bluuebunny/crossref_metadata_2025_split huggingface dataset:
Recent Advances with Sulfonated Silica Ceramic Carbon Electrodes for Fuel Cells
Authors: Easton E. Bradley , Acheampong Richard , Alipour Moghadam Esfahani Reza , Cavallari Veronica J , Moghaddam Reza B. , Fruehwald Holly M , Afsahi Foroughazam 
Published: February 2020

Sulfonated silica-based ceramic carbon electrodes (SS-CCE) are prepared using low-cost organosilane precursors that are mixed with the carbon-supported platinum (Pt/C) catalyst in monomer form, and subsequently polymerized and coated onto a gas diffusion layer in a single step. Our lab has demonstrated that that SS-CCEs can achieve similar H2/O2 fuel cell performance as conventional Nafion-based electrodes [1, 2]. Furthermore, these electrode structures display excellent tolerance to dry operating conditions, due to the proton conductivity of the sulfonic acid moiety and the hygroscopic nature of the SiO2 backbone. This is a major advantage over conventional Nafion-based fuel cell electrodes which require the use of heavily humidified gas feeds and are limited to temperature below 80 °C. Therefore SS-CCEs have great potential to improve PEMFC efficiency by reducing parasitic power losses required for gas humidification. Furthermore, they have the potential to reduce the required catalyst loading and extend the operating temperature range of PEMFCs. While these results have been promising, there are few detailed studies of SS-CCE structure-property. Likewise, their durability in operating fuel cells have yet to be proven.
In this presentation, we will give an overview of our group’s recent progress towards optimization the synthesis and structure of SS-CCEs. In particular, we have found hydrothermal conditions to be a promising way to enhance performance, promoting a more homogenous distribution of silicate ionomer and more effective bonding to the carbon surface [3]. Likewise, accelerated stress tests indicate that the silicate ionomer also serves to stability the Pt catalysts and enhance its durability [4]. This, along with their tolerance to high temperatures/low relative humidity conditions leads to improved stability of SS-CCE-based fuel cell systems.

References

[1] J.I. Eastcott, E.B. Easton, Journal of Power Sources, 245 (2014) 487-494.
[2] J.I. Eastcott, K.M. Yarrow, A.W. Pedersen, E.B. Easton, Journal of Power Sources, 197 (2012) 102-106.
[3] R. Alipour Moghadam Esfahani, R.B. Moghaddam, I.I. Ebralidze, E.B. Easton, Applied Catalysis B: Environmental, 239 (2018) 125-132.
[4] R. Alipour Moghadam Esfahani, H.M. Fruehwald, F. Afsahi, E.B. Easton, Applied Catalysis B: Environmental, 232 (2018) 314-321.

Figure 1
Development of Mesoporous Carbon Fibers for PEFC Catalyst Supports
Authors: Huang Ting-Wei , Nagayama Mayumi , Sasaki Kazunari , Hayashi Akari 
Published: February 2020

Introduction

PEFCs have been known as an energy technology with high efficiency and low carbon emission. Among the components of PEFCs, the electrocatalyst layer is an important component to determine PEFC performance and mainly made by noble metal particles dispersed on carbon supports. In order to increase the efficiency and durability of electrocatalysts, our group has been focusing on developing novel carbon supports, and we have previously demonstrated the improvement of durability by utilizing mesoporous carbon (MC) with 6-8 nm pore size [1]. Even though the nanostructure of electrocatalysts has been successfully controlled, further control of the microstructure of electrocatalyst layers is required to improve efficiency of PEFC. In this study, we are trying to control the microstructure though making our MC into fibers with an electrospinning technique.

Experimental

MC fibers (MCFs) were synthesized by electrospinning the solution containing the resol-formaldehyde type resin polymer and Pluronic F127, after adding polyvinyl alcohol (PVA) as a polymer additive. Then, Pluronic F127 was removed by heat treatments to generate mesopores. MCFs were characterized by N2 sorption in order to analyze their mesoporosity. To make comparison on mechanical strength and conductivity among Vulcan® carbon black, MC, and MCF, FIB-SEM observation and electro-impedance measurements were performed, respectively, after spray printing carbon dispersions on the substrate. Electrochemical analyses were performed by both half-cell measurements in the solution and full-cell measurements with membrane-electrode assemblies (MEAs), after successful Pt deposition into mesopores of MCF.

Results and discussion

The morphology of MCF is shown in Figure 1, and both the fiber structure and mesopores were confirmed. The N2 adsorption measurement indicated the pore size of MCF is around 4-6 nm, which is slightly smaller than the pore size of MC. Regarding to the mechanical strength, MCF showed smaller change in the thickness after compression in comparison to the regular MC and Vulcan® carbon black. This probably comes from higher elasticity provided by the fiber structure. Moreover, according to the conductivity measurements, MCF showed higher conductivity than MC and Vulcan® carbon black. The higher conductivity is probably due to the fact that the fiber-fiber contact provides a better conductive path than the particle-particle contact.
From electrochemical analyses through half-cell measurements, Pt deposited MCF catalyst (Pt/MCF) showed similar ECSA and ORR activity to Pt deposited MC catalyst (Pt/MC). However, based on better mechanical strength and conductivity of MCF, advantages on full-cell measurements with MEAs are expected. Details of preparation and evaluation of MEAs will be discussed.

References

[1] Minamida　Y, Noda　Z, Hayashi　A,　and Sasaki　K, Development of MEAs with Pt/Mesoporous Carbon as a Cathode Catalyst. ECS Transactions, 64 (3) 137-144 (2014).

Figure 1
Fully Ordered Pt3Co Intermetallic Nanoparticles Derived from MOFs for Oxygen Reduction in PEMFCS
Authors: Wu Gang 
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) are considered to be a promising power source for electric vehicles and stationary residential applications. However, current PEMFCs have several problems that need to be overcome including high cost, insufficient power density, and poor performance durability. Current Pt-based cathodes for the oxygen reduction reaction (ORR) are primarily responsible for these issues. Development of advanced Pt-based catalysts are crucial for solving these problems in order for large-scale application of PEMFCs to be feasible. Recently, highly ordered PtM alloy catalysts have exhibited significantly enhanced activity and stability for the ORR in PEMFCs, which have attracted substantial attention. Based on our ongoing research projects [1-3], in this presentation, we introduced our recent progress to develop low-PGM catalysts with emphasis on the innovative synthesis methods of using pre-doped transition metals such as Co or Ni into metal–organic-framework (MOF)-derived carbon as the sources to prepare highly ordered PtM catalysts. As an example, ordered Pt3Co intermetallic nanoparticles through a facile thermal treatment of Pt nanoparticles supported on Co-doped MOF-derived carbon. Atomically dispersed Co sites are originally embedded into MOF-derived carbon. Then we can accurately control the diffusion of Co into Pt crystals and form ordered Pt3Co structures. It is very crucial for the formation of the ordered Pt3Co to carefully control the doping content of Co into the MOFs and the heating temperatures for Co diffusion. The optimal Pt3Co nanoparticle catalyst has achieved significantly enhanced activity and stability. The highly ordered intermetallic structure was retained after the accelerated stress tests made evident by atomic-scale elemental mapping. Fuel cell tests further verified the high intrinsic activity of the ordered Pt3Co catalysts. The new synthesis approach provides an effective strategy to develop active and stable Pt alloy catalysts by leveraging the unique properties of MOFs such as 3D structures, high surface areas, and controlled nitrogen and transition metal dopings. This concept also provides a solution to take advantages of current atomically dispersed PGM-free catalyst to develop high-performance low-PGM cathode catalysts.
References:

X. Wang, S. Hwang, Y.-T. Pan, K. Chen, Y. He, S. Karakalos, H. Zhang, J. S. Spendelow, D. Su, G. Wu, Nano Letters 2018, 18, 4163.

Chen, S. Hwang, J. Li, S. Karakalos, K. Chen, Y. He, S. Mukherjee, D. Su, G. Wu, Nanoscale 2018, 10, 17318.

Liang, F. Ma, S. Hwang, X. Wang, J. Sokolowski, Q. Li, G. Wu, D. Su, Joule 2019, 3, 956.
Thin Film Morphological Characteristics of a Perfluorinated Anion Exchange Membrane
Authors: Divekar Ashutosh G , Buggy Nora C , Dudenas Peter J , Kusoglu Ahmet , Seifert Soenke , Pivovar Bryan S. , Herring Andrew M. 
Published: February 2020

Perfluorinated anion exchange membranes are promising materials for alkaline fuel cell applications. Our previous work indicates they have high conductivity of >100 mS/cm at 80ᵒC and 95%RH.(1) They have also displayed good fuel cell performance of 1W/cm2.(2) We have also performed transmission small- and wide-angle X-ray scattering (SAXS/WAXS) of the bulk membrane to understand the bulk morphology.(3) Properties of Perfluorinated sulfonic acid (PFSA) ionomers as thin films have been thoroughly investigated in the past.(4) However, there is no literature about thin film characterization of perfluorinated anion exchange polymer and hence there is a lack of understanding about the interfacial properties. Here, we have studied the structure of these materials using Grazing-incidence small-angle x-ray scattering (GISAXS). Polymer solutions of different concentrations were used to spin-cast the thin films onto silicon substrates with native oxide layer and also coated with silver and Platinum.. Ellipsometry was used to obtain a calibration curve of thin film thickness vs. concentration of the polymer solution (wt%). From GISAXS, we can conclude that the polymer chains align horizontally parallel to the plain silicon as well as silver substrate. This alignment becomes significant at higher film thicknesses. Understanding the interfacial alignments of polymer on potential catalyst surfaces will help us better design them for optimal fuel cell performance or other electro-chemical applications.
References:

A. G. Divekar, M.-C. Kuo, A. M. Park, A. R. Motz, Z. S. Page-Belknap, Z. Owczarczyk, H. Long, S. Seifert, C. M. Maupin, M. A. Yandrasits, Y. Yang, B. S. Pivovar and H. A. M., Journal of Polymer Science: Part B (2019).

T. J. Omasta, A. M. Park, J. M. Lamanna, Y. Zhang, X. Peng, L. Wang, D. L. Jacobson, J. R. Varcoe, D. S. Hussey, B. S. Pivovar and W. E. Mustain, Energy & Environmental Science, 11, 551 (2018).

A. G. Divekar, A. M. Park, Z. R. Owczarczyk, S. Seifert, B. S. Pivovar and A. M. Herring, ECS Transactions, 80, 1005 (2017).

M. A. Modestino, A. Kusoglu, A. Hexemer, A. Z. Weber and R. A. Segalman, Macromolecules, 45, 4681 (2012).

Figure 1
Electroreduction of Oxygen on Carbide-Derived Carbon Supported Pd Catalysts
Authors: Lüsi Madis , Erikson Heiki , Merisalu Maido , Käärik Maike , Leis Jaan , Sammelselg Väino , Kaljuvee Tiit , Tammeveski Kaido 
Published: February 2020

In recent years there have been multiple studies trying to improve the activity and stability of Pd-based catalysts for oxygen reduction reaction (ORR).1 The primary goal is to substitute Pt used for the fuel cell applications. In this work the standard borohydride reduction method was used to deposit Pd on different carbon materials, which were prepared from various metal carbides. These carbide-derived carbon (CDC) materials had varying amounts of micro and mesopores and were further ball-milled to obtain smaller carbon particle sizes. The influence of the support material on the prepared catalysts was studied. From the obtained catalysts it was observed that low micro-porosity lead to a higher order of agglomeration of the deposited Pd particles with electrochemical surface area being 3 times smaller in alkaline solution as compared to highly microporous Pd/CDC2. Obtained Pd/C catalysts were studied using thermogravimetry, scanning electron microscopy, cyclic voltammetry, and CO stripping. The ORR was explored using the rotating disk electrode (RDE) method. From Figure 1 it is evident that the Pd particles have a higher order of agglomeration on Pd/CDC3 and Pd/CDC4, which were the two catalysts with the lowest amount of micropores in the original CDC material. The results of thermogravimetric analysis indicated around 20% of Pd deposition for all studied catalysts except for Pd/CDC3 characterized with smaller mass loss compared with the others, which could be due to fewer sites where Pd can deposit. The results of the thermogravimetric analysis also indicated that the Pd deposition shifted the thermooxidation temperature of the materials to lower values compared to the Pd-free CDC materials. RDE polarization curves were measured in both 0.1 M KOH and 0.1 M HClO4 solution. According to the Koutecký–Levich analysis the number of electrons transferred per O2 molecule for all the catalyst was around 4. There are notable differences in the diffusion-limited current plateaus, which could be due to different coverage of the Pd/C catalysts due to the larger carbon particles present in some of the CDC materials, even though the CDC materials were ball-milled, still rather large (2-6 μm) carbon particles could be observed depending on the CDC material. In alkaline media, the specific activity (SA) values increased with the number of mesopores and decreased with the increase of the number of micropores, where highest SA could be observed for Pd nanoparticles supported on CDC3 and CDC4.

Figure
1
. SEM images of a) Pd/CDC1, b) Pd/CDC2, c) Pd/CDC3, d) Pd/CDC4, e) Pd/CDC5, and f) Pd/Vulcan carbon.
Reference

H. Erikson, A. Sarapuu, J. Solla-Gullon, and K. Tammeveski, J. Electroanal. Chem., 780, 327-336 (2016).

Figure 1
(Invited) Novel Insights in the Activity, Selectivity and Durability of Fenc, Mn-Oxides and Fenc/Mn-Oxide Composites for ORR Catalysis in Alkaline Electrolyte and AEMFC
Authors: Jaouen Frederic , Santori Pietro Giovanni , Speck Florian Dominik , Cherevko Serhiy , Peng Xiong , Mustain William E. , Varcoe John R. 
Published: February 2020

While high power densities are reached with proton-exchange membrane fuel cells (PEMFCs), several drawbacks hold their large-scale commercialization. In particular, the sluggish oxygen reduction reaction (ORR) at the cathode requires significant amount of platinum. Among PGM-free catalysts, iron-nitrogen-carbon catalysts have hitherto shown the highest initial activity toward ORR and especially those that have been subjected to NH3 pyrolysis. However their performance in PEMFC decays too fast. In contrast, prospects for active and durable Fe-N-C catalysts competitive to Pt catalysts are good in alkaline environment, and the advent of high performance anion exchange membrane (AEM) now offers the possibility to investigate this in AEM fuel cell (AEMFC).
This presentation will first report on the ORR activity, stability and operando spectroscopic identification of Fe-N-C catalysts in alkaline electrolyte, with materials comprising only FeNx moieties. To further increase the ORR selectivity toward water formation, the activity and stability of different Mn-oxide polymorphs for ORR and hydrogen peroxide electro-reduction (HPRR) were studied. The properties of a composite comprising the most stable Mn-oxide and Fe-N-C material were also studied, confirming that HPRR is facilitated when Mn2O3 is added to Fe-N-C. At the same time, however, we show that HO2
- is harmful to the MnOx catalyst itself, increasing the manganese dissolution.
FeNC and FeNC/Mn2O3 cathodes were then tested in AEMFC based on radiation-grafted AEM and AEI and compared to performance obtained with a Pt-based cathode. The results show high and comparable ORR activity at 0.9 V between cathodes based on 1.0-1.5 mgFeNC cm-2 and 0.4-0.5 mgPt cm-2. Peak power densities in the range of 1.1-1.7 W·cm-2 were reached in O2-fed AEMFC with such FeNC cathodes, depending on the operating conditions. Results from stability testing are also very promising, and in strong contrast to instability of the same FeNC material in PEMFC. While some performance gap still remains at high power density between highly Pt-loaded cathode and such FeNC cathode, the results show a promising application of FeNC for high performance AEMFC.
Acknowledgements:
The project CREATE leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 721065.
Synthesis of Poly(norbornene) Anion Conducting Membranes for Alkaline Electrochemical Devices: Structure-Property Relationships
Authors: Mandal Mrinmay , Huang Garrett , Kohl Paul A 
Published: February 2020

Anion-exchange membranes (AEMs) are used in electrochemical energy storage and conversion devices such as batteries, fuel cells, and electrolyzers. The development of AEMs with long-term alkaline stability and high anion conductivity (i.e. hydroxide, carbonate and bicarbonate) is of current interest. The benefits over proton-exchange membrane (PEM) devices include the use of non-precious catalysts, facile reaction kinetics, and reduced fuel crossover. However, the issues with the low ionic conductivity, poor stability at high pH, and high water uptake are need to be addressed.
A series of homopolymers and block copolymers containing non-hydrolysable backbone and long-chain head-group tethers based on vinyl addition and ring-opening metathesis polymerization (ROMP) of norbornenes were synthesized for use in AEM fuel cells. The focus of this talk is on the structure-property relationships of poly(norbornene) anion exchange membranes. Polymers were cross-linked with N,N,N′,N′-Tetramethyl-1,6-hexanediamine (TMHDA) to control the water uptake, and improve the mechanical properties. The structure property relationship of AEMs towards high ionic conductivity was correlated with ion-exchange capacity (IECs), number and size of the blocks, molecular weight, and polydispersity. The membranes had record high conductivity of 212 mS/cm at 80 °C and low water uptake. The long-term alkaline stability showed <1% conductivity loss in over 1200 h at 80 °C. The membranes have been used in anion-exchange membranes fuel cells and electrolyzers.
(Invited) Efficient pH-Gradient-Enabled Microscale Bipolar Interfaces in High Performance Direct Borohydride Fuel Cells
Authors: Wang Zhongyang , Parrondo Javier , He Cheng , Sankarasubramanian Shrihari , Ramani Vijay 
Published: February 2020

Electrochemical energy conversion devices usually operate at uniform pH or over a narrow pH range. The uniform pH environment of these devices frequently hampers the facility of one of the half-cell reactions. In proton exchange membrane fuel cells (PEMFCs)/ proton exchange membrane water electrolyzers (PEMWEs), where both the anode and cathode operate at acidic pH, the H2 oxidation/evolution reaction is quite facile while the O2 reduction/evolution reaction is sluggish. In anion exchange membrane fuel cells (AEMFCs)/ anion exchange membrane water electrolyzers (AEMWEs), the converse is true. Moreover, the chemical stability of some reactants depends strongly on the pH.
Direct borohydride fuel cells (DBFCs), operating with NaBH4 as a fuel and H2O2 as the oxidant have attracted a lot of attention due to their high theoretical cell voltages and tactical advantages, particularly for defense-related applications. DBFCs have a high energy density of 9.3 kWh kg-1 and specific capacity of 5.67 kAh kg-1 based on NaBH4 oxidation in alkaline media [1], although the practical energy density will be lowered upon accounting for the added weight of KOH solution required to stabilise NaBH4. Using liquid hydrogen peroxide as the oxidant, the DBFC is a safe and attractive low temperature power source for unmanned underwater vehicles (UUVs) as they exhibit excellent energy and power density, are safe, given the high flash point of NaBH4, and do not release any gaseous effluents, enabling operation at neutral buoyancy [2]. One challenge for this system is the separation between the anolyte fuel (1.5M NaBH4 in 3M KOH) and catholyte oxidant streams (15% H2O2 in 1.5M H2SO4), while another is the high instability of NaBH4 in acidic or even neutral pH [3]. Herein, a pH-gradient-enabled microscale bipolar interface (PMBI) is demonstrated for maintaining pH control of the anolyte and catholyte compartments of the fuel cell. The PMBI employed to separate anolyte and catholyte was based on an anion exchange membrane (AEM) interface in conjunction with a cation exchange membrane (Nafion®) separator. The DBFC with the PMBI yielded a current density of 330 mA/cm2 at 1.5 V and a promising peak power density of 630 mW cm-2 at 1 V in a 25-cm2 active area cell [4]. Using a recessed planar electrode (RPE) in conjunction with TEM, we show that the PMBI maintained a sharp local pH gradient (0.82 pH units/nm on average) at the electrocatalytic reaction site.

References

[1] J. Milikić, G. Ćirić-Marjanović, S. Mentus, D.M.F. Santos, C.A.C. Sequeira, B. Šljukić, Electrochimica Acta, 213 (2016) 298-305.
[2] C.G. Arges, V. Prabhakaran, L. Wang, V. Ramani, International Journal of Hydrogen Energy, 39 (2014) 14312-14321.
[3] M. Chatenet, Nature Energy, 4 (2019) 261-262.
[4] Z. Wang, J. Parrondo, C. He, S. Sankarasubramanian, V. Ramani, Nature Energy, (2019).
The Effect of Gas Diffusion Layer on the Stability of PEM Unitized Regenerative Fuel Cell
Authors: Zhang Xinrong 
Published: February 2020

Proton exchange membranes(PEM) unitized regenerative fuel cell (URFC) combines the fuel cell (FC) and water electrolyzer (WE) in a single stack. It has been widely considered as energy conversion and storage devices to store off-peak electricity in the form of hydrogen, especially when integrated with intermittent renewable energy resources. One of the main performance challenge in URFCs is material corrosion and the formation of Ti oxides at the interface between titanium surface and anode catalyst layer in WE mode. In this paper, porous sinter titanium as metallic gas diffusion layer (GDL) which is closely related to the anode catalyst layer was coated with IrO2-Ta2O5 oxide materials as protective coating, and the effect of IrO2-Ta2O5 coating on cycle stability of URFCs was validated.
As a result, URFCs exhibited that the excellent performance and long-term cycle stability in both FC mode and We mode, what is more, the degradation rate of URFCs was around 1.2% during hundred hours cycle operation in both FC-mode and WE-mode at the current density of 500 mA/cm2. It demonstrated that IrO2-Ta2O5 oxide protective coating improved the corrosion-resistive performance in WE mode and slowed down the formation of Ti oxides at the surface of the metallic GDL. Hence, it further reduced the interfacial contact resistance and improve the cycle stability of URFCs.