bluuebunny/crossref_metadata_2025 huggingface dataset:
Heteropoly Acid Functionalized Membranes for High Performance and Chemically Stable Fuel Cell Operation
Authors: Motz Andrew R , Kuo Mei-Chen , Bender Guido , Pivovar Bryan S. , Herring Andrew M.
Published: February 2020

There is still a need for membranes that operate in proton exchange membrane (PEM) fuel cells at hotter and drier conditions than can be achieved with current materials, >100°C and <50%RH. One approach pursued by us and independently by Kunz and co-workers was the use of inorganic super acids, such as the heteropoly acids (HPAs). HPAs are a sub group of the large class of metal oxygen clusters known as polyoxometalates in which a central heteroatom is surrounded by a number of W or Mo oxygen octahedra. For proton conductivity it is desirable that a strong negative charge be delocalized across the whole anion so that the proton will be as dissociated as possible. This limits the choice of HPA to the spherical tungsten based Keggin anion with as light as possible a heteroatom. This limit is reached with Si as the P based HPA is known to decompose in the presence of peroxide and the electron deficient nature of B renders the spherical Keggin anion unstable. Many fundamental studies have been undertaken on solid state HPA systems. In addition the Si based HPA are known to decompose oxygenated radicals and so offer a path to the development of a PEM that is oxidatively stable under fuel cell operating conditions. These studies indicated that despite the original report in the early 80’s that HPA had the highest proton conductivity reported at that time, that when dry there proton conductivity was disappointingly low at moderate temperatures.

The key is to distribute the HPA on a perfluorinated polymer backbone in such a way that the natural tendency of the HPA to cluster and crystalize is suppressed. Using dehydroflourination chemistry we have learnt to functionalism PVDF type polymers with molecules that can act as anchor points for lacunary HPA, where a lacunary HPA has 1,2 or 3 tungsten oxygen clusters removed to give bonding points. After much research we now can produce these materials in large area thin film membranes. The base material outperforms the state of the art PEM under standard conditions and has the highest chemical stability of any PEM proposed to date. We are now varying the HPA structure to try and avoid the HPA clustering issue, these membranes are being sprayed on gas diffusion electrodes which act as the support to the tin films. This is allowing us to run these as fuel cells at higher temperatures to asses the potential of HPA functionalized membranes in these applications.
On the Mechanism Responsible for the Catalytic Activity of Platinum for Oxygen Reduction Reaction (ORR) and predicting a cost effective replacement for Pt toward ORR
Authors: Reda Mahmoud R. , Reda Ghazi
Published: February 2020

Pt is required as a catalyst for both oxygen reduction reaction (ORR) and hydrogen evolution reaction(HOR) . This means that any type of fuel cell or a configuration to split water into hydrogen and oxygen require platinum as a catalyst. Currently, much of the cost of fuel cells arises from the need for precious metal catalysts – primarily Pt – to drive the necessary electrochemical reactions. For example, the cost of the Pt alone in a PEFC for a small 100 kW car is higher than the cost of an entire 100 kW gasoline engine. And there is another problem. During the course of the lifetime of a fuel cell, the Pt cathode suffers from oxidation, migration, loss of active surface area, and corrosion of the carbon support. Impurities, as well as methanol diffusing from the anode side of DMFCs, can also ‘poison’ the catalyst, reducing its activity and efficiency. So not only do fuel cells rely on a high-price commodity for their operation, they also require a high density of that expensive material. Understanding the mechanism responsible for such material is necessary to reduce the cost of fuel cells and water splitting configuration. It is well known that the crystal structure of platinum is an face centered cubic (FCC). In this case the lattice constants which influence the bandgap energy are equal a. In fact it may be that the bandgap energy is inversely proportional to the inverse of the a**(3) [1] Based on the idea that the lattice constant influence the bandgap and the fact that the bandgap energy is the energy required to move the bonded valence electrons to free conduction band which is the energy required to do the rate limiting step for the ORR or HER, a mechanism for the effect of platinum will be derived.

Reference

[1] R. Da1ven, Phys. Rev. B, 8,12 1973

[2]D. Bensaid , International Journal of Metals, 2014 (2014), Article ID 286393, 7 pages
Enhanced Electrocatalytic Activity over Structurally Ordered Intermetallic PdCu3 Nanoparticles
Authors: Gunji Takao , Noh Seung Hyo , Ando Fuma , Tanabe Toyokazu , Han Byungchan , Ohsaka Takeo , Matsumoto Futoshi
Published: February 2020

Structurally ordered phase of PdCu3 nanoparticles (NPs)/carbon black (CB), in which PdCu3 has a Cu3Au-type structure, was prepared by co-reduction of Pd and Cu precursor using ethylene glycol as reducing agent and annealing procedure. The obtained catalysts were characterized by using X-ray diffraction technique (XRD), transmission electron microscopy (TEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). The XRD and STEM measurements allowed us to confirm the crystal structures of both atomically disordered Pd-Cu NPs/CB and ordered intermetallic PdCu3 NPs/CB. From the TEM and EDS measurements, it was found that PdCu3 NPs are uniformly dispersed on the CB surface and the atomic ratio of Pd and Cu is 25.3 : 74.7. The DFT calculations suggested that the as-prepared PdCu3 NPs have a uniformly ordered structure of Pd and Cu atoms without segregation of Pd and/or Cu, while the Cu-free surface structured PdCu3 NPs, which are formed by a so-called electrochemical dealloying, i.e., the surface and sub-surface Cu dissolution from the PdCu3 ordered structure, possess a superior electrocatalytic activity for the ORR compared with Pd NPs/CB. This catalytic activity can be explained reasonably based on the measured d – band center value and the theoretical calculation of catalyst – oxygen binding energies. In addition, a possibility of PdCu3 NPs/CB as a cathode catalyst in direct methanol fuel cells is discussed briefly.
Performance of Carbon-Supported Pt Nanoparticles Covered by Silica Layers with Low Ionomer in Polymer Electrolyte Fuel Cells
Authors: Ohnishi Tomohiro , So Magnus , Takenaka Sakae , Tsuge Yoshifumi , Inoue Gen
Published: February 2020

Developed novel catalysts has been enhanced its activity and durability by researchers. There are some approaches to enhance Pt activity such as alloy, core-shell, and nanoframe and to improve durability by covered catalysts such as Silica, carbon, and organic compound. However, as for evaluation of catalyst, it is generally difficult to reflect half-cell results to membrane electrode assembly (MEA) one after screening of catalysts in electrolyte by half-cell method. There is morphology of catalyst layers (CLs) structure such as secondary porous, tortuosity, and porosity in addition to morphology of catalysts such as Pt specific surface, activity, and carbon support pore. Therefore, it is necessary to design CLs to bring out the performance without loss(1,2). The amount of ionomer around Pt/C is focused. It is also important factor influencing CLs structure. Although ionomers contribute the proton conduction, an excess of it prevents diffusion of oxygen to decrease porosity. Thus, decreasing ionomer amount is better in terms of oxygen diffusion. However, it is difficult to prepare the CLs loading low amount of ionomers by typical coating method since ionomers have a role in binding between secondary particles and increasing viscosity of ink. The catalyst by coverage Silica layer produced by Takenaka et al. is focused. Covering silica is one of the useful method to improve durability of Pt/C(3,4). The surface characteristics is transmuted by covering silica on the Pt/C. And then, it is available to keep the good dispersion ink even if low ionomer/carbon mass ratio (I/C). In this work, CLs with low I/C and effect of silica coating is evaluated by output performance using catalyst covered silica layer.

CLs was prepared using by inkjet method. I/C enable to be reduced down to 0.25 in standard sample (TEC10V50E, Tanaka kikinzoku kogyo). Below this value, it is difficult to prepare the CLs to agglomerate the secondary particles since ionomers is not enough as a binder. As for silica catalyst, it is available to reduce I/C down to 0.05 while ink keeps good dispersion. The dispersibility is enhanced by difference between surface characteristics. Low I/C samples were showed performance same as typical method of I/C = 1.0 in high humidity. It is possible to get the good performance with low I/C. In addition, output covered silica layer is better than standard sample in low humidity. The result indicates that silica plays a role in humectant-like.

Inoue and M. Kawase, J. Power Sources, 327(14), 1, (2016).

Kotoi, G. Inoue, and M. Kawase, ECS Trans., 75, 385, (2016).

Takenaka, H. Matsumori, K. Nakagawa, H. Matsune, E. Tanabe, and M. Kishida, J. Phys. Chem. C, 111(42), 15133, (2007).

Takenaka, H. Matsumori, T. Arike, H. Matsune, and M. Kishida, Top. Catal., 52(6-7), 731, (2009).
A New Perspective on the Degradation of Polymer Fuel Cell and a Method to Overcome Durability Limit
Authors: Yang Seungyong , Han Byungchan , Kim Tae-Young
Published: February 2020

Polymer electrode membrane fuel cells (PEMFC) are a major obstacle to commercialization due to durability problems caused by corrosion of the carbon support that occurs under special conditions such as start-up and shut-down. Under these conditions, the PEMFC cell voltage generates 1.3 V or more, which accelerate the corrosion of the support in the catalyst layer. In many research groups reported as a main cause of performance decrease and durability reduction by carbon support corrosion. First, the carbon support surface is oxidized and the flooding phenomenon. Second, platinum is removed due to support deterioration. Third, the pores size changes in the catalyst layer. However, these main causes do not explain precisely the cause of the performance drop and increase oxygen diffusion resistance in the mass transport area during carbon support corrosion. In this study, we investigate the causes of the increase of the oxygen diffusion resistance and the decrease of the performance during the corrosion of the support from the viewpoint of the ionomer binder, which is one of the compositions of the catalyst layer, in addition to the cause of the durability drop. Then, various methods have been sought to minimize the degradation of the ionomer during electrode degradation. The ionomer is a polymer and has a motion under high temperature and high humidity conditions. Therefore, the ionomer on the support surface is rearranged during the corrosion of the support. In order to minimize ionomer rearrangement using strong corrosion resistance material CNT is added as a sub-support to overcome the limitation of PEMFC durability, observed that there was little change in oxygen transfer resistance generated during electrode degradation.
Molecular Dynamics Study of the Thickness Dependence of Structure and Mass Transport in Ionomer Thin Film
Authors: Kobayashi Koichi , Mabuchi Takuya , Inoue Gen , Tokumasu Takashi
Published: February 2020

Polymer electrolyte fuel cells (PEFCs) are promising for automobiles and various applications because of their high power density and low operating temperature. The cost must be reduced without sacrificing performance of cells by decreasing Pt loading. However, at lower Pt loading, the efficiency decreases because mass transport losses largely increase at higher current density. Proton transport resistance is one of the causes of the losses. It is considered that proton transport property in ionomer thin films is improved with increasing the thickness of the films, whereas oxygen transport resistance increases with increasing the thickness. Ionomer thin films with high proton conductivity are required even though the thickness is thin. For this reason, we obtained the thickness dependence of proton transport property and structure property in ionomer thin films using a molecular dynamics method.

As the ionomer thin film, Nafion was employed. We constructed a system of the ionomer thin film on carbon surface. The contact angle of carbon surface was set at 90 degrees. To analyze the thickness dependence of proton transport property and structure property, the films with the thickness of 4-10 nm were made by changing the number of the Nafion chains. The analyses have carried out by changing water content to 3 and 14. To analyze a correlation between the dynamics and structural properties of Nafion thin films, dynamics properties were evaluated by self-diffusion coefficient obtained from mean square displacement of protons, and structural properties were evaluated by mass density distributions and maximum water cluster length. We found that at high water content, self-diffusion coefficient of protons has hardly changed by the change of ionomer thickness, whereas at low water content, diffusion coefficient has a peak when the ionomer thickness is around seven nm. At this surface wettability, water cluster connectivity was highest when the thickness is around seven nm, and liquid molecule was concentrated at near ionomer/carbon interface and near ionomer/gas interface in the case of low water content. However, in the case of high water content, water cluster connectivity has hardly changed by the change of thickness. We find the thickness dependence of water cluster connectivity. Self-diffusion coefficient increases with increasing maximum cluster length.

Acknowledgment

This research is supported by New Energy and Industrial Technology Development Organization (NEDO). We use Integrated Supercomputation System at Institute of Fluid Science. I appreciate all the support we received from everyone.
Advances in Ptni Nanowire Extended Thin Film Electrocatalysts
Authors: Alia Shaun M , Neyerlin K.C. , Hurst Katherine , Zack Jason W. , Mauger Scott A , McNeary William W , Weimer Alan , Medlin Will , Zaccarine Sarah , Ngo Chilan , Pylypenko Svitlana , Buechler Karen , Pivovar Bryan S.
Published: February 2020

Fuel cells offer tremendous promise in pushing society towards a more sustainable energy system by enabling the production of renewable fuels with zero criteria pollutant emissions. One key barrier for such a future energy system for fuel cell adoption s the need for platinum group metals for catalysis and the quantities required for efficient performance. It has been a long-standing goal to continually increase performance and durability of electrochemical devices, and one promising approach has been the development and implementation of extended thin film electrocatalysts.1

Our team has extensively investigated extended surface catalysts as a novel platform for increased performance and durability at lower cost.2,3,4 This presentation will highlight the advances of our team in the synthesis and implementation of extended surface electrocatalysts with a focus on PtNi nanowires (NWs) produced by atomic layer deposition (ALD) . We have demonstrated the ability to obtain high performance PtNi NWs following ALD deposition by a series of steps that include annealing under reducing conditions and acid leaching. This results in high activity and surface area catalyst that have limited Ni remaining, thereby mitigating issues of potential Ni contamination when assembled into MEAs.

These catalysts have been incorporated into fuel cells investigating several different processing variables including catalyst loading, ionomer to catalyst ratio, and inclusion of carbon. Through optimization efforts, we have been able to achieve mass activities that surpass US Department of Energy targets for both performance and durability as demonstrated in Figure 1. These results have started to show the potential of extended surface electrocatalysts in cell testing. This presentation will discuss the factors that have allowed these performances to be achieved and future work to further advance both the inherent electrochemical properties of these catalysts and also the MEA performance of fuel cells based on these materials.

Figure 1. Polarization curves for PtNiNW based on initial cell performance and after 5,000 cycles of carbon corrosion testing.

Mark K. Debe∗, Alison K. Schmoeckel, George D. Vernstrom, Radoslav Atanasoski, Journal of Power Sources 161 (2006) 1002–1011.

Shaun Alia, Svitlana Pylypenko, Arrelaine Dameron, KC Neyerlin, Shyam Kocha, Bryan Pivovar, J. Electrochem. Soc. 2016 163(3): F296-F301.

Shaun M. Alia, Svitlana Pylypenko, K.C. Neyerlin, Shyam S. Kocha, and Bryan S. Pivovar, J. Electrochem. Soc. 2015 162(12): F1299-F1304.

Shaun M. Alia, Svitlana Pylypenko, K.C. Neyerlin, David A. Cullen, Shyam S. Kocha, Bryan S. Pivovar, ACS Catalysis, 4, 2680, 2014.

Figure 1
Durability of Long-Life Low Power Fuel Cells
Authors: Borup Rod L. , Stariha Sarah , Baker Andrew M. , Rockward Tommy , Langlois David A. , Wilson Mahlon S. , Rau Jon
Published: February 2020

Fuel cells have the potential to provide very low uninterrupted power for long periods (several decades) of time. The specifications for these applications can vary tremendously from transportation fuel cells that are a large driving force behind fuel cell development. For these applications, the fuel and oxidant supply are often required to be stored for the entire lifetime of the application; these systems have higher inherent safety and overall higher system energy density than batteries for these prolonged operational times.

Many of the technical challenges are application dependent but can include:

Fuel/oxidant loss (due to membrane/plates/seals permeability)

Membrane degradation and thinning (due to high cell voltages)

Passive system water management

Operation in uncontrolled environments (including operation a large temperature range and unpredictable/uncontrollable ambient atmospheres)

Control of power transients (microwatt to watt power levels)

The primary degradation modes expected for these applications involve the electrode layer, loss of catalytic activity, membrane thinning, changing hydrophobicity of carbon materials (which impacts water management) and corrosion of metallic bipolar plates (including increasing contact resistance). Electrode degradation involving performance loss of the cathode catalyst layer includes catalyst particle agglomeration, catalyst support corrosion, losses of catalyst layer porosity and loss of catalyst layer proton conductivity due to ionomer degradation. Depending on the systems load requirements, potential cycles can be many millions of cycles over decades long continuous operation. To minimize catalyst degradation, we expect that a Pt-black electrode will be superior compare to the Pt supported on carbon electrodes that are the preferred for transportation applications. To examine the durability of these catalysts we are conducting Accelerated Stress Testing (ASTs); Figure 1 shows an on-going test of a Pt-black catalyst over 1.3 million cycles. The square wave cycling induces Pt dissolution and re-precipitation (Ostwald ripening) of the platinum thus decreases the catalyst surface area. From Figure 1, catalyst surface area loss appears to have reached 30-35% loss, but has not substantially increased after about 750,000 cycles.

To avoid large amounts of hydrogen loss due to membrane cross-over, we are exploring multiple layers of membrane to make a thick, mechanically reinforced and chemically stabilized membrane. A primary method to examine membrane degradation is to examine radical attack of the membrane at OCV conditions. Membrane thinning was measured at approximately 1.7 - 4.2 micron/year over a 2.4 year test with H2/air, at 25 C, which over a 20 year operational life extrapolates to34 - 83 micron. This suggests that a membrane of > 200 micron thick will be required for a 20 year operational life at low power levels.

Figure 1
Designing Cathode Layers for PEFC with the Low Platinum-Loading
Authors: Uda Keisuke , Noda Zhiyun , Nagayama Mayumi , Sasaki Kazunari , Hayashi Akari
Published: February 2020

Introduction

Since the reduction of platinum-loadings in polymer electrolyte fuel cells (PEFCs) is essential for the further spread of their technology, many researchers have been working on this subject. Among those studies, the importance of controlling and optimizing structures of catalyst layers including the carbon frame has been reported for designing highly efficient PEFC with the low platinum-loading.1 In this study, membrane electrode assemblies (MEAs) with various platinum-loadings in the cathode are made and evaluated as a fundamental approach to reduce the platinum-loading. Then, we are trying to understand minimum requirement of platinum and to correlate resulting overvoltages with structures of cathode layers, and we are accordingly aiming to design highly efficient PEFC with the low platinum-loading.

Experimental

MEAs with various platinum-loadings in the cathode were prepared with 46% Pt deposited Ketjen black (TEC10E50E) and Nafion® by a spray printing method.2 Then, MEAs were evaluated in terms of impedance, IV performance, and ECSA. The thickness of catalyst layers were also measured by FIB-SEM. For further designing ideal electrocatalysts, electrocatalysts with different amounts of Pt deposition were made using Vulcan carbon as a carbon support and platinum(II) acetylacetonate as a platinum precursor through thermal reduction.3

Results and discussion

MEAs with the fixed anode (0.30 mgPt/cm2) and the varied cathodes (0.05 – 0.40 mgPt/cm2) have been prepared and evaluated in our study. Then, the minimum requirement of platinum in the cathode has been determined to 0.15 – 0.20 mgPt/cm2 through correlating the platinum-loading with activation overvoltage. Furthermore, the requirement of sufficient thickness of cathode layers has been found for reducing concentration overvoltage.4

In this report, the correlation between carbon amounts and concentration overvoltage was further evaluated by preparing MEAs with 0.05 – 0.60 mgPt/cm2 cathodes. Since decrease in the gas diffusion pathway by decreasing the cathode layer also leads to increase in the concentration of water produced by fuel cell reactions in the cathode layer, there should be the optimum thickness in terms of sufficient fuel diffusion. As a result, the optimum thickness was found to be 8.24 µm in this study. Since the importance of cathode thickness was realized for designing PEFC with the low platinum-loading, electrocatalysts with reduced Pt deposition on carbon were prepared in order to increase the cathode thickness even with reduced platinum-loadings. Consequently, successful reduction of concentration overvoltage was suggested from our experimental results. Obtained results will be explained more in details.

(1) M. Lee, et al., Electrochimica Acta, 56 (2011) 4783-4790.

(2) M. Okumura, et al., J. Electrochem. Soc., 164 (9), F928 (2017).

(3) A. Hayashi, et al., Electrochemica Acta, 53, 6117 (2008).

(4) K. Uda, et al., ECS Trans., 80 (8), 789 (2017).

Figure 1
Fe/N/C Cathode Catalyst Prepared from a Low Content of Fe Precursor to Obtain Atomically Dispersed Metal Center
Authors: Nabae Yuta , Nagata Shinsuke , Aoki Tsutomu , Tanida Hajime , Imai Hideto
Published: February 2020

The development of Pt-free catalysts is strongly desired for globalization of proton exchange membrane fuel cells. Our research group has been developing Pt-free cathode catalysts obtained by pyrolyzing Fe containing polyimide nano-particles. While this sort of polyimide derived cathode catalysts shows very good performance, the structure of the Fe center was obscure. Furthermore, the previous synthesis of the catalysts started from a relatively large amount of Fe additives (2 wt%); therefore, extraordinary Fe species require to be washed out using HCl, the process of which was redundant.

In the present study, we tried to avoid the acid washing process by starting from a lower amount of Fe additives to simplify the synthetic procedure and increase the fraction of atomically dispersed Fe centers. Polyimide nano-particles were synthesized by the precipitation polymerization of pyromellitic acid dianhydride and 1,3,5-tris(4-aminophenyl)benzene with 0.3-0.5 wt% of Fe(acac)3 (acac = acetylacetonate). The Fe-containing polyimide precursor was heated at 600 °C for 5 h in a nitrogen atmosphere, and then heated again to 800 and 1000 °C for 1 h each in an ammonia atmosphere (50% balanced by nitrogen). Any acid washing was not performed during the whole synthetic procedure. The chemical composition of the resultant carbon was determined using a CHN elemental analyzer (PerkinElmer 2400-II) and an electron probe micro analyzer (Jeol JXA-8100): C 88.3 wt%, H trace, N 2.6 wt% and Fe 1.7 wt%. The Brunauer, Emmett and Teller (BET) surface area was determined to be 1360 m2 g-1 (Bel Japan Belsorp mini II).

Thus obtained Pt-free cathode catalyst was tested under H2-O2 fuel cell conditions. Figure 1 shows the I-V performance curves for the membrane electrode assembly (MEA) with the obtained catalyst. The measured and IR-free voltages at 2 A cm-2 reached 0.45 and 0.65 V, respectively; and the maximum power density was 0.89 W cm-2, suggesting the newly synthesized catalyst exhibits an extremely high performance as a Pt-free cathode catalyst.

Figure 1
Activity and Durability Insights for Atomically Dispersed (AD)Fe-N-C Oxygen Reduction Catalysts
Authors: Chung Hoon T , Cullen David A. , Yin Xi , Komini Babu Siddharth , More Karren L. , Myers Deborah J , Zelenay Piotr
Published: February 2020

To reduce greenhouse gases (GHG) emission, we need to move away from fossil-based energy sources. Electrochemical energy conversion systems (EECSs), like fuel cells, are broadly considered to be alternative systems to the currently dominant internal combustion energy-generation systems (ICESs). Among several types of fuel cells, polymer electrolyte fuel cells (PEFCs) are the most suitable one for vehicle applications. Nanoparticle platinum (Pt) catalysts are now used as state-of-the-art catalyst for the PEFCs. However high price, scarcity, and monopolized global distribution of Pt place significant limitations on these energy conversion systems. Particularly oxygen reduction reaction (ORR) at the cathode is inherently slower by six orders of magnitude than hydrogen oxidation reaction at the anode, thus requiring higher Pt loading. Platinum group metal free (PGM-free) ORR catalyst development thus has been a continuous research theme for several decades by many research groups.

Metal-nitrogen-carbon (M-N-C) type catalysts have demonstrated the highest activity and durability among several types of PGM-free catalysts. Recently there has been a significant improvement in ORR activity, however further improvement in activity is still needed to compete with Pt catalyst. Furthermore good durability of these catalysts has not been demonstrated. Understanding of active site that has not been clarified yet is a core for solving these issues.

Recently we directly observed FeN4 moiety in (CM+PANI)-Fe-C catalysts [1]. If FeN4 is an active site for ORR, increasing the number of this moiety, i.e., making atomically dispersed (AD) Fe, will be a pathway for improving the ORR activity. Thus to achieve high density of FeN4, we synthesized fiber-type zeolitic imidazolate framework (ZIF-F) as a precursor for (AD)-Fe-N-C catalysts (Fig. 1 (a)), in which FeN4 structure already exist. Heat-treatment converts this ZIF-F into fibrous N-doped carbons (Fig. 1(b). Fe atoms are dispersed atomically without aggregation in the fibrous N-doped carbons (Fig. 1(c)). Importantly, electron energy loss spectroscopy (EELS) demonstrates that N is cordinated to the Fe atoms (Fig. 1(d)). Thus we could construct FeNx moieties within the (AD)-Fe-N-C catalysts.

In this presentation, we will present the activity and durability of this (AD)-Fe-N-C catalyst in rotating disk electrode (RDE) and fuel cells in conjunction with diverse analysis tools. This will give some insights for the nature of activity/durability for M-N-C type ORR catalysts.

Hoon T, Chung, David A. Cullen, Drew Higgins, Brian T. Sneed, Edward F. Holby, Karren L. More, Piotr Zelenay, “Direct atomic-level insignt into the active sites of a high-performance PGM-free ORR catalyst”, Science, 357, 479 (2017).

Acknowledgments

This research is supported by DOE Fuel Cell Technologies Office, through the Electrocatalysis Consortium (ElectroCat).

Figure 1
Mixture of Transition Metal Oxides (MoNi, MoCoW and NiCo) As Electrocatalysts for ORR and HER
Authors: Béjar José Eduardo García , Álvarez-Contreras Lorena , Chávez Abraham Ulíses , Arriaga Luis G. , Arjona Noé
Published: February 2020

Oxygen reduction reaction (ORR) remains as the limiting reaction in fuel cells for its successful used as energy source due to its slow kinetic and, noble metals such as Pt and Pd are still some of the most active materials. This is the reason why attention has focused on finding another kind of catalyst that allows decreasing the usage of noble metals, either through using non-metallic materials or using less noble metals with specific morphologies such as core-shell structures. In addition, hydrogen evolution reaction (HER) is a key reaction for electrochemical hydrogen compression. The kinetic limiting steps for ORR and HER can be decreased using mixtures of metal transition oxides (MMTOs) as alternative electrocatalysts; several MMTOs have been reported in literature presenting good catalytic activity and great stability, these qualities make them a sustainable solution to traditional ORR catalysts. In this work we describe the use of Mo, Co and Ni oxides as electrocatalysts for ORR. The research was carried out using three different combinations MoNi, MoCo-W (W as particle stabilizer) and NiCo. The electrocatalytic activity was studied by rotating disc electrode (RDE), the kinetic parameters were obtained from the Koutecky-Levich and Tafel plots. X-ray diffraction (XRD) indicated that the MoCo-W and MoNi materials have an amorphous structure, while NiCo presented the diffraction peaks corresponding to Co3O4 and Ni. The particle size and morphology were studied by Transmission electron microscopy (TEM), where all materials presented sizes below 20 nm. These materials showed overpotentials lower than 170 mV for both, ORR and HER compared with commercial Pt/C (30 wt.%). Finally, a tolerance study was performed where, MoCoW and NiCo exhibited excellent tolerance to several alcohols (methanol, ethanol, glycerol, ethylene glycol).
Electrochemical Behavior Characterization of Metal Oxide Catalysts for Oer in Alkaline Media
Authors: Ion-Ebrasu Daniela , Spinu-Zaulet Adnana , Enache Stanica , Dragan Mirela , Schitea Dorin , Patularu Laurentiu G , Jianu Catalin , Carcadea Elena , Varlam Mihai , Petrov Konstantin
Published: February 2020

In Polymer Electrolyte Conducting OH- Cations Electrolysis (PEM.OH-) the significant overpotential occurs at the anode side where the oxygen evolution reaction (OER) takes place. Improving OER kinetics would indeed favor a widespread market penetration of (PEM.OH-) electrolysers. Since iridium is quite expensive and, as a typical secondary metal, resource limited, many research efforts have been directed towards the development of OER catalysts with a reduced amount of Ir or based on other transition metal oxides. The paper presents comparative study regarding Oxygen Evolution Reaction (OER) of the LaCoO3 catalysts in alkaline media. The material has been obtained by an original one step method. The effect of various parameters such as the catalyst and PTFE loading and fabrication technique on the electrode performance are described. The catalytic activity of the OER in 0.1 M KOH was determined from Tafel plots, obtained from galvanostatic current-voltage measurements as well as by the Rotating Disk Electrode (RDE) method. Long term tests have been conducted showing a good stability of the catalysts for the OER in 0.1 M KOH. The best electrode performance was used to prepare a home-made 10.89 cm2 cell that was tested in different KOH concentrations in domain of 0.1 to 0.5 M KOH and a commercially available anion exchange ionomer Fumasep FAS-30.
Characterization of Methanol-Functionalized Onion Waste and Graphene-Based Carbons As Anode Catalysts for Microbial Fuel Cell Applications
Authors: Duarte-Urbina Omar José , Fernández-Luqueño F. , Vargas-Gutiérrez G. , Sanchez-Castro Maria Esther , de la Torre Saenz Luis , Escobar Beatriz , Alonso-Lemus Ivonne Liliana , Rodriguez-Varela F.J.
Published: February 2020

Microbial fuel cells (MFCs) represent a sustainable alternative to generate energy from wastewater treatment, reducing the consumption and pollution of fossil fuels, which are used in traditional technologies. An effective way to improve the performance of MFCs is the use metal-free carbon-based anode catalysts, which have shown high catalytic activity with significantly lower cost than noble metals. In this study, the synthesis and characterization of methanol-functionalized carbon catalysts is reported. Onion waste has been thermochemically treated via carbonization, chemical activation with ZnCl2 and pyrolysis at 400, 600 and 800 ºC (named CCA4, CCA6 and CCA8, respectively). Graphite flakes have been ball milled in the presence of thiourea and ZnCl2, followed by pyrolysis at a 500 ºC in order to obtain the graphene catalyst (named GNS). Subsequently, the carbons have been submitted to surface functionalization with methanol using the intermittent microwave heating technique to produce the CCA4f, CCA6f, CCA8f and GNSf catalysts. Anodes have been fabricated by depositing catalytic layers (separately) of CCA4f, CCA6f, CCA8f and GNSf on gas diffusion electrodes. The catalytic activity of the anodes has been evaluated by cyclic voltammetry (VC) in a three electrodes half-cell, using Pharmaceutical Wastewater (PWW) as electrolyte, and compared to that of a gas diffusion electrode without catalyst. The results show that the mechanochemical treatment of graphite in the presence of thiourea modifies its crystalline structure producing the heteroatoms-doped GNS. Meanwhile, CCA4, CCA6 and CCA8 have an amorphous structure self-doped with the N and S heteroatoms. The catalysts are thermally stable at 700 ºC and exhibit a highly heterogeneous morphology. Nitrogen adsorption-desorption and BET analyses indicate that the activation with ZnCl2 promotes the formation of mesoporous structures with average pore size ranging from 11.38 (GNSf) to around 2 nm (CCA4f, CCA6f and CCA8f). Moreover, the specific surface areas of CCA4f, CCA6f and CCA8f (1468, 1611 and 1269 m2 g-1, respectively) are approximately 20 times higher than that of GNSf (69.7 m2 g-1). The electrochemical characterization demonstrates that the increase in activation temperature improves the catalytic activity of the CCAf series of catalysts for the oxidation of organic matter in the PWW electrolyte. The current density (j) decreases in the order CCA8f>CCA6f>CCA4f. On the other hand, the catalytic activity of GNSf is less than those of CCA8f and CCA6f, but similar to CCA4f. The results show that the metal-free CCAf carbons have the potential to be used as anode catalysts in MFCs.
Wood-Based Carbon Materials Modified with Cobalt Nanoparticles As Catalysts for Oxygen Reduction and Hydrogen Oxidation
Authors: Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus , Stagniūnaitė Raminta , Kepenienė Virginija , Sukackienė Zita , Niaura Gediminas , Drabavičius Audrius , Andrulevičius Mindaugas , Kruusenberg Ivar , Kaare Kätlin , Volperts Aleksandrs , Dobele Galina , Zurins Aivars
Published: February 2020

In the present study, wood-based carbon materials were investigated as catalysts for the electro-reduction of oxygen (ORR) and electro-oxidation of hydrogen (HOR) in an alkaline medium. Activated wood-based carbon and black liqueur were doped with cheap nitrogen precursor, dicyandiamide (DCDA) and were modified with cobalt nanoparticles. The doping was done by pyrolysing samples at 800 °C in the presence of DCDA. The cobalt nanoparticles were deposited on the the N-doped wood-based carbon and N-doped black liqueur using morpholine borane as a reducing agent. The synthesized catalysts were characterized using TEM, XPS, Raman Spectroscopy and ICP-OES. For electrochemical measurements, the glassy carbon (GC) electrodes were modified with synthesized catalysts and the experiments were carried out in 0.1 M KOH solution employing rotating disk electrode (RDE) method. For modifying the electrodes, a suspension (4 mg ml–1) was made in 2% polyvinylidenefluoride in N-methyl-2-pyrrolydone solution.

It was found that the N-doped wood-based carbon and N-doped black liqueur samples modified with cobalt nanoparticles show good activity for oxygen reduction and hydrogen oxidation. The combination of metal nanoparticles and N-doped wood-based carbon and N-doped black liqueur opens up new possibilities for design of the next generation catalysts.

Acknowledgment

This research was funded by a grant (M-ERA.NET-1/2016) from the Research Council of Lithuania. The author’s research was performed in cooperation with the University of Tartu (Estonia), Latvian State Institute of Wood Chemistry (Latvia) and Horizon Pulp&Paper Ltd (Estonia) under the M-ERA.NET 2 project “Wood-based Carbon Catalysts for Low-temperature Fuel Cells (WoBaCat)“ (reg. No. project3213).
Electroatalytic Activity of Palladium-Copper Nanostructures Supported on Graphene Oxide for Formic Acid Oxidation
Authors: Medina Rojano Víctor Alberto , Juárez Marmolejo Leticia , Aldana-González Jorge , Montes de Oca-Yemha Maria Guadalupe , Romero-Romo Mario Alberto , Palomar-Pardavé Manuel Eduardo
Published: February 2020

Low temperature fuel cell technology is set to occupy a central role in powering society in the near future. Several challenges emerge in the preparation of electrocatalysts to improve the operation, use and commercialization of fuel cells. Bi-metallic nanostructures are potential materials to use as electrocatalysts in this application. This research studies the electrocatalytic activity of palladium-copper nanostructures supported on graphene oxide as electrocatalysts for the formic acid oxidation reaction (FAOR). The Pd-Cu nanostructures were synthesized through the impregnation method using tetrachloropalladium acid and sodium borohydride. The Pd and Cu precursors were mixed in appropriate quantities to obtain Pd:Cu molar 1:1 ratios. The Pd-Cu nanostructures were characterized via X-rays diffraction, XRD, transmission, TEM, and scanning electron, SEM, microscopies. The electrocatalytic activity of the Pd-Cu nanostructures was evaluated for the FAOR. Figure 1 shows the cyclic voltammetries used to determine the electroactive area using the CO adsorption/desorption. The FAOR is shown in Figure 1B, where Pd-Cu is the electrocatalyst displaying the largest anodic current density as compared with Pd and commercial Pd.

Figure 1
Nitrogen Doped Graphene with High Performance for Oxygen Reduction Reactions
Authors: Li Shanshan , Shi Zhihao , Chen Yingjie , Yu Liyan , Dong Lifeng
Published: February 2020

Nowadays, ever-growing demand for fuel cells has inspired great effort to seek alternative cathode materials to replace current commercial Pt/C catalyst. Spinel catalysts with low cost and adjustable properties revealed fascinating prospects. Unique nanostructures were designed to increase active sites, facilitate kinetics, and decrease mass transport resistance. Meanwhile, both direct and mediate coupling between Ag and MFe2O4 were proposed to enhance their catalytic activities. Furthermore, different conductive matrixes such as graphene, carbon nanotube and fiber have been utilized as support for these materials to improve conductivity. Heteroatoms such as N and S introduced into graphene lattice were proposed to transfer neighboring carbon atoms to “active regions” with enhanced catalytic activity. The integration of metal oxide nanoparticles with heteroatom-doped graphene demonstrated superior oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) activities. However, as to the deposition of dumbbell nanocomposites on N or S doped graphene, binding to different components might introduce different electron transfer and active sites.

Herein, Ag-MnFe2O4 nanoparticles were synthesized and deposited on N-doped graphene (N-rGO) and S-doped graphene (S-rGO), respectively. According to their reduction peaks, N-rGO demonstrated higher catalytic activity than S-rGO. Moreover, Ag-MnFe2O4 nanoparticles on N-rGO (Ag-MnFe2O4/N-rGO) showed more enhanced effects than those particles on S-rGO (Ag-MnFe2O4/S-rGO). Thus, Ag-MnFe2O4/N-rGO can be developed to replace Pt for ORR.
Multiblock Anion Conducting Copolymers Based on Vinyl Addition and Ring-Opening Metathesis Polymerization of Norbornenes
Authors: Mandal Mrinmay , Huang Garrett , Kohl Paul A
Published: February 2020

Anion-exchange membranes (AEMs) have widespread applications in electrochemical devices. The development of AEMs with long-term alkaline stability and high hydroxide ion conductivity is currently of interest. The use of non-precious catalysts, facile reaction kinetics and reduced fuel crossover are some of the benefits over proton-exchange membranes (PEMs). However, the present limitations of AEMs include low ionic conductivity, poor stability at high pH, and high water uptake.

A series of multiblock copolymers based on vinyl addition and ring-opening metathesis polymerization (ROMP) of norbornenes was synthesized for use in AEM fuel cells and electrolyzers (Scheme 1). The mechanical and thermal stability, ionic conductivity of both sets of polymers are discussed in detail. The long-term (>1200 h) alkaline stability results are promising.

Financial support provided by the ARPA-E IONICS program for M.M. and G.H. is gratefully acknowledged.

Figure 1
(Invited) PGM-Free Bifunctional Electrocatalyst for Oxygen Reduction and Evolution Reactions in Reversible Alkaline Fuel Cells
Authors: Wu Gang
Published: February 2020

The intrinsic instability of carbon largely limits its use for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) as a bifunctional catalyst in reversible fuel cells or water electrolyzers. Herein, we discovered that Mn doping has a promotional role in stabilizing nanocarbon catalysts for the ORR/OER in alkaline media. Stable nanocarbon composites are derived from an inexpensive carbon/nitrogen precursor (i.e., dicyandiamide) and quaternary FeCoNiMn alloy via a template-free carbonization process. In addition to FeCoNiMn metal alloys/oxides, the carbon composites comprise substantial carbon tube forests growing on a thick and dense graphitic substrate. The dense carbon substrate with high degree of graphitization results from Mn doping, while active nitrogen-doped carbon tubes stem from FeCoNi. Catalyst structures and performance are greatly dependent on the doping content of Mn. Various accelerated stress tests (AST) and life tests verify the encouraging ORR/OER stability of the nanocarbon composite catalyst with optimal Mn doping. Extensive characterization before and after ASTs elucidates the mechanism of stability enhancement resulting from Mn doping, which is attributed to (i) hybrid carbon nanostructures with enhanced resistance to oxidation and (ii) the in situ formation of the β-MnO2 and FeCoNi-based oxides capable of preventing carbon corrosion and promoting activity. Note that the improvement in stability due to Mn doping is accompanied by a slight activity loss due to a decrease in surface area. This work provides a strategy to stabilize carbon catalysts by appropriately integrating transition metals and engineering carbon structures.
P2G System Technology Development Aiming at Building a CO2-Free Hydrogen Society
Authors: Sakamoto Masaki , Izuhara Daisuke , Sotouchi Hiroko , Aoyagi Fukuo
Published: February 2020

The government's "Basic Energy Plan" decided on April 11, 2014 has been decided to promote initiatives aimed at realizing "hydrogen society", a society that utilizes hydrogen in everyday life and industrial activities It was. Following this, the Ministry of Economy, Trade and Industry will formulate the "Hydrogen / Fuel Cell Strategy Roadmap" in June 2014 and aim to establish a CO2-free hydrogen supply system around the year 2040.

According to the Government's "Long-Term Energy Supply and Demand Outlook" published in July 2015, the renewable energy ratio to total electricity generation in FY 2030 is estimated to be 22 to 24%. On the other hand, renewable energy has large output fluctuations due to the influence of the natural environment, and geographically unevenly, there are concerns such as suspension of connection to the transmission and distribution electric power network. One solution to this problem would be the Power-to-Gas system utilizing the conversion using electric power from renewable energy into hydrogen. The obtained hydrogen can reduce CO2 emissions by replacing fossil fuels in heating sector.

At the Agency for Natural Resources and Energy, the report of the "CO2 Free Hydrogen Working Group" was compiled in March, In the report, technical issues such as low cost and high efficiency of various technologies including water electrolysis equipment, improvement of durability, improvement of utilization rate were taken as technical issues.

In this research, we demonstrate technological development from hydrogen production using renewable energy to transportation, storage and use in the real society, and establish the basic technology for practical application of "Power to Gas system".

ACKNOWLEDGEMENT

This work was partially supported by the New Energy and Industrial Technology Development Organization (NEDO) of Japan.
Highly Accelerated Mass Transport within Jungle-Gym-Type Ir Electrocatalyst for Water Electrolyzers
Authors: Kim Ye Ji , Jung Yeon Sik
Published: February 2020

Hydrogen is an efficient and clean energy carrier, as well as a fuel for transportation and various other applications. Polymer electrolyte membrane water electrolysis (PEMWE) has shown to be a promising method for producing pure hydrogen without significant additional compression.[1] However, understanding the relationship between nanostructure and activity is one of the current challenges faced by water electrolysis for analyzing and improving IrOx-based catalysts for the OER. Herein, in order to confirm the effect of controlling the nanostructure, jungle-gym-structured Ir OER catalysts were fabricated using solvent-assisted nanotransfer printing (S-nTP). They are composed of vertically stacked nanowire array with a periodicity. They showed 4 higher mass activity than that of iridium black powder(2-4 nm in diameter). To measure the electrochemically active surface area, the integrated surface charge was calculated from the cyclic voltammetry in the range of 1.0 – 1.4 V vs RHE. The jungle-gym-type Ir catalyst recorded 2.3 times higher integrated surface charge compared to that of iridium black powder. If the mass activity is normalized by the integrated surface charge, turnover frequency (TOF) can be calculated, which is associated with the specific current density per electrochemically active surface area. [2] TOF values 1.8 times higher than iridium black were observed in the case of jungle-gym-structured one. The efficiency of the catalyst utilization has been maximized due to the novel structure, achieving a high ratio of surface area to the mass of the structure as high as that of Ir Black catalysts. Moreover, the jungle-gym nanostructure within the catalyst layer enhanced the intrinsic activity of the catalyst due to the accelerated mass transport within the catalyst layer.

Reference

[1] Aricò, A. S., et al. "Polymer electrolyte membrane water electrolysis: status of technologies and potential applications in combination with renewable power sources." Journal of Applied Electrochemistry2 (2013): 107-118.

[2] Abbott, Daniel F., et al. "Iridium oxide for the oxygen evolution reaction: correlation between particle size, morphology, and the surface hydroxo layer from operando XAS." Chemistry of Materials18 (2016): 6591-6604.