bluuebunny/crossref_metadata_2025 huggingface dataset:
On-Chip Microsupercapacitors Using Ultrathin Lipon Film
Authors: Sallaz Valentin , Oukassi Sami , Poulet Sylvain , Voiron Frédéric , Bedjaoui Messaoud , Salot Raphaël , Berardan David
Published: February 2020

On-chip solid-state micro-supercapacitors (MSCs) have been the center of massive researches over the recent years due to their wide range of applications (wearables, IoT, etc.), and the unremitting need for miniaturization and high electrical performances1. Moreover, MSC are known to gather high power density and extremely long cycle life2. In particular, the use of stable solid-state electrolytes in MSC is required to overcome safety issues (electrochemical and temperature instabilities) and enable easy packaging for on-chip integration3.

Lithium phosphorous oxinitride (LiPON) solid-state electrolyte has aroused a growing interest for MSCs due to its well-known excellent electrochemical properties (ionic conductivity, potential and temperature stability, etc.)4. Furthermore, the recently proved feasibility of ultrathin and conformal films deposition5,6 makes LiPON a particularly interesting candidate for energy storage solutions with high aspect ratio architectures. To the best of our knowledge, no study has reported on the use of ALD LiPON for MSCs.

In this work, we propose a thorough study of a 2D-planar ultrathin LiPON film for inorganic solid-state on-chip MSC. We obtained an uniform and homogeneous 10nm thick LiPON from the LiOtBu-DEPA chemical reaction. The elemental composition of the as deposited LiPON is determined by X-ray Photoelectron Spectroscopy as Li1.75PO2.5N0.6. The associated ionic conductivity is calculated around 10-8 S/cm at 25°C, and an activation energy of 0.62 eV is extracted using Electrochemical Impedance Spectroscopy within 20-50°C range.

TiN/LiPON/Ti MIM structures have been considered to characterize our MSC. The fabricated device exhibits typical capacitance values as high as 100 µF/cm² for scan rates up to 1 V/s. The capacitive and faradaic dependences of MSC will be discussed. A good cycling ability (>103 cycles) within the 0 – 3V voltage range is also recorded by applying a constant current of 100 µA/cm². Rate dependence and voltage stability window of MSC will also be reported.

References:

1. F. Béguin, V. Presser, A. Balducci and E. Frackowiak, 2014, 2219–2251.

2. N. A. Kyeremateng, T. Brousse and D. Pech, Nat. Nanotechnol., 2016, 12, 7–15.

3. Y. Huang, Y. Huang, M. Zhu, W. Meng, Z. Pei, C. Liu, H. Hu and C. Zhi, ACS Nano, 2015, 9, 6242–6251.

4. L. Le Van-Jodin, F. Ducroquet, F. Sabary and I. Chevalier, Solid State Ionics, 2013, 253, 151–156.

5. T. Göhlert, P. F. Siles, T. Päßler, R. Sommer, S. Baunack, S. Oswald and O. G. Schmidt, Nano Energy, 2017, 33, 387–392.

6. A. J. Pearse, T. E. Schmitt, E. J. Fuller, F. El-Gabaly, C. F. Lin, K. Gerasopoulos, A. C. Kozen, A. A. Talin, G. Rubloff and K. E. Gregorczyk, Chem.
Mater., 2017, 29, 3740–3753.

Figure 1
Perforation Optimization of DMFC Anode Porous Medium
Authors: Alrashidi Abdullah , Liu Hongtan , Zhang Xu
Published: February 2020

Carbon Dioxide management is essential to the development of Direct Methanol Fuel Cell Anode. CO2 bubbles evolution at the anode can create large mass transport loss and block the sites where the triple phase boundary occurs for the electrochemical reaction. The gas can be trapped in the Gas diffusion layer (GDL) and block the channels from the incoming fuel [1-2]. Researchers have studied the mechanism and the dynamics by visualizations of how CO2 bubbles evolve from the catalyst layers [3-5]. Some studies have been done to the anode structure to improve the performances by modifying the material, wettability, porosity and thickness [6-8]. However, disagreements have been confirmed from different design aspects to whether those modifications reduce the mass transport loss or not [9-11]. In this study, pathways/perforations were created by laser perforating the Gas Diffusion layer (GDL) to enhance the mass transport from and to the catalyst layer. Results have shown superiority of the perforated GDL over the conventional GDL. Further optimization of the perforation diameter, the spacing along the lateral and channel directions have been accomplished. First, the perforation diameter size was investigated with minimum number of holes, 16 holes, spaced with 2 millimeters in lateral and channel directions over the 1 cm^2 active area of the electrode, as can be seen in Figure 1A. The 60-micron diameter showed little improvement over the virgin GDL while further increase of the diameter caused massive mass transport loss. Secondly, further optimization of the spacing in the lateral and channel directions in Figure 1B, it was found that the 60-micron diameter with 1 millimeter in lateral spacing and 2 millimeter in channel spacing increased the maximum power density by roughly 30% compared to virgin GDL.

Figure1: A) Different perforation diameter ranging from 60-500 micron with 16 holes; B) Spacing optimization in lateral and channel directions.

Figure 1
Electrocatalytic Performance of Palladium-Based Electrocatalysts Supported on Carbon Nanotubes for Formic Acid Oxidation
Authors: Juárez-Marmolejo Leticia , Montes de Oca-Yemha Maria Guadalupe , Palomar-Pardavé Manuel , Romero-Romo Mario Alberto , Ezeta-Mejía Araceli , Arce-Estrada Elsa , Pérez-Rodríguez Sara , Lázaro Maria Jesus
Published: February 2020

Recently, the study of carbon supports like carbon nanotubes (CNT) has intensified. The interaction between the support and nanoparticles improved the efficiency and durability of fuel cells (FCs), decreasing the electrocatalyst poisoning and in some cases it can modify the particle size. Palladium based nanostructured electrocatalysts, supported on glassy carbon [1], carbon black Vulcan [2] and CNT [3] are used in electrochemical energy storage devices such as FCs.

In the present work, Pd and PdFe nanoparticles supported on CNT with and without functionalization (CNT and CNTox) were used for Formic Acid Oxidation Reaction (FAOR) in acid media. Electrocatalysts were synthesized by the borohydride reduction method with a metal loading of 20 wt.%. The CNTs were synthesized by the methane catalytic decomposition, and subjected to an oxidation treatment with nitric acid, named as CNTox. The morphology, composition and structural properties were studied by Transmission Electron Microscopy (TEM), Scanning Electron Microscopy-Energy Dispersive X-ray (SEM-EDX) and X-Ray Diffraction (XRD). The FAOR was evaluated in acid media in a conventional three-electrode cell by means of cyclic voltammetry and chronoamperometry. From the steady state current density it was found that that Pd and PdFe supported at CNTox allowed improving the catalytic activity in comparison with the non-oxidized support as shown in Figure and Table 1.

Figure 1.Potentiostatic transients of the Pd base electrocatalysts supported at CNT and CNTox at 0.4 V for 900 seconds and Table 1. Comparison of steady-state current density of synthesized electrocatalysts to the potential of 0.4 V.

I.E. Espino-López, M. Romero-Romo, M.G. Montes de Oca-Yemha, P. Morales-Gil, M.T. Ramírez-Silva, J. Mostany, M. Palomar-Pardavé. Journal of The Electrochemical Society 166 (2019) D3205.

L. Juárez-Marmolejo, S. Pérez-Rodríguez, M.G. Montes de Oca-Yemha, M. Palomar-Pardavé, M. Romero-Romo, A. Ezeta-Mejía, P. Morales-Gil, M.V. Martínez-Huerta, M.J. Lázaro. International Journal of Hydrogen Energy 44 (2019) 1640.

H. Yan, Z. Bai, S. Chao, Q. Cui, L. Niu, L. Yang, J. Qiao, K. Jiang, Ionics 20 (2014) 259.

Figure 1
The First Durable Imidazolium-Based Radiation Grafted Anion Exchange Membranes for Alkaline Fuel Cells: The Impact of Water Management
Authors: Mahmoud Ahmed Mohamed Ahmed , Yoshimura Kimio , Hiroki Akihiro , Maekawa Yasunari
Published: February 2020

Recently, Radiation grafted anion exchange membranes (AEM) gained increasing interest for alkaline fuel cell applications due to their high performance such as the highest power density ever reported for alkaline fuel cells (>2W/cm2). 1 However, their durability under operating fuel cell conditions still the biggest challenge.2 In our group, several radiation grafted AEMs, having several imidizalium-based graft-polymers consisting of N-vinyl (NVIm), 2-methyl-1-vinyl- (NVMIm), 2-methyl-4-vinyl- (4VMIm), and 2-(4-ethenylphenyl)-imidazolium (2StIm) graft-polymers, have been developed.3,4 In this work, the durability of the membrane-electrode-assembly (MEA) consisting imidazolium based radiation grafting AEMs under the supply of H2 and O2 at 60 °C was investigated in comparison to the MAE with common benzyl trimethylammonium (BTMA) based membranes. The core of this study is to investigate the effect of water management and specifically the dew point of the flow gas at anode and cathode sides on the performance and durability of imidazolium based membranes. For example, by tuning the due points for NVMIm-AEM the maximum power density increased from 115 to 200 mW/cm2. On the other hand, In spite of the low durability of 4VMIm membranes under in-situ alkaline durability in solution,5 the 4VMIm retained 75 % of the initial voltage after 240 h under fuel cell conditions, that was more durable than BTMA-based MEA (Figure 1). This study reveals the main role of water management of AEMs not only on the performance but also on the membrane durability. The study discloses an alternative durable AEMs for the new generation of alkaline fuel cells and other energy applications.

References:

1- L. Wang, M. Bellini, H. A. Miller, J. R. Varcoe J. Mater. Chem. A
2018, 6, 15404.

2- A. M. A. Mahmoud, K. Miyatake J. Mater. Chem. A.
2018,6, 15456.

3- K. Yoshimura, A. Hiroki, H-C. Yu, Y. Zhao, H. Shishitani, S. Yamaguchi, H. Tanaka, Y. Maekawa J. Memb. Sci.
2019, 573, 403-410.

4- Maekawa et.al, Soft Matter, 2018,14, 9118-9131.

5- Maekawa et. al, ECS Trans.
2017, 80, 8, 979-987.

Figure 1
Sol-Gel Assisted Synthesis of Encased Polymer Electrolyte Fuel Cell Cathode Catalysts
Authors: Farghaly Ahmed A. , Myers Deborah J.
Published: February 2020

State-of-the-art polymer electrolyte fuel cell (PEFC) cathode catalyst layers (CCLs) are composites of proton-conducting perfluorosulfonic acid (PFSA) ionomer and platinum alloy catalyst particles. The PFSA is in the form of agglomerates dispersed throughout the CCL and also as a thin film coating the carbon support and platinum alloy particle surface.1 The thin PFSA film on the catalyst surface has been shown to both decrease oxygen reduction reaction (ORR) activity and cause high oxygen transport resistance.2-4 Such ionomer-catalyst surface interactions can negatively affect both PEFC performance and durability.

This talk will describe an approach to addressing the issues of ionomer poisoning of ORR activity, local oxygen transport resistance, and the lack of PEFC cathode performance durability by encasing Pt and Pt alloy catalyst particles in the cavity of a 3D porous inorganic framework. Platinum (Pt) and platinum alloys (PtxMy) encased in 3D porous inorganic nanocrystal catalysts have been prepared by a sol-gel process combined with chemical reduction. Catalysts with 5, 10 and 20 Pt/PtxMy wt% have been prepared and their ORR activity has been evaluated using the thin-film rotating disk electrode (TF-RDE) technique. The platinum content in the encased catalysts has been determined using inductively coupled plasma mass spectrometry (ICP-MS) and X-ray fluorescence (XRF). The morphology, crystal structure, and spatial distributed of the metal nanoparticles have been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and energy-dispersive X-ray spectroscopy, respectively.

References

C. Cetinbas, R. K. Ahluwalia, N. N. Kariuki, and D.J. Myers, J. Electrochem. Soc.,
165(13), F1051 (2018).

Kongkanand and M. F. Mathias, J. Phys. Chem. Lett., 7, 1127 (2016).

Subbaraman, D. Strmcnik, A. P. Paulikas, V. R. Stamenkovic, and N. M. Markovic, Chemphyschem, 11, 2825 (2010).

Subbaraman, D. Strmcnik, V. Stamenkovic, and N. M. Markovic, J. Phys. Chem. C, 114 8414 (2010).

Acknowledgements

This work was supported by the United States Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office. Argonne is a U.S. Department of Energy Office of Science Laboratory operated under Contract No. DE-AC02-06CH11357 by UChicago Argonne, LLC.
Effect of Carbon Support on Fe-N3/C Model Active Site for the Oxygen Reduction Reaction
Authors: Fruehwald Holly M , Zenkina Olena V , Easton E. Bradley
Published: February 2020

Non-precious metal catalysts for the oxygen reduction reaction (ORR) are of great interest for fuel cell technology due to their low cost and wide availability of materials. Development of these catalysts has been a constantly growing area. However, there have been very few literature reports that provide insights into the precise nature of the structure and geometry of the catalytically active sites formed in these materials.

In the current literature, the most commonly proposed catalytically active site(s) for ORR corresponds to Fe-N2+2/C geometry. This is typically produced through a high temperature pyrolysis step to obtain this desired configuration in the active sites[1]. However, the pyrolysis step is very disadvantageous due to the production of a distribution of nitrogen functional groups on the surface which can negatively affect the activity of the catalyst, since only nitrogen functionalities with specified geometry are considered to be the most active for ORR[2,3]. As well, high temperature treatments increase the cost of production, and can be quite energy demanding. Thus, high-temperature treatment makes it difficult to design a surface rich in a specific active site for the desired application.

The work presented here demonstrates a model system for a non-precious metal catalyst for the ORR achieved by covalently functionalizing a conventional carbon support with a nitrogen-rich ligand. The terpyridine ligand geometry allows the formation of well-defined active catalytic sites when covalently attaching an N3/C functionality to the carbon surface, leaving exposed the most active sites for the ORR. Room temperature metal-ligand coordination with Fe results in desired Fe-N3/C moieties on the surface. We demonstrate that this system can be prepared using mild reaction conditions and does not require high temperature treatment for improved activity, in fact heat treatment to this system was detrimental to the activity. The Fe-N3/C support was subjected to electrochemical studies in both acidic and basic aqueous media and demonstrates the potential of this system to be used as a model for an Fe-N3/C active site for ORR.

References

[1] M. Lefèvre, E. Proietti, F. Jaouen, J.-P. Dodelet, Science
2009, 324, 71-74.

[2] F. Charreteur, F. Jaouen, S. Ruggeri, J.-P. Dodelet, Electrochimica acta
2008, 53, 2925-2938.

[3] H. M. Fruehwald, I. I. Ebralidze, O. V. Zenkina, E. B. Easton, ChemElectroChem
2019, 6, 1350.

Figure 1
Surface Coating with Porous Zirconia Layers Prepared By Atomic Layer Deposition for Stabilizing Fuel Cell Catalysts
Authors: Lim Jinhyuk , Koo Junmo , Kang Eun Heui , Park Jong Seon , Kim Keun Hee , Choi Hyung Jong , Shim Joon Hyung
Published: February 2020

Many automakers have recently developed and commercialized electric vehicles that operate on polymer electrolyte membrane fuel cells (PEMFCs). The most important component in PEMFCs is the platinum catalyst. Fuel cell electric vehicles are expected to be particularly useful for heavy-duty cars including buses and trucks that operate at relatively high power for a relatively long-term per charge. Under these operating conditions, it is important to minimize aggregation of platinum (Pt) catalysts that tend to agglomerate in long-term high current (or high power) conditions. In this study, we propose the surface coating of zirconia (ZrO2) using atomic layer deposition (ALD) to prevent the aggregation of fuel cell catalysts. ALD is the most advanced technology for thin film deposition because it can control thickness and composition at the atomic scale. Another advantage of ALD is conformal coating along the surface of complex 3D features. With these unique properties, ALD has successfully demonstrated uniform surface coatings on nanoparticles. One cycle of ALD is generally less than 0.1 nm in many cases, which can in principle form a porous film. We selected ZrO2 as a coating material because of its high thermal and phase stability. As a result, we have succeeded in uniformly depositing ALD ZrO2 as a porous film on the surface of the nano-size metal catalyst, and confirmed that it is truly effective in preventing agglomeration of catalysts in a long-term fuel cell operation.
Understanding Electrochemical Degradation of Polymer Electrolyte Fuel Cell Catalysts Using Time-Resolved Measurements
Authors: Kariuki Nancy N. , Papadias Dionissios D. , Myers Deborah J. , Ahluwalia Rajesh
Published: February 2020

The catalysts of choice in polymer electrolyte fuel cells (PEFCs) remain Pt-based nanoparticles on high-surface-area carbon support. One critical challenge facing commercialization of this fuel cell is the gradual decline in performance during operation, mainly caused by the loss of electrochemical surface area (ECA) of the Pt or Pt alloy nanoparticles at the cathode and, if an alloy, loss of the base metal alloying component (e.g., Co, Ni, or Fe). In this respect, the understanding of the dominant mechanisms of the loss of ECA and loss of oxygen reduction activity, such as the electrochemical dissolution of Pt or the base metal, is of vital importance. Several mechanisms for dissolution of platinum have been proposed including direct Pt dissolution and electrochemical oxidation of the Pt surface atoms followed by chemical dissolution of the resulting Pt surface oxide. Our previous measurements on PtCo catalyst showed that degradation of PtCo/C catalysts due to Pt dissolution is greatly accelerated by the reduction of PtOx species formed at potentials >0.9 V and that accelerated Co loss is also associated with reduction of the oxides formed at >0.9 V. 1

This presentation will outline effects of type of Pt alloy catalyst (e.g., solid solution, ordered intermetallic, shape-controlled) on Pt and alloying element dissolution rates as a function of number of accelerated stress test cycles. Studies are performed to quantify the amount of dissolved base metal and Pt during potentiodynamic conditions in an electrochemical flow cell system connected to an inductively-coupled plasma-mass spectrometer (ICP-MS) capable of detecting trace concentrations (<ppb) of dissolved elements in solution. The electrochemical data combined with the ICP-MS data are used to evaluate the influence of various factors such as potential, potentiodynamic profile parameters (e.g., scan rate, upper and lower potential limits), atomic structure, and base metal content on the dissolution processes of alloy catalysts in acidic electrolytes at room temperature. Fundamental models will be developed to explain the mechanisms of degradation process for the various catalyst types under various potential conditions.

References

K. Ahluwalia, D. D. Papadias, N. Kariuki, J. K. Peng, X. P. Wang, Y. Tsai, D. Graczyk, and D. J. Myers, J Electrochem Soc, 165, F3024 (2018)

This work was supported by the U.S. Department of Energy, Energy Efficiency and Renewable Energy, Fuel Cell Technologies Office under the auspices of the Fuel Cell Performance and Durability Consortium (FC-PAD). Argonne National Laboratory is managed for the U.S Department of Energy by the University of Chicago Argonne, LLC, also under contract DE-AC-02-06CH11357.
Computational Screening of Single-Atom Electrocatalysts for Oxygen Reduction Reaction By Machine Learning Algorithm
Authors: Lin Shiru , Chen Zhongfang
Published: February 2020

In this work, we advanced emerging descriptor-based screening and machine learning techniques to identify new families of catalysts to be synthesized. We present a computaional flow to evaluate the catalysis performance of single-atom catalysts for oxygen reduction reaction (ORR). The onset potentials of single-transitional metal on graphene defects computed by density funtional theory (DFT) were used as our input data, and electronegativity of metal atoms and surrounding atoms (C, N or B), the coordinate numbers of central metal atoms and neighbor atoms were set as the intrinsic features for predicting catalysis performance. We used random forest algorithm to train the machine learning model, and employed this moderl to generate prominent single-atom catalysts for ORR. The predictive model can predict the onset potential directly from the structural properties of single-atom-base systems, which is a great progress from the models which can only predict the adsorption energy of intermediates. Therefore, we applied various single-atom catalysts systems with structural information, and the model screened out the most promising ones among them. This work demonstrates that the collocation of traditional computational chemistry and data-driven science can rapidly expand computing power and solve the most challenging catalysis problems!
Theoretical Prediction of the Distribution of Spin Moment on Metal-N-C Catalyst Embedded in Truncated Graphene Sheets
Authors: Oguz Ismail Can , Jaouen Frederic , Mineva Tzonka
Published: February 2020

As a pristine graphene nanostructure, zigzag graphene nanoribbons (ZGNRs) has received considerable interest over the past decade due to the presence of polarizable edge states1. It has also been employed as a model system for non-precious metal catalysts since it can host a variety of active sites2. Among various classes of catalysts, metal (Me) and nitrogen co-doped graphene has been emerging as promising electrocatalysts in oxygen reduction reaction (ORR). Furthermore, it has also been shown that porphyrin-like Me vacancy embedded in graphene is more stable at edges than far-away from the edges3. In the light of those recent studies, the change of spin states on the edge and in the bulk caused by Fe and N co-doping is an essential factor to tune the electronic and magnetic states on graphene. Therefore, unraveling spin interactions between co-doped metal-nitrogen complex and edge states (illustrated in Fig. 1) can control the electronic conductivity of doped graphene sheets and electron density at metal active sites, which is essential for their applications in electrocatalysts.

In this work, the effect of nitrogen-metal and vacancies in the bulk and edge configurations on the spin polarization on graphene materials will be presented as obtained from two computational methodologies: plane waves and atomic-centered Gaussian functions. There are some drawbacks on each DFT code regarding magnetic calculations. Sensitivity of the value of total magnetic moment in VASP obtained from Bravais lattice depends on k-point sampling, smearing parameters and stress applied to unit cell. On the other hand, the initial spin moment guess on each atom is not implemented on deMon2k to be able to obtain anti-ferromagnetic states of graphene.

Finally, the ORR reactivity as a function of (a) the metal location in graphene and (b) the edge truncations will be discussed.

Figure 1:

Suppression of spin polarization in edge modification by Fe
N4

Acknowledgement: This work is supported by the LabEx CheMISyst ANR-10-LABX-05-01.

References

Son, Y.-W.; Cohen, M. L.; Louie, S. G. Half-metallic graphene nanoribbons. Nature
2006, 444, 347

Zitolo, A. et al. Identification of catalytic sites for oxygen reduction in iron- and nitrogen-doped graphene materials. Nature Materials
2015,
14, 937–942

Holby, E. F.; Taylor, C. D. Control of graphene nanoribbon vacancies by Fe and N dopants: Implications for catalysis. Appl. Phys. Lett.
2012,
101, 064102

Figure 1
Comparing Mitigation Techniques for Effective CO Mitigation in a Polymer Electrolyte Fuel Cell
Authors: Sarma Paran Jyoti , Gardner Chris , Chugh Sachin , Sharma Alok , Kjeang Erik
Published: February 2020

The presence of carbon monoxide impurities in hydrogen can be a major deterrent to polymer electrolyte fuel cell (PEFC) performance. CO molecules present in hydrogen fuel rapidly get adsorbed on the platinum (Pt) active sites at the anode electrode and deactivate the surface reactions responsible for hydrogen oxidation [1]. On the other hand, obtaining 99.999% hydrogen purity requires major purification processes driving up the cost of hydrogen fuel [2]. To realise an economical hydrogen fuel price for fuel cell applications, reformate hydrogen containing CO can be used along with a suitable mitigation technique to reduce the adsorption of CO on Pt surface by means of oxidation or stripping. Catalyst modifications, air bleeding [3] and pulsed oxidation [4, 5] are commonly used techniques to resolve CO contamination issues in fuel cells. However, a detailed comparison of these techniques to define the efficiency as well as performance improvement in presence of CO contaminated fuel is not available.

In this work, we present a comparison of results and scientific explanation of the use of various mitigation techniques to alleviate the effect of CO on the performance of a PEFC. Experiments were carried out on a single cell fuel cell at 80 ºC having modified anode catalyst (Pt/C and Pt-Ru/C) and a Pt/C cathode catalyst. CO mixed with pure hydrogen was fed to the anode and air was fed to the cathode. The cell potential was monitored when the fuel source was switched from pure hydrogen to CO doped hydrogen at a constant current density to study the impact of poisoning. Anode catalyst modification with ruthenium resulted in 200 mV increase in CO tolerance compared to platinum at a constant current density. Air bleeding in presence of Pt/C and Pt-Ru/C showed similar results in performance which caused a gradual potential loss when operated for extended periods. However, when pulsed oxidation was employed, the cell potential remained close to pure hydrogen potential ranges even for longer testing periods.

Acknowledgement: This work was supported by Indian Oil Corporation (R&D) and Simon Fraser University under the SFU-IOCL joint PhD program in clean energy.

[1] M. Abdollahi, J. Yu, P. K. T. Liu, R. Ciora, M. Sahimi, T. T. Tsotsis, J. Membrane Science, 390-391, 32 (2012)

[2] D. Jansen, J. W. Dijkstra, R. W. van den Brink, T. A. Peters, M. Stange, R. Bredesen, A. Goldbach, H. Y. Xu, A. Gottschalk, A. Doukelis, Energy Procedia 1, 253 (2009)

[3] L-Yu Sung, B-Joe Hwang, K-Lin Hsueh, W-Nien Su, C-Chung Yang, J. Power Sources 242 (2013) 264-272

[4] C.G. Farrell, C.L. Gardner and M. Ternan, J. Power Sources, 117, 282 (2007)

[5] A. H. Thomason, T. R. Lalk, A. J. Appleby, J. Power Sources 135 (2004) 204-211
Chemical Structure Control of Metal-Reduced Organic Framework-Supported Nitrogen-Doped Graphene Catalyst for Oxygen Reduction Reaction
Authors: Zhuang Shiqiang , Singh Harsimranjit , Lee Eon Soo
Published: February 2020

Nitrogen-doped graphene (N-G) has a huge potential in many electrochemical systems such as fuel cells due to the high raw material cost of platinum group metal (PGM) catalysts. However, there is a significant gap between the current level of electrochemical performance of N-G catalysts and that of PGM catalysts. Here we report an advanced metal-reduced organic framework-supported N-G catalyst (N-G/MOF-x) prepared by functionalizing ZIF-8 and N-G using nanoscale high energy wet ball milling method. The chemical structure control of the N-G/MOF was studied by characterizing the variation of elemental composition and chemical bonding composition of synthesized samples throughout targeted grinding speeds. The results proved that the chemical interaction between ZIF-8 and N-G caused the reduction of nitrogen, oxygen and zinc atoms, and also the variation of chemical bonding composition in N-G/MOF-x. The reduction rate of zinc was gradually increased with the increasing grinding speed, and reached to 82% of zinc loss at 650 RPM. The characterization of carbon and nitrogen bonding composition confirmed that the loss of nitrogen, oxygen and zinc atoms was caused by the decomposition of the C-N-Zn heteroatom contents in ZIF-8 and the O-containing functional groups in N-G, and influenced by the grinding speed. The decomposition ZIF-8 not only influenced the pore structure, but also modified the chemical structure and the surface distribution of N functional groups-constituted active sites in N-G/MOF-x. The N-G/MOF catalyst has comparable electrochemical performance to 10 wt% Pt/C catalyst. The successful accomplishment of the N-G/MOF catalysts will provide the substantial way to the cost-effective and fuel-efficient energy conversion system.
Moving Anion Exchange Membrane Fuel Cells Towards Realistic Operating Conditions
Authors: Ul Hassan Noor , Adabi Firouzjaie Horie , Mustain William E.
Published: February 2020

Anion Exchange Membrane fuel cells have been touted as a potentially very low cost energy conversion device for both transportation and stationary applications. On the positive side, the past couple of years has seen a meteoric rise in the achievable peak power density and longevity of these devices – in fact > 3 W/cm2 peak power and > 1000 h life have been demonstrated. The biggest criticism of this recent work is that essentially all of these ultra-high performing cells have achieved such performance at very high reacting gas flow rates (typically 1 L/min in 5cm2 cells) with ultra-high purity O2 and H2. It is likely that these operating conditions have been needed to overcome mass transport limitations in existing cell architectures – either anode flooding or low electrode porosity from ionomer swelling. Such high reactant stoichiometries and the use of high purity gases are not realistic operating conditions for deployed fuel cells. Therefore, this study will focus in two areas. The first is the development of strategies to allow AEMFCs to operate at much lower flow rates (at least 1/5th of previous reactant stoichiometries) while achieving comparable performance. The second focus area will be the use of air at the cathode, both CO2-containing (400 ppm) and CO2-free. The end result of this work has been much better utilization of the reacting gases as well as a much better understanding of how to stabilize AEMFC operation for long runs in order to test the true durability of active materials in-situ.
Improving Reactant and Proton Transport in Catalyst Layers for Direct Alcohol Fuel Cells
Authors: Hauenstein Pascal , Thiele Simon
Published: February 2020

Direct alcohol fuel cells (DAFC) produce electricity from liquid fuels such as methanol, ethanol etc., where the alcohol is oxidized at the anode and oxygen is reduced on the cathode side of the fuel cell. Operation of alcohol fuel cells is attractive because of the exceptionally high volumetric energy density and easy handling of liquid fuels in comparison to pressurized hydrogen. [1] Especially direct methanol fuel cells (DMFC) have been widely investigated as portable power sources. However, even with these relatively simple fuels, the reaction kinetics of the electro-oxidation are slow in comparison to hydrogen oxidation. Furthermore, DAFC suffer from severe reactant crossover through the membrane, leading to low open circuit voltages and poor overall performance. [2] In order to solve crossover issues, manufacturing of various composite membranes and additional alcohol blocking layers become more and more important in this research field. [3] Nonetheless, also understanding and improving reactant and proton transport in catalyst layers for DAFCs is very important in order to improve current densities and reduce costs, as less expensive platinum group metal catalysts are needed. Commonly, very high loadings on the anode side of DAFC result in thick catalyst layers, which suffer from poor reactant transport and high proton resistances and flooding, especially in the high current density regions.

Our work to be presented is focused on novel architectures of membrane electrode assemblies (MEAs) for applications in direct alcohol fuel cells to target these problems and improve the physical properties of the catalyst layer with a focus on different ionomers, different ionomer contents, and pore size distribution.

[1] R. P. O'Hayre, F. B. Prinz, S.-W. Cha, W. G. Colella, Fuel cell fundamentals, Third edition ed., Wiley, Hoboken, 2016.

[2] C. Xu, A. Faghri, X. Li, T. Ward, International Journal of Hydrogen Energy
2010, 35, 1769–1777.

[3] P. Prapainainar, N. Pattanapisutkun, C. Prapainainar, P. Kongkachuichay, International Journal of Hydrogen Energy
2019, 44, 362–378.
Bio Derived Electrocatalyst : Co2p Nanoparticles Supported on Heteroatom Doped Carbon for Highly Efficient Oxygen Reduction
Authors: Lee Dong Wook , Jang Injoon , Jang Jue-Hyuk , Lee Kwan Young , Yoo Sung Jong
Published: February 2020

The biggest issue in the fuel cell, which is believed to be the promising candidate as the next generation power source, is the oxygen reduction reaction (ORR). Due to the relatively high ORR activity, Pt-based catalysts are used predominantly, however, the scarcity, high cost and unsatisfactory durability of Pt make it difficult for commercialization of fuel cell. In this work, we developed a heteroatom doped carbon supported Co2P catalyst through the eco-friendly and simple method using bean sprouts. Final product exhibits excellent ORR activity and superior durability in alkaline media. The value of the half wave potential of NBSCo is 10 mV higher than that of commercial Pt/C. The excellent oxygen reduction activity is attributed to the synergistic effect of Co2P and N-doped carbon. NBSCo was applied in anion exchange membrane fuel cell (AEMFCs). At the optimized cathode composition, the NBSCo produce the max power density of 172 mW cm-2. It is considered to be competitive performance and it has demonstrated the potential for application to energy storage systems.
Structure-Transport Relationships of Anion Exchange Membranes
Authors: Luo Xiaoyan , Kusoglu Ahmet
Published: February 2020

Anion exchange membrane (AEM) fuel cells are emerging energy conversion technologies. A significant challenge in these devices lies in the core component, the AEM, which must possess high ionic conductivity to minimize Ohmic losses and exhibit chemical stability in highly basic conditions. A significant amount of effort has been expended to develop new anion exchange polymers with enhanced transport functionality. However, understanding of how anion transport in these polymers is related to hydration and nano-morphology is far from adequate. In this work, we report a systematic study on PAP-TP-85, an AEM with promising cell performance.1 A commercial AEM (Fuma FAA3) is used for comparison in this study. Membrane water uptake and anion conductivity in liquid and vapor as well as the impact of various anion forms on these properties are investigated. Small-angle X-ray scattering (SAXS) is used to probe hydrated AEM nanostructure, which is correlated to the membrane uptake and transport properties. Our results show that these AEMs lack a phase-separated nanostructure, regardless of their counter-anion form and hydration level. This is associated with their weak electrolytes behavior, which also explains their lower ion conductivity values (compared to proton exchange membranes), despite having higher water content and greater ion exchange capacity (IEC). Water content plays a more significant role than the temperature in controlling the anion conductivity of these weak electrolytes in water vapor. Comparing the water content in liquid vs. saturated vapor, both AEMs show Schroeder’s paradox regardless of counter-anion form. This study also demonstrates the importance of hydration level and ion concentration for anion transport in amorphous AEMs and provides further understanding into their parameters governing their structure-transport relationship and sheds light into designing AEMs with improved performance.

Wang, J.; Zhao, Y.; Setzler, B. P.; Rojas-Carbonell, S.; Ben Yehuda, C.; Amel, A.; Page, M.; Wang, L.; Hu, K.; Shi, L.; Gottesfeld, S.; Xu, B.; Yan, Y., Poly(aryl piperidinium) membranes and ionomers for hydroxide exchange membrane fuel cells. Nature Energy
2019.
(Invited) Poly(norbornene) Hydroxide Conductive Polymers: Stable, High Conductivity Hydroxide Conducting Block Copolymer Membranes and Their Applications
Authors: Kohl Paul A , Mandal Mrinmay , Huang Garrett
Published: February 2020

Block copolymer, anion-exchange membranes (AEM) were synthesized using the vinyl-addition polymerization and ring-opening metathesis polymerization of norbornene monomers. The intended use is for use electrochemical devices operating at high pH including fuel cells, electrolyzers, and flow batteries. The focus of this talk is on the impact very high conductivity AEM with low water uptake on device performance. The low molecular weight of the norbornene monomers enabled the design of very high ion exchange capacity (IEC) membranes, up to 4.73 meq/g. A wide variety of norbornene monomers are available allowing for the synthesis of membranes with optimized properties. The norbornene backbone is an all-hydrocarbon structure giving the polymers excellent chemical stability in 1 M NaOH at 80°C. The monomers were synthesized into a multi-block copolymer with hydrophilic and hydrophobic blocks. AEM membranes were solvent cast with and without a supporting polymer reinforcement. The hydrophobic, ion-conducting block of the copolymers formed a lamellar phase during casting.

Tetrablock copolymers synthesized by vinyl-addition reaction had an IEC of 1.88 meq/g and conductivity of 123 mS/cm at 80°C. Light cross-linking was found to provide a critical control of water uptake allowing the incorporation of very high IEC without unwanted water uptake. Without light cross-linking, unwanted water uptake would cause swelling and softening of the membrane at high IEC values, as with other AEMs. Thus, the path to achieving exceptionally high ionic conductivity includes high mobility ion channels (achieved here through the use of block copolymers), and light crosslinking to permit the use of high IEC values (e.g. approaching 4 meq/g). The best performing membrane had an ionic conductivity of 212 mS/cm at 80°C. There was little or no drop in ionic conductivity over 1,000 h of aging in 1 M NaOH at 80°C. This is the highest reported hydroxide conductivity at 80°C to date for a chemically stable AEM. The number of bound and free water molecules per ion pair were measured in order to analyze the role of water. The membranes are suitable for electrochemical devices and were used in AEM fuel cells and electrolyzers.
Development of ACLS Electrodes for a Water Electrolysis Cell
Authors: Yoshinaga Norihiro , Kanai Yuta , Fukazawa Taishi , Nakano Yoshihiko , Mei Wu
Published: February 2020

1.Introduction

Water electrolyzers are important devices for power-to-gas systems. Compared with other types of water electrolyzers, polymer electrolyte membrane (PEM) electrolyzers have the advantages of quick response, small footprint, ability to generate high gas pressure than other types of electrolyzers, and high durability against ON/OFF cycling1. The anode of PEM electrolyzers is conventionally an iridium oxide electrocatalyst powder combined with a platinum coating layer on a porous titanium layer (PTL)2,3. However, these noble metal catalysts are scarce and expensive, and reducing their use is essential for PEM electrolyzers. At Toshiba, we have developed an alternating catalyst layer structure (ACLS) catalytic electrode composed of multiple iridium oxide sheets and air gap layers without a platinum coating layer and fabricated by a sputtering process, and we are studying its application in PEM electrolyzers. In this presentation, we report the results of comparisons between powder and ACLS electrocatalysts used in PEM electrolyzers.

2.Experimental

First, iridium together with pore-forming metal was sputtered onto a commercially available PTL substrate and then only pore-forming metal was sputtered, and this process was repeated to deposit multiple layers (Figure 1). Then, the pore-forming metal was removed to prepare the ACLS anode. The loading of iridium metal was adjusted by the number of iridium layers. Next, an MEA was made by hot pressing of the ACLS anode, Nafion115®, and the Pt/C cathode. A conventional sprayed iridium oxide powder layer on Nafion115 and a platinum-coated PTL substrate was prepared for reference. Water electrolysis performance of the MEAs was measured in a single-cell configuration by supplying water to the anode side at 80℃ and applying current to the cell under atmospheric pressure.

3
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Results and discussion

Figure 2 shows the water electrolysis cell voltage at 2 A/cm2 for each type of anode with various iridium loadings. At a low iridium loading (0.1 mg-Ir/cm2), the voltage of the ACLS electrocatalyst (1.8 V) was lower than that of the powder catalyst (2.0 V). From Tafel plot analysis, this result is attributed to the low diffusional overpotential of the ACLS anode. We assume that its optimal porous structure increases the diffusivity of water and oxygen gas in the catalyst layer. Moreover, the ACLS anode showed almost no voltage rise up to 7000 h of operation without platinum coating on the PTL. The ACLS is effective for reducing the amount of noble metals used in PEM electrolyzers.

(1) K. E. Ayers et al., ECS Transactions, 41,15 (2012).

(2) C. Rakousky et al., J. Power Sources, 326, 120 (2016).

(3) C. Rozain et al., Appl. Catal. B Environ., 182,153 (2016

Figure 1
(Invited) Oxygen Evolution Reaction on M-Iridium Oxide (M=Ni, Co) Surfaces: Insights from First-Principles Computations and Experiments
Authors: Balbuena Perla B. , Camacho-Forero Luis E , Godinez-Salomon Fernando , Rhodes Christopher P.
Published: February 2020

Electrolysis of water to produce hydrogen using proton exchange membranes (PEM) is of great interest especially if the production can be coupled to a source of renewable energy, where the renewable hydrogen cycle could be achieved. The oxygen evolution reaction (OER) takes place at the anode of a PEM water electrolyzer and it is known to be the rate-determining step in the overall electrolysis process. Therefore, the catalytic activity for the OER must be improved, which only can be accomplished with a better knowledge and understanding of the OER mechanism. In this work, density functional theory calculations are used to analyze the OER reaction pathways on RuO2, IrO2, and M-doped Ir oxides (with M= Ni, Co) in order to get deeper insights of the importance of each of these stages in the water electrolysis process. The DFT studies are used to interpret and complement experimental synthesis, characterization, and electrochemical evaluation studies of novel Ir-Ni oxy-hydroxide 2-dimensional nanoframe electrocatalysts.
(Invited) Advanced in Situ Characterization of Energy Conversion Electrocatalysts
Authors: Shviro Meital , Gocyla Martin , Park Seongeun , Carmo Marcelo , Dunin-Borkowski Rafal E. , Stolten Detlef
Published: February 2020

Sluggish reaction kinetics to split water into hydrogen and oxygen are hindering the market penetration of water electrolyzers for renewable energy storage.1 It is therefore of paramount importance to design the next generation of electrocatalysts, which offer enhanced performance and maximize catalyst utilization, while guaranteeing a durability of approximately 50.000 hours. However, current synthesis and characterization methods for electrocatalysts are not satisfactory. In particular, innovative and transformative characterization methods are required to provide a detailed experimental understanding of physical-chemical/electrochemical relations between the atomic structures of electrocatalysts and their activity, stability and degradation.2

Here, we show how in situ transmission electron microscopy (TEM) and identical-location TEM can be used to follow dynamic changes in electrocatalyst morphology, faceting and elemental segregation under real electrochemical working conditions. We study the relationship between nanoparticle morphology, composition and activity and demonstrate the ability to tune the structure-stability relationships of bimetallic nanoparticles for use as electrocatalysts.

References

(1) Carmo, M.; Fritz, D. L.; Mergel, J.; Stolten, D. A Comprehensive Review on PEM Water Electrolysis. Int. J. Hydrogen Energy
2013, 38 (12), 4901–4934.

(2) Shviro, M.; Gocyla, M.; Schierholz, R.; Tempel, H.; Kungl, H.; Eichel, R. A.; Dunin-Borkowski, R. E. Transformation of Carbon-Supported Pt-Ni Octahedral Electrocatalysts into Cubes: Toward Stable Electrocatalysis. Nanoscale
2018, 10 (45), 21353–21362.
Development of Membrane Electrode Assemblies for State-of-the-Art Anion Exchange and Proton Exchange Membrane Electrolysis
Authors: Motz Andrew R , Capuano Christopher B , Ayers Katherine E.
Published: February 2020

Proton exchange membrane (PEM) electrolysis and anion exchange membrane (AEM) electrolysis are both able to directly produce high purity hydrogen from electricity and water. Key benefits of electrolysis using polymer membrane separators include a quick response rate, enabling load following, and ability to operate with high differential pressure. Operation under differential pressure allows for simultaneous electrolysis and electrochemical compression, simplifying overall system design. The development and stack integration of new, high performance electrolysis materials must include consideration of operating range and durability under differential pressure to maintain the technologic benefits.

PEM electrolyzers are commercially available on the megawatt scale and produce hydrogen fuel that is increasingly cost competitive with fossil fuel in select parts of the world. Better utilization of low cost electricity from renewable energy (wind and solar) is one route to additional hydrogen cost reductions, for which a wide current operating range is beneficial. Thinner membranes, more active catalysts, and better electrode design enable high currents at acceptable cell efficiencies. Performance and durability data will be presented on state-of-the-art PEM electrolyzer materials operating under differential pressure.

AEM electrolyzers are not currently commercially available, but promise membrane, catalyst, and balance of stack cost reductions. To begin to compete with PEM technology, performance and durability need to be improved. This work focuses on membrane stability under differential cell pressure and material integration into high performance AEM electrolyzers.