bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Membrane Development and Transport Study for Redox Flow Batteries
Authors: Wang Wei 
Published: February 2020

This presentation describes the membrane development and transport study at PNNL for the redox flow batteries. Several topics will be covered in the talk including the development of the PTFE/SiO2 porous separator and the research on the correlation between the Nafion membrane microstructure and the vanadium redox flow battery performance. The impact of the equivalent weight on the microstructure of the membrane and thus the performance of VRBs is systematically studied. By tailoring the equivalent weight and membrane thickness, the new membrane contains optimal pore geometry with extremely low vanadium-ion permeability was developed. In addition, its area resistance is comparable to, and its cost is significantly less than, the widely used Nafion 115 membrane. Excellent VRB single-cell performance (89.3% energy efficiency at 50mA∙cm-2) was achieved along with a stable cyclical capacity over prolonged cycling (>200 cycles). The chemical composition (Figure 1), pore geometry, transport properties and flow cell performance will be reported.
In addition, a detailed study on the ions transport behavior across the membrane and its impact on the redox flow battery performance will be presented, using vanadium redox flow battery as an example. In operando study on the vanadium ion crossover unveiled the mechanisms contributing to the battery capacity fading, as well as the state-of-charge changes along cycling. The studies were carried out on various membranes, such as cation exchange membrane and porous separators.

Figure 1.
19F MAS-NMR spectra measured at an 11.7 T magnetic field with a spinning speed of 13.5 kHz for NDM142, NDM220, and NDM221 membranes. The circles and red line represents the experimental spectra and the fitted curve with deconvolution analysis, respectively (see text for details). The asterisk (*) indicates MAS spinning side bands.

Figure 1
Stability and Efficiency Improvement of Sulfonated Poly(para-phenylene): Study of Random Co-Polymer for Proton Exchange Membrane for Fuel Cell
Authors: Skalski Thomas , Britton Benjamin , Peckham Timothy J , Holdcroft Steven 
Published: February 2020

Sterically-encumbered, sulfonated poly(phenylene)s are an interesting group of hydrocarbon materials for use in low Pt-content catalyst layers because they potentially offer high conductivity, high thermo-oxidative stability, and appear less-prone to strong adsorption on Pt – a process that typically reduces the electroactive surface area. Frequently, polymers like poly(phenylene)s are randomly post-functionalized in order to introduce proton-conducting properties.(1-3) However, as randomly-functionalized materials are not ideal as proton conductors, a new synthetic route has been developed in order to obtain well-defined pre-functionalized monomers for the synthesis of sulfonated poly(phenylene)s. Using a variety of NMR pulse sequences, the isomers resulting from different couplings (e.g., meta-meta) of arylene moieties has been studied through an examination of several small molecule, model compounds. Furthermore, a series of random copolymers has been made in which the ionic content was varied by alteration of the monomer feed ratios. Finally, the properties (e.g., proton conductivity, chemical stability, fuel cell performance as membrane and catalyst ionomer) have been extensively studied.(4)
(1) Maier, G.; Meier-Haack, J. Advances in Polymer Science
2008, 216, 1
(2) Otsuki, T.; Kanaoka, N.; Iguchi, M.; Mitsuta, N.; Soma, H.; (Honda Motor Co., Ltd., Japan; JSR Corporation). Application: US, 2004, 13
(3) Fujimoto, C. H.; Hickner, M. A.; Cornelius, C. J.; Loy, D. A. Macromolecules
2005, 38, 5010
(4) T. J. G. Skalski, B. Britton, T. J. Peckham and S. Holdcroft, Journal of the American Chemical Society, 2015, 137, 12223

Figure 1
High Performance, High Catalyst-Efficiency Hydrocarbon Fuel Cells
Authors: Holdcroft Steven , Britton Benjamin , Skalski Thomas 
Published: February 2020

While perfluorinated sulfonic acid (PFSA) membrane and ionomer materials such as Nafion® form the standard for high-performance proton-exchange membrane fuel cells (PEMFCs), the limited and difficult chemistry of perfluorinated materials hampers further material development to extended fuel cell performances and lifetimes, while the high cost of perfluorinated materials contributes to the cost barrier limiting the ubiquity adoption of fuel cells for energy generation. One method of reducing cost is the US Department of Energy target of 0.0625-0.125 mg PGM/cm2 as a catalyst loading. However, at low to ultra-low catalyst loadings, PFSAs exhibit a substantial increase in resistivity attributed to oxygen mass transport losses, particularly in the far Ohmic region of polarization data, causing disproportionate reductions to achievable power densities.
Hydrocarbon proton-exchange materials offer the potential for solutions to material issues inherent to PFSAs, with established, varied chemistry allowing for versatile material innovation. Properties such as lower fuel crossover and improved operation in desirable operational conditions such as reduced relative humidity (RH) or high temperature has been well established. Together with the lower cost of basic materials and the ability to recycle catalyst layers, these properties make the demonstration of high performance, fully hydrocarbon PEMFC operation significantly of interest to the field.
Here, hydrocarbon proton-exchange materials are shown that exhibit significant radical stability and high conductivities. Furthermore, these materials form thin membranes and are soluble in low-boiling, polar solvents necessary for incorporation as ionomer into catalyst inks that create high-quality catalyst layers. MEAs and catalyst layers were formed, incorporated into fuel cells, and characterized in situ by IV polarization, CV, CA, LSV, and EIS, and ex situ by mercury porosimetry and SEM. As ionomers, these exhibit reduced mass transport losses compared to PFSA ionomers, a result of substantially smaller increases to oxygen mass transport losses than PFSAs exhibit as catalyst layer loadings are decreased. As fully hydrocarbon fuel cells, improved interfaces lead to improved water transport and lower total resistivity attributable to membrane and ionomer congruency, thereby achieving higher power densities than directly comparable PFSA references using rigorously optimized conditions and catalyst loadings. These high-performance hydrocarbon proton-exchange materials may thereby represent a fully hydrocarbon alternative to PFSA materials for hydrogen fuel cells.
Proton Exchange Membranes Based on Polymeric Ionic Liquids for Fuel Cell Applications
Authors: Ortiz Sainz De Aja Alfredo , Díaz Vejo Mariana , Ortiz Uribe Inmaculada 
Published: February 2020

One of the most promising technologies for power generation are Proton Exchange Membrane Fuel Cells (PEMFCs). PEMFCs are electrochemical devices which convert directly the chemical energy of oxidation-reduction reactions into electrical energy. These electrochemical devices have high electric efficiency and low environmental impact [1].
Several authors are working in the upcoming commercialization of this technology. However, there are technical aspects that must be overcoming before their implementation. The proton exchange membrane, which is the key component of a PEMFC, needs a considerable improvement regarding its performance without external humidification [2]. This is of great importance because it allows working at temperatures above 80 ºC and eliminate the management of water.
Concerning this aspect, many authors are working incorporating ionic liquids as proton exchange components in PEMFCs. Ionic liquids, which are in liquid state at room temperature, have attractive properties for this application, such as thermal and electrochemical stability and high anhydrous conductivity.
There are several strategies in order to incorporate ionic liquids inside the proton exchange membrane. One of them deals with the polymerization of an ionic liquid monomer [3]. This option avoids the leak of the ionic component during the fuel cell operation.
In this work, membranes based on polymeric ionic liquids have been designed for their use as electrolytes without external humidification. For this purpose, the ionic liquids 1-(4-sulphobutyl)-3-vinylimidazolium trifluoromethanesulphonate [HSO3-BVIM][OTF], 1-sulfobutyl-3-metylimidazolium 2-sulfoethylmethacrylate [SBMIm][SEM] and 1-sulfobutyl-3-vinylimidazolium 2-sulfoethylmethacrylate [SBVIm][SEM] were polymerized under ultraviolet light. The ionic conductivity and fuel cell performance were tested without external humidification.

References

[1] Z. Wojnarowska, J. Knapik, M. Díaz, A. Ortiz, I. Ortiz, M. Paluch, Macromolecules, 2014, 14, 4056-4065.
[2] M. Díaz, A. Ortiz, I. Ortiz, J. membra. Sci., 2014, 469, 379-396
[3] D. Mecerreyes, Prog. Polym. Sci., 2011, 36, 1629-1648.

Acknowledgements

This research was supported by the Ministry of Education and Science under the project CTQ2012-31639 (MINECO, SPAIN-FEDER 2001-2013). Mariana Díaz also thanks MINECO for the FPU fellowship (AP2012-3721).
Proton-Conducting SnP2O7 Electrolyte for Intermediate Temperature PEMFC Under Low Humidificatio
Authors: Lee Kwan-Soo , Kim Yu Seung , Kreller Cortney R , Wilson Mahlon S. , Mukundan Rangachary 
Published: February 2020

Current fuel cells for transportation and residential applications use polymer electrolyte membrane fuel cells (PEMFCs) which require platinum catalysts and operate below 80 °C due to water management issues. However, PEMFCs operating at 100 °C or higher temperatures in anhydrous conditions do not need a humidifier, and do not suffer from water management issues created by the presence of liquid water. Excessive amount of liquid water in the electrode can flood the backing and catalysts layers at lower temperatures leading to poorer fuel cell performance. Furthermore, such intermediate temperature PEMFCs can solve the problem of carbon monoxide (CO) poisoning of the anode electrocatalyst leading to relaxation of the hydrogen fuel quality standards, thus lowering infrastructure costs. Finally, higher operating temperatures allow for simpler cooling systems in transportation applications, which results in smaller and lighter radiators. These advantages mean that a paradigm shift in fuel cells for transportation and residential applications can be achieved with an intermediate temperature proton conducting solid-electrolyte that can operate above 150 °C.
Unfortunately, electrolyte membranes and ionomers developed so far do not have satisfactory conductivity and performance in the above temperature ranges, at low-humidity, or in non-humidified conditions. The further advancement of higher temperature PEMFCs relies on the development of membranes that possess the desired electrochemical and mechanical properties in dry (< 30% RH) and hot (> 100 oC) conditions.
In this study, we have developed an organic/inorganic composite membrane using a SnP2O7 (TPP) inorganic conductor and evaluated the fuel cell performance under various conditions. Membrane electrode assemblies (MEA) were prepared from these membranes and gas diffusion electrodes (GDE) were optimized using either LANL ionomer dispersion or various commercial gas diffusion layer (GDL). A maximum power density (> 600mW/cm2 ) has been obtained for fuel cell operation at ≈ 220 oC under less than 2 % humidification condition.
Enhancement of ORR Activity and Durability of Pt Single Crystal Electrodes Modified with Alkylamines
Authors: Saikawa Keiichiro , Nakamura Masashi , Hoshi Nagahiro 
Published: February 2020

1. Purpose
Fuel cell is high-efficiency and clean energy system. However, high overpotential of oxygen reduction reaction (ORR) and large Pt loading in electrocatalyst are grave issues for the general use.
Miyake et al. reported that platinum nanoparticles modified with octylamine (OA) and alkylamine with pyrene group (PA) give higher activity and durability at the molar ratio OA/PA=7/3 compared with bare Pt nanoparticles [1]. However, the platinum nanoparticles are not shape controlled or well-defined. We have investigated surface structures which enhance the ORR activity and durability using Pt single crystal electrodes modified with OA/PA. The surfaces examined are Pt(100), Pt(110), Pt(111), Pt(331)=3(111)-(111) that has the highest ORR activity [2] and Pt(775)=7(111)-(111). In the notation of high index planes such as n(hkl)-(mno), the value of n, Miller indices (hkl) and (mno) show the number of terrace atomic rows, the structures of terrace and step, respectively.

2. Experimental
Linear sweep voltammograms of the ORR were measured with rotating disk electrode (RDE). Potential was scanned from 0.05 V (RHE) to 1.0 V (RHE) at scanning rate 0.010 V s-1 and rotation rate 2000 rpm. The activity for the ORR was estimated using the specific activity at 0.90 V (RHE) j
k according to the Koutecky-Levich equation.
Durability test was conducted using rectangular wave from 0.60 V step to 1.0 V.
All the potentials were referred to RHE.

3. Result and Discussion
The ORR activities of Pt(111) modified with OA/PA = 9/1, 8/2, 7/3 (molar ratio) were twice or three times higher than that of bare Pt(111). The ORR activity increases with the increase of the ratio of PA. The activity of Pt(775) = 7(111)-(111) modified with OA/PA=9/1 was also higher than that of bare Pt(775). Pt(100) and Pt(110) modified with OA/PA=9/1 gave lower ORR activity than bare electrodes. These results show that PA on wide (111) terrace enhances the ORR activity.
The ORR activity of Pt(111) was enhanced after the durability test because active (110) type defects are formed on the surface. The ORR activity of Pt(111) modified with OA/PA was 1.8 mA/cm2 after 2000 cycles, higher than that of bare Pt(111) 1.0 mA/cm2. Adsorbed amines on wide (111) terrace preserved the high activity after the durability test. The activity after 2000 cycles decreased with the increase of the ratio of PA. This result differs from the previous study [1]. The ORR activity of Pt(775) modified with OA/PA was as high as that of bare Pt(775) after the durability test. Durability of Pt(775) was not improved by OA/PA modification.

4. Acknowledgement
This work was supported by New Energy Development Organization.

5. References
[1] K. Miyabayashi, H. Nishihara, M. Miyake, Langmuir, 30, 2936 (2014)
[2] N. Hoshi, M. Nakamura, A. Hitotsuyanagi, Electrochim. Acta, 112, 899 (2013)
Synthesis of Pt Catalysts Supported on W/Ta-Doped TiO2 As a Highly Durable Electrocatalyst for PEFCs
Authors: Ketpang Kriangsak , Kakinuma Katsuyoshi , Iiyama Akihiro , Uchida Makoto 
Published: February 2020

One of the technical problems impeding commercial use of polymer electrolyte fuel cells (PEFCs) is the degradation of the carbon support under startup/shutdown (SU/SD) conditions, which leads to severe and eventually drastic reduction of the performance due to agglomeration, dissolution, or detachment of Pt nanoparticles. Thus, nanoceramic supports (NCSs) with both high electrical conductivity and durability under SU/SD operating conditions have been actively developed to replace the commercial carbon support.[1-6] Titanium dioxide (TiO2) doped with aliovalent cations is also a candidate as a high durability cathode NCS. We synthesized Pt catalysts supported on tantalum and tungsten-doped TiO2with unique microstructure, involving a fused-aggregated network, and evaluated the oxygen reduction reaction (ORR) activity and durability under SU/SD operation conditions.
We prepared the NCSs by a flame spray synthesis method. The morphology of the NCSs, which was investigated by use of transmission electron microscopy (TEM), had nanoparticles with a partially fused aggregated network structure, similar to that of carbon black (Fig. 1(a)(b)). The crystal structures of the NCSs included rutile and anatase. The surface areas, which were estimated using the Brunauer-Emmett-Teller (BET) technique, were greater than 30 m2g-1. The electrical conductivities, which were measured by use of the two-probe method, were as high as 10-4 S/cm at room temperature under a pressure of 19 MPa (Fig. 2). The NCSs were confirmed to be extremely stable in 1.0 M H2SO4 at 80 oC under air atmosphere. Pt nanoparticles, which were loaded on the NCSs by a colloidal method, were uniformly dispersed on the surface (Fig. 1(c)(d)). The Pt loadings were 19 wt% (Pt/Ta-TiO2) and 19.4 wt% (Pt/W-TiO2), determined by ICP-MS. Pt particle sizes were 4 nm (Pt/Ta-TiO2) and 10 nm (Pt/W-TiO2), determined by TEM. The ORR activity increased with increasing heat treatment temperature and reached that of a commercial carbon-supported Pt catalyst (c-Pt/CB). The durability of Pt/Ta-TiO2 under SU/SD conditions was superior to that of the c- Pt/CB.

Figure 1
A Successive One-Pot Synthesis of Au@Pt - q ML/C with Enhanced Ethanol Oxidation Activity in Alkaline Media
Authors: Wu Kuang-Heng , Wang Han , Jiang Bei , Cai Wen-Bin 
Published: February 2020

Direct ethanol fuel cells raise the possibility for clean and high efficient energy utilization. Noble Pt-group metals are still essential for electrocatalysts related to such fuel cells. Yet, the high cost and limited reserve of Pt-group metals (especially Pt) as well as the sluggish oxidation kinetics of ethanol molecule call for facile synthesis of low-Pt-content efficient catalysts. Both experimental and simulated investigations suggested alcohol oxidation activity could be improved by coating a monolayer (ML) of Pt on Au [1]. To address the major challenge of scalable synthesis of practical carbon-supported catalysts, here we report a successive and convenient synthesis of Au@Pt-qML/C (qML: quasi-monolayer) using CO as the reducing and capping agents for Pt-qML deposition on Au/C [2]. The Au core with an average diameter of ca. 5 nm was first obtained by reducing HAuCl4 with NaBH4, and Pt-qML was later coated on Au surfaces in one pot through introducing CO and controlled amount of Pt(II). The Au core- Pt shell structure was examined through XRD, EDX, IR and electrochemical measurements. A remarkable enhancement towards ethanol oxidation reaction was obtained on the as-formed Au@Pt-ML/C as compared to that on the state-of-the art commercial Pt/C.

Acknowledgements
：Financial supports from NSFC (grant No. 21273046 and 21473039）and the 973 Program (No. 2015CB932303) of MOST are highly appreciated
References:
[1] M. Li, P. Liu, R.R. Adzic, J. Phys. Chem. Lett., 3, 3480 (2012).
[2] H. Wang, K. Jiang, Q.L. Chen, Z.X. Xie, W.B. Cai. Chem. Commun.,
52, 374 (2016).

Figure 1
Novel Catalyst Support Based on Mesoporous Cobalt and Molybdenum Carbide for Enhanced ORR Kinetics in Alkaline Fuel Cells
Authors: Nikolic Vladimir M , Perovic Ivana M , Saponjic Aleksandra P , Kokunesoski Maja , Tosic Milos P , Milovanovic Dubravka , Marceta Kaninski Milica P 
Published: February 2020

Abstract

The kinetics of the oxygen reduction reaction (ORR) greatly influences the performance and the costs of electrodes in fuel cells. Commercial platinum based electrocatalysts exhibit the highest performance, but also increase the cost of the fuel cells. On the other hand, carbon based platinum catalyst support is subject to oxidation, which causes agglomeration of the Pt nanoparticles and decrease in performance of the fuel cells. In order to overcome these issues, we have developed and prepared novel catalyst support based on cobalt and molybdenum carbides. Synthesis of CoMoC was done by chemical method, followed by the high temperature treatment. Since the high temperature preparation of the carbides usually produces low surface area materials, we have developed and prepared a specific carbon based matrix, where Co and Mo based precursors were added. High temperature treatment was done at several temperatures, from 750°C to 1200°C. Structural and morphological characterizations were done using XDR, SEM/EDX and BET analysis, and the obtained results show the formation of the mesoporous non-stoichiometric CoMoC, having the highest value of surface area of 97 m2g. It was shown that the increase in the preparation temperature leads to increase in the mixed carbide stoichiometry, which was ascribed to the high temperatures needed to transform molybdenum oxide into stable carbide. This catalyst support was used to deposit platinum nanoparticles via boron hydride reduction method to obtain several electrocatalyst having 1-10% Pt on the catalyst support. The electrochemical measurements with the prepared CoMoC and different Pt/CoMoC were done using cyclic voltammetry and linear sweep voltammetry on the RDE in alkaline solution. The stability of the prepared catalyst support and catalysts was evaluated using accelerated test procedure by cycling the potential between 0.65 and 1.0 V in oxygen rich alkaline solution. The ORR kinetics parameters were determined and we found comparable performance of the 10% Pt/CoMoC with the commercial Pt/C (40%), which was ascribed to the non-stoichiometric nature of the catalyst support.
Development on Measuring Methods of Catalyst Layer Structure Parameters Under Operating Condition of PEFCs
Authors: Yokoyama Koji , Oyama Junpei , Ohashi Masato , Sugawara Seiho 
Published: February 2020

In order to familiarize fuel cell vehicles (FCV), its system cost reduction is a critical issue. High current density operation is an effective approach, but it is necessary to reduce activation overvoltage, IR loss and concentration overvoltage. In particular, the concentration overvoltage must be decreased to increase oxygen flux at high current density. In order to reduce concentration overvoltage, oxygen gas diffusion characteristics in gas diffusion layer (GDL) and microporous layer (MPL), oxygen dissolution and diffusion characteristics in ionomer, reduction of oxygen local flux to platinum and influence analyses of water retention in MEA to PEFC performance have been researched by various approaches. In recent years, not only water retention in GDL / MPL but the effect of water retention in catalyst layer (CL) on cell performance has been reported by advancement of MEA inside visualization technique. However, relationship between the catalyst layer structure parameters and liquid water retention characteristics has not been found out yet. In this study, to find out this relationship and influence of water retention in CL to oxygen transport resistance and PEFC performance, porosity/tortuosity (ε/τ) measuring method has been developed under operating condition of PEFC as first step. The ε/τ of CL did not change with temperature (25-80 deg.C) under dry environment, which is reasonable due to low thermal expansion coefficient of each CL material. Currently, we are planning this technique to humidity control and the results will be reported.

Acknowledgments
This research was financially supported by New Energy and Industrial Technology Development Organization (NEDO), Japan.