 7 mm-thick CNT/CNF sublayer. A large amount of Pt deposited on the surface of the CNT/CNF sublayer (Fig. 1(c)), while only a small amount deposited on the surface of the CNF sublayer (Fig. 1(d)). This could provide an indication of how Pt was distributed inside the buckypaper since the Pt distribution was quite uniform within each sublayer. The pictures of surface morphology showed the Pt preferred to grow on the surface of CNT instead of CNF. Although, the mechanism of selective deposition of Pt on CNT/CNF buckypaper is not fully understood, the most possible reasons we suppose are: (1) CNT has much higher surface area and more surface defects resulting in more anchor sites for Pt nucleation; and (2) a higher deposition current on CNTs because of their higher conductivity.
By applying this double-layered buckypaper as a cathode catalyst layer, the MEA exhibited excellent power performance with a relative low Pt loading. The rated powers of 1.5 W/cm2 and 0.8 W/cm2 at 0.65 V were achieved with a cathode Pt loading of 0.2 mgPt/cm2 (Fig. 2) for oxygen and air, respectively. The Pt utilization was better than the current state-of-the-art value (>0.4 mgPt/cm2) achieved by the conventional Pt/C catalys at a comparable cell (0.8–1.0W/cm2) output. The CNT/CNF buckypaper-based Pt catalyst has also shown good durability under an accelerated degradation test in a mimic cathode environment. This was due to the high corrosion resistance of CNF and its high graphitization degree. Hence, we evaluated the durability of catalyst support for Pt/DLBP in a MEA per US DOE’s suggested protocol.

Figure 1
A Urine/Cr(VI) Fuel Cell: Electrical Power from Processing Heavy Metal and Human Excretion
Authors: Xu Wei , Fan Zheng , Wu Xingxing , Wu Zucheng 
Published: February 2020

Hexavalent chromium (CrO4
2-, Cr2O7
2-, CrO3, CrF6, etc.) is seriously hazardous substance inducing various point mutations in DNA and oxidative changes in proteins due to its strong oxidational properties[1]. Notably, Cr(VI) is strongly oxidative which can oxidize most organics such as urine in wastewater. Thus, it is possible to develop a fuel cell by using hexavalent chromium and urine as fuels according to the following reaction mechanism:
Anode reaction: CO(NH2)2+6OH-→N2+CO2+5H2O+6e E0= -0.746 V vs. SHE
Cathode reaction: Cr2O7
2-+14H++6e→2Cr3++7H2O E0= +1.33 V vs. SHE
Overall reaction: CO(NH2)2+Cr2O7
2-+8H+→N2+CO2+2Cr3++6H2O E0= +2.076 V

This work shows a strategy of reducing Cr(VI) by human urine with self-generation electricity via a urine/Cr(VI) fuel cell (UCrFC), in which urine functions as fuel and Cr(VI) severs as electrons acceptor. Urine is electro-oxidized on carbon supported nano-Ni catalyst at anode and Cr(VI) is electro-reduced at catalyst-free cathode in acid medium[2,3]. An ion selective separator, consisting of an anion exchange membrane (AEM) and a cation exchange membrane (CEM), AEM||KClaq||CEM separator, is introduced to improve the cell performance by hindering the crossover of dichromate and ammonium.
A maximum power density of 3400 mW m
-2
(159 times to microbial fuel cells[4]) was achieved with an OCV of 1.3 V (twice of that in microbial fuel cells[4]) in AEM||KClaq||CEM-UCrFC, when using 50 mg L-1 Cr(VI) in 0.25 M H2SO4 as catholyte and neat urine as anolyte. The apparent first-order kinetic constants of Cr(VI) reduction were -0.224, -0.145 and -0.118 h-1, respectively, when initial concentration of Cr(VI) were 13, 22 and 50 mg L-1. Total organic carbon and total nitrogen removal from urine were observed in 71 h in the anode chamber, with removal efficiency of 79.2% and 78.4%, respectively. At the same time, ~93% of Cr(VI) was removed in the cathode chamber. A high cathodic coulombic efficiency of more than 98% was achieved. One liter of fresh urine could reduce about 28 g of Cr(VI) via UCrFC. This fuel cell provides an alternative technology for using waste (human urine) to treat another waste (hexavalent chromium), and is potentially applicable to other waste/waste system.

References:
1. A. D. Dayan, A. J. Paine, Hum. Exp. Toxicol.
2001, 20, 439-451.
2. W. Xu, H. Zhang, G. Li & Z. Wu, Scientific Reports, 2014, 4: 5863.

3. B. Yu, H. Zhang, W. Xu, G. Li & Z. Wu, Scientific Reports, 2014, 4: 5860..

4. L. P. Huang, X. L. Chai, S. A. Cheng, G. H. Chen, Chem. Eng. J.
2011, 166, 652-661.
Proton Conductivity and Gas Barrier Properties of Graphene Oxide for PEMFC Membranes
Authors: Bayer Thomas , Selyanchyn Roman , Fujikawa Shigenori , Sasaki Kazunari , Lyth Stephen Matthew 
Published: February 2020

Treatment of graphite by the modified Hummers method results in exfoliation of the graphene layers and the introduction of oxygen-containing surface functional groups.1 The resulting graphene oxide offers interesting possibilities for a wide range of applications in areas as diverse as e.g. humidity sensing,2 molecular sieving,3 gas barriers,4 dielectrics,5 and fuel cells.6,7

Polymer electrolyte membrane fuel cells (PEMFCs) are seen as a sustainable energy source for the future. So far the most commonly used membrane in PEMFCs is Nafion, due to its high mechanical and chemical stability as well as its high proton conductivity. However Nafion is expensive, has limited performance at temperatures > 100°C,8 and has only moderate gas barrier properties (leading to fuel crossover in very thin membranes). Graphene oxide membrane fuel cells (GOMFCs) have displayed reasonable power densities at room temperature,7and with some improvements could act as an electrolyte in low temperature fuel cells.
Here, the proton conductivity, fuel cell performance, fuel crossover of graphene oxide paper with different oxygen content, surface morphology, and surface functional groups are investigated by impedance spectroscopy, membrane electrode assembly testing, and gas permeation measurements. The manufacturing techniques for production of graphene oxide membranes and the optimal thickness of membranes are also discussed.
References:
1. Zhu, Y. et al., Adv. Mater.
22,3906–3924 (2010).
2. Borini, S. et al., ACS Nano
7,11166–11173 (2013).
3. Joshi, R. K. et al., Science
343,752–4 (2014).
4. Yoo, B. M. et al., Polym. Sci.
131,n/a–n/a (2014).
5. Wang, D.-W. et al., J. Mater. Chem.
22,21085 (2012).
6. Tateishi, H. et al., J. Electrochem. Soc.
160,F1175–F1178 (2013).
7. Bayer, T. et l. , J. Power Sources
272,239–247 (2014).
8. Yee, R. S. L. et al., Chem. Eng. Res. Des.
90,950–959 (2012).

Figure 1
Water Uptake in Novel, Water-Stable, Heteropoly Acid Films
Authors: Motz Andrew R , Horan James L , Kuo Mei-Chen , Herring Andrew M 
Published: February 2020

Operating a fuel cell at high temperature and low humidity can reduce catalyst and heat and water management cost in addition to improved tolerance to fuel impurities [1]. Traditional perfluorinated sulfonic acid proton exchange membranes do not operate well under these conditions, due to a need for high hydration to facilitate proton transport. Heteropoly acids (HPA)s have demonstrated promise for high temperature, low humidity fuel cell operation, but often are not immobilized, resulting in premature fuel cell performance loss[2]. In order to overcome this, a novel, chemically and thermally robust chemistry has been explored. Phenyl phosphonic acid side chains are grafted onto a 3M polyvinyl fluoride-co-hexafluoropropylene, FC-2178. These phenyl phosphonic acid (PPA) side chains then react with lacunary silicotungstic acid, thus immobilizing the HPAs, via covalent bonds. Different levels of PPA attachment have been explored, giving different ion-exchange capacities.

31P and 1H NMR have been used to determine the side chain attachment and IEC of the PPA functionalized FC-2178. The immobilized tungsten content was measured using PIXE (Proton Induced X-ray Emission) elemental analysis. Knowledge of the IEC and tungsten content elucidates the contributions to IEC from both PPA and HPA. SAXS and AFM have been used to determine the membrane morphology. Samples with a continuous conducting phase have shown proton conductivities up to 20 mS/cm at 110°C and 50% RH.
References
[1] Chandan, A.; Hattenberger, M.; El-kharouf, A.; Du, S.; Dhir, A.; Self, V.; Pollet, B. G.; Ingram, A.; Bujalski, W., High temperature (HT) polymer electrolyte membrane fuel cells (PEMFC) – A review. Journal of Power Sources
2013, 231, 264-278.
[2] Herring, A. M., Inorganic–Polymer Composite Membranes for Proton Exchange Membrane Fuel Cells. Journal of Macromolecular Science, Part C: Polymer Reviews
2006, 46, 245-296.
Relating Direct Methanol Fuel Cell Performance to Measurements in a Liquid Half Cell
Authors: Pedersen Christoffer Mølleskov , Tynelius Oskar , Lund-Olesen Torsten , Hales Jan Harry , Christensen Leif Højslet , Stephens Ifan E. L. , Chorkendorff Ib 
Published: February 2020

Direct methanol fuel cells (DMFC) could act as a replacement for batteries in low power electronics. For instance, micro—DMFC’s could be used to power hearing instruments[1]. The power output of a DMFC is limited by the sluggish kinetics of both the methanol oxidation reaction (MOR) on the anode and the oxygen reduction reaction (ORR) on the cathode. Thus far, to achieve high power densities with a single cell, the catalyst loadings have been increased much as possible (20 mg/cm2 PtRu/C on anode and 4 mg/cm2 Pt/C on cathode). More active catalysts would yield higher power densities which in turn would allow further miniaturization or powering more advanced and more power hungry devices.
The activity of fuel cell catalysts is often probed in the form of thin films in liquid half cells. However, it is challenging to mimic the conditions in an actual DMFC. On the other hand, it can also be problematic to extract the catalyst activity from a fuel cell measurement.
In this work, we attempt to narrow the gap between fuel cell testing and liquid half-cell measurements. First, by placing a custom reference electrode within the fuel cell, we can determine the potential at the anode and cathode under in-operando conditions. This in turn, allows us to directly correlate our measurements to those performed in a liquid half-cell at the same potential. For our half-cell measurements, we have tested different catalysts (Pt/C, PtRu/C) for the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR) in the presence of methanol. By comparing the two measurements, we make recommendations for performing liquid half-cell measurements under realistic conditions.
[1] J.H. Hales, C. Kallesøe, T. Lund-Olesen, A.-C. Johansson, H.C. Fanøe, Y. Yu, et al., Micro fuel cells power the hearing aids of the future, Fuel Cells Bull. 2012 (2012) 12–16. doi:10.1016/S1464-2859(12)70367-X.
Electrocatalysis in Water Electrolysis
Authors: Gottesfeld Shimshon 
Published: February 2020

In a recent publication, generation of active surface sites by the overpotential was described as a common pattern in fuel cell electrocatalytic processes [1]. This paper discusses the applicability of the same pattern to the electrocatalytic processes in the water electrolyzer .
A wide variety of electrocatalytic processes taking place at either functionalized surfaces , oxide surfaces ,or “metal” surfaces, are all , in fact, surface redox mediated . This means that the electrode potential defines the steady state population of active sites ,suggesting that the role of the potential in active site generation must be incorporated in the pre-exponential factor of the overall rate expression. In fact, the potential driven active site generation serves to “ignite” the faradaic process. This explains why the E0
redoc

system of M/MOx , or MOx+n/MOx+n+m surface couples , must be as close as possible to E0
cell process , to enable high conversion efficiency as well as higher rates at low overpotentials.
It will be shown here, that, consideration of this general pattern/mechanism of electrocatalytic processes, facilitates understanding of the relative activities of various OER electrocatalysts ,in either acid or alkaline environments. The Pourbaix diagram, provides good insight into the expected relative activities in these, surface redox mediated electrocatalytic processes, together with the other important information regarding expected relative stabilities in acid and in alkali.

[1] Shimshon Gottesfeld , ECS Trans. 2014 61(31): 1-13
Influence of the Interfacial Water Transfer on the Analysis of Dynamic Sorption and Desorption Experiments in Nafion® Membrane
Authors: Didierjean Sophie , Perrin Jean-Christophe , Xu Feina , Maranzana Gael , Mainka Julia , Lottin Olivier 
Published: February 2020

Water sorption and desorption in Nafion
®
117 membranes in acid form were studied by means of dynamic experiments as a response of relative humidity steps from 20% to 80% using a balance IGASORP (Hiden Isochema Ltd) which allows the measurement of very small mass variations with an accuracy of about 1 mg. The recorded mass variations with time of the membrane samples were analyzed by means of the least squares method based on a model that takes into account a transfer resistance at the interface between the membrane and the surrounding humid gas [1]. As the diffusion time is small (the diffusion coefficient being large), the diffusive internal resistance can be neglected compared to the interfacial resistance so that the water content of the membrane can be assumed uniform, which was confirmed using NMR imaging [2]. The model predicts than the kinetics of sorption is much faster than the kinetics of desorption, and the comparisons with the experimental results show a good agreement and give the value of the corresponding mass transfer coefficients (Figure 1). These results also agree with the results reported by Satterfield and Benziger [3] and they contribute to the debate concerning the existence of an interfacial resistance as reported in the recent review of Weber et al. [4]. For the experimental conditions considered in this study, the membrane is in equilibrium with the humid gas at the interface but the main resistance to water transfer is located in the humid gas phase.
REFERENCES

C.W. Monroe, T. Romero,W. Merida, M. Eikerling, Journal of Membrane Science 324 (2008) 1-6

M. Klein, J.-C. Perrin, S. Leclerc, L. Guendouz, J. Dillet and O. Lottin, ECS Transactions, 58 (1) 283-289 (2013)

M.B. Satterfield and J.B. Benziger, Non-Fickian vapor sorption dynamics by Nafion membranes, J. Phys. Chem. B, 2008, 3693-3704

Weber et al. A critical review of modeling transport phenomena in polymer-electrolyte fuel cells. Journal of the electrochemical society, 161 (12), F1254-F1299 (2014)

Figure 1
Random and Triblock Copolymers with Phosphonium Cations for Alkaline Fuel Cells
Authors: Liu Ye , Zhang WenXu , Zhang Bingzi , Yang Yuan , Coughlin Bryan E , Yan Yushan , Liberatore Matthew W , Herring Andrew M 
Published: February 2020

Comparing with well-studied proton exchange membrane fuel cells (PEMFCs), a strongly competitive candidate of alkaline fuel cell (AFC) by using anion exchange membrane (AEM) as solid electrolyte has been joined attention1,2 Researchers worldwide are searching for new AEM electrolytes met with both long operation life and sufficient ionic conductivity in order to realize good AFC performance.3,4

Block copolymers are expected with highly ordered morphology, which will have interesting influence on the water uptake as well as conductivity performance. In our study, we compare tris(2,4,6-trimethoxyphenyl) phosphonium functionalized AEMs with both triblock (Figure 1. (a)) and random (Figure 1. (b)) backbone structures. The reason investigating on the bulky phosphonium cation is that attaching electron-donating functional groups (2,4,6-trimethoxyphenyl) has been tested beneficial for improvement of the chemical stability based on our previous study.5Besides, based on exploration on water uptakes, morphologies, conductivities and transport properties, Insights on block and random copolymer structures impact on fuel cell performance are developed. A further understanding of correlations between hydration number/morphology and conductivity performance are investigated. In this study, water uptake and hydration number are measured through dynamic vapor sorption (DVS). Conductivities under different relative humidity are performed by electrochemical impedance spectroscopy (EIS). Water transportation is measured by pulsed field gradient NMR (PFGNMR) and anion transportation is calculated via Mitra equation based on conductivity result. Morphologies are obtained from small angle X-ray scattering (SAXS) and atomic force microscopy (AFM).

Reference

[1] J.R. Varcoe, P. Atanassov, D.R. Dekel, A.M. Herring, M.A. Hickner, P.A. Kohl, A.R. Kucernak, W.E. Mustain, K. Nijmeijer, K. Scott, Anion-exchange membranes in electrochemical energy systems, Energy & Environmental Science 7 (2014) 3135-3191.
[2] G. McLean, T. Niet, S. Prince-Richard, N. Djilali, An assessment of alkaline fuel cell technology, Int. J. Hydrogen Energy 27 (2002) 507-526.
[3] V. Neagu, I. Bunia, I. Plesca, Ionic polymers - VI. Chemical stability of strong base anion exchangers in aggressive media, Polym. Degrad. Stab. 70 (2000) 463-468.
[4] A.A. Zagorodni, D.L. Kotova, V.F. Selemenev, Infrared spectroscopy of ion exchange resins: chemical deterioration of the resins, React. Funct. Polym. 53 (2002) 157-171.
[5] Y. Liu, J. Wang, Y. Yang, T.M. Brenner, S. Seifert, Y. Yan, M.W. Liberatore, A.M. Herring, Anion Transport in a Chemically Stable, Sterically Bulky Α-C Modified Imidazolium Functionalized Anion Exchange Membrane. J. Phys. Chem. C 118 (2014) 15136-15145.

Figure 1
PEM Fuel Cells - Critical Power
Authors: Sookhoo Ryan 
Published: February 2020

Critical applications demand a high reliability of power to ensure our safety, functionality and security. Energy diversity is key to achieving a high quality of power where and when it is needed; hydrogen fuel cells are essential to accomplishing this. As traditional technologies advance and cutting edge products are created, they demand reliable and safe hydrogen solutions to fill the energy gaps.
Critical power applications require flexibility from the power generation mix of technologies, whenever and wherever needed. Fuel cell systems offer competitive runtime with diesel generators while providing the same reliability as batteries. Fuel cell systems can remain in standby for extended periods of time without any maintenance or impact to their fuel source, and can react when needed. Further, fuel cells offer a competitive solution over incumbent technology, by providing higher reliability, durability, economic and environmental improvements.
We will discuss how Hydrogenics fuel cell technology and design innovations, are being adopted in aviation, mobility and underwater applications.
Method to Resolve Transport Distance for Oxygen Diffusion in the Land-Channel Geometry of a PEMFC
Authors: Shrivastava Udit N , Tajiri Kazuya 
Published: February 2020

Abstract

Land-channel geometry is known to cause significant current density distribution in the land-channel direction of a PEMFC. Previously, many modeling studies and a few experimental studies have shown significant variation of current density in the land-channel direction such as [1-2]. There are two prime sources of such variation: (1) non-uniform transport distance for gas diffusion from channel to the catalyst layer, and (2) non-uniform transport distance for product water generated at catalyst layer to the channel. Baker et. al. defined a shape factor f (> 1) that removes anisotropy originated from land-channel geometry and gas diffusion layer (GDL) properties to provide resultant thickness of fh where h is thickness of a GDL [3].
We present a method to evaluate local transport distance in the land-channel geometry of a PEMFC. A segmented cell is developed to measure current density and high frequency resistance distribution in land-channel direction at sub-millimeter resolution of 350 μm. In this study, 1 mm wide land and channel configuration and GDL without microporous layer is used. Limiting current analysis reported in literature [4] is utilized to measure local limiting current at given resolution and then transport resistances were estimated.

H. Ju. J. of Power Sources, 191, 259 (2009).

U.N. Shrivastava, K. Tajiri. J. of Electrochem. Soc., 162, F722 (2015).

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

J. St-Pierre, B. Wetton, G.-S. Kim, and K. Promislow, J. of Electrochem. Soc., 154, B186 (2007).