bluuebunny/crossref_metadata_2025 huggingface dataset:
Activity of Pt Extended Network Electrocatalyst Structures Made from Spontaneous Galvanic Displacement
Authors: Neyerlin K.C. , Larsen Brian A. , Pylypenko Svitlana , Kocha Shyam S. , Pivovar Bryan S.
Published: March 2013

Pt nanotube electrocatalysts were produced from Ag nanowire templates via spontaneous galvanic displacement (SGD). Following electrochemical dissolution of residual silver the Pt nanotube electrocatalysts had electrochemical surface areas (ECA) of 40 m2/gPt. Coupled with specific activities for the oxygen reduction reaction on the order of 1000 μA/cm2 Pt at 0.9V, Pt nanotube electrocatalysts produced mass activities greater than 400 mA/mgPt. Nafion content in the electrocatalyst ink was investigated and shown to have a positive effect only at a concentration of 1μL5wt%/mLink. All other concentrations of Nafion that were examined in the range of 0-100 μL5wt%/mLink resulted in a decrease in measured ECA. The addition of carbon black to the RDE ink of Pt nanotube electrocatalysts was also investigated and found to have a modest, but positive effect on both ECA and specific activity regardless of the Nafion content.
Analyzing the Effect of Ultra-Low Pt Loading on Mass and Specific Activity of PEM Fuel Cells
Authors: Kriston Akos , Xie Tianyuan , Kim Taekeun , Jung Won Suk , Gamliel David , Murphy Brian , Genesan Prabhu , Popov Branko N.
Published: March 2013

The mass and specific activities are intensively used as the characterization parameters for the effectiveness of the catalyst in a fuel cell. These quantities were found to be independent of catalyst loading, but the data presented in this work shows that the mass and specific activity are not independent of the loading at ultra-low Pt loadings. In this work the dependence of mass activity on platinum loading was studied. A one dimensional simplified agglomerate-based macro-homogeneous model was developed and solved analytically and numerically to understand the effects of porosity, agglomerate size, and Pt loading on the mass activity.
Structural Change of the Pt/C Electrocatalyst in Humidified Air Observed by In Situ TEM
Authors: Shimizu Takahiro , Imamura Daichi , Yaguchi Toshie , Kanemura Takashi , Kamino Takeo
Published: March 2013

In situ TEM observation of the Pt/C electrocatalyst was conducted to analyze the structural change of Pt nano particles and carbon support under the pseudo cathode environment. The Pt nano particles were observed to move actively on the support in humidified air, while the particles to remain at their original position on the support in dry air. The in situ high-resolution TEM revealed that the driving force behind the active movement of Pt particles was the oxidation of carbon support selectively at the interface between Pt particle and carbon support, accelerated by water. It appears that the humidity of the air plays an important role in the degradation of the Pt/C electrocatalyst.
Structural Control and Evaluation of PEMFC Catalyst Layers by Blending Platinum-Supported/Stand-Alone Carbon Black
Authors: Suzuki Takahiro , Tsushima Shohji , Hirai Shuichiro
Published: March 2013

In proton exchange membrane fuel cells, catalyst layers are one of the most important components to achieve both higher performance and cost reduction. In this study, a method to control the structure of the catalyst layers by blending platinum-supported and stand-alone carbon black was adopted. Catalyst layers in which either thickness or platinum loading were independently controlled were synthesized and evaluated in fuel cell operation. It was clarified that lowering platinum loading deteriorated cell performance while thinning catalyst layer showed better performance. These results indicate that local transport in the catalyst layers plays an important role on cell performance in severe operating conditions.
Influence of Ink Composition on the Electrochemical Properties of Pt/C Electrocatalysts
Authors: Kocha Shyam S. , Zack Jason W , Alia Shaun M , Neyerlin K.C. , Pivovar Bryan S.
Published: March 2013

Nanoparticle platinum on carbon black supports (Pt/high surface area carbon or Pt/HSC and Pt/Vulcan), widely used to benchmark novel electrocatalysts for proton exchange membrane fuel cells (PEMFCs), were characterized in rotating disk electrode (RDE) setups using multiple ink formulations. The oxygen reduction reaction (ORR) specific activity measured in 0.1 M HClO4 was higher by a factor of ~1.8 when Nafion ionomer was excluded from Pt/HSC inks/electrodes and substituted with trace amounts of a non-ionic surfactant for improved dispersiblity. Pt/Vulcan electrocatalysts did not exhibit this enhancement when Nafion was replaced with trace surfactant; however, eliminating both Nafion and the surfactant raised its specific and mass activity by a factor of ~1.8. The electrochemical areas for optimized inks/electrodes with and without Nafion were relatively unchanged at ~100 m2/g for Pt/HSC and ~65 m2/g for Pt/Vulcan. The higher measured activities have significant implications for established conventions regarding 'particle size effects'.
Analysis of Oxygen Transport Resistance of Nafion Thin Film on Pt Electrode
Authors: Kudo Kenji , Morimoto Yu
Published: March 2013

To clarify the rate determining process for the oxygen transport in a catalyst layer of polymer electrolyte fuel cells, the oxygen transport resistance of a Nafion thin film was precisely evaluated using a microelectrode technique for cast Nafion films with 30-150 nm thickness and data analysis on the relationship between the Nafion thickness on the Pt electrode and the diffusion-limited current density on the electrode. While the oxygen transport resistivity inside the Nafion thin film was roughly equal to that of Nafion thick membrane, the interfacial resistance at the Pt/Nafion or Nafion/gas interface was estimated to be equivalent to 60-80 nm thickness of Nafion film and to account for the dominant part of the total oxygen transport loss in a real PEFC electrode, especially with a low platinum loading.
Effect of High Oxygen Permeable Ionomers on MEA Performance for PEFC
Authors: Yamada Kohta , Hommura Satoru , Shimohira Tetsuji
Published: March 2013

Asahi Glass Co., Ltd. (AGC) has been developing the perfluorinated ion exchange polymers (ionomers) in order to improve the performance, durability and robustness of MEA for PEFC. In the present report, the effect of the high oxygen permeable ionomers on MEA performance is described. The oxygen permeability of new ionomers was determined by means of potential step chronoamperometry (PSCA) using a Pt microelectrode. It was confirmed that the new ionomers had higher oxygen permeability compared with standard ionomer, and the permeability strongly depended on the ionomer density. And, the MEA performance was improved by using the high oxygen permeable ionomers for MEA cathodes. These results suggested that the high oxygen permeable ionomer was available for the reduction of Pt loading in MEA cathodes.
Catalyst Degradation: Nanoparticle Population Dynamics and Kinetic Processes
Authors: Rinaldo Steven G. , Lee Wendy , Stumper Jürgen , Eikerling Michael
Published: March 2013

Nanoparticle catalysts dispersed on high surface area electronic support materials are used in a wide range of low-temperature applications. Nano-sized particles afford a high active surface area per unit volume of an electrocatalytic medium. However, the gain in active surface area for desired surface reactions is offset, in part, by enhanced rates of degradation processes that cause losses in catalyst mass, catalyst surface area and electrocatalytic activity. We present a dynamic model of surface area loss phenomena utilizing population balance equations in particle space to account for nanoparticle dissolution, redeposition, coagulation and detachment. Dissolution emerges as a key mechanism of degradation and for Pt-based nanoparticles, we examine the underlying kinetics of Pt oxidation that dictate the rates of Pt dissolution.
Cathode Catalysts Degradation Mechanism from Liquid Electrolyte to Polymer Electrolyte Membrane Fuel Cells
Authors: Marcu Alina Ana-Maria , Toth Gabor , Pietrasz Patrick
Published: March 2013

Single-cell and half-cell degradation test procedures are evaluated for carbon supported Pt catalysts. Half-cell analyses are employed in identification of specific test parameters for evaluation of cathode catalysts. Single-cell measurements run at 100 % relative humidity (RH) evaluate the impact of catalysts degradation on fuel cell performance. The measurements in both setups show a 20 % deviation of the electrochemical surface area loss (ECSA), while the oxygen reduction reaction (ORR) activity losses were comparable. The quantification of specific degradation mechanism as Pt dissolution and particle agglomeration and correlation with surface area and oxygen reduction activity is discussed.
The Influence of Experimental Conditions on the Catalyst Degradation in the Accelerated Durability Test Using a Rotating Disk Electrode
Authors: Nagai Tomoyuki , Murata Hajime , Morimoto Yu
Published: March 2013

Accelerated durability tests were carried out for a carbon-supported platinum catalyst using a rotating disk electrode at various rotation rates for various amounts of the catalyst. The loss of the normalized electrochemical surface area (ECSA) of Pt increased with increasing the rotation rate and/or decreasing the catalyst amount. The detailed analysis showed that the reciprocal of the normalized ECSA loss rate linearly increases with the increase in the reciprocal of square root of angular speed or the catalyst amount. By extrapolating these linear relations to zero, the ECSA loss rate at the hypothetical conditions, in which all the dissolved Pt ions would flow out to the electrolyte without re-deposition, was obtained.
Durable, OER-Active Compositions of Pt, Ir, and Ru for PEM Fuel Cell Start-Stop Protection
Authors: Harlow Jessie E. , Stevens David A , Sanderson Robbie J. , Watson Cody W , Crowtz Timothy C. , Dahn J. R. , Haugen Greg M. , Atanasoska Liliana L , Vernstrom George D. , Atanasoski Radoslav T.
Published: March 2013

The catalytic performance under simulated transient start-up and shut-down conditions is evaluated for five potential cathode-side catalyst compositions containing Pt, Ir and Ru. Experiments using the rotating disk electrode technique showed that samples containing a solid solution of Ir and Ru on top of a Pt base layer were the most active and the most durable over 1000 simulated start-stop events.
Effect of Nanosheet Size on Activity and Durability of RuO2 Nanosheet Pt/C Catalyst
Authors: Chauvin Christophe , Liu Qingfeng , Saida Takahiro , Lokesh Koodlur Sannegowda , Sakai Toshio , Sugimoto Wataru
Published: March 2013

Composite catalyst (RuO2ns-Pt/C) composed of commercial carbon supported Pt (Pt/C) and various size RuO2 nanosheets (RuO2ns) were synthesized.The improvement in ORR activity and durability of the different catalysts has been evaluated and is discussed as a function of the size of RuO2ns. The RuO2ns size was found to greatly influence the catalytic properties with smaller RuO2ns giving better performance than larger ones. Composite catalyst with small sized RuO2ns exhibit initial activity 2 times higher than Pt/C catalyst and improved activity retention rate.
Subsurface Enrichment of Highly Active Dealloyed Pt-Ni Catalyst Nanoparticles for Oxygen Reduction Reaction
Authors: Gan Lin , Heggen Marc , Strasser Peter
Published: March 2013

We present the synthesis of homogenous PtNi and PtNi3 alloy nanoparticles by organic solution approach, which showed 4-5 fold increases in Pt-mass normalized activity of oxygen reduction reaction (ORR) compared to conventional Pt catalyst after electrochemical dealloying. Using aberration-corrected scanning transmission electron microscopy and electron energy loss spectroscopy, we found that there is a strong tendency of subsurface enrichment of Ni in the dealloyed Pt-Ni nanoparticles at a higher initial Ni composition (PtNi3), which therefore resulted in unusual core-shell fine structures. Based on this, a correlation of near-surface compositions to the ORR activities of the dealloyed Pt-Ni catalyst nanoparticles was established.
PEMFC Nanoparticle Catalyst Dealloying from Kinetic Monte Carlo Simulations
Authors: Puchala Brian , Lin Shih-kang , Wang Ligen , Morgan Dane
Published: March 2013

We present a kinetic Monte Carlo (KMC) simulation method to study the dealloying behavior of Pt1-xCox nanoparticles. The method uses the modified embeded atom method (MEAM) to model the thermodynamics of the Pt1-xCox alloy, along with kinetic parameters fit to ab initio calculations and experimental data. We have validated the method by using ramped potential simulations. Ramped potential simulations show that dissolution occurs at the potential value expected from measured dissolution potentials.
Pt-Sn(Oxidized Shell)/C and Pt-Sn(Reduced)/C as Cathode Catalysts for the Oxygen Reduction Reaction in Polymer Electrolyte Fuel Cells: Catalyst Performances and Characterization
Authors: Samjeské Gabor , Nagamatsu Shin-ichi , Nagasawa Kensaku , Imaizumi Yoshiaki , Takao Shinobu , Sekizawa Oki , Yamamoto Takashi , Uruga Tomoya , Iwasawa Yasuhiro
Published: March 2013

To address the problems (high price, insufficient total activity and deactivation) related to usage of pure Pt as cathode catalysts for oxygen reduction reactions (ORR) in polymer electrolyte fuel cells (PEFC), carbon-supported Pt-Sn(oxidized shell)/C and Pt-Sn(reduced)/C were used as membrane electrode assembly (MEA) cathode catalysts in PEFC. I-V-load curves in the initial load-cycles showed an increase of the performance for Pt-Sn(oxidized shell)/C, but no increase in the performance was observed with Pt-Sn(reduced)/C and standard Pt/C　catalysts. The observed increase in the performance for the Pt-Sn(oxidized shell)/C catalyst may be due to an synergy effect of Pt-nanoparticle core and SnOx-cluster shell formed on the Pt nanoparticle surface. In-situ XAFS at Pt LIII-edge and Sn K-edge under the PEFC operating conditions showed the absence of electron transfer from Sn to Pt and also no changes in the Sn state, indicating its stability. The in situ XAFS for the Pt-Sn(oxidized shell)/C also revealed that Pt nanoparticles made Pt-O bondings at higher voltages than 1.0 V vs. RHE, but the coordination number of Pt-O bonds was much smaller than that for Pt/C. Thus, the Pt-Sn(oxidized shell)/C is a promising candidate as a MEA cathode catalyst in a PEFC system.
Mixed Metal Oxides as Corrosion-Resistant Catalyst Supports for Polymer Electrolyte Fuel Cells
Authors: Kumar Amod , Ramani Vijay K.
Published: March 2013

Metal oxides RuO2-SiO2, and Mo and Ta doped TiO2 were studied as possible non-carbon electrocatalyst supports for polymer electrolyte fuel cells (PEFCs). RuO2-SiO2 mixed metal oxides offered the best combination of BET surface area, electron conductivity and support stability among the supports studied. RuO2-SiO2 (0.5:0.5) showed high BET surface area of ~290 m2g-1 and high electron conductivity of ~5 Scm-1. It also possessed outstanding support stability and comparable catalyst stability when compared to state-of-the-art Pt/C electrocatalyst. Under fuel cell operating conditions of 80 {degree sign}C and 75% RH, the RuO2-SiO2 (0.5:0.5) electrocatalyst yielded mass and area specific activities of 50 mAmgPt-1 and 156 µAcm-2 respectively at 0.9 V vs RHE.
Titania and Carbon Nanotube Composite Catalyst Supports for Durable Electrocatalyst Performance
Authors: Rigdon William A , Sightler Joshua Jerome , Larrabee Diana , McPherson Eli , Huang Xinyu
Published: March 2013

The development of dual phase composite catalyst supports from carbon nanotubes and metal oxides can resist performance degradation. Carbon nanotubes provide a conductive framework and titanium oxides can form a strong bond with platinum catalysts. The combination of this composite material has been shown to offer some improvements in the performance durability of this electrocatalyst in the cathode of a polymer electrolyte fuel cell.
Effects of Tin Dioxide Loading on ORR Activity and Durability of Pt/C Catalyst
Authors: Kinumoto Taro , Eguchi Naoki , Matsuoka Miki , Tsumura Tomoki , Toyoda Masahiro
Published: March 2013

Pt/Ketjen black catalysts having various loading amounts of tin dioxide particles, Pt/x-SnO2/KB (x = 0, 17, 58), were prepared and their ORR (oxygen reduction reaction) activity and the durability were studied. The ORR activity of Pt/58-SnO2/KB is higher than that Pt/0-SnO2/KB. Durability of Pt for each catalyst was investigated by repeatedly potential pulse test between 0.6-1.0 V. It is clarified that the durability given as ECA remaining is higher than by tin dioxide loading. Therefore, loading of SnO2 particles would give increase ORR activity as well as durability of Pt catalyst.
Improvement in Activity of Highly Durable Silica-Coated Pd/CNT Cathode Catalysts for PEFC by Addition of Cu
Authors: Takenaka Sakae , Miyata Hiroyuki , Tsukamoto Tomohiro , Matsune Hideki , Kishida Masahiro
Published: March 2013

We have previously demonstrated that silica-coated Pd cathode catalysts show high durability under severe cathode conditions in polymer electrolyte fuel cells (PEFCs), while Pd catalysts without silica-coating seriously deactivate under the same conditions due to the dissolution of Pd metal. However, the activity of silica-coated Pd catalysts for the oxygen reduction reaction (ORR) was inferior to that of Pt catalysts used in state of the art PEFCs. In the present study, the ORR activity of Pd catalysts was improved by addition of Cu. Cu-added Pd catalyst prepared with a conventional impregnation method using mixed aqueous solutions of PdCl2 and Cu(NO3)2 had an ORR activity twice that of Pd catalysts. XRD and XAFS studies showed alloy formation between Pd and Cu. Thus, Pd-Cu alloys showed higher activity for the ORR compared with Pd metal.
Synthesis and Electrochemical Characterization of Carbon Supported Platinum Grown by Template Assisted Gas Phase Deposition
Authors: Bult Justin , Neyerlin K.C. , Christensen Steven , Dameron Arrelaine , Kocha Shyam S. , Zack Jason W , Pivovar Bryan S. , Hurst Katherine
Published: March 2013

Platinum catalysts remain one of the primary cost and durability concerns for polymer electrolyte fuel cells. The most common approach to produce Pt/C catalysts is to deposit Pt nanoparticles onto carbon supports. In this study, we first synthesize Pt particles on a sacrificial template and subsequently backfill with a carbon support. We utilize an anodized aluminum oxide (AAO) template in conjunction with atomic layer deposition of platinum and chemical vapor deposition to achieve this process in an all gas-phase synthesis. Following platinum deposition, carbon is deposited into the AAO pores via chemical vapor deposition to support the platinum nanoparticles and to provide electrical continuity, creating a uniquely stabilized Pt particle on carbon. These materials are then recovered from the template by dissolution of the AAO and characterized by microscopy and electrochemical measurements. The initial results from these studies show promising performance metrics and suggest further development of these materials.
Highly Durable Indium Tin Oxide Modified Carbon Supporters for Polymer Electrolyte Membrane Fuel Cells
Authors: Joo Hye-sook , Park Jun-Young , Kim DoHyang , Choi Hanshin
Published: March 2013

Pt nano-particle-attached carbon black particles (Pt/C) are synthesized by an arc plasma deposition (APD) process to improve electrocatalyst properties for polymer electrolyte membrane fuel cell applications. Thanks to the fine Pt particle size and high Pt particle number density by high resolution-transmission electron spectroscopy image analysis, the electrochemical active surface area of the catalyst is higher than a commercial Pt/C. However, Pt/C particles synthesized by APD process show limitations in Pt content and long-term stability in cyclic voltammetry experiments. Therefore, carbon black supporting Pt particles are modified by depositing indium-tin oxide (ITO) nano-particles by APD technique. Pt-ITO/C electrocatalysts formed by the APD process show high electrochemical performance with enhanced durability due to inertness of conductive metal oxides in oxidative conditions.
The Mechanism of the Improvement in Catalytic Activity of Ir Modified by V Compared to Pure Ir/C
Authors: Li Bing , Yang Daijun , Lin Rui , Yu Zhuoping , Ma Jianxin
Published: March 2013

The Ir-V/C catalyst was successfully synthesized by EG method as novel, suitable cathode catalyst for PEMFCs. The XRD showed that the interatomic Ir-Ir distances in the Ir-V/C catalyst were decreased, which can result in more facile O2 adsorption and reduction due to the modified surface and electronic properties. EDS and ICP-MS results indicated that the catalyst contained negligible V content, indicating a beneficial dealloying effect resulting from HCl addition during catalyst synthesis. With a loading of 0.4 mgIr cm-2 Ir-V/C, it achieved a maximum power density of 517.2 mW cm-2, which is higher than the maximum power density of 367.2 mW cm-2 obtained for pure Ir/C. In-situ CV results indicated that the loss of the transition metal effectively improved the overall ECSA of Ir-V/C and particle surface roughness of Ir. This provides a higher density of active sites that can adsorb and subsequently reduce oxygen molecules during fuel cell operation.
ORR Activity of Nb Oxide Based Catalyst Prepared from Nb Compound Including C and N
Authors: Hara Kohei , Ishihara Akimitsu , Matsumoto Masashi , Arao Masazumi , Imai Hideto , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori , Ota Ken-ichiro
Published: March 2013

The development of a non-precious metal cathode catalyst is strongly required for Polymer Electrolyte Fuel Cells (PEFCs) because the cost of platinum and precious metal catalyst is very high. In our previous study, we have reported that oxide-based compounds prepared from group 4 and 5 metal carbonitrides had a high oxygen reduction activity. In this paper, the ORR activity of Nb oxide-based catalysts prepared by heat treatment of the Nb carbide, Nb nitride and Nb carbonitiride under low oxygen pressure was evaluated. Among this, the specimen prepared from Nb carbonitride had a highest ORR activity. We found amorphous carbon on the surface high active catalysts by raman spectroscopy and elemental analysis. Carbon on the surface might affect the ORR activity.
Preparation of Highly Active Zr Oxide-Based Oxygen Reduction Electrocatalysts as PEFC Cathode
Authors: Yin Shihong , Ishihara Akimitsu , Kohno Yuji , Matsuzawa Koichi , Mitsushima Shigenori , Ota Ken-ichiro , Matsumoto Masashi , Arao Masazumi , Imai Hideto
Published: March 2013

In order to make the PEFC gain in popularity, we are working on preparing the non-precious metal catalysts for the cathode oxygen reduction reaction (ORR). Our researches are focus on the oxide-based compounds of group 4 and 5 metals. We have reported that the oxide-based compounds, in particular, partially oxidized carbonitrides of Zr1 Nb2, and Ta3 had high stability and high catalytic activity for the ORR in acidic solution. But it is hard to prepare the fine particle catalysts to improve the ORR activity by using carbonitrides compounds. So we tried to prepare the oxide-based compounds by different starting material.
Coaxial TiN-CNT Composites as Effective Low Temperature Fuel Cell Electrocatalyst Supports
Authors: Higgins Drew Christopher , Chen Zhongwei
Published: March 2013

Coaxial titanium nitride (TiN) coated carbon nanotubes (TiN-CNTs) were fabricated by a simple two-step procedure. These novel materials were utilized as Pt electrocatalyst support materials for the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR). By effectively coupling the unique physicochemical properties of TiN and CNTs, improved performance in comparison to commercial Pt/C was observed, indicative of the favourable catalyst-support interactions provided.
Nitrogen-Doped Activated Graphene Supported Platinum Electrocatalyst for Oxygen Reduction Reaction in PEM Fuel Cells
Authors: Choi Ja-Yeon , Lee Dong Un , Chen Zhongwei
Published: March 2013

Highly active and durable platinum catalyst was successfully synthesized employing nitrogen-doped activated graphene as a catalyst support material. The physical characterization using XRD and TEM indicates the presence of nitrogen-doping on graphene leads to uniform distribution of Pt nanoparticles and effective formation of active sites exposed for reaction. The electrocatalytic activity for oxygen reduction reaction of Pt/N-AG catalyst was confirmed by half-cell measurement, Accelerated durability test (ADT) was also conducted to investigate the durability of the catalyst by running the half-cell test for 1000 cycles in N2 saturated electrolyte. The catalyst demonstrates superior electrocatalyst activity and durability over Pt/XC72 catalyst for ORR under the studied conditions, rendering graphene as an ideal replacement to traditional nanostructured carbon support materials.
Catalytic Activity and Stability of Ta Compounds for Oxygen Reduction Reaction
Authors: Mitsushima Shigenori , Fujita Yoshio , Ishihara Akimitsu , Ohgi Yoshiro , Matsuzawa Koichi , Matsumoto Masashi , Arao Masazumi , Imai Hideto , Kohno Y. , Ota Ken-ichiro
Published: March 2013

Durability is essential to electrocatalyst for fuel cell application. In this study, electrochemical stability of partially oxidized tantalum carbonitride (Ta-CNO), which is one of non-precious metal electrocatalyst for oxygen reduction reaction, has been investigated. The activity was the most stable around the rest potential in oxygen atmosphere, where was ca. 1.0 V vs. RHE, in chronoamperometry. It significantly decreased in higher potential range than the rest potential, and slightly decreased in lower potential range than the rest potential. Activity decrease ratio of the Ta-CNO was almost the same to a conventional Pt/C with rectangular potential wave between 0.6 to 1.0 V vs. RHE. The activity decrease of the Ta-CNO of the mixture with carbon black was larger than that of the Ta-CNO itself for both in constant potential and potential cycling.
Evaluation of Nitrogen Species and Microstructure of Silk-Derived Activated Carbon as Non-Precious Metal Catalyst for PEFC Cathode
Authors: Fukunaga Hiroshi , Shimoyama Takuya , Takahashi Nobuhide , Takatsuka Toru , Kishimoto Hiroshi
Published: March 2013

Silk-derived activated carbon (SAC) was prepared by steam activation and milling process. SAC yield increased by using milling process instead of steam activation. However, surface area decreased. By ball milling process, nitrogen and oxygen species, which existed inside the as-prepared SAC, appeared at the surface, thus decreasing ORR activity. ORR activity recovered by sintering after milling. By ammonia treatment of SAC, atomic ratio of nitrogen (expecially pyridine-type) increased. Change in graphite-type nitrogen was small. EORR showed little change with and without ammonia treatment. Oxygen reduction current showed remarkable increase, due to increase in surface area. The results suggest that, for SAC, EORR is dominated by the degree of carbonization and current is dominated by the surface area.
Metropolis Monte Carlo Search for Non-Precious Metal Catalyst Active Site Candidates
Authors: Holby Edward Frank , Wu Gang , Zelenay Piotr , Taylor C. D.
Published: March 2013

Non-precious metal oxygen-reduction catalysts have the potential to out-perform the rare and expensive platinum group metals used for oxygen reduction reaction at the cathode of low temperature polymer electrolyte fuel cells. Understanding and optimizing non-precious metal catalyst activity is dependent upon an atomistic understanding of active site structures. Unfortunately, there exists a tremendously large configurational active site search space comprised of C, N, Fe (and/or Co), and a variety of edge termination and defect structures. We here present a stochastic search methodology that we have developed and applied to identification of candidate structure attributes using graphene as a template matrix material.
Low-Cost, High-Efficiency Non-PGM Cathode Catalysts Using MOFs as Precursors
Authors: Zhao Dan , Shui Jiang-Lan , Chen Chen , Comment Sean , Reprogle Briana , Liu Di-Jia
Published: March 2013

Oxygen reduction reaction (ORR) represents the most important electrochemical process in a proton exchange membrane fuel cell (PEMFC). An effective catalyst with improved active site design and support architecture could reduce the kinetic barrier, lower the electrochemical overpotential, and enhance the mass transfer as well as energy conversion efficiency. Conventional PEMFC cathode catalysts contain the platinum group metals (PGMs) which contributes significant fraction of the overall stack cost. We report herein our recent progress in developing low-cost, high-efficiency non-PGM catalysts for fuel cell using metal-organic framework (MOF) based compounds as the precursors. New approaches to prepare the catalysts with high surface area and active site density are demonstrated, supported by detailed characterization studies.
Alkalinity of Non-Precious Metal Catalysts for Oxygen Reduction
Authors: Leonard Nathaniel Dean , Ganesan Selvarani , Nallathambi Vijayadurga , Calabrese Barton Scott
Published: March 2013

Low-cost oxygen reduction catalysts composed of pyrolyzed metal/nitrogen/carbon (MNC) compounds involve the association of metal atoms with nitrogen species integrated into a conductive carbon support. Currently, the nature of the active site is not completely understood due to complexities introduced by pyrolysis on high surface-area supports. The present work considers the impact of surface alkalinity on the activity of MNC catalysts prepared using a high-pressure pyrolysis method. It is shown that increased Bronsted-Lowry basicity correlates to more active catalysts.
Nitrogen-doped Graphene as an Active Electrocatalyst for Oxygen Reduction Reaction
Authors: Lee Dong Un , Yu Aiping , Chen Zhongwei
Published: March 2013

Nitrogen-doped graphene (NG) sheets are synthesized by thermal reduction and ammonia treatment of graphene oxide (GO). Scanning electron microscopy has revealed a voile-like morphology of NG sheets, which highly contrasts from the stacked layers observed with GO. X-ray photoelectron spectroscopy has verified successful nitrogen-doping of NG sheets, and Raman spectroscopy has confirmed a higher degree of deformation in NG sheets due to the incorporation of heterogeneous nitrogen atoms. To evaluate NG sheets as a highly active oxygen reduction reaction (ORR) electrocatalyst, half-cell electrochemical testing has been employed using rotating disk electrode (RDE) in an alkaline aqueous electrolyte. NG sheets demonstrate a pseudo four-electron pathway O2 reduction, and a comparable ORR performance to that of a commercial carbon supported platinum (Pt/C) catalyst. This excellent ORR activity of NG sheets is most likely due to the active sites created by nitrogen-doping in the graphene sheets.
Development of Electrocatalyst for Anion-Type Polymer Electrolyte Fuel Cell Using KOH-Doped Polybenzimidazole
Authors: Fujigaya Tsuyohiko , Nakashima Naotoshi
Published: March 2013

Anion-exchange membrane fuel cells (AEMFC) are emerged as a alternative technology to overcome technical and cost issues of proton-exchange membrane fuel cells (PEMFC). In the present study, we describe a new electrocatalyst for AEMFC composed of carbon nanotubes (CNTs), KOH-doped polybenzimidazole (PBI) and platinum nanoparticles (Pt), in which CNTs are wrapped by KOH-doped PBI in nanometer thickness and Pt are efficiently loaded on the wrapping layer. In the electrocatalyst, it is revealed that CNTs and KOH-doped PBI layer functions as electron- and hydroxide-conductive path, respectively, and large exposed surface of Pt are allows an effective access of the fuel gas. Membrane electrode assembly fabricated with the electrocatalyst shows a high power density of 256 mW cm-2. To the best of our knowledge, this is the highest value in the AEMFC system measured in a similar experimental condition.
A Ternary Catalyst for Dimethyl Ether Electrooxidation
Authors: Li Qing , Wu Gang , Bi Zhenxing , Johnston Christina M. , Zelenay Piotr
Published: March 2013

While dimethyl ether (DME) has been long viewed as a promising alternative fuel for direct fuel cells, DME electrooxidation in general and at PtRu catalysts in particular has remained kinetically handicapped relative to methanol oxidation at PtRu alloys. In this work, a ternary carbon-supported PtRuPd catalyst was developed for DME electrooxidation using the polyol method. The as-synthesized PtRuPd/C catalyst shows higher activity for DME oxidation than the state-of-the-art Pt50Ru50/C catalyst (HiSPEC® 12100) in both the electrochemical cell and fuel cell testing. The effect is likely due to the activation of the C-O bond cleavage by Pd. An extensive physical characterization, including XRF, TGA, SEM, TEM and XRD, was conducted to provide insights into the composition, morphology, and structure of the PtRuPd/C catalyst.
Development of High Performance Direct Formic Acid Fuel Cell Using Hyper Branched Polymer as a Catalyst Stabilizer
Authors: Tsujiguchi Takuya , Kojima Misaki , Iwakami Takanori , Nakagawa Nobuyoshi , Kojima Keisuke
Published: March 2013

A hyperbranched polymer was used as a catalyst stabilizer for use in a direct formic acid fuel cell, DFAFC, to obtain a high performance with a low catalyst loading. The catalyst ink was prepared by the mixing of Pd nanoparticles stabilized by a hyper branched polymer (H-Pd) and carbon black, which was then calcinated at 300 oC and 500 oC in flowing nitrogen to investigate the effect of the stabilizer residual on the catalytic activity for the formic acid oxidation. It was found that the catalytic activity of the H-Pd was 6 times higher than that of Pd black with a 500 oC calcination. In this condition, a cluster of Pd nanoparticles was observed. By using this catalyst as an anode catalyst of the DFAFC, a 6 times higher power density could be obtained compared to the case using Pd black.
Carbon-TiO2 Composite Nanofibers as a Promising Support for PtRu Anode Catalyst of DMFC
Authors: Abdelkareem Mohammad Ali , Ito Yudai , Tsujiguchi Takuya , Nakagawa Nobuyoshi
Published: March 2013

Carbon-TiO2 composite nanofibers, (C-TiO2) NF, have been fabricated by electrospinning and used as a support for PtRu nanoparticles for the catalyst of methanol oxidation. The catalytic activity and durability of the prepared catalyst was compared with that supported on carbon black, Vulcan XC-72R, and TiO2 nanoparticles. The crystal structure and electrocatalytic properties of the as-obtained catalysts have been investigated by X-ray diffraction, cyclic voltammetry and chronoamperometry. The PtRu prepared on the (C-TiO2) NF support showed a significant increase in the activity and durability, where the anodic peak current density increased by three times and the anodic potential shifted around 0.15 V compared to that supported on Vulcan XC-72R. The high stability and activity of the catalyst prepared on the (C-TiO2) NF would be related to the role of the TiO2 in decreasing the CO poisoning and the role of the carbon in keeping the high conductivity of the carbon support as well as the better dispersion of the catalyst nanoparticles on the nanofiber support.
Quantitative Analysis of CO2 Generation during Ethanol Electrooxidation on Pt-Sn/C and Pt-SnO2/C
Authors: Kaneda Shotaro , Matsuzawa Koichi , Kohno Yuji , Mitsushima Shigenori
Published: March 2013

Direct ethanol fuel cells (DEFCs) attract many attentions recently, since ethanol has high energy density, and is a safety fuel. In addition, it can be easily produced from biomass. The biggest technical challenge for ethanol electrooxidation is the break of C-C bond without by-products such as acetaldehyde and acetic acid. As an ethanol electrooxidation catalyst, Pt-Sn/C has higher current density than Pt/C. However, there are few reports on the quantitative analysis of CO2 generation. In this study, we have determined electrochemical activity of various compositions of Pt-SnO2/C and Pt-Sn/C which were made by the colloidal method in order to develop a better catalyst for the complete oxidation of ethanol. The quantity of CO2 generation was determined during chronoamperometry to evaluate the rate of complete oxidation. Pt-Sn/C had higher activity for CO2 generation than Pt-SnO2/C, and the hexagonal PtSn might have an activity for C-C bond cleavage.
Investigation of Electrocatalytic Activity of the Nanostructured Au-Cu Catalyst Deposited on the Titanium Surface towards Borohydride Oxidation
Authors: Tamasauskaite-Tamasiunaite Loreta , Balčiūnaitė Aldona , Vaiciukevičienė Aušrinė , Stankevičienė Ina , Selskis Algirdas , Norkus Eugenijus
Published: March 2013

Well-adherent gold-coated copper films (Au/Cu), with particles of a few nanometers in size have been fabricated on the titanium surface by a two-step process which involves electroless copper deposition followed by spontaneous galvanic displacement of Cu by Au from its chloro-complex solution. The morphology and composition of the fabricated catalysts have been characterized using field-emission scanning electron microscopy and energy dispersive X-ray analysis. The electrocatalytic activities of the nanostructured Au(Cu) catalysts deposited on the titanium surface have been investigated towards the oxidation of BH4
- ions in an alkaline medium by cyclic voltammetry and chronoamperometry. The nanostructured Au(Cu)/Ti catalysts exhibit a significantly higher electrocatalytic activity and stability towards the electrooxidation of BH4
- ions in an alkaline medium as compared to that of bare Au or Cu/Ti.
Enhanced Electrocatalytic Performance for Methanol Oxidation via Insertion of Ruthenium Oxide Particles into Pt and Polyaniline-Poly(Acrylic Acid-co-Maleic Acid) Composite Electrode
Authors: Kuo Chung-Wen , Kuo Zheng-Yan , Wu Tzi-Yi , Chen Jing-Yuan , Li Wen-Bin
Published: March 2013

Polyaniline (PANI) is doped with poly(acrylic acid-co-maleic acid) (PAMA) containing HCl to obtain PANI-PAMA film. Platinum particles are deposited into the PANI-PAMA film via electrochemical deposition to obtain PANI-PAMA-Pt composite electrodes. Subsequently, ruthenium oxide (RuO2) particles are incorporated into the composite electrodes by cyclic voltammetry for 20 and 60 cycles to obtain PANI-PAMA-Pt-RuO220 and PANI-PAMA-Pt-RuO260 composite electrodes, respectively. X-ray diffraction analysis explains a decrease in the number of Pt crystalline facets for the incorporation of RuO2 into PANI-PAMA-Pt. Cyclic voltammetry results and chronoamperometric response measurements demonstrate that the PANI-PAMA-Pt-RuO220 electrode has the best activity and stability toward methanol oxidation among the three electrodes.
Investigations of the Anodic Oxidation of Ethanol under Forced Convection and Ambient Conditions
Authors: Meier Jan O. , Cremers Carsten , Stimming Ulrich , Tübke Jens
Published: March 2013

The electro-oxidation of ethanol was investigated in alkaline solution (0.5 M ethanol and 0.1 M NaOH) on a polycrystalline platinum electrode. The electrode was positioned in a flow channel (channel electrode) which ensures controllable and defined convection conditions in the electrode surrounding. Moreover, a flow through UV-Vis absorbance cell was used for intermediate (acetaldehyde) detection and its quantification. It was experimentally observed that the intermediate current efficiency is a function of flow rate. Furthermore, the intermediate current efficiency increases with increasing surface poisoning during ethanol oxidation. From the experimental results it can be estimated that the intrinsic current efficiency for the pathway to acetaldehyde is at least 73(3)%. Hence, the current efficiency for pathways leading directly via surface reactions to other reaction products is at most 27(3)% (both are integral values over 15 min of oxidation at 0.6 V vs. RHE).
Analysis of Mechanism of Oxygen Reduction Reaction on Non-Noble Metals in Alkaline Solution by Scanning Electrochemical Microscopy
Authors: Teranishi Rie , Higuchi Eiji , Chiku Masanobu , Inoue Hiroshi
Published: March 2013

Scanning electrochemical microscopy was applied for elucidating the mechanism of oxygen reduction reaction (ORR) at some non-noble metals such as Co and Fe in an alkaline aqueous solution. Transient oxidation current of HO2
- produced by the reduction of oxygen at each non-noble metal substrate was detected at an ultramicroelectrode as a probe which was positioned at a given distance. Theoretical transient oxidation current of HO2
- was also calculated and fitted to the experimental one to evaluate rate constants of three elementary reactions in ORR. The mechanism of ORR at each non-noble metal was discussed with the rate constants, and compared to that at the noble metals we had elucidated.
Molecular Dynamics Simulations of Hydroxide Solvation and Transport in Anionic Exchange Membranes
Authors: Lindberg Gerrick E. , Knight Chris , Felberg Lisa E. , Voth Gregory A.
Published: March 2013

In this work we present efforts to understand the properties of hydroxide in anion exchange membranes. First, we review the available reactive hydroxide molecular models and rationalize the selection of a model. Then aqueous cation systems are introduced as an analogue for anion exchange membranes. We show that hydroxide solvation structure has minimal temperature dependence, but that the concentration has a strong effect dependent on the identity of the cation. Last the electrostatic potential is calculated for four cations used in anion exchange membranes. The electrostatic field is shown to have a very different size, shape and intensity for the cations considered, which we postulate will lead to different local environments around the cations.
Fundamental Studies of Alkaline Exchange Membranes towards Optimization in a Fuel Cell Environment
Authors: Herring Andrew M. , Vandiver Melissa A. , Maes Ashley M , Sarode Himashu N , Coughlin E. Bryan , Knauss Daniel M. , Yan Yushan , Lindberg Gerrick E. , Knight Christopher , Voth Gregory A. , Herbst Daniel , Witten Thomas A. , Liberatore Matthew W.
Published: March 2013

There is increasing interest in the alkaline exchange membrane (AEM) fuel cells as this device, if realized, could allow the use of inexpensive metal catalysts and the oxidation of a variety of convenient liquid fuels. While there have been some dramatic early achievements, there is still a need for a fundamental study of anion transport, cation stability and the formation of robust thin films in this area. We have undertaken a comprehensive study of anion transport and AEMs where theory is linked to well-defined model systems, both in solution and in the solid state, which are characterized using very careful environmental control such that the models can be validated and used predictively. We are also fabricating a number of structured copolymer AEMs that can be produced readily in large quantities, allowing us to understand film formation coupled with transport and stability.
Development of Alkaline Exchange Ionomers for Use in Alkaline Polymer Electrolyte Fuel Cells
Authors: Poynton Simon D. , Zeng Rong , Kizewski Jamie , Ong Ai Lien , Varcoe John R.
Published: March 2013

Alkaline polymer electrolyte fuel cells (APEFCs) using a quaternary ammonium functionalized ethylene-co-tetrafluoroethylene radiation grafted alkaline membrane were tested under fuel cell conditions using five anion exchange ionomers. The effect of ionomer type played a significant influence over the peak power densities achieved, ranging from 41 to 311 mW cm-2.
Alkaline Durable Anion Exchange Membranes Based on Graft-Type Fluoropolymer Films for Hydrazine Hydrate Fuel Cell
Authors: Yoshimura Kimio , Koshikawa Hiroshi , Yamaki Tetsuya , Maekawa Yasunari , Yamamoto Kazuya , Shishitani Hideyuki , Asazawa Koichiro , Yamaguchi Susumu , Tanaka Hirohisa
Published: March 2013

Anion exchange membranes (AEMs) having polyvinylimidazolium grafts were synthesized by radiation-induced graft polymerization of N-vinylimidazole (NVIm) or the coplymerizaiton with styrene onto poly(ethylene-co-tetrafluoro-ethylene) (ETFE) film, followed by N-alkylation and ion exchange reactions. The alkaline durability of the membranes was evaluated in 1M KOH at 60 and 80{degree sign}C. The AEM consisting of the homopolymer and copolymer (1:1 molar ratio) grafts (AEM2 and AEM3) with the ion exchange capacity (IEC) of 0.86 and 1.18 mmol g-1 exhibited ionic conductivity of 23 and 63 mS cm-1, respectively. The homopolymer-type AEM2 showed alkaline stability at 60 {degree sign}C for 270 hours, but degraded at 80 {degree sign}C for ca. 150 hours. In contrast, the copolymer-type AEM3 kept its ion conductivity above 10 mS cm-1 in 1M KOH at 80 {degree sign}C for 250 h. The alkylimidazolium group in the copolymer grafts is a promising anion exchange group in AEMs for highly alkaline durable fuel cells.
Highly Anion-Conducting Porous Polymer Electrolyte Membrane for Alkaline Fuel Cells
Authors: Zarrin Hadis , Fowler Michael , Chen Zhongwei
Published: March 2013

A highly anion-conductive porous polymer electrolyte membrane based on polybenzimidazole (PBI) was developed for alkaline fuel cells. The pores are introduced by leaching out the pore-forming agent (dibutyl phthalate), after making the membrane, comprised of it. The porosity increase the attraction of electrolytic solutions (e.g., potassium hydroxide), which results in the enhancement of plasticized PBI's ionic conductivity. The morphology, physico-chemical properties, thermal stability, and the hydroxide conductivity of the KOH-doped porous PBI membranes were characterized, using different spectroscopic and microscopic analysis methods. It was observed that the hydroxide conductivity of 70 wt.% porous PBI was 6 times higher than that of commercial FAA anion exchange membrane. The excellent performance of KOH-doped PBI makes it a promising membrane material for alkaline fuel cells.
Membrane Electrode Assemblies Based on Hydrocarbon Electrolytes with Nitrile Groups for Direct Methanol Fuel Cells
Authors: Hürter Stefan , Müller Martin , Wippermann Klaus , Guiver Michael D. , Scoles Ludmila , Stolten Detlef
Published: March 2013

Sulfonated poly(aryl ether ether nitrile)s - sPAEEN are promising materials for reducing the methanol permeation from anode to cathode due to the strong polar interchain interactions caused by the nitrile functional groups. This feature allows the preparation of membranes with high proton conductivities and low crossover of methanol and water. Despite similar specific conductivities and lower thickness of the hydrocarbon membranes compared to Nafion 115, HC-MEAs prepared by a classic hot-pressing step show 40-70 % higher values for the cell resistances compared to Nafion 115 based MEAs. Therefore the MEA preparation procedure was changed to reduce losses due to poor lamination between the Nafion-based GDE and the hydrocarbon membrane. The impact of the type of sPAEEN membrane and the MEA preparation together with the cell performance data will be compared with state-of-the art Nafion-based cells and discussed in terms of consequences for the operating conditions for a DMFC system.
Predicting Carbonate and Bicarbonate Ion Transport in Alkaline Anion Exchange Membranes
Authors: Kiss Andrew Michael , Myles Timothy D , Grew Kyle N , Peracchio Aldo A , Nelson George J , Chiu Wilson K.S.
Published: March 2013

Carbon dioxide present in the oxidant stream of alkaline anion exchange membrane (AEM) fuel cells has introduced complications with the conversion of the AEM from a hydroxide ion form to one with carbonate and bicarbonate species present. This conversion reduces the ionic conductivity of the membrane which can decrease the performance of the fuel cell. By studying transport in a SnowPure Excellion I-200 AEM, the effective diffusion coefficients of the membrane can be predicted using relationships based on kinetic gas theory. The numerical predictions can be validated using a model to compare ionic conductivity results with experimental results.