bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent Advances with Sulfonated Silica Ceramic Carbon Electrodes for Fuel Cells
Authors: Easton E. Bradley , Acheampong Richard , Alipour Moghadam Esfahani Reza , Cavallari Veronica J , Moghaddam Reza B. , Fruehwald Holly M , Afsahi Foroughazam
Published: February 2020

Sulfonated silica-based ceramic carbon electrodes (SS-CCE) are prepared using low-cost organosilane precursors that are mixed with the carbon-supported platinum (Pt/C) catalyst in monomer form, and subsequently polymerized and coated onto a gas diffusion layer in a single step. Our lab has demonstrated that that SS-CCEs can achieve similar H2/O2 fuel cell performance as conventional Nafion-based electrodes [1, 2]. Furthermore, these electrode structures display excellent tolerance to dry operating conditions, due to the proton conductivity of the sulfonic acid moiety and the hygroscopic nature of the SiO2 backbone. This is a major advantage over conventional Nafion-based fuel cell electrodes which require the use of heavily humidified gas feeds and are limited to temperature below 80 °C. Therefore SS-CCEs have great potential to improve PEMFC efficiency by reducing parasitic power losses required for gas humidification. Furthermore, they have the potential to reduce the required catalyst loading and extend the operating temperature range of PEMFCs. While these results have been promising, there are few detailed studies of SS-CCE structure-property. Likewise, their durability in operating fuel cells have yet to be proven.

In this presentation, we will give an overview of our group’s recent progress towards optimization the synthesis and structure of SS-CCEs. In particular, we have found hydrothermal conditions to be a promising way to enhance performance, promoting a more homogenous distribution of silicate ionomer and more effective bonding to the carbon surface [3]. Likewise, accelerated stress tests indicate that the silicate ionomer also serves to stability the Pt catalysts and enhance its durability [4]. This, along with their tolerance to high temperatures/low relative humidity conditions leads to improved stability of SS-CCE-based fuel cell systems.

References

[1] J.I. Eastcott, E.B. Easton, Journal of Power Sources, 245 (2014) 487-494.

[2] J.I. Eastcott, K.M. Yarrow, A.W. Pedersen, E.B. Easton, Journal of Power Sources, 197 (2012) 102-106.

[3] R. Alipour Moghadam Esfahani, R.B. Moghaddam, I.I. Ebralidze, E.B. Easton, Applied Catalysis B: Environmental, 239 (2018) 125-132.

[4] R. Alipour Moghadam Esfahani, H.M. Fruehwald, F. Afsahi, E.B. Easton, Applied Catalysis B: Environmental, 232 (2018) 314-321.

Figure 1
Development of Mesoporous Carbon Fibers for PEFC Catalyst Supports
Authors: Huang Ting-Wei , Nagayama Mayumi , Sasaki Kazunari , Hayashi Akari
Published: February 2020

Introduction

PEFCs have been known as an energy technology with high efficiency and low carbon emission. Among the components of PEFCs, the electrocatalyst layer is an important component to determine PEFC performance and mainly made by noble metal particles dispersed on carbon supports. In order to increase the efficiency and durability of electrocatalysts, our group has been focusing on developing novel carbon supports, and we have previously demonstrated the improvement of durability by utilizing mesoporous carbon (MC) with 6-8 nm pore size [1]. Even though the nanostructure of electrocatalysts has been successfully controlled, further control of the microstructure of electrocatalyst layers is required to improve efficiency of PEFC. In this study, we are trying to control the microstructure though making our MC into fibers with an electrospinning technique.

Experimental

MC fibers (MCFs) were synthesized by electrospinning the solution containing the resol-formaldehyde type resin polymer and Pluronic F127, after adding polyvinyl alcohol (PVA) as a polymer additive. Then, Pluronic F127 was removed by heat treatments to generate mesopores. MCFs were characterized by N2 sorption in order to analyze their mesoporosity. To make comparison on mechanical strength and conductivity among Vulcan® carbon black, MC, and MCF, FIB-SEM observation and electro-impedance measurements were performed, respectively, after spray printing carbon dispersions on the substrate. Electrochemical analyses were performed by both half-cell measurements in the solution and full-cell measurements with membrane-electrode assemblies (MEAs), after successful Pt deposition into mesopores of MCF.

Results and discussion

The morphology of MCF is shown in Figure 1, and both the fiber structure and mesopores were confirmed. The N2 adsorption measurement indicated the pore size of MCF is around 4-6 nm, which is slightly smaller than the pore size of MC. Regarding to the mechanical strength, MCF showed smaller change in the thickness after compression in comparison to the regular MC and Vulcan® carbon black. This probably comes from higher elasticity provided by the fiber structure. Moreover, according to the conductivity measurements, MCF showed higher conductivity than MC and Vulcan® carbon black. The higher conductivity is probably due to the fact that the fiber-fiber contact provides a better conductive path than the particle-particle contact.

From electrochemical analyses through half-cell measurements, Pt deposited MCF catalyst (Pt/MCF) showed similar ECSA and ORR activity to Pt deposited MC catalyst (Pt/MC). However, based on better mechanical strength and conductivity of MCF, advantages on full-cell measurements with MEAs are expected. Details of preparation and evaluation of MEAs will be discussed.

References

[1] Minamida　Y, Noda　Z, Hayashi　A,　and Sasaki　K, Development of MEAs with Pt/Mesoporous Carbon as a Cathode Catalyst. ECS Transactions, 64 (3) 137-144 (2014).

Figure 1
Towards High-Performance Proton Exchange Membrane Fuel Cells Using Polymer Coated Heteroatom Doped Partially Unzipped Carbon Nanotubes As Catalyst Support
Authors: Ramaprabhu Sundara , Seshadhri Garapati Meenakshi , Nechiyi Divya , Bacsa Wolfgang
Published: February 2020

Enhancing the durability and reducing the cost of Proton Exchange Membrane Fuel Cells (PEMFC) are the bottlenecks for the commercialization. Platinum is reported as the best electrocatalyst for both anode and cathode due to its optimum binding energy towards hydrogen, oxygen atoms and products during the hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR). The electrocatalyst loading at the anode and the cathode can be minimized by dispersing Pt nanoparticles (NPs) on high surface area and conductive carbon support material. The durability and performance of PEMFC depend on the interaction between the support and Pt NPs as well as the number of active sites available for the reactions, which can be enhanced by selective coating of proton conducting polymer on the hetroatom doped supporting material. In the present work, we have synthesized highly proton conducting polymer polyvinyl phosphonic acid (PVPA) coated heteroatom doped partially unzipped carbon nanotubes (H-PECNT) and used as the catalyst support material for Pt NPs. The heteroatom doping increases the ORR activity of the support material and the PVPA coating adhere Pt NPs to the support during cycling and also increases the active sites. Moreover, we have coated PVPA on H-PECNT by varying different ratios of PVPA to H-PECNT and to find the optimum PVPA percentage on H-PECNT, which enhances the performance of PEMFC. The single cell measurements deliver a high power density with 6% of PVPA than the commercial Pt/C as well as other PVPA ratios wherein both electronic conductivity of the support material and proton conductivity of PVPA contribute significantly to the performance.
Fully Ordered Pt3Co Intermetallic Nanoparticles Derived from MOFs for Oxygen Reduction in PEMFCS
Authors: Wu Gang
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) are considered to be a promising power source for electric vehicles and stationary residential applications. However, current PEMFCs have several problems that need to be overcome including high cost, insufficient power density, and poor performance durability. Current Pt-based cathodes for the oxygen reduction reaction (ORR) are primarily responsible for these issues. Development of advanced Pt-based catalysts are crucial for solving these problems in order for large-scale application of PEMFCs to be feasible. Recently, highly ordered PtM alloy catalysts have exhibited significantly enhanced activity and stability for the ORR in PEMFCs, which have attracted substantial attention. Based on our ongoing research projects [1-3], in this presentation, we introduced our recent progress to develop low-PGM catalysts with emphasis on the innovative synthesis methods of using pre-doped transition metals such as Co or Ni into metal–organic-framework (MOF)-derived carbon as the sources to prepare highly ordered PtM catalysts. As an example, ordered Pt3Co intermetallic nanoparticles through a facile thermal treatment of Pt nanoparticles supported on Co-doped MOF-derived carbon. Atomically dispersed Co sites are originally embedded into MOF-derived carbon. Then we can accurately control the diffusion of Co into Pt crystals and form ordered Pt3Co structures. It is very crucial for the formation of the ordered Pt3Co to carefully control the doping content of Co into the MOFs and the heating temperatures for Co diffusion. The optimal Pt3Co nanoparticle catalyst has achieved significantly enhanced activity and stability. The highly ordered intermetallic structure was retained after the accelerated stress tests made evident by atomic-scale elemental mapping. Fuel cell tests further verified the high intrinsic activity of the ordered Pt3Co catalysts. The new synthesis approach provides an effective strategy to develop active and stable Pt alloy catalysts by leveraging the unique properties of MOFs such as 3D structures, high surface areas, and controlled nitrogen and transition metal dopings. This concept also provides a solution to take advantages of current atomically dispersed PGM-free catalyst to develop high-performance low-PGM cathode catalysts.

References:

X. Wang, S. Hwang, Y.-T. Pan, K. Chen, Y. He, S. Karakalos, H. Zhang, J. S. Spendelow, D. Su, G. Wu, Nano Letters 2018, 18, 4163.

Chen, S. Hwang, J. Li, S. Karakalos, K. Chen, Y. He, S. Mukherjee, D. Su, G. Wu, Nanoscale 2018, 10, 17318.

Liang, F. Ma, S. Hwang, X. Wang, J. Sokolowski, Q. Li, G. Wu, D. Su, Joule 2019, 3, 956.
The Creation of Catalytic Activity Maps for Alloy Phase Diagrams
Authors: Cao Liang , Niu Le , Mueller Tim
Published: February 2020

We present a method for predicting the catalytic activity of the equilibrium surface of an alloy as a function of composition and temperature, allowing for the identification of the region of the alloy phase diagram that maximizes catalytic activity. This is accomplished by simultaneously treating the strain (due to the equilibrium lattice parameter of the bulk material) and ensemble (due to atomic order near the active site) effects with a lattice-parameter-dependent cluster expansion, where the energy of each cluster is expressed as a quadratic function of lattice parameter. We demonstrate our approach using the (111) surface of Pt–Ni catalysts for the oxygen reduction reaction (ORR), for which we present the catalytic activity of both ordered and disordered phases as a function of composition and temperature. We discuss how the optimal composition differs between the phases and suggest synthesis strategies for optimizing catalytic activity. We discuss other possible applications of our approach, including modeling strain effects that are driven by nanoparticle size effects or the creation of core-shell structures.
Electrode Engineering for High Performing, Long-Life Anion Exchange Membrane Fuel Cells
Authors: Adabi Firouzjaie Horie , Ul Hassan Noor , Mustain William E.
Published: February 2020

Anion Exchange Membrane fuel cells (AEMFCs) have received much attention in recent years due to its potential to lower the cost of polymer-based fuel cells for both mobile and stationary applications. However, AEMFCs have notoriously struggled with low performance and poor durability compared to proton-exchange membrane fuel cells (PEMFCs), despite the fact that each of the individual components of the cell (membrane, catalyst, etc.) shows very strong ex-situ performance. This suggests that the primary issue with modern AEMFCs is not fundamental, but engineering. Therefore, our group has focused on developing methodologies to deploy the most advanced materials available in operating AEMFCs. This has included improving operational protocols (manipulation of temperature, pressure, reacting gas dew points, etc.) to control the cell-level water dynamics [1-2]. We have also focused on component fabrication techniques, most notably tight control over the ionomer:carbon:catalyst loading [3] and hydrophilicity/hydrophobicity of the anode and cathode electrodes. This poster will focus on such electrode designs that have allowed our team to routinely achieve high AEMFC performance (> 2000 mW/cm2 peak power densities) and long life (> 1000 h with minimal loss in operating voltage at 600 mA/cm2).
Non-Precious Metal-Based Electrocatalytic Cathode Materials for Alkaline Membrane Fuel Cells (AMFC)
Authors: Del-Pilar Joselyn , Santiago Mitk'el , Cabrera Carlos R
Published: February 2020

Proton exchange membrane fuel cells (PEMFC) are a promising power technology for vehicles. However, their commercialization has been hindered due to the cathodic process of the oxygen reduction reaction (ORR). The ORR usually uses high-cost platinum-based electrocatalysts, which is also a major drawback towards commercialization. High overpotential, slow kinetics and irreversibility make the ORR the most challenging hurdle for PEMFC’s. Alkaline membrane fuel cells (AMFC) have emerge as an alternative to PEMFC’s as ORR kinetics are greatly improved in alkaline conditions and allows the use of non-noble metals such as cobalt, manganese and iron. The 3d metal oxide family has attracted the attention of researchers as a result of their low-cost and a robust ORR electrocatalytic activity. Here we present the use of M-doped (M = Mn, Co and Zn) ferrites as ORR electrocatalyst for AMFC applications and study their electrocatalytic mechanism using synchrotron-based X-ray absorption (XAS) techniques. Spinel ferrites were doped with manganese (MnFe2O4), cobalt (CoFe2O4) and zinc (ZnFe2O4) by using the co-precipitation method. X-ray diffraction (XRD) confirmed the formation of the spinel phase. The experimental optimal band gaps observed were 1.86 eV, 1.89 eV and 1.88 eV for MnFe2O4, CoFe2O4 and ZnFe2O4 respectively. ORR electrocatalytic activity was then evaluated in N2-saturated and O2-saturated 1.0 M NaOH using rotary disk electrode (RDE) at 1600 rpm. In situ XAS electrochemical characterization will be carried out in order to investigate at an atomic-level changes occurring to the active sites. Beyond just evaluating the ORR activity of the materials, our work seeks to gain an understanding of the in situ electrocatalytic reactions taking place during ORR.

Figure 1
Thin Film Morphological Characteristics of a Perfluorinated Anion Exchange Membrane
Authors: Divekar Ashutosh G , Buggy Nora C , Dudenas Peter J , Kusoglu Ahmet , Seifert Soenke , Pivovar Bryan S. , Herring Andrew M.
Published: February 2020

Perfluorinated anion exchange membranes are promising materials for alkaline fuel cell applications. Our previous work indicates they have high conductivity of >100 mS/cm at 80ᵒC and 95%RH.(1) They have also displayed good fuel cell performance of 1W/cm2.(2) We have also performed transmission small- and wide-angle X-ray scattering (SAXS/WAXS) of the bulk membrane to understand the bulk morphology.(3) Properties of Perfluorinated sulfonic acid (PFSA) ionomers as thin films have been thoroughly investigated in the past.(4) However, there is no literature about thin film characterization of perfluorinated anion exchange polymer and hence there is a lack of understanding about the interfacial properties. Here, we have studied the structure of these materials using Grazing-incidence small-angle x-ray scattering (GISAXS). Polymer solutions of different concentrations were used to spin-cast the thin films onto silicon substrates with native oxide layer and also coated with silver and Platinum.. Ellipsometry was used to obtain a calibration curve of thin film thickness vs. concentration of the polymer solution (wt%). From GISAXS, we can conclude that the polymer chains align horizontally parallel to the plain silicon as well as silver substrate. This alignment becomes significant at higher film thicknesses. Understanding the interfacial alignments of polymer on potential catalyst surfaces will help us better design them for optimal fuel cell performance or other electro-chemical applications.

References:

A. G. Divekar, M.-C. Kuo, A. M. Park, A. R. Motz, Z. S. Page-Belknap, Z. Owczarczyk, H. Long, S. Seifert, C. M. Maupin, M. A. Yandrasits, Y. Yang, B. S. Pivovar and H. A. M., Journal of Polymer Science: Part B (2019).

T. J. Omasta, A. M. Park, J. M. Lamanna, Y. Zhang, X. Peng, L. Wang, D. L. Jacobson, J. R. Varcoe, D. S. Hussey, B. S. Pivovar and W. E. Mustain, Energy & Environmental Science, 11, 551 (2018).

A. G. Divekar, A. M. Park, Z. R. Owczarczyk, S. Seifert, B. S. Pivovar and A. M. Herring, ECS Transactions, 80, 1005 (2017).

M. A. Modestino, A. Kusoglu, A. Hexemer, A. Z. Weber and R. A. Segalman, Macromolecules, 45, 4681 (2012).

Figure 1
Electroreduction of Oxygen on Carbide-Derived Carbon Supported Pd Catalysts
Authors: Lüsi Madis , Erikson Heiki , Merisalu Maido , Käärik Maike , Leis Jaan , Sammelselg Väino , Kaljuvee Tiit , Tammeveski Kaido
Published: February 2020

In recent years there have been multiple studies trying to improve the activity and stability of Pd-based catalysts for oxygen reduction reaction (ORR).1 The primary goal is to substitute Pt used for the fuel cell applications. In this work the standard borohydride reduction method was used to deposit Pd on different carbon materials, which were prepared from various metal carbides. These carbide-derived carbon (CDC) materials had varying amounts of micro and mesopores and were further ball-milled to obtain smaller carbon particle sizes. The influence of the support material on the prepared catalysts was studied. From the obtained catalysts it was observed that low micro-porosity lead to a higher order of agglomeration of the deposited Pd particles with electrochemical surface area being 3 times smaller in alkaline solution as compared to highly microporous Pd/CDC2. Obtained Pd/C catalysts were studied using thermogravimetry, scanning electron microscopy, cyclic voltammetry, and CO stripping. The ORR was explored using the rotating disk electrode (RDE) method. From Figure 1 it is evident that the Pd particles have a higher order of agglomeration on Pd/CDC3 and Pd/CDC4, which were the two catalysts with the lowest amount of micropores in the original CDC material. The results of thermogravimetric analysis indicated around 20% of Pd deposition for all studied catalysts except for Pd/CDC3 characterized with smaller mass loss compared with the others, which could be due to fewer sites where Pd can deposit. The results of the thermogravimetric analysis also indicated that the Pd deposition shifted the thermooxidation temperature of the materials to lower values compared to the Pd-free CDC materials. RDE polarization curves were measured in both 0.1 M KOH and 0.1 M HClO4 solution. According to the Koutecký–Levich analysis the number of electrons transferred per O2 molecule for all the catalyst was around 4. There are notable differences in the diffusion-limited current plateaus, which could be due to different coverage of the Pd/C catalysts due to the larger carbon particles present in some of the CDC materials, even though the CDC materials were ball-milled, still rather large (2-6 μm) carbon particles could be observed depending on the CDC material. In alkaline media, the specific activity (SA) values increased with the number of mesopores and decreased with the increase of the number of micropores, where highest SA could be observed for Pd nanoparticles supported on CDC3 and CDC4.

Figure
1
. SEM images of a) Pd/CDC1, b) Pd/CDC2, c) Pd/CDC3, d) Pd/CDC4, e) Pd/CDC5, and f) Pd/Vulcan carbon.

Reference

H. Erikson, A. Sarapuu, J. Solla-Gullon, and K. Tammeveski, J. Electroanal. Chem., 780, 327-336 (2016).

Figure 1
(Invited) Novel Insights in the Activity, Selectivity and Durability of Fenc, Mn-Oxides and Fenc/Mn-Oxide Composites for ORR Catalysis in Alkaline Electrolyte and AEMFC
Authors: Jaouen Frederic , Santori Pietro Giovanni , Speck Florian Dominik , Cherevko Serhiy , Peng Xiong , Mustain William E. , Varcoe John R.
Published: February 2020

While high power densities are reached with proton-exchange membrane fuel cells (PEMFCs), several drawbacks hold their large-scale commercialization. In particular, the sluggish oxygen reduction reaction (ORR) at the cathode requires significant amount of platinum. Among PGM-free catalysts, iron-nitrogen-carbon catalysts have hitherto shown the highest initial activity toward ORR and especially those that have been subjected to NH3 pyrolysis. However their performance in PEMFC decays too fast. In contrast, prospects for active and durable Fe-N-C catalysts competitive to Pt catalysts are good in alkaline environment, and the advent of high performance anion exchange membrane (AEM) now offers the possibility to investigate this in AEM fuel cell (AEMFC).

This presentation will first report on the ORR activity, stability and operando spectroscopic identification of Fe-N-C catalysts in alkaline electrolyte, with materials comprising only FeNx moieties. To further increase the ORR selectivity toward water formation, the activity and stability of different Mn-oxide polymorphs for ORR and hydrogen peroxide electro-reduction (HPRR) were studied. The properties of a composite comprising the most stable Mn-oxide and Fe-N-C material were also studied, confirming that HPRR is facilitated when Mn2O3 is added to Fe-N-C. At the same time, however, we show that HO2
- is harmful to the MnOx catalyst itself, increasing the manganese dissolution.

FeNC and FeNC/Mn2O3 cathodes were then tested in AEMFC based on radiation-grafted AEM and AEI and compared to performance obtained with a Pt-based cathode. The results show high and comparable ORR activity at 0.9 V between cathodes based on 1.0-1.5 mgFeNC cm-2 and 0.4-0.5 mgPt cm-2. Peak power densities in the range of 1.1-1.7 W·cm-2 were reached in O2-fed AEMFC with such FeNC cathodes, depending on the operating conditions. Results from stability testing are also very promising, and in strong contrast to instability of the same FeNC material in PEMFC. While some performance gap still remains at high power density between highly Pt-loaded cathode and such FeNC cathode, the results show a promising application of FeNC for high performance AEMFC.

Acknowledgements:

The project CREATE leading to these results has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 721065.
Synthesis of Poly(norbornene) Anion Conducting Membranes for Alkaline Electrochemical Devices: Structure-Property Relationships
Authors: Mandal Mrinmay , Huang Garrett , Kohl Paul A
Published: February 2020

Anion-exchange membranes (AEMs) are used in electrochemical energy storage and conversion devices such as batteries, fuel cells, and electrolyzers. The development of AEMs with long-term alkaline stability and high anion conductivity (i.e. hydroxide, carbonate and bicarbonate) is of current interest. The benefits over proton-exchange membrane (PEM) devices include the use of non-precious catalysts, facile reaction kinetics, and reduced fuel crossover. However, the issues with the low ionic conductivity, poor stability at high pH, and high water uptake are need to be addressed.

A series of homopolymers and block copolymers containing non-hydrolysable backbone and long-chain head-group tethers based on vinyl addition and ring-opening metathesis polymerization (ROMP) of norbornenes were synthesized for use in AEM fuel cells. The focus of this talk is on the structure-property relationships of poly(norbornene) anion exchange membranes. Polymers were cross-linked with N,N,N′,N′-Tetramethyl-1,6-hexanediamine (TMHDA) to control the water uptake, and improve the mechanical properties. The structure property relationship of AEMs towards high ionic conductivity was correlated with ion-exchange capacity (IECs), number and size of the blocks, molecular weight, and polydispersity. The membranes had record high conductivity of 212 mS/cm at 80 °C and low water uptake. The long-term alkaline stability showed <1% conductivity loss in over 1200 h at 80 °C. The membranes have been used in anion-exchange membranes fuel cells and electrolyzers.
(Invited) Efficient pH-Gradient-Enabled Microscale Bipolar Interfaces in High Performance Direct Borohydride Fuel Cells
Authors: Wang Zhongyang , Parrondo Javier , He Cheng , Sankarasubramanian Shrihari , Ramani Vijay
Published: February 2020

Electrochemical energy conversion devices usually operate at uniform pH or over a narrow pH range. The uniform pH environment of these devices frequently hampers the facility of one of the half-cell reactions. In proton exchange membrane fuel cells (PEMFCs)/ proton exchange membrane water electrolyzers (PEMWEs), where both the anode and cathode operate at acidic pH, the H2 oxidation/evolution reaction is quite facile while the O2 reduction/evolution reaction is sluggish. In anion exchange membrane fuel cells (AEMFCs)/ anion exchange membrane water electrolyzers (AEMWEs), the converse is true. Moreover, the chemical stability of some reactants depends strongly on the pH.

Direct borohydride fuel cells (DBFCs), operating with NaBH4 as a fuel and H2O2 as the oxidant have attracted a lot of attention due to their high theoretical cell voltages and tactical advantages, particularly for defense-related applications. DBFCs have a high energy density of 9.3 kWh kg-1 and specific capacity of 5.67 kAh kg-1 based on NaBH4 oxidation in alkaline media [1], although the practical energy density will be lowered upon accounting for the added weight of KOH solution required to stabilise NaBH4. Using liquid hydrogen peroxide as the oxidant, the DBFC is a safe and attractive low temperature power source for unmanned underwater vehicles (UUVs) as they exhibit excellent energy and power density, are safe, given the high flash point of NaBH4, and do not release any gaseous effluents, enabling operation at neutral buoyancy [2]. One challenge for this system is the separation between the anolyte fuel (1.5M NaBH4 in 3M KOH) and catholyte oxidant streams (15% H2O2 in 1.5M H2SO4), while another is the high instability of NaBH4 in acidic or even neutral pH [3]. Herein, a pH-gradient-enabled microscale bipolar interface (PMBI) is demonstrated for maintaining pH control of the anolyte and catholyte compartments of the fuel cell. The PMBI employed to separate anolyte and catholyte was based on an anion exchange membrane (AEM) interface in conjunction with a cation exchange membrane (Nafion®) separator. The DBFC with the PMBI yielded a current density of 330 mA/cm2 at 1.5 V and a promising peak power density of 630 mW cm-2 at 1 V in a 25-cm2 active area cell [4]. Using a recessed planar electrode (RPE) in conjunction with TEM, we show that the PMBI maintained a sharp local pH gradient (0.82 pH units/nm on average) at the electrocatalytic reaction site.

References

[1] J. Milikić, G. Ćirić-Marjanović, S. Mentus, D.M.F. Santos, C.A.C. Sequeira, B. Šljukić, Electrochimica Acta, 213 (2016) 298-305.

[2] C.G. Arges, V. Prabhakaran, L. Wang, V. Ramani, International Journal of Hydrogen Energy, 39 (2014) 14312-14321.

[3] M. Chatenet, Nature Energy, 4 (2019) 261-262.

[4] Z. Wang, J. Parrondo, C. He, S. Sankarasubramanian, V. Ramani, Nature Energy, (2019).
The Effect of Gas Diffusion Layer on the Stability of PEM Unitized Regenerative Fuel Cell
Authors: Zhang Xinrong
Published: February 2020

Proton exchange membranes(PEM) unitized regenerative fuel cell (URFC) combines the fuel cell (FC) and water electrolyzer (WE) in a single stack. It has been widely considered as energy conversion and storage devices to store off-peak electricity in the form of hydrogen, especially when integrated with intermittent renewable energy resources. One of the main performance challenge in URFCs is material corrosion and the formation of Ti oxides at the interface between titanium surface and anode catalyst layer in WE mode. In this paper, porous sinter titanium as metallic gas diffusion layer (GDL) which is closely related to the anode catalyst layer was coated with IrO2-Ta2O5 oxide materials as protective coating, and the effect of IrO2-Ta2O5 coating on cycle stability of URFCs was validated.

As a result, URFCs exhibited that the excellent performance and long-term cycle stability in both FC mode and We mode, what is more, the degradation rate of URFCs was around 1.2% during hundred hours cycle operation in both FC-mode and WE-mode at the current density of 500 mA/cm2. It demonstrated that IrO2-Ta2O5 oxide protective coating improved the corrosion-resistive performance in WE mode and slowed down the formation of Ti oxides at the surface of the metallic GDL. Hence, it further reduced the interfacial contact resistance and improve the cycle stability of URFCs.
Analyzing and Improving Performance of Anion Exchange Membrane Water Electrolysis
Authors: Green Zach , Wang Zhang , Shi Wenjuan , Yan Yushan , Xu Hui
Published: February 2020

The utilization of renewable energy has substantially driven more attention into electrolysis technologies. In this scenario, water electrolysis device can be considered as a means of storing energy chemically rather than electronically like batteries. Furthermore, the establishment of H2@scale consortium has presented renewable H2 unprecedented opportunities toward multiple industrial and transport applications. However, current hydrogen production from electrolysis comprises only a small fraction of the global hydrogen market due to its high costs. Anion exchange membrane water electrolysis (AEMWE) enables to use non-precious metal catalyst as the catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). However, the performance of state-of–the art AMWE is still inferior to its count part of proton exchange membrane water electrolysis (PEMWE).

The performance loss of AEMWE has been analyzed using different experiment design, which includes catalyst, ionomer, electrode configuration and operating conditions. In particular, commercial anion exchange membrane and ionomer have been compared with advanced materials by our multiple collaborators. Reversible fuel cell operations and addition of diluted salts or bases can also be used to pinpoint the sources of AEMWE performance loss. Based on the performance analysis, the following strategies can be used to improve the performance of AEMWE. First, anion exchange membrane and ionomer with high oxidative resistance will be adopted. These chemically and electrochemically stable materials will provided a better platform to test the OER or HER catalyst to enable alkaline membrane electrolysis operation. Second, an optimal interaction between the ionomer and the catalyst in the electrode will be established.
A General Method to Probe Oxygen Evolution Intermediates at Operating Conditions
Authors: Tao Huabing , Xu Yinghua , Huang Xiang , Chen Jingguang G , Liu Bin
Published: February 2020

Observation of oxygen intermediates is the key to reveal the factors that limit the OER activity thus design of better catalysts. However, the liquid reaction environment makes it very challenging to probe oxygen intermediates at operating conditions. Although several in situ techniques are reported for the detection of intermediates on some catalysts, these methods apply only to certain circumstances. Therefore, so far, the most knowledge of oxygen intermediates is derived from theoretical simulations.

Herein, we developed a general and feasible method to probe oxygen intermediates. By employing alcohols as probing reagents, the oxygen intermediates can be readily captured. The method is so general and feasible that it can be adopted by every electrochemical laboratory. Besides the guidance for catalyst design, the chemical nature oxygen intermediates revealed from this work also open new opportunities for applying OER electrodes in other reactions.
(Invited) Overview on the European FCH Joint Undertaking Projects & Activities in PEM Fuel Cells and Electrolysis
Authors: Atanasiu Mirela , Tsimis Dionisis , Boillot Lionel
Published: February 2020

The Fuel Cells and Hydrogen Joint Undertaking (FCH JU) was set up in 2008 to accelerate the development of fuel cells and hydrogen technologies in Europe towards commercialization from 2020 onwards. To reach this target the FCH JU brings together resources under a cohesive public-private partnership to ensure commercial focus, to match RTD activities to industry's needs and expectations and to scale-up and intensify links between the Industry Community and the Research Community. Research projects on PEM technology have had a central role within the program with significant funding allocated in order to advance the technology of both PEM fuel cells but also PEM electrolysers.

Regarding fuel cells, the primary focus has been the reduction of the Pt content within catalysts as well as on the improvement of power density. Additionally, significant funding has been dedicated on the improvement of durability as well as on the reduction of cost, particularly through improved manufacturing, while the next wave of research projects aims at the development of PGM free catalysts.

Similarly, for PEM electrolysis continuous support has been provided in order to scale up electrolysers from kW to MW, to improve performance and to reduce costs. This has contributed to the establishment of EU leadership on PEM electrolysis. The next steps are to focus on further improving performance by increasing the current density and operating pressure.
(Invited) Hydrogen in an Integrated Energy System
Authors: Hebling Christopher , Smolinka Tom
Published: February 2020

The transformation of energy systems towards high shares of renewable energy production while phasing out the use of fossile carbon-based energy carriers requires both a highly resilient energy system and an energy carrier which couples the electricity sector with energy consuming sectors like transportation, industry and chemistry. This is why we now see the advent of large-scale water electrolyzers for the production of sustainable hydrogen. Hydrogen will be an important feedstock for fuel cell cars, busses, trucks and trains, but also an important basic chemical for refineries, for the steel production and for various kinds of sustainable chemicals like fertilizers or polymers. This talk will adress the status quo of electrolyzer technologies and techno-economic analyses of power-to-hydrogen plants with high shares of intermittent power supply. The whole value chain from sustainable power generation to the production of liquid energy carriers will be described. An overview of the research activities of the Fraunhofer institute for Solar Energy Systems (ISE) for the realization of an integrated and sustainable energy system will be given as well.

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(Invited) Efficient and Stable Metal Halide Hybrid Perovskite Solar Cells
Authors: Matsushima Toshinori , Adachi Chihaya , Qin Chuanjiang
Published: February 2020

Solar cells can generate free electricity by converting sunlight. Therefore, development of new solar cell materials with higher performance and lower cost fabrication are very important for realizing environmentally friendly and sustainable human society. Recently metal halide perovskites have emerged as the next-generation light absorber in solar cells. Power conversion efficiency of perovskite solar cells has already reached over 20%, which is comparable to existing silicon solar cell technology. However, several issues remain in perovskite solar cells, such as low operational stability under illumination, inclusion of toxic lead, and low thermal stability, and need to be solved for commercialization. Here we show our recent results on metal halide perovskite-based devices. We analyzed working and degradation mechanisms of perovskite solar cells with the aim of enhancing their solar power conversion efficiency and operational durability. The photon-to-electron conversion efficiencies and half lifetimes under continuous illumination for our lead-based perovskite solar cells reached high levels; > 20% and > 20,000 h. Mixing several metal, halogen, and organic ions greatly enhanced the thermal stability of perovskite films, making it possible to obtain perovskite solar cells showing less degradation even at 85 degree Celsius under illumination. We also demonstrated very stable solar cells based on tin-based perovskites with low toxicity. We also used perovskites to fabricate high mobility field-effect transistors, and efficient LEDs and laser devices.

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(Invited) Commercialization of High-Energy Density, Long-Lifetime Li-Ion Cells with Ni-Rich Cathodes
Authors: Dahlberg Kevin , Camardese John , Inman Kristopher , Manev Veselin , Cochran Steven , McKenzie Lisa
Published: February 2020

Li-ion battery-based energy storage is widely regarded as the best technology to realize affordable electrification of the transportation sector, including xEVs and heavy-duty applications including buses, shipping, mining, and agriculture. In order to meet the growing demand and sustainably compete in this rapidly expanding industry, Li-ion cell manufacturers like XALT Energy must overcome several significant R&D and manufacturing challenges. First, these applications require both high energy density and long lifetime, and it is difficult to avoid direct tradeoffs between the two with strategies for higher energy such as higher voltage charging, higher-Ni cathodes like NCM-811, and thicker electrodes. Second, cell manufacturers must predict and replicate numerous performance metrics of commercial-scale cells from small-scale test vehicles, such as coin cells and single-layer pouch cells. Third, the cell lifetimes required in these applications are 1,000’s of cycles and 10’s of years at 25°C, much longer than commercial development cycles, requiring the use of “accelerated” testing with a high level of confidence. All the above represent significant barriers to the adoption of potentially valuable academic breakthroughs and advanced manufacturing. We will discuss how XALT Energy approaches these problems in the context of commercializing a Ni-rich cathode-based “Gen 2” 63 Ah product, and share our perspective of what kinds of advanced manufacturing are of greatest interest to lower cell cost, raise energy/power density, and extend lifetime.
(Invited) Accelerating Optimization of Lithium Ion Battery Manufacturing Via Multiscale Computations
Authors: Franco Alejandro A.
Published: February 2020

Electrochemical performance and lifetime of Lithium Ion Battery (LIB) composite electrodes strongly depend on their manufacturing parameters. Such parameters include the slurry formulation (i.e. the chemistry and amount of active material, carbon, binder and solvent), the temperature used to evaporate the solvent, the pressure applied during the electrode calendering and the time for the electrolyte impregnation. Within the perspective of developing more efficient LIBs at minimal R&D cost, it is important to develop robust tools able to predict the influence of manufacturing parameters on the electrodes mesostructure and the overall cell performance. In this keynote, i discuss the latest research progress in this sense within the ARTISTIC project, funded by the European Research Council (ERC). This project aims at developing and demonstrating a multiscale computational platform able to simulate the LIB manufacturing process and to predict optimal manufacturing parameters of LIBs responding to specific targets (energy density, etc.). Coarse Grained Molecular Dynamics, Discrete Element Method, Lattice Boltzmann and Continuum computational models are combined with deep learning algorithms to reach this objective. Examples of applications of this platform for NMC and graphite-based electrodes are discussed, in strong link with in house experimental characterizations. Physicochemical mechanisms leading to the composite electrode self-organization are discussed and guidelines towards the optimization of the multiple process steps are presented. At the end of the lecture, an experience using an in house Virtual Reality tool, to assess the manufacturing modeling results, will be proposed to the attendees.

[1] ARTISTIC project (European Research Council Consolidator Grant #772873): https://www.u-picardie.fr/erc-artistic/

[2] Franco, A. A., Rucci, A., Brandell, D., Frayret, C., Gaberscek, M., Jankowski, P., & Johansson, P. (2019). Boosting Rechargeable Batteries R&D by Multiscale Modeling: Myth or Reality?. Chemical Reviews. DOI: 10.1021/acs.chemrev.8b00239

[3] Rucci, A., Ngandjong, A. C., Primo, E., Maiza, M., & Franco, A.A., submitted (2019).

[4] Ngandjong, A. C., Rucci, A., Maiza, M., Shukla, G., Vazquez-Arenas, J., & Franco, A. A. (2017). Multiscale Simulation Platform Linking Lithium Ion Battery Electrode Fabrication Process with Performance at the Cell Level. The journal of physical chemistry letters, 8(23), 5966-5972.

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Microscale Simulations of Drying and Calendering Processes to Manufacture Porous Electrodes
Authors: Nikpour Mojdeh , Barrett Nathan , Harrison Chelsea Ann , Wheeler Dean , Mazzeo Brian A
Published: February 2020

Electrodes can suffer from inconsistencies in performance due to heterogeneity in particle arrangements. Manufacturing processes such as drying and calendering significantly alter the microstructure and introduce randomness, making it difficult to predict the final structure of the film, given process inputs. This has a crucial impact on the electrochemical and mechanical properties as well as the ultimate performance and lifetime of the battery [1]. The goal of this work is to analyze the behavior of electrode constituent materials during the drying and calendering steps using a new predictive model of microstructure.

We have developed a model to simulate the drying and calendering processes using the open-source Large-scale Atomic/Molecular Massively Parallel Simulator (LAMMPS) [2]. Within LAMMPS, we developed a customization of smoothed particle hydrodynamics (SPH), which solves the Navier-Stokes equations on particles representing both solid and liquid materials present in the electrode film.

We present here the development of the model and the resulting microstructure predictions for conventional Li-ion battery electrodes. Results are compared to experimental data where available, including microstructures determined from a new freeze-drying technique. Predicted properties such as effective conductivity and degree of heterogeneity can be used in more coarse-grained models to simulate cell performance.

References

[1]
M. Forouzan et al., J. Power Sources 312, 172-183 (2016).

[2] M. Nikpour et al., Meeting Abstracts, no. 3, pp. 268-268. The Electrochemical Society (2018).

Figure 1: Heterogeneous structure of the dried electrode: a) experiment, b) simulation; carbon-binder domain is grey, active material is yellow c) top-view of the dried film

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Efficient 3D Printed Pseudocapacitive Electrodes with Ultrahigh MnO2 Loading
Authors: Yao Bin , Chandrasekaran Swetha , Worsley Marcus A. , Li Yat
Published: February 2020

Retaining sound electrochemical performance of electrodes at high mass loading holds significant importance to energy storage. Pseudocapacitive materials such as manganese oxide (MnO2) deposited on current collectors have achieved outstanding gravimetric capacitances, sometimes even close to their theoretical values. Yet, this is only achievable with very small mass loading of active material typically less than 1 mg cm-2. Increasing mass loading often leads to drastic decay of capacitive performance due to sluggish ion diffusion in bulk material. In this talk, I will demonstrate a 3D printed macroporous graphene aerogel electrode with MnO2 loading of 182.2 mg cm-2, which achieves a record-high areal capacitance of 44.13 F cm-2. The engineered porous structure allows efficient ion diffusion and therefore enables the ultrahigh mass loading of pseudocapacitive materials without sacrificing their gravimetric and volumetric capacitive performance. Most importantly, this 3D printed graphene aerogel/MnO2 electrode can simultaneously achieve excellent capacitance normalized to area, gravimetry, and volume, which is the trade-off for most electrodes. This work successfully validates the feasibility of printing practical pseudocapacitive electrodes, which might innovate the conventional layer-by-layer stacking fabrication process of commercial supercapacitors.

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Long-Life Ni-Rich NMC Cathodes with Heterogeneous Particle Structure Using Advanced High-Speed Synthesis Process
Authors: Chung Youngmin , Shin Youngho
Published: February 2020

Layered Ni-rich cathode material, Li[NixMnyCo1−x−y]O2 (x ≥ 0.8), is one of the most prospective materials for rechargeable lithium-ion batteries (LIBs) due to its high capacity. However, significant challenges remain in order to improve capacity retention during cycling and thermal-abuse tolerance of this material. As one of the promising approaches to overcome barriers, a series of core-shell structured cathode materials with the overall bulk composition of LiNi0.8Mn0.1Co0.1O2 is produced via co-precipitation method where Ni-rich composition (LiNi0.9Mn0.05Co0.05O2) with higher capacity is particle core and Mn-rich composition with higher stability is particle surface.

It is challenging to design and implement heterogeneous structured particles with synergistic effects by combining the advantages of each composition. It is particularly important to develop a process of producing economically and quickly each type of these cathode particles, in which the Ni-rich composition and the Mn-rich composition change continuously or discretely from the particle core to the particle surface. To achieve this goal, a continuous rapid synthesis process for the production of heterogeneous structured cathodes was developed at ANL MERF based on an advanced Continuous Stirred Tank Reactor (CSTR) system and a Taylor Vortex Reactor (TVR) system.

A detailed description of the developed process to mass-produce heterogeneous structured materials economically and rapidly will be presented. The excellent physical and electrochemical properties of Ni-rich NMC cathodes with core-shell or core-gradient particle structures produced by this advanced process will be reported. The produced heterogeneous structured cathodes and commercially available normal NMC materials will be compared through analysis of coin half cell, pouch full cell, SEM, EDS, ICP-MS, DSC, EIS, and other advanced characterization techniques.