bluuebunny/crossref_metadata_2025 huggingface dataset:
Magnetic Structure and Properties of NaFePO4 Polymorphs: Antiferromagnetic Ordering and Spin-Flop Transition
Authors: Barpanda Prabeer , Avdeev Maxim , Ling Chris D
Published: February 2020

In recent years, the cost and sustainability concerns have renewed research efforts on sodium-ion batteries, propelling investigation on various layered oxides and polyanionic family of insertion compounds for low-cost and large-scale cathode applications. These cathode insertion compounds are functional materials, involving redox active 3d transition metals (e.g. Fe/Co/Ni) that are often magnetic in nature. During the Na (de)insertion process involving redox reaction of transition metals and structural alteration, the magnetic magnetic structure/ properties can vary significantly.

We have investigated the magnetic structure and properties of NaFePO4 polyanionic system, which exists in two distinct polymorphs: metastable triphylite and stable maricite. The details of these structures are shown in the figure. Both these polymoprhs undergo antiferromagnetic ordering below 50 K (for triphylite) and 13 K (for maricite). Using the magnetic susceptibility, heat capacity and low temperature neutron powder diffraction, the magnetic structure of these two distinct polymorphs have been solved. The details of these antiferromagnetic structures will be described considering the super- and super-superexchange interactions. In addition, investigating the maricite NaFePO4 polymorph, which consists of edge-sharing FeO6 octahedral chains, we have discovered the occurrence of spin-flop transition below 40 kOe using susceptibility measurement and low-temperature Mossbauer spectroscopy. This spin-flopping (or metamagnetism) phenomenon in maricite NaFePO4 will be described in detail [1-5] to showcase the rich magnetism present in NaFePO4 insertion materials.

References:

P. Barpanda et al, Adv. Energy Mater., 2, 841, 2012.

M. Avdeev et al, Inorg. Chem., 52, 395, 2013.

M. Avdeev et al, Inorg. Chem., 52, 8685, 2013.

M. Avdeev et al, Inorg. Chem., 53, 682, 2014.

M. Avdeev et al, private communication.
Efficient Elimination of Lithium Carbonate/Carboxylates By NiO for Rechargeable Li–O2 Battery
Authors: Hong Misun , Choi Hee Cheul , Byon Hye Ryung
Published: February 2020

The non-aqueous lithium–oxygen (Li–O2) battery has been extensively investigated by virtue of its remarkably high theoretical energy density. However, the Li–O2 cell has suffered from parasitic side reactions due to superoxide (O2
•−) attack and lithium peroxide (Li2O2) activity to non-aqueous electrolytes and carbon cathodes, which form lithium carbonates (Li2CO3) and carboxylates (RCO2Li, R = H or alkyl). These poor-conducting side products deposited on the cathode increase the recharge potential, which triggers the parasitic side reactions further. Some efforts to employ superoxide-tolerant electrolytes, carbon-free cathodes and cycling with limited depth of discharge have alleviated the side reactions whereas the lithium carbonates/carboxylates inevitably formed are overwhelmingly deposited on the cathode for cycling thus terminating the Li–O2 cell operation rapidly.

Here, we present new approach to promote elimination of lithium carbonate/carboxylates using nanoporous nickel oxide (NiO), which enhances cycling performance and round trip efficiency of Li–O2 battery for cycling. The crystalline nanoporous NiO plates that were homogeneously distributed on the entangled carbon nanotubes (CNT) network via hydrothermal synthesis (NiO/CNT) exhibit striking capacity retention of over 70 cycles at a limited discharge capacity of 1000 mAh gCNT
−1 with a stable recharge potential of 4.1 V vs. Li/Li+ in tetraglyme electrolyte. The role of nanoporous NiO is investigated under the cycling at deep depth of discharge. Unlike the first cycle providing predominant Li2O2, the increasing extent of lithium carbonates/carboxylates for cycling are observed by 1H NMR and FTIR spectroscopies. In particular, the lithium carbonates become a main side product over 10 cycles. Interestingly, the NiO/CNT cathodes reveal disappearance of these side products after every recharge and high capacity retention, which are different from NiO-free CNT cathodes providing the accumulated side products and swift capacity fading. Further analysis using anodic potential sweeps of side products in three-electrode cell demonstrate ~300 mV lower oxidation potential on the NiO/CNT than the NiO-free CNT while negligible influence on the electrolyte oxidation, which implies a promoter of nanoporous NiO to eliminate lithium carbonates/carboxylates. TEM images display that the side products seem to transport along the CNT and make a lump close to the NiO, where the decomposition of side products can be carried out actively. The nanoporous NiO has been very stable during deep cycling, where either chemical or structural change is not observed, which indicates that the NiO can contribute toward stable long-term cycling performance of Li–O2 cell.
Conductivity Enhancement of MgMxOy (M=Co, Ni) Oxide Cathodes for Mg Battery Applications
Authors: Tsai Shu-Yi , Fung Kuan-Zong , Ni Chung-Ta
Published: February 2020

Mg batteries have received a lot of interest due to its improved safety of handling, abundance and low cost of magnesium. Furthermore, Mg is more stable in air than Li and may provide capacity as high as 2200 mAh/g or 3830 mAh cm−3. Thus, Mg battery is known to have great potential for many practical applications and becomes one of post LIB technologies. Unfortunately, divalent Mg ions are expected to exhibit slow diffusion in Mg compounds. Thus, to find appropriate cathode materials for Mg battery has been difficult. Recently, MgCo2O4 Spinel Oxide and Mg0.67Ni1.33O2 were found to be potential high voltage (~3V) cathode for Mg batteries based on the work of Tetsu Ichitsubo’s group. The conductivity of MgCo2O4 is in the order of 10-1S/cm. On the other hand, the conductivity of Mg-doped NiO is much lower than that of MgCo2O4 spinel. The electronic conduction of semi-conducting oxides is highly dependent on the hole jumping in between those cations occupying the tetrahedral and/or octahedral sites of oxygen sublattice. Thus, the conductivity of these oxide cathodes may be enhanced by proper substitution of aliovalent cations. Therefore, the objective of this work is to enhance the electrical conductivity of Mg-containing transition metal oxides with either spinel or rock salt structure by the substitution of aliovalent cations with proper valence and ionic radius in the cation sublattice. After the electrical conductivity of cathode materials is improved, the electrochemical property such as capacity, charge/discharge cycles of Mg batteries is expected to be enhanced as well. The conductivity and crystal structure of prepared samples will be examined by using AC-impedance spectroscopy and XRD. The electrochemical properties including CV and cell testing will be conducted after cell assembly using the obtained cathode and Mg anode.
The Chemical Stability of Polymers in Lithium-Air Batteries
Authors: Amanchukwu Chibueze V , Harding Jonathon R , Shao-Horn Yang , Hammond Paula T
Published: February 2020

To continue the technological advances in electric vehicles and other portable devices that lithium-ion batteries have enabled, it is important to investigate newer battery chemistries with much higher energy densities. Of the new battery chemistries currently being investigated, lithium-air (oxygen) batteries are particularly promising because of their high gravimetric energy densities; an order of magnitude greater than lithium-ion. However, several challenges such as electrolyte and positive electrode (e.g., carbon) instability has plagued possible commercialization. Our group has focused on developing solid-state polymer electrolytes for lithium-air batteries to address the failings of current organic liquid electrolytes such as their volatility, flammability, and instability in lithium-air cells. Before utilizing polymer electrolytes in lithium-air, it is important to study their chemical stability in a lithium-air environment. Using a subset of polymers (e.g., poly(acrylonitrile), poly(vinylidene fluoride)) that ubiquitously serve as polymer electrolytes and binders in lithium-ion batteries, we explore their stability in contact with commercial lithium peroxide to understand which polymer backbones and side group functionalities are especially susceptible to nucleophilic attack by the highly reactive superoxide and peroxide species in a lithium-air cell. The presence of an electronegative functional group on the polymer side chain and the presence of nearby hydrogen atoms that become electron deficient due to the electronegative functionality appears to make the polymer more susceptible to degradation in the presence of lithium peroxide. Using knowledge gained from this study, we can better design new polymer electrolytes that are not only ionically conducting, but are stable against chemical attack in a lithium-air cell. This bottom-up approach of understanding the stability of polymers and delineating reactive polymer functional groups will make it possible for smarter design of electrolytes and binders, and bring these novel batteries closer to commercial realization.
High Rechargeable and Efficient Li-O2 Battery Using a Novel Organic Catalyst
Authors: Liu Jia , Renault Stéven , Brandell Daniel , Gustafsson Torbjörn , Edström Kristina , Zhu Jiefang
Published: February 2020

As an advanced large-scale energy storage and conversion system, the rechargeable non-aqueous Li-O2 battery has recently attracted considerable attention because of its high gravimetric density since it was firstly presented in 1996[1]. In an ideal Li-O2 battery, on discharge, O2 is reduced at the cathode, where it combines with Li+ released from the Li-metal anode to yield Li2O2 (oxygen reduction reaction (ORR), 2 Li+ + O2↑ + 2 e- → Li2O2)). On charge, Li2O2 is converted back to Li+ and O2 (oxygen evolution reaction (OER), Li2O2→2 Li+ + O2↑ + 2 e-))[2]. One of the critical challenges which limit the implementation of Li-O2 batteries is the low round-trip efficiency and poor cyclability resulting from a large over-potential. Although the real effect of catalytic activity is controversial and the mechanism of catalyst is not yet clear, it has been widely accepted that the employment of catalyst can minimize the over-potential of Li-O2 battery. Up to now, a number of materials have been employed as cathode catalysts, such as noble metal (alloy), carbon, transition-metal oxide, showing some improvement.

Herein, a highly reversible and efficient Li-O2 cell using Dilithium (2,5-dilithium-oxy)-terephthalate (Li4C8H2O6) as a novel organic catalyst was reported. The mechanism of the increasing efficiency and cyclability was systematically investigated. In addition, operando synchrotron-based XRD (SR-PXD) as a diagnostic tool that allowed us to probe the dynamics for the degradation of Li2O2 during charging process was employed to further study the real-time kinetics of OER in a Li-O2 cell.

REFERENCES

[1] J. Liu, M. Roberts, R. Younesi, M. Dahbi, K. Edström, T. Gustafsson, J. Zhu, The Journal of Physical Chemistry Letters 4 (2013) 4045-4050.

[2] R. Younesi, S. Urbonaite, K. Edström, M. Hahlin, The Journal of Physical Chemistry C 116 (2012) 20673-20680.
Modified Li-Ion Conducting Ceramic Membrane for Improved Performance in Hybrid Li-Air Battery
Authors: Li Yunfeng , Xing Yangchuan
Published: February 2020

Li-air battery (LAB) with non-aqueous electrolytes currently has insurmountable technical challenges in both electrolytes and solid lithium oxide products [1-2]. A hybrid Li-air (HyLAB) system has been reported as an alternative approach [3-8]. Such systems use non-aqueous electrolyte in the anode and aqueous electrolyte in the cathode. A Li-ion conducting ceramic membrane (water impermeable) is used to separate the anode and cathode chambers. While such hybrid system can avoid many problems in the aprotic system, unfortunately, the ceramic membrane is not stable in acidic or alkaline electrolytes.

In this presentation, we report our recent work to modify the ceramic membranes. We will demonstrate that by modifying the Li-ion conducting ceramics it is possible to improve its resistance to corrosion and therefore increase the performance of the HyLABs. We will discuss the technical details of the work in this presentation.

References

[1] P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.-M. Tarascon, Nat. Mater., 11 (2012) 19-29.

[2] G. Girishkumar, B. McCloskey, A.C. Luntz, S. Swanson, W. Wilcke, The Journal of Physical Chemistry Letters, 1 (2010) 2193-2203.

[3] S.J. Visco, E. Nimon, B. Katz, L.D. Jonghe and M. Y. Chu, in The 210th Electrochemical Society Meeting, Cancun, Mexico (2006).

[4] T. Zhang, N. Imanishi, Y. Shimonishi, A. Hirano, Y. Takeda, O. Yamamoto, N. Sammes, Chemical Communications, 46 (2010) 1661-1663.

[5] E. Yoo, H. Zhou, ACS Nano, 5 (2011) 3020-3026.

[6] L. Li, X. Zhao, A. Manthiram, Electrochemistry Communications, 14 (2012) 78-81.

[7] Y. Li, K. Huang and Y. Xing, Electrochimica Acta, 81 (2012) 20.

[8] Y. Li, Z-P. Huang, K. Huang, D. Carnahan, and Y. Xing, Energy & Environmental Science, 6 (2013) 3339.
Characterization and Electrochemical Behaviour of AV4S8 (A=Ga,Ge) Materials as Negative Electrodes of Sodium-Ion Batteries
Authors: Michelet Cédric , Crosnier Olivier , Dupré Nicolas , Guyomard Dominique , Brousse Thierry , Moreau Philippe
Published: February 2020

Lithium-ion batteries have become essential in recent years. Due to both the difficult access and the cost of the alkaline element, a new field of research concerning sodium-ion batteries has recently emerged. Many compounds have been proposed as positive electrodes for Na-ion batteries. However, since sodium does not intercalate into graphite as much as lithium (1), there is a clear need for high capacity materials for negative electrode materials. Intercalation compounds such as Na2Ti3O7 (2) or NaTi2(PO4)3 (3) or Sb-based compounds (4) come usually with a somehow limited capacity (~ 200-400 mAh.g-1). Here, we present the possible use of a class of chalcogenide materials, AV4S8 (A=Ga,Ge), as a negative electrode in sodium-ion batteries.

The reactivity of AV4S8 with Na leads to a remarkable specific capacity of 800 mAh/g for the first discharge at a C/20 rate (1 complete charge in 20 hours), followed by a reversible reaction associated with a 500 mAh/g capacity retained after 30 cycles.

Many experiments were performed in order to understand the reaction mechanism of sodium with the AV4S8 materials. Electrochemical, in situ X-ray diffraction (Figure 1) and transmission electron microscopy experiments suggest that a smooth conversion mechanism is occurring and that the capacity fade is largely due to reactions with the electrolyte at low potential.

EDX and TEM observations, as well as EELS experiments performed at the vanadium L-edge, indicate that a reduction of the vanadium oxidation state occurs during the discharge process. XAS experiments performed at the Vanadium and Germanium K edges also clearly demonstrate that all the elements are involved during the electrochemical processes.

Synthesis, structural characterization and electrochemical behaviour of AV4S8 will be discussed in details in the presentation. Results obtained on the AV4S8 phases are very promising and demonstrate that this new class of materials is a good candidate as a negative electrode for Na-ion batteries.

References

(1). M. M. Doeff, Y. Ma, S. J. Visco,L. C. De Jonghe, J. Electrochem.Soc. 140, L169 (1993).

(2). P. Senguttuvan, G.l. Rousse, V. Seznec, J.-M. Tarascon, M.R. Palacin, Chemistry of Materials, 23, 4109-4111 (2011).

(3). S.I. Park, I. Gocheva, S. Okada, J.-i. Yamaki, J. Electrochem. Soc. 158, A1067-A1070 (2011).

(4). A. Darwiche, C. Marino, M.T. Sougrati, B. Fraisse, L. Stievano, L. Monconduit, Journal of the American Chemical Society, 134, 20805-20811 (2012).
Electrochemical Characterization of La0.9Sr0.1Ga0.8Mg0.2O3-δ Thin Film Electrolyte Deposited by Radio Frequency Magnetron Sputtering
Authors: Endo Yoichi , Terai Takayuki , Suzuki Akihiro
Published: February 2020

Sr and Mg dopoed Lanthunum Gallate (La0.9Sr0.1Ga0.8Mg0.2O3-δ, LSGM) is a well-known electrolyte for solid oxide fuel cell because of the high conductivity. Thin film material can exhibit different characterization from bulk material. Thus, electrochemical characterization of the LSGM thin film electrolyte was measured by impedance spectroscopy in intermediate temperature range under various oxygen partial pressures. In order to prepare the reliable LSGM film, radio frequency magnetron sputtering was used for depositing method. Safire single crystal disk was used as the substrate. As deposited, the film was amorphous. To obtain the crystallized LSGM film, we investigated the influence of the annealing temperature and the heating rate when annealing. By proper post-annealing, crystallized LSGM film was obtained.
Potential Dependent Adsorption and Desorption of Nafion on a Gold and a Platinum Electrode Surface
Authors: Masuda Takuya , Uosaki Kohei
Published: February 2020

Potential dependent adsorption and desorption of perfluorosulfonated ionomer (PFSI) on a gold and a platinum electrode surface was investigated by cyclic voltammetry (CV), electrochemical quartz crystal microbalance (EQCM), and electrochemical atomic force microscopy (EC-AFM) in a Nafion, that is, PFSI, dispersed aqueous solution without any other electrolyte. It was found that electrochemical measurements can be performed in this solution without any significant IR drop. PFSI adsorbed on the gold and platinum surfaces in the double layer region and desorbed from the surfaces when the oxide was formed. Once the oxide was reduced, PFSI readsorbed on the surfaces. These processes took place reversibly.

1) T. Masuda, K. Ikeda, K. Uosaki, Langmuir,
2013,
29, 2420.

2) T. Masuda, H. Fukumitsu, T. Kondo, H. Naohara, K. Tamura, O. Sakata, K. Uosaki, J. Phys. Chem. Soc.,
2013,
117, 12168-12171.

3) T. Masuda, F. Sonsudin, P. R. Singh, H. Naohara, K. Uosaki, J. Phys. Chem. Soc.,
2013,
117, 15704-15709.
HOR in Alkaline Membrane Fuel Cells: Hollow Octahedral Electrocatalysts
Authors: Shviro Meital , Polani Shlomi , Zitoun David
Published: February 2020

We have recently explored the binary system of NixPt1-x alloys for HOR in alkaline membrane fuel cells and demonstrated our ability to generate mainly [111] facets in octahedral nanocrystals using colloidal synthesis. [1] In a further experiment, galvanic replacement reaction has been used to introduce a third metal and has been successful in the case of other PGM, while etching part of the Ni. In some cases, the etching process yields hollow octahedral frames (see figure).

The catalysts are characterized by electrochemical measurements in 0.1 mol/L of KOH using cyclic voltammetry and polarization curves on glassy carbon rotating disc electrodes. After screening of the best electro-catalysts, a full characterization is carried out to probe the atomic structure by HRTEM, HAADF and EELS, in parallel with gas adsorption spectroscopy (mainly FTIR of CO species) and calorimetry to determine the nature of surface sites on the catalyst.

[1] Shviro, M.; Zitoun, D. RSC Adv.
2013, 3, 1380;
Recent Progress in Commercial PEM Fuel Cell Stacks
Authors: Kerkhof Wybe , Coolegem Jorg , Smit Mascha
Published: February 2020

Nedstack produces commercial PEM fuel cell stacks in the range of 2 to 10 kW for stationary applications, including backup power systems for the Telecom industry and energy recovery from byproduct hydrogen in the chlorine industry. Many of our stacks have already been installed in backup and continuous power systems for Telecom worldwide, and have been functioning for a number of years. At the same time, in our 70 kW PEM Power Plant in Delfzijl (Netherlands), which has run for over 40,000 hours, we have shown lifetimes of over 23,000 hours for our XXL stacks under real operational conditions.

An analysis of performance data from operation of Nedstack’s XXL stacks in the Delfzijl PEM power plant, as well as a detailed beginning-of-life and end-of-life characterization, including cyclic voltammetry and electrochemical impedance, will be discussed. Stacks show a steady averaged linear decay rate of only 2.3 mV/1000 hr during operation, resulting in a predicted lifetime of 30,000 hours (for a 10% allowable voltage decay). Based on the results, AST’s were developed for material degradation, which have led to better material selection, as well as an improvement in stack design. These have now led to further improved decay rates, below 2 mV/1000 hr, which corresponds to an expected lifetime of 39,000 hours, based on the assumption of linear decay.Nedstack produces commercial PEM fuel cell stacks in the range of 2 to 10 kW for stationary applications, including backup power systems for the Telecom industry and energy recovery from byproduct hydrogen in the chlorine industry. Many of our stacks have already been installed in backup and continuous power systems for Telecom worldwide, and have been functioning for a number of years. At the same time, in our 70 kW PEM Power Plant facility in Delfzijl (Netherlands), which has run for over 40,000 hours, we have shown lifetimes of over 23,000 hours for our XXL stacks under real operational conditions.

An analysis of performance data from operation of Nedstack’s XXL stacks in the Delfzijl PEM power plant, as well as a detailed beginning-of-life and end-of-life characterization, including cyclic voltammetry and electrochemical impedance, will be discussed. Stacks show a steady averaged linear decay rate of only 2.3 mV/1000 hr during operation, resulting in a predicted lifetime of 30,000 hours (for a 10% allowable voltage decay). Based on the results, AST’s were developed for material degradation, which have led to better material selection, as well as an improvement in stack design. These have now led to further improved decay rates, below 2 mV/1000 hr, which corresponds to an expected lifetime of 39,000 hours, based on the assumption of linear decay.
Design of Highly Durable Electrocatalyst for High-Temperature Polymer Electrolyte Fuel Cell
Authors: Fujigaya Tsuyohiko , Berber Mohamed Reda , Nakashima Naotoshi
Published: February 2020

Phosphoric acid-doped polybenzimidazoles (denoted PA-doped PBIs) have been considered as the most promising substitutive polyelectrolytes and the PEFC employing PA-doped PBIs not only in PEM but also in the catalyst layers (Cat-L) have been developed for high temperature operation. However, recent studies have revealed that leaching of liquid PA from PEM1) and Cat-L2) causes inhomogeneous PA distribution that results in deterioration of PEFC performance during long-term operation.

In this study, in order to prevent acid leaching from the high temperature PEFC system, we used poly(vinylphosphonic acid) (PVPA) in place of PA because PVPA is a polymeric acid and is stably bound to the PBIs via multipoint acid-base reactions. We fabricated a novel electrocatalyst for Cat-L assembled with carbon nanotubes (CNTs), PVPA-doped PBI and platinum (Pt) nanoparticles as an electron-conducting supporting material, electrolyte and metal catalyst, respectively. Bottom-up assembly of nanometer-thick PVPA-doped PBI layer around CNTs is expected to serve as an effective proton conduction pathway via the Grotthuss mechanism. The doping stability of PVPA in addition to the PEFC activity and durability were studied.

We tested the durability of the PVPA-doped MEA by following the protocol proposed by the Fuel Cell Commercialization Conference of Japan (FCCJ)3). As a comparison, the durability of a PA-non-doped MEA (MWNT/PyPBI/Pt electrocatalyst doped with leached PA) was tested. Dramatic drop of the cell voltage was observed for PA-non-doped MEA, while PVPA-doped MEA shows slight decrease (Fig. 1). Such high durability of PVPA-doped MEA shows an extended stability of PEM against degradation, and also shows a continuous connection of the proton path in the Cat-L4).

References

1) Y. Oono, T. Fukuda, A. Sounai, and M. Hori, J. Power Sources 195, 1007-1014 (2010).

2) Y. Oono, A. Sounai, and M. Hori, J. Power Sources 189, 943-949 (2009).

3) A. Ohma, K. Shinohara, A. Iiyama, T. Yoshida, and A. Daimaru, ECS Transactions 41, 775-784 (2011).

4) M. R. Berber, T. Fujigaya, K. Sasaki, and N. Nakashima, Sci. Rep. 3, (2013).
Synthesis of Reduced Graphene Oxides-Supported Binary Catalysts and Its Electrocatalytic Activity
Authors: Jeevagan Arockiam John , Gunji Takao , Hashimoto Masanari , Kaneko Shingo , Tanaka Manabu , Matsumoto Futoshi
Published: February 2020

Proton exchange membrane fuel cells (PEMFCs) have attracted wide attention beacause of their high energy efficiency and environmental freindliness.1 Noble nanoparticles (Pt, Pd) based binary alloys nanoparticles supported on carbon black were widely used in PEMFCs. Highly dispersed Pt based nanoparticles on Vulcan carbon (VC), carbon nanotubes (CNTs),carbon fibres exhibit enhanced electrocatalytic activites in PEMFCs. Recently, graphene nanosheets have been studied extensively as catalyst supports for PEMFCs owing to its high surface area, electrical conductivity and specific thermal/chemical stability.2 Graphene exhibit a unique structure of two-dimensional sp2-bonded carbon atoms with one-atom thickness and possess large surface area and higher electrical conductivity when compared to CNTs.3 But, the efficient immobilization of Pt nanoparticles on graphene surface remains a big challenge. Additionaly, It has been reported that chemical reduction of exfoliated graphene oxide (GO) could act as effective catalyst supporter because of their oxygen-containing functional groups which act as the binding sites for Pt nanoparticles on GO surfaces.4Herein, we demonstrate that, a one-pot synthesis of binary alloy catalyst under alkaline conditions.

Figure 1 shows the pXRD pattern (A) and TEM image (B) of Pt/RGO catalyst. The peaks between 30 and 90 can be indexed to Pt crystals of face-centered cubic structure (fcc). In TEM image, the Pt NPs are showed monodispersity and homogeneity on the RGO support catalyst. The details about the synthesis, characterization and catalytic activity of catalysts would be discussed in the presentation.

References

1. R. Wang, C. Xu, X. Bi and Y. Ding, Energy Environ.

Sci., 5, 5281, (2012).

2. R.H. Baughman, A.A. Zakhidov and W.A. de Heer,

Science, 297, 787, (2002).

3. Y.B. Zhang, Y.W. Tan, H.L. Stormer and P.Kim,

Nature, 438, 197, (2005).

4. B. Seger and P.V. Kamat, J. Phys. Chem. C, 113,

7990, (2009).
Investigation of Nb2O5/Graphene Supported Platinum-Cobalt Nanocomposite as Electrocatalyst for the Alkaline Alcohols Fuel Cells
Authors: Kepeniene Virginija , Vaiciuniene Jurate , Kondrotas Rokas , Pakstas Vidas , Tamasauskaite-Tamasiunaite Loreta , Norkus Eugenijus
Published: February 2020

In the present work, niobium oxide/graphene supported PtCo catalyst with the Pt:Co molar ratio 1:7 (denoted as PtCo(1:7)Nb2O5/GR) was fabricated by means of the rapid microwave heating polyol method. The surface morphology, structure and composition of the synthesized catalyst were examined by transmission electron microscopy, X-ray diffraction and inductively coupled plasma optical emission spectroscopy. The electrocatalytic activity of the synthesized catalyst towards the oxidation of alcohols – ethanol, methanol and ethylene glycol in an alkaline medium was investigated by means of cyclic voltammetry and chronoamperometry.

It has been determined that the Pt loadings was 0.285 mg Pt cm–2 in the synthesized PtCo(1:7)Nb2O5/GR catalyst. For comparison, the bare commercial Pt/C (Sigma-Aldrich) catalyst with 10% wt. Pt with the Pt loading of 0.385 mg Pt cm–2 was used. The electroactive surface areas (ESAs) of the prepared and commercial catalysts were determined from the cyclic voltammograms of PtCo(1:7)Nb2O5/GR and Pt/C catalysts recorded in a deaerated 0.5 M H2SO4 solution at a sweep rate of 50 mV s–1by calculating the charge associated with the hydrogen adsorption.

According to the data of TEM analysis, the Pt nanoparticles of ca. 1-2 nm in size were successively deposited onto the surface of graphene nanosheets.

It has been found that niobium oxide/graphene supported PtCo catalyst with the Pt:Co molar ratios 1:7 show an enhanced electrocatalytic activity towards the oxidation of alcohols in an alkaline medium as compared with that of 10% wt. Pt implicated commercial Pt/C catalyst. Alcohols oxidation current densities were found to be ca. 3 – 40 times higher at the PtCo(1:7)Nb2O5/GR catalyst in comparison with those at the commercial Pt/C catalyst. The prepared catalyst seem to be a promising anodic material for direct alcohols fuel cells.

Acknowledgement

Postdoctoral fellowship is being funded by European Union Structural Funds project ”Postdoctoral Fellowship Implementation in Lithuania”.
Enhancement of Electrocatalytic Activity for Oxygen Reduction Reaction on TiO2-Supported Pt-Based Intermetallic Compound Catalysts
Authors: Tanabe Toyokazu , Gunji Takao , Sasaki Kengo , Jeevagan Arockiam John , Tsuda Takashi , Kaneko Shingo , Saravanan Govindachetty , Abe Hideki , Tanaka Manabu , Matsumoto Futoshi
Published: February 2020

Stable and long-term electrocatalytic performance towards cathodic oxygen reduction reaction (ORR) was achieved by impregnation of Pt-based nanoparticles (NPs) on anatase titania (TiO2) support. For example, organometallic precursors PtCODCl2 and C10H14CuO4 and TiO2 or carbon black (CB) supports were co-reduced using lithium triethylborohydride to achieve intermetallic phase between Pt and Cu on TiO2(or CB) under ambient temperature. Finely dispersed PtCu NPs with an average particle size of 3 nm were achieved through wet-chemical synthetic route.

Potential cycle with PtCu/CB in 0.1 M HClO4 aqueous solution between 0.4-1.1 V (vs. RHE) accelerates ORR (Fig. 1) because of the formation of dealloyed surface of PtCu NPs caused by dissolution of Cu from the surface of PtCu NPs. The dealloyed PtCu/CB showed the highest electrocatalytic activity both in terms of onset potential as well as cathodic current density compared to Pt/CB as well as PtPb/CB and PtNi/CB towards ORR (Fig. 2). The onset potential of PtCu/TiO2 is shifted to higher electric potential by 180 mV compared to Pt/CB (Fig. 3).
Gold-Zinc-Cobalt Deposited on Titanium as Electrocatalysts for Borohydride Oxidation
Authors: Balčiūnaitė Aldona , Lichuina Svetlana , imkūnaitė Dijana , Zabielaitė Ausrine , Selskis Algirdas , Tamaauskaitė-Tamaiūnaitė Loreta , Norkus Eugenijus
Published: February 2020

Investigation of the electrochemical oxidation of borohydride in alkaline solutions on the ZnCo alloy deposited on the titanium surface and modified with gold nanoparticles (denoted as AuZnCo/Ti) is presented. The ZnCo alloy coatings with the thickness of ~5 µm were deposited on the titanium surface (1 x1 cm) via electrodeposition from the electrolyte described in Ref. [1]. Au crystallites were deposited on the ZnCo/Ti surface via the galvanic displacement technique. The ZnCo/Ti catalysts were immersed into the 1 mM HAuCl4 + 0.1 M HCl solution at 25 oC for 0.5, 1 and 5 min, respectively [2].

The morphology, structure and composition of the prepared catalysts were examined by Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray Analysis and Inductively Coupled Plasma Optical Emission Spectroscopy. Electrocatalytic activity of the prepared catalysts was investigated towards the oxidation of borohydride by means of cyclic voltammetry, chronoamperometry and chronopotentiometry.

It has been determined that the AuZnCo/Ti catalysts with Au loadings of 31, 63 and 306 µg cm-2 show enhanced catalytic activity towards electro-oxidation of BH4
– ions as compared to that of ZnCo/Ti or Co/Ti catalysts. The chronoamperometry and chronopotentiometry studies also confirmed a high electrocatalytic activity of the AuZnCo/Ti catalysts for the direct electro-oxidation of BH4
– ions as compared to that of ZnCo/Ti and Co/Ti catalysts.

References

[1] E. Juzeliunas, S. Lichusina. Patent of the Republic of Lithuania No. 5481 26.03.2008.

[2] L. Tamasauskaite-Tamasiunaite, A. Jagminiene, A. Balciunaite, A. Zabielaite, J. Vaiciuniene, A. Selskis, R. Juskenas, E. Norkus. Int. J. Hydrogen Energy 38 (2013) 14232-14241.
Laser Sealing Technique for Fuel Cell Application
Authors: Lin Chih-Chia , Wang Wen-Lin , Shie Ho-yan
Published: February 2020

A complete fuel cell stack comprises several single cells with end plates, collector plates, monopolar plates, gasket, and MEA components. Electron generated from cells can be conducted through bipolar plates. However, the amount of cell components increases with great cell power, which is inconvenient for fuel cell assembly process and mass production. During 2010, fuel cell systems were manufactured more than 15,000, the power of which was more than 8MW. With the market growth of hydrogen energy and fuel cells, developing high-speed modular assembly technique becomes a priority research to meet market requirements. Furthermore, extra back pressure is necessary for fuel gas in the fuel cell stack utilized in transportations to promote the fuel cell performance; gas leakage therefore becomes an important issue with an increase in the amount of cell components and gas pressure.

Consequently, laser welding technique is utilized in fuel cell stack design, which has advantages of narrow welding path and high welding aspect ratio, small amount of deformation for specimens, fast welding velocity, high strength welding, and easily integrated into automation equipment, to achieve the objective for high strength and accuracy modular sealing and promoting production capacity and quality. Parameter analysis for laser welding, optical measurement tests and peel tests are conducted to obtain the optimal welding quality and strength, the sealing strength of which can sustain at least 0.4 MPa stress (4 atm pressure). Moreover, new fuel cell stack structure is subsequently designed for this high strength and accuracy modular sealing technique in the future research.
Morphological Differences in Short Side Chain and Long Side Chain Perfluorosulfonic Acid Proton Exchange Membranes at Low and High Water Contents
Authors: Buratto Steven K , Economou Nicholas J
Published: February 2020

Ionomer membrane materials such as Dupont’s Nafion® (a sulfonated tetrafluoroethylene based fluoropolymer) have long been used as the proton conducting medium in proton exchange membrane (PEM) fuel cells. It has recently been shown that short side chain perfluorosulfonic acid membranes such as Hyflon Ion® developed by Solexis can outperform the benchmark long side chain material, DuPont’s Nafion®. Despite these promising results, a detailed understanding of the relationship between membrane morphology, hydration, and fuel cell performance has yet to be achieved. Using atomic force microscopy (AFM) phase imaging over a wide range of relative humidity and in solution, we compare a Nafion 212 membrane to Hyflon Ion® E87-05 and find evidence of the improved performance in the latter. Hyflon exhibits a higher hydrophilic surface area across all water contents, explaining its higher proton conductivity and fuel cell performance. At high water contents, the surface of Nafion® undergoes significant structural rearrangement and forms large rod-like features parallel to the surface, whereas the Hyflon Ion® membrane undergoes little if any such transition. [see the figure] We show using conductive AFM that these features are insulating, which indicates they most likely consist of a fluorocarbon layer surrounding a hydrophilic core and do not contribute to fuel cell performance. The ability of Hyflon to undergo changes in water content with minimal rearrangement of hydrophilic domains implies an ability to operate more effectively under variable relative humidity.
Invited: Engineering Net Water Balance in Polymer Electrolyte Fuel Cells
Authors: LaManna Jacob M , Mench Matthew M.
Published: February 2020

The motivation of this work is to understand and control the water balance of a polymer electrolyte fuel cell to reduce anode water buildup and degradation. A custom 4.8 cm2 fuel cell with precision liquid coolant control was used to acquire the water balance data. The precision liquid coolant ensures stable, high accuracy thermal boundary conditions for the analysis. The net water drag coefficient was measured by placing high accuracy dew point temperature sensors at the inlets and outlets of the fuel cell to measure water balance. Gradients in pressure, inlet relative humidity, and temperature were used to isolate hydraulic, diffusion, and temperature driven flow through the membrane and porous media.

This presentation will focus on the effects of anode land width, channel shape, and diffusion media tortuosity on net water drag. Using neutron radiography data that has been previously presented (1, 2) coupled with net water drag data, conclusions will be presented relating performance and water transport and storage. Data from this work will build upon an online database of benchmark data for the modeling community made available through this Department of Energy EERE supported program.

Acknowledgements

This work is funded by the United States Department of Energy Efficiency and Renewable Energy (EREE) Program through General Motors under Award Number DE-EE0000470.

1. J. M. LaManna, S. Chakraborty, J. J. Gagliardo and M. M. Mench, International Journal of Hydrogen Energy, 39, 3387 (2014).

2. J. LaManna and M. Mench, Meeting Abstracts, MA2014-01, 646 (2014).
The Role of Gas Diffusion Layer in Cationic Contamination and Mitigation in Polymer Electrolyte Fuel Cells
Authors: Uddin Md. Aman , Park Jaehyung , Wang Xiaofeng , Qi Jing , Pasaogullari Ugur , Bonville Leonard J. , Molter Trent
Published: February 2020

Cationic impurities may get introduced into Polymer Electrolyte Fuel Cells (PEFC) from the ambient air (e.g. roadside contaminants) and from the corrosion of stack and balance of plant components. Recovery from cationic impurities is investigated by simulating the cationic contamination with equilibrium uptake of the membrane electrode assembly (MEA) in a salt solution. The cation uptake into the ionomer was performed by soaking the MEA in 0.9 mM CaSO4 and 29.1 mM H2SO4 solution following Kienitz’s procedure (1). Three different methods were used to soak the MEA into the solution to understand the role of the gas diffusion layers (GDL) (as shown in Figure 1): (A) entire CCM is exposed (50 cm2), (B) portion of the CCM is covered with GDL and the remainder is exposed, and (C) portion of the CCM is covered with GDL and the remainder is covered with PTFE seals used in cell assembly. Prior to soaking, all MEAs were tested to obtain baseline performance. In the first two methods (A and B), significant performance drop were observed due to Ca2+ presence inside the CCM (shown in Figure 2). In case of the third method (C), there were no significant performance changes. Even when the soaking time was increased to more than 4 times in method C compared to method A, cell performance did not change significantly. It is clear that GDL acts as a barrier to the transport of Ca2+ to the CCM. When surfactant was added to the cationic solution to increase the wettability of the GDL, a drop in the performance was observed.

To recover the cell performance, we re-protonated the CCMs in an acidic solution similar to Qi et al. (2). They re-protonated CCMs contaminated at different levels of Al3+ (similar to method A in Figure 1) with ex-situ soak in the acid solution (1 M H2SO4) and recovered the full performance decay. We also recovered the performance back near to the baseline when only the CCM is soaked (method A), but for the other two methods, the cell performance is partially recovered. We also performed in-situ injection of 1-10 mM H2SO4, and the cells were seemingly not affected by the in-situ injection of the acid solution. We conclude that the GDL is hindering the transport of Ca2+ in and as well as out of the MEA. Thus, recovery appears to be possible but additional factors need to be identified that hinder this process.

Acknowledgements

The authors are grateful for the financial support of the Department of Energy (DOE)-EERE, DE-EE00000467 (University of Hawaii, prime contractor, Jean St-Pierre, PI).

References

B. Kienitz, B. Pivovar, T. Zawodzinski and F. H. Garzon, J. Electrochem. Soc., 158, 9 (2011).

J. Qi, X. Wang, U. Pasaogullari, L. Bonville and T. Molter, J. Electrochem. Soc., 160, 9 (2013).
Enzyme Immobilization Using Carbon Nanotubes for Direct Electron Transfer in a Hybrid Membraneless Fuel Cell
Authors: Escalona-Villalpando Ricardo Antonio , Dector Andrés , Galvan-Valencia Marisol , Duron-Torres Sergio Miguel , Ledesma-García Janet , Arriaga Luis Gerardo
Published: February 2020

Hybrid membraneless fuel cells HMFC are devices that use an abiotic catalysts and an enzymatic material, in the anode or cathode, with the main target of provide stability and higher performance. HMFC was evaluated using Glucose oxidase enzyme supported in Multiwalled carbon nanotubes and glutaraldehyde mixtures (GOx/MWCNT-GA) and Pt/C as anode and cathode respectively under ideal conditions. The anode electrode based on GOx/MWCNT-GA was characterized by electrochemical techniques showing a successful direct electron transfer (DET) between GOx and MWCNT to electrode surface. The performance of ideal
HMFC delivers a higher OCP of 1.2 V and a maximum power density of 200 µW cm-2 in the presence of 10 mM glucose as fuel in phosphate buffer (PB) pH 7 as anolyte and oxygen-saturated 0.3M KOH as catholyte. These results show a highest performance reported to HMFC that implement DET in the anode electrode, with potential application in implantable devices inside living organisms.
Ångstrom Resolved Monitoring of Noble Metal Oxide Growth in Nano-Confined Spaces
Authors: Shrestha Buddha Ratna , Baimpos Theodoros , Raman Sangeetha , Valtiner Markus
Published: February 2020

Structure and dynamics at electrochemical solid/liquid interfaces of metal electrodes drive functionality, stability and capabilities in a wide range of important technologies such as batteries, super capacitors, or fuel cells. In particular, with the downsizing of the electrochemical devices, electrochemistry in confined spaces (nanospaces) has become a major focus of current research efforts. We use a newly developed and unique electrochemical surface force apparatus1 in order to unravel electrochemical processes undergoing at well-defined nano-confined electrodes. We can monitor metal-oxide film formation with Å-accuracy during potentiostatic and potentiodynamic polarizations, within nano-confined spaces (less than 10 nm up to 100’s of nm). We report unexpectedly strong electrochemical depletion forces acting between apposing surfaces during active electrochemical processes such as potential pulse application or reduction of oxide. Such forces and the associated electric-field gradients might have significant effect in coarsening or mechanical dissolution of nano-confined spaces and confined particles. In addition, we are also able to reveal a real time in-situ monitoring of electrochemical interfaces with Angstrom resolution. We have, for the first time, monitored oxide growth on noble metals in sulfuric acid solutions in real time, with Ångstrom resolution in thickness and milliseconds resolution in time. Our experiments reveal stark differences of oxide thickness and electronic properties during potentio-dynamic and potentio-static oxide growth on noble metals, which will be discussed in the presentation.

1. Valtiner, M.; Banquy, X.; Kristiansen, K.; Greene, G. W.; Israelachvili, J. N., The Electrochemical Surface Forces Apparatus: The Effect of Surface Roughness, Electrostatic Surface Potentials, and Anodic Oxide Growth on Interaction Forces, and Friction between Dissimilar Surfaces in Aqueous Solutions. Langmuir
2012,
28 (36), 13080-13093.
Synthesis and Characterization of Controllably Branched Anodized Aluminum Oxide Pores
Authors: Gillette Eleanor , Wittenberg Stefanie Sherrill , Banerjee Parag , Lee Sang Bok
Published: February 2020

Well-ordered anodized aluminum oxide (AAO) is a widely known porous material which has been used in a variety of applications. One of the advantages of AAO is its tunable pore diameter and length, which are controlled by the anodizing conditions. Additionally, more complex structures can be produced by modifying the anodization and etching conditions. Here we present a technique for introducing branch points into the pores which allows for controllable branching in sections of the pores while maintaining straight, hexagonally arrayed, regular structures throughout the rest of the alumina membrane.

We also demonstrate that this method can be integrated with a strategy for barrier layer thinning and removal which allows for the use of the underlying aluminum as a current collector. This allows these 3-D networks to be used as electrodes, without having to withstand the normal processing route, which requires wet etches to remove the aluminum and then remove the barrier layer, followed by vacuum deposition of a new current collector. This process is difficult to carry out for very thin membranes, since AAO is brittle and prone to cracking and shattering. This new combination of techniques allows the production and electrochemical characterization of very thin (>3um) porous networks, ranging from well-ordered 1D channels to highly branched 3D networks.

First, we demonstrate electrodeposition into these pores, to confirm the opening of the barrier layer, and to demonstrate that the branched pores are accessible to electrolyte. Then, a variety of networks of different thicknesses and numbers of branch points are characterized by electrochemical impedance spectroscopy. Since this method allows branch points to be added at various intervals along the pores, networks with different numbers of branch points as well as with different spacing between the branch points can be analyzed as well. This study is focused on understanding the movement of electroactive species through porous networks of increasing complexity, as well as demonstrating a new potential template for electrodeposition of 3D electrodes.
A New Understanding of Chemical Expansion in Non-Stoichiometric Cerium Oxide with Elastic Force Dipole
Authors: Er Dequan , Li Junwen , Cargnello Matteo , Fornasiero Paolo , Gorte Raymond J. , Shenoy Vivek B.
Published: February 2020

In this work, a new continuum model, informed by DFT simulations, is developed to predict the chemical expansion observed in non-stoichiometric oxides and is applied to study the expansivity of oxygen vacancies in CeO2. The chemical expansion is a summation of two competing processes: the formation of oxygen vacancy and the change in cation radius. We introduce an elastic dipole tensor to determine the elastic energy per defect introduced to the system around the oxygen vacancy. We show that this tensor, which can be accurately predicted from first-principle DFT calculations, can be used to predict the chemical expansion of ceria as well as other fluorite structure oxides. Compared to previous work which obtains expansivity based on empirical potentials, our work provides an efficient way of computing it directly by DFT calculations. Furthermore, we discuss how the elastic dipole tensor can predict the O2 partial pressure vs O/Ce ratios in strained systems and show that CeO2 can be reduced more easily in the presence of tensile strains.