bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of the Electrochemical Performance of Ptni/MWCNT in Alkaline Media
Authors: Valenzuela-Muñiz Ana Maria , Alonso-Lemus Ivonne , Escobar Beatriz , Verde Gomez Ysmael
Published: February 2020

It is well known that the outstanding properties and characteristics of multi-walled carbon nanotubes (MWCNT) make them attractive materials for diverse applications. For electrocatalytic systems, MWCNT are being exhaustively studied all over the world, and it is been corroborated that this type of materials are appropriate to be used as support of metallic nanoparticles, having a synergistic effect in the electroactivity. However, it has been found also that the MWCNT characteristics as quality (graphitization grade) and purity (amount of amorphous carbon) have a direct influence on the metal anchorage, the electrocatalytic activity as well as the stability. On the other hand, Pt-Ni system is attracting the attention in recent years for its application as PEM fuel cell electrode. The addition of a non-noble metal (Ni in this case) could decrease the cost of the electrocatalyst as well as improve the performance. The research group involved in the present work has been working during years in the design and synthesis of PtNi/MWCNT electrocatalysts using homemade MWCNT of high quality and purity, and analyzing their performance in acidic media for the application in PEM fuel cells. The obtained results are interesting and promising, high activities have been achieved as well as good stability. Nevertheless, in order to diversify the applications, as well as have a complete understanding of the PtNi/MWCNT systems, studies in alkaline media are necessary. Hence, the aim of this paper was to study the electrochemical performance in alkaline media of PtNi/MWCNT homemade electrocatalysts towards the PEM fuel cell reactions. In order to achieve this goal, the studies were performed in a conventional three electrodes cell, using a glassy carbon rod as working electrode, a Pt wire as counter electrode, a Ag/AgCl (KCl Sat) electrode as reference, and 1M NaOH solution as electrolyte. The interesting results obtained as well as the discussion will be presented at the conference.

Acknowledgments: Authors recognize the support to FOMIX-QRoo under grant no. QR00-2011-001-174895
Glycerol Electrooxidation on Well-Shaped Pd Nanoparticles Modified By Bi-Adatoms
Authors: Coutanceau Christophe , Zalineeva Anna , Baranton Stève
Published: February 2020

The electrochemical conversion of glycerol gains more and more attention because glycerol is a by-product of biofuel industries, and for its potency for electric energy or hydrogen and added-value-chemical cogeneration [1]. Due to complex oxidation pathways a large number of useful chemicals may be produced [2]. The control of activity and selectivity can be provided by the electrode potential and the formulation of electrocatalysts. In alkaline medium, palladium is a catalytic metal active for the electrooxidation of small organic molecules [3–5]. Many electrocatalytic reactions on Pd surface are known to be structure sensitive [6,7]. The activity and selectivity of Pd catalysts can also be tuned by modification with p-group atoms, such as Bi [8,9]. Moreover, it has been proposed that the structure of the electrodes (unsupported, self-supported or carbon supported Pd-Bi catalysts) has an important effect on the electrocatalytic behavior, influencing the activity as well as the selectivity of the reaction.

Here, the synthesis of preferentially-shaped Pd nanoparticles, their physico-chemical characterization and their surface modification by spontaneous bismuth adsorption are described, as well as their activity towards glycerol electro-oxidation.

In order to better, understand the role of palladium surface and bismuth modification on polyol oxidation, electrochemical measurements have been carried out on palladium nanocubes and nanooctahedrons with high amount of {100} and {111} surface nanodomains, respectively, and nanospheres without preferential surface orientation. Glycerol electrooxidation has been studied and compared on both nanoparticles, before and after modification by Bi adatoms; in situ infrared spectroscopy measurements of glycerol electrooxidation on Bi-modified Pd surfaces were also performed to determine adsorbed intermediates and reaction products versus Bi surface coverage.

1- M. Simoes, S. Baranton, C. Coutanceau, ChemSusChem 5 (2012) 2106.

2- A. Behr, J. Eilting, K. Irawadi, J. Leschinski, F. Lindner, Green Chemistry 10 (2008) 13.

3- C. Bianchini, P.K. Shen, Chemical Reviews 109 (2009) 4183.

4- E. Antolini, Energy & Environmental Science 2 (2009) 915.

5- M. Simoes, S. Baranton, C. Coutanceau, Applied Catalysis B: Environmental 93 (2010) 354.

6- F.J. Vidal-Iglesias, R.M. Aran-Ais, J. Solla-Gullon, E. Garnier, E. Herrero, A. Aldaz, J.M.

Feliu, Physical Chemistry Chemical Physics 14 (2012) 10258.

7- M. Shao, J. Odell,M.Humbert, T. Yu, Y. Xia, Journal of Physical Chemistry C 117 (2013) 4172.

8- M. Simoes, S. Baranton, C. Coutanceau, Applied Catalysis B: Environmental 110 (2011) 40.

9- A. Zalineeva, S. Baranton, C. Coutanceau, Electrochem. Comm. 34 (2013) 335.
Pd-Based Bimetallic and Trimetallic Catalyst for Direct Formic Acid Fuel Cells
Authors: Hu Shuozhen , Noborikawa Jennifer , Haan John , Scudiero Louis , Ha Su
Published: February 2020

Direct formic acid fuel cell (DFAFC) has generated great attraction in the field of energy systems, especially when it combines with carbon dioxide (CO2) electrochemical reduction unit. This whole system is referred as regenerative direct formic acid fuel cell. In regenerative DFAFCs, formic acid is oxidized at the anode of fuel cell to produce electricity along with CO2 and water (H2O). These CO2 and H2O then can be reduced to formic acid through an electrochemical reduction process using renewable energy sources, such as solar energy or wind energy. Therefore, the CO2-derived fuels hold interesting prospects for future energy systems based on non-fossil energy sources. In the regenerative DFAFC system, formic acid is used as the energy carrier and it is important to efficiently oxidize formic acid at the fuel cell’s anode to achieve a high system performance. Among the anode catalysts, Pd-based bimetallic or trimetallic catalysts have attracted a lot attention due to their better activity and stability than pure Pd toward formic acid oxidation [1-3]. In addition, the lower cost due to the use of less expensive transition metals makes these Pd-based bimetallic catalysts promising material for developing cheaper DFAFC.

In this study, we synthesize PdCu/C and PdNi/C alloys via metal salt reduction method. The nominal atomic ratio of Pd:Cu and Pd:Ni is 3:1. TEM images shows the particle sizes are about 5 nm, 7 nm, and 6 nm for Pd/C, PdCu/C and PdNi/C, respectively. Then, PdCu/C and PdNi/C are physically mixed by weight ratio of 1:1 and annealed at 400 °C in Ar. To make comparison, PdCu/C and PdNi/C are also annealed at the same condition separately. Cyclic voltammetry results indicate that, before annealing, PdCu/C shows the best activity toward formic acid oxidation (See Figure 1 (a)). When the samples are annealed at 400 °C, both the PdCu/C and physical mixture samples show the activity enhancements, while the activity of PdNi/C sample is not affected by the annealing process, as shown in Figure 1 (b). Based on the CV data, it is clear that the physical mixture sample is most affected by the annealing process as it shows the most activity enhancement. Consequently, after the annealing process, the physical mixture sample shows the best activity. For an example, at 0.1V (vs. Ag/AgCl), the annealed physical mixture sample shows the current density of 2.71 mA/cm2, which is a factor of 1.5 higher than that of annealed PdCu/C sample. To investigate the effect of the annealing process to different samples and their electrochemical activity toward the formic acid oxidation, TEM and X-ray photoelectron spectroscopy are used.

References

1. Suo, Y. G., Hsing, I. M., Electrochimica Acta, 2011, 56 (5): p. 2174-2183.

2. Dai, L., Zou, S. Z., Journal of Power Sources, 2011, 196 (22): p. 9369-9372.

3. Du, C. Y., Chen, M., Wang, W. G., Yin, G. P., Acs Applied Materials & Interfaces, 2011, 3 (2): p. 105-109.
A Carbon-Based Non-Precious Metal Catalyst Mnhmta/C for Oxygen Reduction Reaction
Authors: Si Yujun , Xiong Zhongping , Li Minjiao
Published: February 2020

A non-precious metal catalyst for oxygen reduction reaction was prepared by heat-treating a precursor from the mechanical mixture of acetylene black, hexamethylenetetramine and MnCl2.4H2O. The precursor contains 1.0g of acetylene black, 1.0g of hexamethylenetetramine and 0.50g of MnCl2.4H2O. The precursor was heat-treated at 700℃ for 2 hours. In the heat-treating, a nitrogen gas was used as protective gas to get an inertia atmosphere. And the protective gas was controlled as following two modes: one is that the protective gas was shut after 30 minutes and before heat-treating, the other is that the protective gas was not shut in the thorough heat-treating process. The resulted products were labelled as MnHMTA/C(A) and MnHMTA/C(B), respectively. Figure 1 shows the catalytic activity towards oxygen reduction reaction of the two catalysts. It can be seen that the MnHMTA/C catalyst exhibits good activity to oxygen reduction reaction with an onset reduction potential of 0.55V (vs. SCE). In addition, the activity of MnHMTA/C(B) is better than MnHMTA/C(A). The reason is that the decomposed product of hexamethylenetetramine will exhaust with nitrogen gas in the preparation of MnHMTA/C(A), which affects the formation of active sites and worsens the catalytic activity of the MnHMTA/C(A) catalyst.

Acknowledgments

This work was supported by the Specialized Research Fund for the Doctoral Program of Sichuan University of Science and Engineering (No. 2012RC16) and the Opening Project of Key Laboratory of Green Catalysis of Sichuan Institutes of High Education (No. LYJ1206, LYJ1401).

Figure 1 Linear sweep voltammograms of (a) acetylene black, (c) MnHMTA/C(A) and (d) MnHMTA/C(B) catalysts in 0.5M H2SO4 solution saturated by O2, and (b) MnHMTA/C(A) catalyst in 0.5M H2SO4 solution saturated by N2
。
Degradation of Polymer Electrolyte Membrane Fuel Cell Under Pressure Cycle
Authors: Jung Ju Hae , Yoo Sung Jong , Kim Hyoung-Juhn , Jang Jong Hyun , Nam Suk Woo , Cho Eun Ae
Published: February 2020

Polymer electrolyte membrane fuel cell (PEMFC) is known as environmentally friendly energy sources for portable, backup power, and transportation applications. The performance and durability of PEMFC are affected by operating conditions such as the temperature, pressure, and humidification. Many studies have investigated of operating back pressure. An increase of back pressure can significant improved thermodynamics, kinetics and mass transfer in PEMFC. Wang et al. [1] studied the effect of different fuel cell operating temperatures, cathode and anode humidification temperatures, pressures and various combinations of these parameters experimentally. They found that cell performance is increased under high pressure operation due to the increase of reactant partial pressure and the exchange current density. Zhang et al. [2] carried out experiments on PEMFC at pressures of 1–3 atm. They confirmed that a low gas flow rate and a high back pressure improved the PEMFC performance using the Nafion 112 membrane at 0% RH. However, membrane electrode assemblies (MEAs) are degraded by operation of high back pressure in PEMFC. Because of the polymer chains of membrane breaks by radical attack as chemical degradation due to gas permeability. Also, mechanical degradation on MEAs occurs in many forms including cracks, pinhole and blisters by the operation of high back pressure.[3]

In this study, we examined effects of pressure cycle operation during the constant current (CC) mode on degradation of PEMFC. After pressure cycle, open circuit voltage (OCV) and current density at 0.6V were seriously decreased with increases in resistance and decreases in electrochemical active surface area (ECSA). In addition, we confirmed the pinhole in membrane, decrease in the catalyst layer thickness and interfacial separation in gas diffusion layer (GDL). Therefore, the pressure cycle generated the severe degradation in MEAs and they can the cause of early life failures.

References

[1] Wang L, Husar A, Zhou T, Liu H., Int J Hydrogen Energy, 28 1263, (2003).

[2] Zhang J, Tang Y, Song C, Cheng X, Zhang J, Wang H., Electrochim Acta
52, 5295 (2007).

[3] S. Vengatesan, M.W. Fowler, X.-Z. Yuan, H. Wang, J. Power Sources
196, 5045 (2011).
Electrochemical Performance of MEAs with Pt/SnO2 Mixed with Conductive Fillers
Authors: Nagamatsu Yohei , Kanda Kohei , Noda Zhiyun , Hayashi Akari , Sasaki Kazunari
Published: February 2020

1.
Introduction

　Polymer electrolyte fuel cells (PEFCs) have been attracted for both automobile and residential use. However, PEFCs still have some problems to be solved, such as durability. In particular, during the actual operating condition of fuel cell vehicles (FCVs), carbon supports, which have advantages of high conductivity, high specific surface area, and high porosity, are easily degraded through oxidation at the cathode side. Therefore, in our laboratory, SnO2 supports were rather focused on as popular alternative oxide-based support materials because of their thermodynamic stability. Durability as electrocatalysts has been confirmed in the half-cell [1, 2]. Nevertheless, the agglomeration of SnO2 particles leads to low performance when MEAs are made with SnO2 based electrocatalysts. Thus, the objective of this research is to develop MEAs with high performance and durability using SnO2supports.

2. Experimental

　Nb-doped SnO2 was prepared to increase the electric conductivity in this study. Sn0.98Nb0.02O2 was synthesized via an ammonia co-precipitation method, using SnCl2・2H2O and NbCl5. Pt nanoparticles were decorated on such a metal oxide support utilizing a platinum acetylacetonate complex. I-V characteristics of MEAs were evaluated as well as their ohmic resistance measured by an impedance method. Further, based on the protocol recommended by the Fuel Cell Commercialization Conference of Japan (FCCJ) [3], Durability of MEAs was investigated at the potential cycle of 1.0 ~ 1.5V, and also their microstructures were evaluated by a field emission scanning electron microscope (FESEM).

3. Results and Discussion

　By comparing the durability of MEAs made with three different cathode electrocatalysts, such as Pt/Carbon, Pt/Sn0.98Nb0.02O2, and Pt/Sn0.98Nb0.02O2+5wt.%VGCF-H (a conductive filler), MEA made with Pt/ Sn0.98Nb0.02O2+5wt.%VGCF-H showed the highest performance and durability [4]. Furthermore, optimization of the ratio of Nafion and VGCF-H was performed. As shown in Fig. 1, MEA with Pt/ Sn0.98Nb0.02O2+25wt.%VGCF-H+13wt.%Nafion showed highest I-V performance in this study. The microstructure with good distribution of conductive fillers is also shown in Fig. 2. This suggests that it is possible to reduce the ratio of Nafion and further optimize the amount of VGCF-H. Durability and microstructures of MEAs will be discussed in detail.

References

1) F. Takasaki, S. Matsuie, Y. Takabatake, Z. Noda, A. Hayashi, Y. Shiratori, K. Ito, and K. Sasaki, J. Electrochem. Soc., 158(10) B1270-B1275 (2011).

2) A. Masao, S. Noda, F. Takasaki, K. Ito, and K. Sasaki, Electrochem. Solid-State Lett., 12(9), B119 (2009).

3) A. Ohma et al., ECS Trans, 41755 (2011).

4) K. Kanda, Z. Noda, Y. Nagamatsu, T. Higashi, S. Taniguchi, S.M. Lyth, A. Hayashi, and K.Sasaki, ECS Electrochem. Lett., 3(4) F15-F18 (2014).
Inverse Opal Structure Platinum Electrode for Improving a Membrane-Electrode Assembly Performance of Polymer Electrolyte Membrane Fuel Cell
Authors: Cho Yong-Hun , Kim Ok-Hee , Sung Yung-Eun , Choe Heeman
Published: February 2020

The ordered macroporous inverse opal structures electrode would be attractive structure for various applications in electrochemical device. The inverse opal structured platinum electrode was directly fabricated for application of membrane-electrode assemblies (MEA) in polymer electrolyte membrane fuel cells (PEMFC). The electrode was prepared by pulse electro–deposition following polystyrene colloidal crystal template on gas diffusion layers, without any additional transfer process at the electrodes. The performance of the inverse opal electrode-based MEA in the PEMFC was higher than that of a traditional MEA with Pt/C catalyst because of the morphological advantages of inverse opal structure.
Optimization of Operation Conditions for Alkaline Membrane Fuel Cells
Authors: Watanabe Shin , Isomura Takenori , Yamaguchi Masao , Negishi Takayuki , Sadasue Kazuyuki , Hironaka Yoshimi , Oda Kengo , Matsumura Yasunori , Kikkawa Yuki , Okamura Takaaki , Furuya Hirotoshi , Yanagi Hiroyuki
Published: February 2020

We have been developing materials for Alkaline membrane fuel cells(AMFCs) for about 10 years. Alkaline membrane fuel cell (AMFC) is one of the polymer electrolyte fuel cells (PEFCs) which uses anion exchange membrane and anion conductive ionomer as polymer electrolyte materials. AMFCs have some advantages over proton-exchange membrane fuel cells(PEMFC) 1-2).

(1) The high pH environment of AMFCs allows the use of non platinum catalysts.

(2) The kinetics of the ORR reaction is more facile in alkaline environment than in acid environment.

AMFCs have 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 AMFCs, namely CO2 self-purging phenomena3), which could be a solution against serious CO2
problem in AMFCs4-6), and the effective water transport from anode to cathode side, which prevent the lack of water needed for cathode reaction7).

In this presentation, we are going to show some new aspects for AMFC operation conditions such as temperature, water management and choice of materials.

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).
Microwave-Assisted Synthesis of Graphene Supported Silver and Platinum-Silver Nanoparticles for Application in Fuel Cells
Authors: Jagminiene Aldona , Matuseviciute Agne , Balciunaite Aldona , Vaiciuniene Jurate , Kondrotas Rokas , Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus
Published: February 2020

This work is focused on the preparation of the graphene supported silver and platinum-silver catalysts (denoted as Ag/GR and PtAg/GR) as electrocatalysts for the oxidation of borohydride, hydrazine and formaldehyde in an alkaline medium. The Ag/GR and PtAg/GR catalysts were prepared via rapid microwave heating method.

Transmission Electron Microscopy and Inductively Coupled Plasma Optical Emission Spectroscopy were employed to characterize the morphology, structure and composition of the synthesized catalysts. The kinetics of borohydride, hydrazine and formaldehyde oxidations was investigated on the the graphene supported silver and platinum-silver catalysts by a variety of electrochemical techniques (cyclic voltammetry, chronoamperometry and chronopotentiometry).

The data of electrochemical oxidation of borohydride, hydrazine and formaldehyde on the graphene supported silver and platinum-silver catalysts synthesized by means of microwave heating irradiation under various conditions are presented.

Acknowledgement

This research was funded by a Grant (No. ATE-08/2012) from the Research Council of Lithuania.
Investigation of Passive DEFC Mini-Stacks at Ambient Temperature
Authors: Vélez-Denhez Alejandra , Córdoba-Moreno Marlina Olyissa , Lizcano-Valbuena William H.
Published: February 2020

In this work we show the results of ministacks of direct ethanol fuel cells (DEFC) at 25 oC. Result obtained with a passive DEFC using 2 mgPtRu/C in anodes and 3 mg of Pt in cathodes, when the alcohol concentration was 1 M, showed a power density equal to 0.875 mWcm-2 for electrodes with area equal to 25 mm2 . Results related with Nafion content in the catalytic layers are discussed. Stacks using three similar cells showed 2.4 mWcm-2 indicating the good performance of the system.

The performance of mini stacks operated with electrodes of 5 mm2 showed the dependence of the mass transport of ethanol and of the configuration of the stacks (zig zag and flip flop). The better results were obtained with a zig zag interconexion.

A comparison from fuel cell performance was done using ethanol and methanol. The best result of the stack using methanol (5M) was 60% higher than when ethanol (2M) was used.
Hydrogen Production on an Ethanol Dehydrogenation Reactor Coupled to a Conventional PEMFC
Authors: Sato André Gustavo , Silva Gabriel Cristiano da , Paganin Valdecir Antonio , Ticianelli Edson A.
Published: February 2020

On board hydrogen storage has become a key factor for the technical viability of fuel cell driven electric vehicles. As the volumetric energy density of hydrogen is very low, on board storage of hydrogen remains a challenge in terms of weight, volume, kinetics, safety, and cost. Hydrogen can be produced from the steam reforming of ethanol (SRE) in a single-reactor usually operated in the temperature range of 823–1073 K so to avoid coke formation and to obtain high hydrogen yield. However, above 823 K the reverse water-gas shift reaction becomes thermodynamically favored to form carbon monoxide due to the high selectivity for the formation of C–C bond cleavage products (methane and CO), against the steps of C–O bond cleavage product (ethylene). Such formation of CO should be avoided because the PEMFC (proton exchange membrane fuel cell) conventional anode can only tolerate less than 10 ppm of CO, when operating in a low-temperature range (353–393 K). On the other hand, copper-based catalysts have been successfully employed for the selective conversion of ethanol to ethyl acetate or acetaldehyde.The best results for selective conversion to ethyl acetate has been achieved with ZrO2-supported copper catalysts, even though it provides 2 electrons/ethanol molecule against 12 electrons from ethanol dehydrogenation. However CO-free hydrogen gas phase and liquid fine chemicals can be produced at temperatures as low as 523 K. In this work we present results of a system which comprises an ethanol dehydrogenation catalytic unit coupled to a conventional PEMFC. Ethanol is first dehydrogenated over a Cu/ZrO2 catalyst bed, and then the gas effluent is trapped in a simple cold condenser enabling a gas current rich in H2 to feed a PEMFC with Pt/C electrodes. Chromatography showed that the liquid effluent is formed essentially by ethyl acetate which has heat of combustion between ethanol and gasoline. Thus, in a hybrid propulsion system for vehicles, the electricity generated by the fuel cell may feed an electric motor, while ethyl acetate may be used as fuel of an internal combustion engine. Chronoamperometry (at a cell potential of 0.7 V) showed apparent stability of the cell performance at about 300 mA cm-2 (with H2 produced from ethanol dehydrogenation) whilst at 550 mA cm-2 with pure H2 (from a cylinder). Cyclic voltammetry of the anode and cathode after four hours of reaction showed ease recovery to the fuel cell start conditions. The unprecedented and challenging development combines on line hydrogen production with a liquid renewable feedstock (ethanol) which employs low cost copper-based catalyst. Based on electrochemical experiments, the integrated system proved to be feasible, and so may play an important role to the progress of hybrid ethanol-hydrogen fuel cell vehicles.
Evaluation of Durability with MEAs Made by Graphitized Carbon Supports
Authors: Hayashi Akari , Zhao Xiaojing , Minamida Yasuto , Kitamura Masahiko , Noda Zhiyun , Sasaki Kazunari
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are attractive energy device for our future society. Even so, improvement of durability is still desired. Especially for fuel cell vehicles (FCVs), carbon oxidation derived by the start/stop cycle becomes a problem. We have been working on surface graphitized carbon supports to increase the durability toward carbon oxidation. Up to date, durability of electrocatalyts has been improved as much as twice in the half-cell reaction just through the heat treatment of carbon supports [1]. In this study, MEAs are prepared with such electrocatalysts. Their initial performance and durability was evaluated in detail by both electrochemical and electron microscopic methods.

In this study, MEAs, whose diameter was about 8 mm, were used. For the anode, commercially available Pt/Ketjen black (TEC10E50E, TKK corp.) was in use. For the cathode, Pt deposited on Vulcan carbon or on graphitized Vulcan carbon materials, named as Pt/VC or Pt/GVC, were prepared in our lab. Here, Pt/GVC was made through the heat treatment at 1600 oC. For the electrochemical analyses, I-V characteristics were evaluated. Regarding to durability, the potential cycle tests assuming the start/stop cycle of FCVs, which suggested by Fuel Cell Commercialization of Japan (FCCJ) [2], were used. Furthermore, nanostructures of cathode layers were observed using Hitachi HF-3300.

Initial IV characteristics of MEAs with Pt/VC and Pt/GVC were almost the same. However, their durability resulted in different. MEA with Pt/GVC showed much improved durability. To understand the change in microstructures of the cathode layer, a part of cathode layer was picked up by a FIB microprobe, placed on the microgrid, and observed by SEM/STEM at the same time. As shown in Fig. 1, in case of Pt/VC cathode layer, more Pt particles were observed after the 5000 potential cycle test. Surprisingly, a lot of Pt particles existed inside carbon supports, which was clearly understood form the amount of Pt on carbon surface in the SEM image. Such embedded Pt particles were much suppressed in case of Pt/GVC cathode layer. Our new methods to study degradation process using in-situ SEM/STEM observation will be also discussed.

Reference

[1] Z. Zhao et al., Electrochim. Acta, 97, (2013) 33.

[2] A. Ohma et al., ECS Trans, 41 (2011) 755.
Effect of through-Plane Polytetrafluoroethylene Distribution in a Gas Diffusion Layer
Authors: Ito Hiroshi , Nakano Akihiro , Iwamura Takuya , Someya Satoshi , Munakata Tetsuo
Published: February 2020

During operation of a proton exchange membrane fuel cell (PEMFC), the oxygen reduction reaction rate at the cathode is the limiting kinetic step and determines the maximum operating current density. This rate strongly depends on the transport rate of oxygen from the flow channel to the catalyst sites. Although the electrolyte membrane needs liquid water to retain proton conductivity, the oxygen gas transport can be greatly hindered when liquid water accumulates either in the catalyst layer (CL) or the gas diffusion layer (GDL) of the cathode. Consequently, for optimal water management and performance in PEMFCs, water retention/expulsion properties must be carefully balanced.

We previously investigated the relationship between the treatment process of polytetrafluoroethylene (PTFE) and the resulting PTFE distribution in through-plane direction of carbon papers [1]. The dependence of PTFE distribution on the PTFE drying conditions was examined using SEM-EDS analysis. The EDS image maps revealed that the PTFE distribution strongly depended on the drying condition; PTFE-drying under atmospheric pressure created highly heterogeneous PTFE distributions in the through-plane direction, with high concentrations near both the upper and lower surfaces, whereas PTFE-drying under vacuum pressure created a relatively uniform PTFE distribution.

In this study, in order to investigate the effect of PTFE though-plane distribution on the water discharge characteristic, limiting current measurements were performed under various humidity conditions using a small-scale PEMFC, which has the electrode area of 1 cm2. Based on the limiting current measurement, we could evaluate the gas transport resistance through the carbon paper GDL [2,3]. Because the small-scale cell was applied, we could minimize the effect of the distribution of current density and humidification, that is, the effect of local flooding across the flow channel depending on the change of humidification.

References

H. Ito et al., J. Power Sources , 248, 822 (2014).

D. R. Baker et al., J. Electrochem. Soc., 156, B991 (2009).

N. Nonoyama et al., J. Electrochem. Soc., 158, B416 (2011).
Niobium Carbide Based Catalyst Supports for PEMFC Cathodes
Authors: Nabil-Moreau Yannick , Cavaliere Sara , Jones Deborah , Roziere Jacques , Hards Graham , Sharman Jonathan , Harkness Ian
Published: February 2020

Recent research has shown that alternative compositions such as metal carbides and nitrides can potentially present the required properties of conductivity and (electro)chemical stability to replace the carbon blacks conventionally used as electrocatalyst supports in Proton Exchange Membrane Fuel Cells (PEMFC). We are currently investigating a range of synthesis routes leading to electronically conductive and chemically stable support materials based on NbC with controlled morphologies and porosity. For instance, a template-assisted method associated with specific thermal treatments1 has led to a nanostructured carbide with a high specific surface area (70 m2
g-1) and an electronic conductivity comparable to that of carbon (103 S.m-1), while a synthesis route involving electrospinning and reduction in methane provides niobium carbide nanofibres. Furthermore, hollow structures with controlled porosity can be obtained by varying the synthesis parameters. These various supports have been catalysed by deposition of platinum nanoparticles, synthesised by a microwave assisted polyol method. This contribution will describe the chemical and electrochemical characterisation of Pt on NbC-based supports, and compare the properties to those of other candidate support materials such as titania and tin oxide.

1. J. Bernard D'Arbigny, G. Taillades, M. Marrony, D. J. Jones, J. Roziere, Chemical Communications, 47, 7950-7952 (2011).
Enzyme Engineering via Rationally Designed Intermolecular Interactions: Applications towards Bioelectrocatalysis
Authors: Gao Yingning , Zhu Jie , Lin Jyun-Liang , Wheeldon Ian
Published: February 2020

In nature we find many examples of enzymes and multienzyme stuctures where catalysis is enhanced by well-designed molecular interactions between the enzymes and their substrates. Two compelling examples are the enzyme superoxide dismutase (SOD) and the bifunctional enzyme thymidylate synthase-dihydrofolate reductase (TS-DHFR). SOD, one of the fastest known enzymes (kcat » 1.5 ´ 109 M-1s-1), uses charge complementarity to produce substrate-enzyme interactions that enhance enzyme kinetics by directing the substrate to the enzyme’s active site. A positively charge patch on the surface TS-DHFR restricts diffusion of a negatively charged reaction intermediate to a pre-defined channel between two active sites, sequestering the intermediate along the enzyme’s surface and preventing diffusion to the bulk. This bounded diffusion promotes substrate channeling, enhancing pathway catalysis by protecting the intermediate from undesired side reactions. These examples are informative: They suggest that rational design of substrate-enzyme interactions can be used to enhance enzyme catalysis. In this work we engineer new enzyme structures with quantifiable binding interactions between the enzyme and its substrate. We hypothesize that the engineered molecular interactions will lead to increases in local substrate concentrations thereby enhancing enzyme catalysis. We confirm this hypothesis by demonstrating control over the apparent Michaelis constant (KM) of horseradish peroxidase (HRP) modified with a double stranded DNA structure that exhibits sequence dependent binding of phenolic HRP substrates. We extend this work to a second experimental system and demonstrate enhanced catalysis with an alcohol dehydrogenase (AdhD) through rationally designed molecular interactions between the NAD+ co-factor mimic nicotinamide mononucleotide (NMN+) and a double stranded DNA structure conjugated near the enzyme’s active site. Demonstration of rationally designed kinetic enhancements with enzyme co-factors such as NMN+ is an important demonstration with respect to bioelectrocatalysis as many such systems rely on this type of co-factor. We aim to extend this work towards other co-factor and substrates relevant to electrochemical biosensor and enzymatic biofuel cells.
Microstructure at the Ionic Liquid/Electrode Interface
Authors: Haverhals Luke M. , Zibart Christina , Egan Bryce , Parr Daniel
Published: February 2020

In the past decade, ionic liquids (ILs) have been investigated as electrolytes for energy conversion applications such as capacitors
[i]

,[ii]
, batteries
[iii]

,[iv]
, fuel cells
[v]

,[vi]
, and solar cells.
[vii]

,[viii]
While significant progress has been made towards utilizing these remarkably adaptable materials for specific applications, much work remains to generate technologically and economically relevant devices and processes. Fundamental characterizations of IL-based electrolyte/electrode systems are crucial to continued development for these enterprises.
[ix]
In specific, detailed descriptions and understanding of electrolyte/electrode interfaces are prerequisites to engineered progress because adsorbed species and their associated interfacial dynamics play critical roles in determining device efficiencies.
[x]

,[xi]
Our initial studies focus on spectroscopic techniques such as surface enhanced infrared absorption (SEIRA) spectroscopy to characterize interfacial structure and dynamics between ionic liquid media and electrode surfaces during electrochemical perturbation. More specifically, we will discuss characterizations of ILs composed of imidazolium-based cations with alkylsulfate, tetrafluoroborate, thiocyanate, dicyanamide, and bis(trifluoromethylsulfonyl)imide anions at noble metal electrodes (i.e, Au).

[i]. T. Sato, G. Masuda, K. Takagi, Electrochim. Acta, 2004, 49, 3603-3611.

[ii]. A. Orita, K. Kamijima, M. Yoshida, J. Power Sources, 2010, 195, 7471-7479.

[iii]. A. S. Best, A. I. Bhatt, A. F. Hollenkamp, J. Electrochem. Soc., 2010, 157, A903-A911.

[iv]. J.-K. Kima, A. Matica, J.-H. Ahnb, P. Jacobsson, J. Power Sources, 2010, 195, 7639-7643.

[v]. S.-Y. Lee, A. Ogawa, M. Kanno, H. Nakamoto, T. Yasuda, M. Watanabe, J. Am. Chem. Soc., 2010, 132, 9764-9773.

[vi]. M. Guo, J. Fang, H. Xu, W. Li, X. Lu, C. Lan, K. Li, J. Membr. Sci., 2010, 362, 97-104.

[vii]. P. K. Singh, N. A. Jadhav, S. K. Mishra, U. P. Singh, B. Bhattacharya, Ionics, 2010, 16, 645-648.

[viii]. C.-P. Lee, P.-Y. Chen, R. Vittal, K.-C. Ho, J. Mater. Chem., 2010, 20, 2356-2361.

[ix]. C. Aliaga, C. S. Santos, S. Baldelli, Phys. Chem. Chem. Phys., 2007, 9, 3683-3700.

[x]. A. J. Bard, L. R. Faulkner, Electrochemical Methods: Fundamentals and Applications, 2nd ed., 2002, John Wiley & Sons, Inc., New York, NY.

[xi]. M. Yoshida, A. Yamakata, K. Takanabe, J. Kubota, M. Osawa, K. Domen, J. Am. Chem. Soc., 2009, 131, 13218-13219.
Nitrogen-Containing Carbon Nanostructures (CNx) Iron-Nitrogen-Carbon (Fe-N-C) as Non-Noble Metal Catalysts for Oxygen Reduction Reaction (ORR) in Acidic Media
Authors: Ozkan Umit S. , Mamtani Kuldeep , Singh Deepika , Tian Juan , Miller Jeffrey T
Published: February 2020

Large scale commercialization of Proton Exchange Membrane Fuel Cells (PEMFCs) for power generation is hindered by their high cost, most of which is attributed to noble metal based cathode catalysts (platinum). Considerable research has been carried out to develop non-noble metal cathode catalysts for catalyzing the Oxygen Reduction Reaction (ORR). Despite significant work on developing these transition metal containing carbon materials as ORR catalysts, much is still unknown with regards to their active site. We have previously reported on the role of the transition metal and nitrogen in two classes of carbon-based materials, i.e., nitrogen-containing carbon nanostructures (CNx) and iron-nitrogen-carbon (Fe-N-C) catalysts. Our current research focuses on gaining further insights into these catalysts and establishing differences in their ORR activity and stability. Detailed characterization of these materials has also been performed using techniques such X-ray photoelectron spectroscopy (XPS), Temperature Programmed Oxidation (TPO), X-ray Absorption Near Edge Spectroscopy (XANES), Extended-X-ray Absorption Spectroscopy (EXAFS), Superconducting Quantum Interference Device (SQUID) magnetometry, Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES) and Mössbauer Spectroscopy.
Electrochemical Dissolution in the Presence of Time Delayed Feedback
Authors: Organ Levent
Published: February 2020

It is well known that time-delayed systems can exhibit rich dynamical behavior ranging from simple oscillations to high-dimensional chaos.[1, 2] Such systems are studied extensively in optoelectronic[3] and biological[4] systems. In electrochemical systems, time-delayed feedback can be used for the control of dynamics, e.g., for the stabilization of unstable steady states and periodic orbits[5]. In this study, the dynamical features of a prototype, negative differential resistance electrochemical model [6] is studied in the presence of various forms of delayed feedback. Specifically, the double layer potential drop is fed back with delay that is either discrete or in a distributed form using a delay kernel. In the latter case, the system was analyzed in a framework of an extended system of ordinary differential equations using an auxiliary variable. The behavior of the system at different parameter values is explored with a virtual space-time representation [7] technique. The features of various virtual spatial states in the form of rotating waves, cluster formation, and turbulence are discussed. Finally, comments are made on possibility of formation of virtual chimera states[8] in the electrochemical system with external delayed feedback.

References:

[1] Giacomelli, G., Marino, F., Zaks, M. A., Yanchuk, S., EPL, Vol. 99, 58005, 2012.

[2] Larger, L., Goedgebuer, J. P., Phys. Rev. E, 69, 036210, 2004.

[3] Larger, L., Proc. R. Soc. A, Vol. 371, 20120464, 2013.

[4] Bocharov, G., Rihan, F. A., J. Comp. and Appl. Math., Vol. 125, 183, 2000.

[5] Kiss, I.Z., Kazsu, Z., and Gaspard, V., Chaos, Vol. 16, 033109, 2006.

[6] Koper, M. T., M., Gaspard, P., J. Chem. Phys., 96, 7797, 1992.

[7] Arrecchi, F. T., Giacomelli, G., Lapucci, A., Meucci, R., Phys. Rev. A., Vol. 45, R4225, 1992.

[8] Larger, L., Penkovsky, B., Maistrenko, Y., Phys. Rev. Lett., Vol. 111, 054103, 2013.
A Metal-Ion Adsorbent Based on Composite of Graphene Oxide/Poly (1-(3-aminopropyl) Pyrrole)
Authors: Qin Hongyi , Gong Tao , Cho Yujin , Lee Changgu , Kim Taesung
Published: February 2020

A novel metal-ion adsorbent was developed based on graphene oxide (GO) and poly (1-(3-aminopropyl) pyrrole. Firstly, GO was covalently functionalized by 1-(3-aminopropyl) pyrrole (APP) monomer by an esterification reaction between the carboxyl groups of GO and the amine groups of APP. Subsequently, a GO/poly (1-(3-aminopropyl) pyrrole) (poly (GO-APP)) composite was prepared by in situ crosslinking polymerization.

The chemical structure of poly (GO-APP) composite was determined by a series of characterization methods, such as Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Scanning electron microscopy (SEM) and Thermogravimetric analysis (TGA).

The poly (GO-APP) was a hard solid material like a coal (Figure a), which is due to the crosslinked polymerization between GO and polymer. In this composite system, the GO is a crosslinking agent like a polyfunctional monomer, which can turn the linear polymer into crosslinked network polymer to increase the stiffness, strength and stability of poly (GO-APP).

This poly (GO-APP) composite is used for the adsorption of metal ions. As shown in Figure b, the absorption capacity of poly (GO-APP) was much larger than that of GO. The sorption of metal ions is based on both nitrogen and oxygen functional groups. The oxygen-containing functional groups in GO and the protonated amine groups in APP can bind to cations easily. Moreover, the chemical affinity of metal ions for amine groups is stronger than that for oxygen-containing functional groups. Therefore, the absorption capacity increases with the content of APP monomer.

Besides, the poly (GO-APP) showed a conducting property due to the conjugated π-π system in the main chain of copolymer, which will greatly expand the application fields of poly (GO-APP) composite.
Hydrothermal Carbonization to Produce Materials for Electrochemical Capacitors
Authors: Donne Scott W , Latham Kenneth , Ferguson Adam
Published: February 2020

Hydrothermal carbonization has gained increased interest over the last 15 years as a highly effective and environmentally friendly way to produce highly functional carbon materials. Compared to other carbon doping methods, hydrothermal carbonization represents one of the simplest and easiest routes, as elements dissolved in the initial hydrothermal solution are readily incorporated into the carbon structure. In terms of electrochemical performance, nitrogen doped into the carbon structure has been found to significantly improve the electrochemical performance of supercapacitors by increasing pseudocapacitive behaviour. In this study, we have investigated the chemical structure, morphology and electrochemical performance of hydrothermal carbons produced from sucrose which contain varying degrees of nitrogen doping. The hydrothermal treatment produced carbons with a spherical morphology with a wide variety of carbon functionalities littering the surface. Electrochemically, these carbons displayed a wide range of psudocapacitive behaviour as well as electrical double layer capacitance, delivering capacitance up to 120 F/g in three cell electrodes with 0.5 M H2SO4 as the electrolyte.
Electrochemical Behavior of Carbon Nanostructured Electrode Material for Supercapacitor Application
Authors: Prakash Ramakrishnan , Shanmugam Sangaraju
Published: February 2020

Electrochemical capacitors or supercapacitor (SCs) have been considered as one of the most promising energy storage devices for portable electronics, hybrid electric vehicles and stand-by power system. Especially in electric vehicles, SCs can couple with a fuel cell or battery to store and deliver the energy at a short period of time. Since, SC stores energy by electrostatic interaction between electrode-electrolyte interfaces based on the Electrical double layer phenomenon, so the amount of charge stored directly dependent on the surface area of any electrode material [1,2]. Porous carbon material recognized as a potential electrode material for SC owing to large surface area, chemical stability and low cost [3]. A large variety of porous carbons, such as activated carbons, aerogels, templated carbons, carbide-derived, carbon nanotubes, graphene and carbon nanofibers have been studied as EC electrode materials. However, many of the carbonaceous materials showed disadvantages such as the high ionic resistance, low electrical conductivity and low compatibility of conductive pathways to store charge, which unfavorable for high energy storage and high power devices criteria. So the performance of ECs does not only depends on the physical, but also intimately on the chemical properties of the electrode material. So the strategy of pseudocapacitance is required in the carbon framework. It has been reported that hetero atom (N, S, P and B) doping on carbon structure enhances the surface wettability as well as the electronic conductivity of the materials without compromising the long term cycle stability [4].

In the present work, we have investigated the morphological effect of nitrogen doped three different carbon nano-structures. Different nano-structures electrode materials such as rod, hollow and boat shaped are prepared using a coaxial electro-spinning technique and followed by carbonization, under inert (Ar.) atmosphere. The x-ray diffraction, Raman spectroscopy, x-ray photo-electron microscopy and high resolution transmission electron microscopy results reveal the synthesized carbon materials exhibit turbo-static carbon with poor sp2 graphitic carbon. The electrochemical properties of all the three electrode materials have been studied using cyclic voltammogram and galvanostatic charge-discharge using a symmetric type two electrode system configuration with aqueous as electrolyte medium, and analyzed to know their electrochemical properties. Long term cycle stability tests show excellent capacity retention.

References

(1). A. S. Arico, B. Scrosati, J. M. Tarascon, W. Van Schalkwijk, Nat. Mater., 4 (2005) 366-377.

(2). R. Kotz, M. Carlen, Electrochim. Acta., 45, (2000) 2483-2489.

(3). E. Frackowiak, F. Be´guin, Carbon, 39 (2001) 937-950.

(4). D. Hulicova, M. Kodama, H. Hatori, Chem. Mater., 18 (2006) 2318-2326.
Electrochemical and Thermal Characterization of a Graphene-Based Electrochemical Double-Layer Capacitor (EDLC)
Authors: Kang Jin Hee
Published: February 2020

Graphene-based electrodes are of great interest for developing high performance electrochemical double-layer capacitors (EDLCs) due to their excellent electrochemical properties, low electric resistance and unique structures. Meanwhile, EDLCs have become more attractive not only to offer high power and energy densities but also to withstand a harsh temperature ranges [1]. Since temperature effects can be crucial to estimate the rational evaluation of degradation, energy efficiency and lifetime, it requires better understanding of temperature-dependent electrochemical properties especially at electrode/electrolyte interfaces. In this study, the performance of an EDLC, assembled with two identical graphene electrodes and the 1M Et4NBF4/PC electrolyte in a coin cell, is systemically characterized under various operating temperature conditions, ranged from -30 °C to 60 °C. Graphene deposition is carried out by using the vacuum filtration method. This method yields an electrically strong conductive and thermally stable nano-structured graphene paper [2]. Electrochemical characterization techniques including cyclic voltammetry (CV), constant charging/discharging (CCD) and electrochemical impedance spectroscopy (EIS) are performed to evaluate capacitance retention, energy and power densities, internal resistance variation and interfacial processes at the double-layer region. In addition, EIS data is simulated with the proposed electric equivalent circuit in order to investigate the temperature dependency on interfacial reactions with respects to mass transfer (diffusion) and electrode kinetics (charge transfer) [3]. Each reaction is represented by electrical resistive elements in the equivalent circuit, and its values are correlated with the activation energy to quantitatively rationalize the observed behaviour of diffusion and the charge transfer kinetics with temperature.

References:

[1] R. Kotz, M. Hahn, R. Gallay, Journal of Power Sources, 154 (2006) 550-555.

[2] H. Chen, M.B. Mueller, K.J. Gilmore, G.G. Wallace, D. Li, Advanced Materials, 20 (2008) 3557.

[3] J.W. Jinhee Kang, Shesha H. Jayaram, Aiping Yu, Xiaohui Wang, Electrochimica Acta, 115 (2014) 587-598.