bluuebunny/crossref_metadata_2025_split huggingface dataset:
High Surface Area Perovskite Oxide-Based Oxygen Reduction Reaction Electrocatalysts
Authors: Pylypenko Svitlana , Christ Jason M , Batson Tim , Cadigan Christopher A. , Tong Jianhua , O'Hayre Ryan 
Published: February 2020

Development of effective precious-metal free oxygen reduction reaction (ORR) electrocatalysts is highly desirable as projections indicate that the costs associated with Pt can contribute up to half of the overall cost of low-T fuel cells and electrolyzers. Development of inexpensive and effective catalysts for the ORR also has ramifications for other applications, including metal-air batteries and water splitting.There exists a variety of chemistries and classes of non-precious catalyst materials used for the ORR in alkaline media, including non-precious metal alloys, perovskite oxides, spinels and pyrolyzed metal macrocycles. For perovskite oxide (ABO3) catalysts, activity is strongly affected by the B cation and activity can be tuned by A and/or B-site doping. Therefore, identification of doping strategies to tune the perovskite catalyst structure and chemistry to achieve maximum intrinsic catalytic activity is of major importance. Performance of these materials is also limited by the very low surface areas yielded by current synthesis methods. Current soft-chemistry approaches that allow high surface areas are generally only successful for the production of simple (e.g. binary) oxides.
Our catalyst development approach involves i) doping strategies to tune the perovskite catalyst structure and chemistry to achieve maximum intrinsic catalytic activity; ii) novel synthesis processes for the production of compositionally-complex perovskite oxide catalysts with magnitude higher surface areas than those reported in the literature using current techniques; and iii) functionalization of the carbon support to create composite C/oxide catalysts with optimized performance. Combined, these advances allow for greatly improved ORR performance as demonstrated in Figure 1, which shows the evolution of ORR activity for a Ca0.9La0.1Al0.1Mn0.9O3-
δcatalyst (as quantified by rotating disc electrode) after successive implementation of the strategies discussed above. Structure-property correlations to address the interdependence between catalytic activity and variables related to materials composition, structure, and morphology will be presented.
Figure 1. Oxygen reduction mass activities of Ca0.9La0.1Al0.1Mn0.9O3-
δ

Figure 1
Investigation of PtCo/Graphene and PtCoRu/Graphene Catalysts for Oxygen Reduction Reaction
Authors: Kepeniene Virginija , Stagniunaite Raminta , Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus 
Published: February 2020

The electrocatalytic oxygen reduction reaction (ORR) is an important process in energy converting systems such as low temperature proton exchange membrane fuel cells (PEMFCs). Therefore, understanding the oxygen reduction mechanistic pathways in terms of developing an efficient and stable catalyst has been the main research interest over several decades.
In the present study a rapid microwave heating method was used to prepare the graphene supported PtCo and PtCoRu catalysts with the different Pt:Co and Pt:Co:Ru molar ratios. The catalytic activity of the PtCo/graphene and PtCoRu/graphene catalysts, for oxygen reduction reaction was investigated by linear scan voltammetry in the cathodic direction at 5 mV s–1 in the 0.5 M H2SO4 solution saturated with O2 at a temperature of 25 oC. Physical characterization of the catalysts was performed by X-ray Diffraction, High Resolution Transmission Electron Microscopy, Energy Dispersive X-ray Analysis and Inductively Coupled Plasma Optical Emission Spectroscopy techniques. The cyclic voltammetry has been used to estimate the electrochemically active surface areas of the catalysts.
It was found that the PtCo/graphene and PtCoRu/graphene catalysts prepared by means of microwave synthesis show enhanced activity towards oxygen reduction as compared with that at bare Pt/graphene catalyst. The PtCo/graphene and PtCo /graphene catalysts show higher onset potentials, as well as higher current densities towards oxygen reduction reaction as compared with those at the bare Pt/graphene catalyst.
Third-Body Effects of Surfactants Adsorbed on Pt Electrocatalysts in Proton Exchange Membrane Fuel Cells
Authors: Chung Young-Hoon , Jang Jong Hyun , Kim Soo Jin , Chung Dong Young , Park Hee Young , Cha In Young , Sung Yung-Eun , Yoo Sung Jong , Kim Hyoung-Juhn , Henkensmeier Dirk , Kim Jin Young 
Published: February 2020

In the high-temperature PEMFCs that utilize H3PO4-doped polybenzimidazole (PBI) membranes, Pt poisoning by H3PO4 is an important technical issue, while higher ORR kinetics are expected at elevated operating temperatures (~ 180oC).1 In this study, the surface of Pt nanoparticles was modified by surfactant adsorption, in order to enhance ORR activity and decrease H3PO4 poisoning. Previously, the Conway group reported so-called the “third-body (or ensemble) effect”, which refers to the blocking of poisonous spectator species on the electrocatalyst.2

When commercial Pt/C catalysts were modified by oleylamine (OA), ORR activity could be significantly enhanced, due to the variation in the electronic structure of the Pt nanoparticles.3 The ORR activity of the OA-adsorbed Pt/C was decreased by 29% when H3PO4 was added to the electrolyte solution, whereas the activity decay was much larger for untreated Pt/C (53%). This can be understood as a result of the third-body effect by the adsorbed oleylamine molecules.
In addition, a direct synthesis procedure was studied to produce OA-adsorbed Pt/C.4 The Pt/C nanoparticle electrocatalysts were prepared by conventional colloidal-reduction method, but the surfactant removal step by heat-treatment or acid treatment was eliminated. The morphology and crystal structure were analyzed by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The surface modification by surfactant was confirmed by near-edge X-ray absorption fine structure (NEXAFS) and cyclic voltammetry (CV).
The synthesized Pt/C electrocatalysts were characterized by half-cell test, and the expected third-body effect of adsorbed surfactants could be confirmed. A membrane electrode assembly (MEA) was fabricated with synthesized Pt/C and a homemade H3PO4-doped para-polybenzimidazole (p-PBI) membrane, and its single cell performance was evaluated at 160oC. As the MEA compression during cell assembly is an important factor, catalyst layer thickness were similarly controlled. In the low-current density region, the cell voltage of the MEA with synthesized OA-adsorbed Pt/C was higher than that with untreated commercial Pt/C. From extrapolation in Tafel plots, the kinetic current densities were measured to confirm the third-body effect for Pt nanoparticles supported on carbon substrate. Cell voltage was stable over 150 h, indicating that the adsorbed surfactants are durable under high-temperature conditions.
References
1. R. Gisbert, G. Garcı´a and M. T. M. Koper, Electrochim. Acta 55 (2010) 55 7961.
2. H. Angerstein-Kozlowska, B. MacDougall and B. E. Conway, J. Electrochem. Soc. 120 (1973) 756.
3. Y.-H. Chung, D. Y. Chung, N. Jung, Y.-E. Sung, J. Phys. Chem. Lett. 4 (2013) 1304.
4. Y.-H. Chung, S. J. Kim, D. Y. Chung, H. Y. Park, Y.-E. Sung, S. J. Yoo, J. H. Jang 51 (2015) 2968.
A FIB-SEM Study on Correlations between PEFC Electrocatalyst Microstructure and Cell Performance
Authors: Okumura Makito , Nagamatsu Yohei , Noda Zhiyun , Tachikawa Yuya , Daio Takeshi , Hayashi Akari , Sasaki Kazunari 
Published: February 2020

The electrocatalyst layer of the polymer electrolyte fuel cells (PEFCs) has a complicated porous microstructure. Since the structure allows gas transport, proton transport, and water management, cell performance depends strongly on their 3-dimensional microstructure. Understanding on the correlations between the electrocatalyst microstructure and the cell performance is therefore essential in improving the PEFC electrochemical performance. The purpose of this study is thus to clarify these correlations using focused-ion-beam coupled scanning electron microscopy (FIB-SEM).
We used the standard electrocatalyst (TEC10E50E)and prepared model cells with the electrode area of 1cm2. We then varied the Nafion ratio in the electrocatalyst layer to systematically modify the electrocatalyst microstructure. After model cell preparations, IV performance was measured and each electrode overvoltage was separated. We then observed electrocatalyst microstructure by the FIB-SEM technique to examine the correlations between the 3D microstructure and the cell performance. In addition, we analyzed cell performance and electrocatalyst microstructure of Pt/SnO2-based electrocatalysts to examine the structural difference from the standard Pt/C electrocatalyst layer.
Figure 1 shows IV characteristics of several cells with different Nafion contents. In case Nafion ratio was 28wt.%, IV performance was the highest. In case Nafion ratio was less than 28wt.%, whilst IV performance was lower than that of 28wt.%, the cells can still generate high current densities. On the other hand, in case Nafion ratio was higher than 28wt.%, the cells can exhibit a lower cell voltage due to a much higher concentration overvoltage. This is because gas transport pathway in the electrocatalyst layer is filled with Nafion ionomer with increasing Nafion ratio. In order to examine the correlations between the cell performance and the microstructure, 3D microstructure of the electrocatalyst layers was systematically examined by FIB-SEM. As an example, Figure 2 shows 3D microstructure of the electrocatalyst layer with the Nafion ratio of 28wt.%. Similarly, we observed other Pt/C electrocatalyst samples with different Nafion contents. The Pt/SnO2-based electrocatalyst layer was also analyzed for the comparison. Details on the FIB-SEM observation conditions and the microstructure-performance correlations are presented at the symposium.

Figure 1
Multiscale Model of Proton Transport in Perfluorosulfonic-Acid Membrane
Authors: Crothers Andrew Robert , Radke Clayton J. , Weber Adam Z 
Published: February 2020

To optimize polymer-electrolyte-fuel-cell performance, it is critical to improve transport properties of the polymer membrane. The typical fuel-cell membrane is a perfluorosulfonic-acid ionomer that consists of a hydrophobic backbone with hydrophilic side chains terminated by a sulfonic acid group. The polymer phase separates into hydrophilic domains that are on the order of nanometers and enables water and proton transport around the surrounding hydrophobic matrix that provides structural integrity. Although there have been concerted efforts to use molecular-level theory and simulations to understand ion and water transport inside a single pore, there is a need to develop a robust multiscale methodology to bridge molecular descriptors through mesoscale structures to macroscopic properties. In this poster, we present a methodology for such an approach.
Building on previous multiscale modeling efforts1, we use a resistor-network paradigm to describe ionomers as a network of conductive nodes and throats. The effective network resistance is a function of the connectivity of the network and transport resistance between each neighboring node. We use common imaging methods to extract the network geometry from direct imaging of the ionomer2. Molecular theory and simulations are used to describe and calculate the proton conductivity in throats as a function of size. Kirchhoff's circuit laws are applied on each node in the system and the effective resistance across the membrane is determined for ion conduction. Once designed, a poroelastic model is used to change node and throat sizes and subsequent network connectivity with water content and swelling.

Acknowledgements

This work was funded by the Assistant Secretary for Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office, of the U. S. Department of Energy under contract number DE-AC02-05CH11231 and by a National Science Foundation Graduate Research Fellowship under Grant No. DGE 1106400

Citations

[1] J. T. Gostick and A. Z. Weber, “Resistor-Network Modeling of Ionic Conduction in Polymer Electrolytes,” Electrochimica Acta.
[2] F. I. Allen, L. R. Comolli, A. Kusoglu, M. A. Modestino, A. M. Minor, and A. Z. Weber, “Morphology of Hydrated As-Cast Nafion Revealed through Cryo Electron Tomography,” ACS Macro Lett., vol. 4, no. 1, pp. 1–5, Jan. 2015.

Figure 1. 3D projection of pore-network generated from skeletonization of cryo-TEM tomography image of Nafion ionomer. The green cylinders show throats of the hydrophilic network connecting nodes, shown as red balls. The background is a cutaway of the network where blue is the hydrophilic domain and black the hydrophobic backbone.

Figure 1
Improved Performance of Alkaline Membrane Fuel Cells
Authors: Watanabe Shin , Kikkawa Yuki , Oda Kengo , Okamura Takaaki 
Published: February 2020

We have been developing materials for Alkaline membrane fuel cells(AMFCs) for about 10 years. AMFC is one of the polymer electrolyte fuel cells (PEFCs) which uses anion exchange membrane and anion conductive ionomer as polymer electrolyte materials. AMFC has some advantages over proton-exchange membrane fuel cells(PEMFC) 1-2).
(1) The high pH environment of AMFC allows the use of non platinum catalysts.
(2) The kinetics of the ORR reaction is more facile in alkaline environment than in acidic environment.
AMFC has been attracting worldwide attentions, and the number of report is increasing year by year.
We have already demonstrated the relatively high AMFC performances with hydrogen fuel, and have confirmed several features specialized to AMFC, namely CO2 self-purging phenomena3), which could be a solution against serious CO2
problem in AMFC4-6), and the effective water transport from anode to cathode side, which prevent the lack of water needed for cathode reaction7).
To make the AMFC being popular FC, there are some issues to be resolved.
a) Few low-cost non-Pt or non-precious metal catalysts are known.
b) Low power density.
c) Low durability of electrolyte materials.
The absence of good HOR catalysts with non precious metal is an big issues for the people in this field. But, with the considerable efforts for the development of electrolyte materials, the operating conditions and so on, some researchers have achieved the power density of 1W/cm2
8).
Now, we are focusing on the durability of electrolyte materials. The corsslinking between polymer chains is one of an effective way to improve the durability of electrolyte materials. We have investigated some aspects of crosslinking reagents, and have achieved some improvement on the durability of electrolyte materials for AMFC.

References

H. A. Gasteiger , FC-EXPO 2008, Technical conference fc-10.

J. R. Varcoe, R. C. T. Slade, E. Lam How Yee, S. D. Poynton, D. J. Driscoll, D. C. Apperley, Chem. Mater., 19, 2686 (2007)

L. A. Adams, S. D. Poynton, C. Tamain, R. C. T. Slade, J. R. Varcoe, ChemSusChem, 1, 79 (2008).

H. Yanagi, K. Fukuta, ECS transactions, 16, 257 (2008).

K. Fukuta, H. Inoue, S. Watanabe, H. Yanagi, ECS transactions, 1
9, 23 (2009).

H. Yanagi, S. Watanabe, K. Sadasue, T. Isomura, H. Inoue, K. Fukuta, Abstract of 216th ECS Meeting, #341 (2009).

T.Isomura, K.Fukuta, H.Yanagi, S.Ge and C.Y. Wang, Abstract of 219th ECS Meeting, #221 (2011).

Y. Wang, G. Wang, G. Li, B. Huang, J. Pan, Q.Liu, J. Han, L. xiao, J. Lu, L. Zhuang, Enegy Environ. Sci. 8,177(2015)
Adsorption Behavior of Nafion Ionomers on Au and Pt Surfaces
Authors: Masuda Takuya , Uosaki Kohei 
Published: February 2020

Adsorption behavior of perfluorosulfonated ionomer, i.e., Nafion, on gold and platinum electrode surfaces was investigated by various techniques including cyclic voltammetry, electrochemical quartz crystal microbalance, and electrochemical atomic force microscopy in an aqueous solution containing Nafion as an only electrolyte without any other electrolyte. It was shown that Nafion acts as an aqueous electrolyte and electrochemical measurements can be performed in this solution.
Nafion did not adsorb on the gold surface at 0 V (vs. Ag/AgCl) and started to adsorb at 0.45 V in a lying-down configuration. The adsorbed amount increased as the potential was made more positive. In the potential range between 0.75 and 1.0 V, Nafion aggregated at the surface. Those aggregated Nafion desorbed from the surface by keeping the potential at 0 V.
Nafion also desorbed from the surface upon the gold oxide formation. When the gold oxide was reduced, Nafion re-adsorbed on the surface. Thus, adsorption behavior of Nafion is similar to that of the sulfate anion, implying that sulfonate groups of Nafion play an important role in adsorption of Nafion on gold surfaces.
In contrast, Nafion adsorbed on the platinum surface without any significant morphology change in the potential range between 0.1 and 0.8 V despite the fact that the adsorbed amount of the sulfate anion increases as the potential goes more positive. When the potential was kept at 1.1 V where the place-exchange oxide is formed, Nafion desorbed from the surface. Once the platinum oxide was reduced, Nafion re-adsorbed on the surface.
The interaction of fluorocarbon chains on a bare platinum surface and the desorption of Nafion upon the oxide formation were confirmed by surface x-ray scattering in an MEA-like configuration.

References:

1) T. Masuda, K. Ikeda, K. Uosaki, Langmuir,
2013,
29, 2420.

2) T. Masuda, H. Fukumitsu, T. Kondo, H. Naohara, K. Tamura, O. Sakata, K. Uosaki, J. Phys. Chem. Soc.,
2013,
117, 12168-12171.

3) T. Masuda, F. Sonsudin, P. R. Singh, H. Naohara, K. Uosaki, J. Phys. Chem. Soc.,
2013,
117, 15704-15709.
Comparison of Electrocatalytic Properties of PtCo/Graphene Catalysts for Ethanol, Methanol and Borohydride Oxidation
Authors: Kepeniene Virginija , Tamasauskaite-Tamasiunaite Loreta , Antanaviciute Kornelija , Balciunaite Aldona , Norkus Eugenijus 
Published: February 2020

In this study the graphene supported PtCocatalysts (denoted as PtCo/GR) with diferent molar ratios of Pt and Co were fabricated by means of the rapid microwave heating method with the aim to use them in an alkaline fuel cells, using ethanol, methanol and borohydride as fuel.The synthesized catalysts were examined by Transmission Electron Microscopy, X-ray Ddiffraction and Inductively Coupled Plasma Optical Emission Spectroscopy. The electrochemically active surface areas of the prepared catalysts were determined from the cyclic voltammograms of the different PtCo/GR catalysts recorded in a deaerated 0.5 M H2SO4 solution at a sweep rate of 50 mV s–1 by calculating the charge associated with the hydrogen adsorption (220 µg cm-2). The electrocatalytic activitiy of the synthesized catalysts was investigated towards the oxidation of ethanol, methanol and borohydride in an alkaline medium by means of cyclic voltammetry and chronoamperometry.
It was found that the PtCo/GR catalysts with an average particle size of ca. 1-3 nm were synthesized by means of microwave heating of Pt(IV) and Co(II) salts in ethylene glycol solutions. The synthesized PtCo/GRcatalysts with the different Pt:Co molar ratios show an enhanced activity towards the oxidation of H2 generated by catalytic hydrolysis of BH4
– and direct oxidation of BH4
– ions as well as methanol and ethanol oxidation as compared with that at the graphene supported bare Co and Pt catalysts. It should be noted that the electrocatalytic activity of the PtCo/GR catalysts depends on the molar ratio of Pt:Co in the catalysts and type of fuel.
Tailored DC/Sputtered Niobium Oxide Properties for PEM Electrolysis Application
Authors: Ion-Ebrasu Daniela , Enache Stanica , Rizoiu Alexandru , Filip Mihaela , Preda Silviu , Varlam Mihai , Fruth Victor , Stefanescu Ioan 
Published: February 2020

The fast renewable energy source penetration is creating often mismatch in grid power demand, and is making the case for new energy storage solutions. Hydrogen-based energy conversion technology is considered the most tenable large and long-term scale alternative, and proton exchange membrane (PEM) water electrolysis is seen as one of the most efficient and simple ways to obtain high purity hydrogen [1]. An important drawback in these systems is represented by the oxygen evolution reaction (OER) that is strongly influenced by the catalysts stability against oxidation potential [2].
The aim of this work was to tailor the niobium oxide properties using DC-magnetron sputtering deposition, and to correlate its structure with their electrocatalytic activity toward the Oxygen Evolution Reaction for PEM Electrolyser applications. The influence of the working parameters (deposition pressure, sputtering power and thickness) towards catalysts structure is studied by Uv-Vis and FTIR spectroscopy, X-ray diffraction (XRD), SEM, Rutherford Back Scattering experiments, and four-points resistivity measurements. AC impedance measurements, and cycling voltammetry for electrochemical surface area (ECSA) determination is carried out. The Niobium oxides are deposited on various substrates from transparent (optical glass) for optical and electrical measurements, to highly conductive glassy carbon for compositional and electrochemical investigations.
[1] C. Rozain Caroline, P. Millet, Electrochimica Acta, 131 (2014) 160-167.
[2] V. K. Puthiyapura,, S. Pasupathi, S. Basu, X. W, H. Su, N. Varagunapandiyan, B. Pollet, K. Scott, Int. J. of. Hydrogen Energy, 38 (2013) 8605-8615.