bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Gas-Phase Detection of Volatile Organic Compounds Using a Solid-State Conductive Polymer Electrolyte
Authors: Willis Christina Nicole , Saffary Yalda , Misra Mano , Mohanty Swomitra K. , Tripathy Anurag
Published: February 2020

Rapid screening of tuberculosis by evaluation of associated volatile organic compounds (VOCs) in breath has been shown to be a promising technology that is significantly faster and more convenient than traditional sputum culture tests. Methyl nicotinate and methyl p-anisate have been isolated as specific biomarkers for the mycobacterium tuberculosis, as they are not found in high concentrations in ambient air or the breath of healthy patients, but should be readily present in all patients with active TB. These VOCs can be electrochemically detected using a solid-state sensor based on metal-functionalized 3D titanium dioxide nanotube arrays (TNAs), as shown by Bhattacharyya et. al. [1]. This chronoamperometric method uses a two-electrode system, in which the pure titanium back of the sensor functioned as both the counter and reference electrode, meaning that the applied current is highly dependent on the resistance of the nanotubes and difficult to reproduce from sensor to sensor. This work will discuss two improvements to the current method: 1) a move to a three-electrode system using a solid electrolyte, and 2) potential scanning electrochemical methods used for detection.

To improve reproducibility and specificity of the sensor, the platform has been modified to use a solid-state, conductive electrolyte in order to create a gas phase three-electrode system. A conductive polymer of known resistance is used to separate the functionalized TNA from the silver-painted counter and reference electrodes. Doing this ensures more consistent interactions with the analyte of interest between sensors. In addition to the electrode changes, new scanning potential methods such as cyclic voltammetry (CV) and square wave voltammetry (SWV) have shown promise in detecting the analytes more specifically than chronoamperometry. For example, running cyclic voltammetry using cobalt functionalized sensors shows a reduction peak at about -0.5 V vs a silver quasi-reference electrode when exposed to methyl nicotinate vapor. Results comparing different electrochemical methods and specific responses to the biomarkers will be presented.

[1] D. Bhattacharyya, Y. R. Smith, S. K. Mohanty, and M. Misra, “Titania Nanotube Array Sensor for Electrochemical Detection of Four Predominate Tuberculosis Volatile Biomarkers,” J. Electrochem. Soc., vol. 163, no. 6, pp. B206–B214, 2016.
(Invited) The Role of Advanced Characterisation in Understanding the Initiation and Propagation of Failure in Li-Ion Batteries
Authors: Shearing Paul R.
Published: February 2020

Recent years have witnessed a number of high profile failures of Li-ion batteries; from cell-phones to aircraft, it is essential to improve understanding of failure mechanisms in order to design solutions to effectively mitigate the risks of cell thermal runaway. The increasingly diverse and demanding range of applications for Li-ion batteries necessitates a redoubling of efforts to tackle safety issues. Here, we apply a suite of in-situ and operando characterisation tools to understand safety and failure criteria over a range of time and length scales.

At the electrode length scale, we utilise high resolution X-ray computed tomography to examine the complex, heterogeneous microstructures characteristic of Li-ion batteries. These can be effectively combined with imaged based modelling tools to explore the local electrochemical and physical behaviour, which can be correlated with electrochemical and thermal measurements. We can extend these investigations into the fourth dimension to explore the change in electrode morphology with time, to evaluate the role of microstructure evolution on cell degradation and failure.

At the cell length scale, we utilise a combination of high-speed X-ray imaging, thermal imaging, calorimetry and acoustic spectroscopy, to understand the nucleation and propagation of failure in devices.

In concert, these tools provide unique insight into degradation and failure process from the particle to the cell scale, from sub-second thermal runaway, to long term in-situ degradation studies. Increasingly we are equipped to evaluate new innovations in Li-ion battery technology, and moreover to effectively design and optimise next generation battery chemistries.
(Invited) Influence of Cell Design Features on Low Temperature Cycling Performance and Safety Assessed with Accelerated Rate Calorimetry and Micro X-Ray Computed Tomography
Authors: Love Corey T , Carter Rachel E. , Klein Emily J
Published: February 2020

Often cell design features like form factor and electrode dimensions are guided by weight and cost demands. However, these features strongly influence the safety of the cell by altering the probability and/or severity of a failure. Herein we assess the performance and safety of various cylindrical cell designs subjected to low temperature charge/discharge cycling. Specifically, cylindrical aspect ratio and the presence of a center mandrel is compared. During isothermal low temperature cycling, a radial thermal gradient develops, since the skin of the cells is steadily cooled while the active materials are warmed due to Joule heating during the flow of ions and electrons.1 This thermal gradient induces lithium metal plating2-3 near the cell core which causes (1) capacity loss and (2) mechanical deformation. With variation in aspect ratio, the intensity of the thermal gradient is modulated and with incorporation of a mandrel, typically made of steel, some core heat is dissipated. For each cell, capacity fade is quantified, followed by examination of the mechanical deformation with micro x-ray computed tomography. Finally, cell safety is assessed with accelerated rate calorimetry. The low temperature cycled cells initiate thermal runaway at temperatures as low as 50˚C and can exhibit dramatic rare and dangerous failure modes like jelly roll ejection.

Mistry, A. N.; Smith, K.; Mukherjee, P. P., Electrochemistry Coupled Mesoscale Complexations in Electrodes Lead to Thermo-Electrochemical Extremes. ACS Appl Mater Inter
2018,
10 (34), 28644-28655.

Carter, R.; Love, C. T., Modulation of Lithium Plating in Li-Ion Batteries with External Thermal Gradient. ACS Appl Mater Inter
2018,
10 (31), 26328-26334.

Love, C. T.; Baturina, O. A.; Swider-Lyons, K. E., Observation of Lithium Dendrites at Ambient Temperature and Below. ECS Electrochem Lett
2015,
4 (2), A24-A27.
Investigation of Lithium-Ion Battery Interface Degradation Mechanism through EIS Analysis Under Various Cycling Conditions
Authors: Dong Bo , Li Yige , Ozkan Cengiz , Ozkan Mihri
Published: February 2020

Lithium-ion batteries have attracted enormous attention in the past decade both in the academia and in the industry due to their extreme high energy and power density compared with the conventional battery systems. Stepping into 2019, the lithium-ion battery industry unprecedentedly focuses on the fast charging and diagnosis solutions, especially for the dynamic battery systems. However, the complicated environmental conditions, such as vibration, extreme temperature change, overcharging or overdischraging, fast charging, various testing techniques, combined with insufficient understanding of the State of Health (SOH) of the commercial batteries lead to thermal runaway, aging and explosion issues to the batteries.

Stemmed from that fact, EIS (Electrochemical Impedance Spectroscopy) technique has been proposed to accurately determine the SOH of the commercial batteries. EIS has been proved to be an effective approach to investigate the electrochemical, structual and dynamical properties of the electrochemical systems, especially the interfaces. The study focuses on the effects of one of the most concerning technique "fast charging" and one testing technique, GITT (Galvanostatic Intermittent Titration Technique). Under pre-design conditions, EIS with pre-built equivalent circuit is then implemented at specific conditions to further gather the electrochemical and structural properties of the interfaces inside the battery at proper voltages. Finally, the electrochemical and structual degradation mechanism especially of the interfaces under various conditions is achieved, which inspires further investigation on the comprehensive analysis and determination of the SOH of the lithium-ion batteries. The proposed approach has shown better accuracy and more in-depth analysis compared with the existing techniques.
(Invited) Lithium Plating and Its Impact on the Safety of Lithium-Ion Cell
Authors: Zhang Jianbo , Liu Zhongxiao , Dong Peng , Li Zhe
Published: February 2020

Lithium plating is prone to occur in lithium-ion cell (LIC) under quick charging at low temperature. The morphology, distribution, and amount of plated lithium depends on the operation conditions and cell design, and in turn, will cause capacity fade and may induce short circuit or even dramatic safety events. This talk will introduce our systematic study on the interrelationship among the operation conditions, the plated lithium, and the safety characteristics using both coin cells and pouch cells. Key safety parameters are extracted from the accelerated rate calorimeter test of new and lithium-plated cells. The events leading to the thermal runaway are examined and compared with multi-physics measurement, including pressure, stress, and electrochemical impedance spectroscopy (EIS) etc. Implications for the cell design improvement, battery management optimization, and early detection techniques will be discussed.
Long–Term Aging – Overdischarge Degradation Mechanisms Interplay in Li-Ion Pouch Cells
Authors: Juarez-Robles Daniel , Jeevarajan Judith A. , Mukherjee Partha P.
Published: February 2020

Battery Management Systems (BMS) ensure that cells within a module are cycled appropriately even though the cells may have a different capacity. For large commercial applications, modules may have a few thousand cells making it more challenging to monitor and control each cell individually. A capacity imbalance will not only affect the module performance but it can lead to an overcharge/overdischarge condition on the single cells.

Overdischarge occurs when a Li-ion cell is discharged below its safe electrochemical window. If the cell is extremely overdischarged, a reverse potential condition takes place followed by the dissolution of the copper current collector. In a module without an adequate BMS, overdischarge can occur frequently. Its interaction with the natural aging degradation of the cell may pose a threat to safety issue.

In this work, the interaction between aging and overdischarge in Li-ion cells is studied. The aim is accomplished by aging single pouch cells at different overdischarge levels, prior and after the onset of reverse potential. Electrochemical and morphological characterization of the abused cells will be conducted. Results will provide insights on the interaction of the two degradation mechanisms and the interaction of their corresponding effects.
Post-Chemical Modification of Doped Sites of Locally Functionalized Single-Walled Carbon Nanotubes for Multistep Photoluminescence Modulation
Authors: Shiraki Tomohiro , Shiga Tamehito , Nakashima Naotoshi , Fujigaya Tsuyohiko
Published: February 2020

Locally functionalized single-walled carbon nanotubes (lf-SWNTs) have local defects on the sp2 carbon networks of the tube structures through chemical modification using ozonization and diazonium chemistry.[1-8] They emit redshifted photoluminescence (PL) with high efficiency compared to original PL (E
11) of pristine SWNTs. The newly generated PL (E
11*) of lf-SWNTs shows PL wavelength variation and selective wavelength shifts based on the modified molecule structures. For example, protonation of amino groups[1] and molecular recognition[6, 7] at the doped sites effectively induced wavelength shifting of E
11* PL. Such external stimuli responsiveness, therefore, is expected to develop advanced sensing and imaging materials and optical devices using the near infrared (NIR) PL functions.

In this study, the doped sites are newly designed as a chemical reaction platform for versatile modulation of the E
11* PL.[8] We employ imine chemistry at the doped sites of lf-SWNTs. Imine bond is formed by a condensation reaction between aldehyde and amine groups. The dynamic bonding feature also allows reversible bond formation and exchange reactions of the bound molecules.

Firstly, aromatic aldehyde-modified lf-SWNTs (lf-SWNTs-CHO) were synthesized. Chemical reactions for imine formation using lf-SWNTs-CHO were examined by mixing various aniline derivatives. The lf-SWNTs-CHO showed a PL peak at 1140 nm (E
11*) which was redshifted than the E
11 PL (980 nm). When p-methylaniline, p-bromoaniline or p-nitroaniline was mixed with the lf-SWNTs-CHO, wavelength shifts of the E
11* PL occurred, which provided different wavelength shift values Dl (= λ(E
11*) − λ(E
11)) of 154, 163, and 165 nm, respectively. The result indicates that the observed wavelength shifts of E
11* depend on the chemical structures of the bound aniline derivatives in the imine bond. Moreover, additional chemical reactions including exchange reactions of the bound aniline derivatives and the Kabachnik-Fields reaction realized further wavelength changes in the E
11* PL of the lf-SWNTs.

Thus, the present approach using post-modification of the doped sites achieves multistep PL modulation based on the local chemical reactions.

References: [1] Schatz, G. C. and Wang, Y. et al., J. Am. Chem. Soc.
2016, 138, 6878. [2] Htoon, H. and Doorn, S. K. et al., Nat. Photon.
2017, 11, 577. [3] Shiraki, T. and Nakashima, N. et al., Sci. Rep.
2016, 6, 28393. [4] Shiraki, T. and Nakashima, N. et al., Nanoscale.
2017, 9, 16900. [5] Shiraki, T. and Nakashima, N. et al., Chem. Commun.
2017, 53, 12544. [6] Shiraki, T. and Nakashima, N. et al., Chem. Commun.
2016, 52, 12972. [7] Shiraki, T. and Nakashima, N. et al., Chem. Eur. J.
2018, 24, 9393. [8] Shiraki, T., Nakashima, N., Fujigaya, T. et al., Chem. Eur. J.
2018, 24, 19162.

Figure 1
Compromised Power Capability of Yarn-Shaped Supercapacitors and Its Mitigation Strategies
Authors: Gao Wei
Published: February 2020

Supercapacitors are known to have superior power densities over batteries due to their surface-centered charge-discharge processes. Recently, increasing attention has accumulated in the fiber or yarn shaped supercapacitor (FSC) systems, mainly due to their high flexibility and pliable nature, leading to potential applications in wearable electronics, microrobots, medical implants, and smart textiles. However, one of the major limitations that occurs when supercapacitors are made into fiber/yarn shapes, is the increased equivalent series resistance (ESR) due to the fibrous geometry adopted here. For instance, even the best FSC reported will exhibit several hundred ohms of resistance at one-meter length, which however is usually neglected by researchers in their publication.

To directly tackle this issue, here we report our strategies of using a metallic core filament in the yarn supercapacitors development in our lab. With detailed materials and process engineering, we are able to boost the power density by one order of magnitude. Sealing strategies and other alternative solutions for this issue will also be discussed.
Ba0.5Sr0.5CoxFe1-XO3-Δ: Investigation and Use of Multicationic Pseudocapacitive Oxides
Authors: Brousse Thierry , Lannelongue Pierre , Le Vot Steven , Fontaine Olivier , Bodin Charlotte , Douard Camille , Crosnier Olivier , Iadecola Antonella , Favier Frederic
Published: February 2020

BSCFs oxides have been prepared by sol-gel process followed by high temperature treatment. The resulting powders show the same perovskite structural arrangement as well as identical morphology characteristics. BSCFs electrodes were tested in 5M LiNO3 aqueous electrolyte, and have demonstrated promising pseudocapacitive behavior while performances depend on the Co/Fe ratio. A maximum capacitance of 87 F.g-1 was obtained for the electrode based on the BSCF material with x = 0.80. Charge storage mechanism was investigated by in situ X-Ray Absorption Spectroscopy carried out on the ROCK beamline at SOLEIL Synchrotron (France) at both Fe and Co K-edges. Both Co and Fe were found being electrochemically involved in the charge storage mechanism. XAS in situ measurements allow to propose an advanced description of the charge storage mechanism. It shows the involvement of electrolytic cations but also of oxygenated moieties.

BSCFs oxides were also investigated in asymmetric devices using FeWO4 or activated carbon as negative electrode. These two devices were operated between 0 and 1.6 V and have demonstrated a remarkable cycling ability with a high capacitance retention over 45,000 cycles. The advantages and limits of high density oxides with pseudocapacitive behavior operated in devices will also be highlighted in this study.
Analysis of PEFC Gas Transport by Combination of X-Ray Radiography and Numerical Simulation
Authors: Naito Hiroshi , Kawamura Katsuyuki , Sakai Katsunori , Sasabe Takashi , Hirai Shuichiro
Published: February 2020

Polymer Electrolyte fuel cell ( PEFC ) is one of well established power-generating equipment and has become a focus of attention. The power generation process of PEFC includes a chemical reaction producing water. In a usual operating condition, water condenses inside MEA, and this liquid water accumulation is considered to affect the degradation of performance by preventing oxygen transport to the catalyst layer. In this study, to understand this phenomena, we have conducted a visualization of liquid water using X-ray microscope, and a two-dimensional numerical simulation of gas transport inside MEA. First, we have obtained liquid water distribution inside MEA by the X-ray visualization ( fig.1 ), and then incorporate the liquid water distribution into the numerical simulation as a reduced mean porosity ( i.e. reduced effective diffusion coefficient) as shown in fig.2. The resultant oxygen distribution with a condition of 3A/cm2current density, 40℃cell temperature, 80% relative humidity and 1atm gas pressure, shows lower oxygen concentration above land ( fig.3 ). In the presentation we will focus on effects of liquid water accumulation in detail by comparing with a simulation neglecting liquid water accumulation.

Figure 1
Engineering PGM-Free Electrodes to Facilitate Improved Performance for the Oxygen Reduction Reaction in Polymer Electrolyte Fuel Cells
Authors: Osmieri Luigi , Wang Guanxiong , Neyerlin K C
Published: February 2020

With the aiming of reducing stack cost, the investigation of platinum group metal (PGM)-free catalysts for oxygen reduction reaction (ORR) has gained a lot of interest in the recent decades,1 with the majority of focus on improved electrocatalysis via various precursors and synthesis methods. The most promising PGM-free catalysts in terms of activity are carbon-based materials doped with nitrogen and active transition metals (like Fe, Co, and Mn), obtained by high temperature pyrolysis.2

The literature regarding synthesis, characterization, and rotating disk electrode (RDE) performance of this class of PGM-free materials is abundant, with many works reporting beginning of life performance testing in PEFC. Relative to the extensive literature on electrocatalyst fabrication, a less extensive and rigorous examination of PGM-free electrode design has been performed.

A number of variables like ionomer content, catalyst deposition method (e.g. spray coating, blade coating, hand painting), ink concentration, ink solvent composition and ink evaporation rate may influence PEFC performance. All of these process variables, along with the properties of the electrocatalyst itself, can alter the electrode ionomer distribution,3 resulting is significant differences in gas transport and electrode proton conductivity.3–5

In this work, we examine the impact of ionomer content, ink deposition method, and ink solvent composition on the PEFC performance of a commercially available PGM-free catalyst (Pajarito Powder LLC). Electrode properties will be assessed using different electrochemical diagnostics techniques. The viability of H2 limiting current will be discussed as a means to extract the pressure dependent and independent mass transport resistance of the electrode layer.6,7 Cyclic voltammetry and electrochemical impedance spectroscopy will be used to determine electrode capacitance and subsequently related to ionomer coverage and proton conductivity8,9 and contrasted with SEM images of MEA cross sections.

Through this methodology we will demonstrate how the electrode fabrication process plays a crucial role in electrode properties and the absolute performance.

References:

U. Martinez et al., Adv. Mater., 1806545, 1806545 (2019).

Y. Shao, J.-P. Dodelet, G. Wu, and P. Zelenay, Adv. Mater., 1807615, 1807615 (2019).

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Cyclic Hygral Swelling and Shrinkage Behavior of Fuel Cell Membranes
Authors: Sadeghi Alavijeh Alireza , Bhattacharya Sandeep , Kjeang Erik
Published: February 2020

Mechanical membrane durability is a key factor for the overall lifetime of PEM fuel cells. It is therefore important to understand the impact of the dynamic membrane hygral swelling and shrinkage characteristics on the in-situ mechanical stresses and the associated mechanical durability. In this work, an in-depth experimental investigation was carried out to determine the cyclic hygral swelling and shrinkage properties of four commonly used types of fuel cell membranes: Nafion® NRE211, two different expanded polytetrafluoroethylene (ePTFE) reinforced perfluorosulfonic acid ionomer membranes, and one hydrocarbon membrane. In addition to the bare membranes, the effect of coating the membranes with catalyst layers on the hygral swelling/shrinkage behavior was also investigated. Tensile specimens were subjected to ex-situ hydration and dehydration cycles using a dynamic mechanical analyzer (TA Instruments Q800 DMA) equipped with an environmental chamber, wherein the dynamic swelling and shrinkage characteristics as well as the residual stresses were measured for each membrane by displacement sensor and load cell, respectively. Hydrocarbon and reinforced PFSA ionomer membranes revealed higher shrinkage than swelling at each RH cycle, resulting in an overall shrinkage. Inside a fuel cell stack where membrane swelling and shrinkage is constrained, the observed shrinkage would result in internal tensile stress in the membrane and adjacent components, and hence reduce the overall membrane mechanical durability. The accumulation of residual stress during successive RH cycles was therefore measured explicitly using a custom-designed constrained shrinkage test and compared to the tensile properties of each individual membrane. For example, the hydrocarbon membranes analyzed in this work showed large residual stresses (severe contraction) during confined shrinkage at 80oC that exceeded their yield stress, and are therefore deemed prone to failure after repeated RH cycles. In addition, the hygral swelling and shrinkage behavior of each membrane was compared to the corresponding catalyst-coated membranes and the reinforcement offered by the catalyst layers was determined. The identified swelling and shrinkage properties, generalized into three different categories of overall cyclic behavior, have vital implications for the development of durable fuel cell membranes and membrane electrode assemblies. In addition to providing good mechanical strength, the membranes are also expected to accommodate or preferably eliminate progressive shrinkage stresses during dynamic fuel cell operation.
A High-Performance Membrane Electrode Assembly for PEM Fuel Cell with Poly (ether sulfone) Nanofibers As Effective Membrane Reinforcements
Authors: Zhao Yang , Li Xue , Wang Shubo , Xie Xiaofeng
Published: February 2020

Direct membrane deposition is introduced as a novel polymer electrolyte membrane fabrication method. This method is extended to fabricate a high-performance membrane electrode assembly for polymer electrolyte membrane fuel cell with poly (arylene ether sulfone) nanofibers as effective membrane reinforcements. The nanofibers are directly electrospun onto gas diffusion electrodes. By spray-coating ionomer dispersion into the pore space of nanofiber mats, composite membranes of 15 μm thickness are fabricated. The introduction of the electrically and ionically insulating nanofibers do not hamper the cell performance. At 80 ℃ and 75% relative humidity, the power density of the fuel cell employing direct membrane deposition, 2.85 W/cm2, is about 1.36 times higher than that of the reference fuel cell (2.09 W/cm2) with Nafion® 211. Its cell resistance (28 mΩ·cm2) is much lower than that of the membrane electrode assembly fabricated by the catalyst coating membrane method (46 mΩ·cm2). The performance differences between two fabrication methods are systematically analyzed by electrochemical impedance spectroscopy. Even though the thickness of the polymer electrolyte (15 μm) is much lower than that of Nafion® 211, it shows much higher internal short resistance because of the existence of nanofibers.
Effect of Carbon Corrosion on Wettability of PEM Fuel Cell Electrodes
Authors: Fang Zhengyuan J , Star Andrew , Fuller Thomas F.
Published: February 2020

Large transport resistances at high current densities hinder the proton-exchange-membrane fuel cells from reaching performance-cost-durability targets. Extensive carbon corrosion in the cathode catalyst layers has been shown to correlate to pore closures and increase in surface oxides of carbon support, which has been associated with the increase in wettability of the catalyst layers. This study investigated effects of changes in microstructure and surface oxides on the change of wetting properties of cathode catalyst layers after different accelerated stress tests. The apparent contact angles were measured over a broad range of cathode carbon mass losses at 0.3 mgPt/cm2. The apparent contact angles fell sharply after small extent of carbon loss followed by a plateau, and decreased again after 123 µg/cm2 (35% carbon support loss in the cathode). The microstructural changes were characterized by surface roughness (Atomic Force Microscopy) and porosity (focus-ion-beam scanning electron microscopy and thermogravimetric analysis). The surface roughness and porosity were used to parameterize Wenzel’s and Cassie-Baxter’s models, respectively, to elucidate the changes in Young’s contact angle. The fittings of the two models revealed that the cathode catalyst layers sustained their wettability after up to 35% of carbon support loss due to the increases in the proportion of hydrophobic fluorocarbon chains on the surface of the catalyst layer from XPS. The results suggest that the mass-transfer resistance cannot be ascribed to greater liquid saturation of the pore structure before the cell significantly fell below the DOE’s technical target.
A Synthetic Route for the Preparation of PtRu-Ni Core-Shell Nanoparticles Using Polydopmaine Protective Coating for a CO Tolerant Electrocatalyst
Authors: Lee Hojin , Kim Hansung
Published: February 2020

Carbon supported PtRu-Ni/C catalysts with a Ni-rich core structure are prepared through high temperature treatment of as-prepared polyol PtRu/C catalysts. It is well acknowledged that in conventional PtRu alloys, Ru prevents the adsorption of carbon monoxide on Pt surface via bifunctional mechanism. Also, the ligand effect of Ni is known to alter the electron structure of Pt for increased methanol oxidation reaction (MOR). In this work, the optimal Ni amount is determined for enhanced MOR and high resistance to carbon monoxide poisoning. The diffusion of Ni into the core of the catalysts is conducted by controlling the temperature during heat treatment. The as-prepared polyol PtRu/C catalysts have carbonized polydopamine layer on the surface, which prevents particle segregation during high temperature heat treatment. The carbon layer also partakes the role of transferring Ni particles into the core of the catalyst. When compared to using the polyol method to directly fabricate PtRu-Ni/C catalysts, this method is far more superior. Because Ni has a very low reducing power, most of it is lost during polyol process, and the final product has an extremely low Ni content.

In this study, Energy-dispersive X-ray spectroscopic line scan profile and X-ray photoelectron spectroscopic analysis confirm that the PtRu-Ni/C catalyst has a Ni-rich core and PtRu-rich shell structure. From Cyclic voltammograms for methanol oxidation and polymer electrolyte membrane fuel cell tests using CO containing H2 gas, the core-shell structured PtRu-Ni/C alloy formed by high-temperature annealing is demonstrated to have higher tolerance to CO poisoning than PtRu/C catalysts synthesized by co-deposition via the polyol method.
On the Activity of Electrospun Tantalum Doped SnO2 for Durable ultra-Low PGM Fuel Cell Cathodes
Authors: Haidar Fatima , Jimenez Morales Ignacio , Cavaliere Sara , Jones Deborah J. , Rozière Jacques
Published: February 2020

Despite the advances in the development of Proton Exchange Membrane Fuel Cells (PEMFCs), some locks still need to be lifted before they are deployed on a large scale:

i) Reduce the amount of platinum group metals (PGM) used in the electrodes by increasing the mass activity of the supported catalyst.

ii) Improve durability of the electrodes by replace the conventional carbon support

In particular, for the cathode side, carbon blacks (e.g. Vulcan XC-72) are conventionally used as a support materials for Pt and Pt-alloy nanoparticles. These materials exhibit high electric conductivity, controlled chemical properties, and high surface area that are of interest in PEMFCs application as electrocatalyst supports. However, carbon blacks are oxidized at the high voltage experienced at the cathode side (e.g. in stop/start conditions) leading to PEMFC major failure due to support corrosion leading to catalyst particles sintering or detachment [1,2].

Alternative supports based on tin oxide have attracted research interest due to their high corrosion resistance and promotion of activity for oxygen reduction reaction (ORR)[3]. The drawback is their low electrical conductivity, that in this work was tackled by doping with tantalum. Ta-doped SnO2 conducting fibers were synthetized by electrospinning followed by calcination [4] (Figure 1). This support was catalyzed with platinum nanoparticles prepared by a microwave-assisted polyol method and characterized for their physico-chemical and electrocatalytic properties towards ORR. In particular, stability to voltage cycling at high potential was evaluated by ex situ electrochemical analysis. A very significant mass activity of 470 A / gPt has been reached with 7.4wt.% of Pt homogenously deposited onto Ta-doped SnO2 nanofibers [5,6]. In addition, improved electrochemical stability was demonstrated with the retention of 70 % of the mass activity up to 10000 cycles from 1 to 1.6 V/RHE.

Figure 1:

SEM micrograph of 1%at. Ta-doped SnO2 nanofibers.

References

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Senoo, K. Taniguchi, K. Kakinuma, M. Uchida, H. Uchida, S. Deki, and M. Watanabe, ElectroChem. Commun. 2015, 51, 37–40.

Jiménez-Morales, S. Cavaliere, D. Jones, and J. Rozière, Phys. Chem. Chem. Phys. 2018, 20, 8765–8772
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Figure 1
Synthesis of Pt-Rare Earth Metal Alloy Nanocatalysts
Authors: Hu Yang , Jensen Jens Oluf , Cleemann Lars Nilausen , Brandes Benedikt Axel , Li Qingfeng
Published: February 2020

Further enhanced performance of platinum nanocatalysts towards the oxygen reduction reaction (ORR) in fuel cells can be achieved by alloying platinum with a secondary metallic element, typically late transition metals such as Ni and Co.(1-4) Recent theoretical and experimental studies have shown that Pt- Rare earth (RE) metal alloys exhibit remarkable ORR activities, among the highest of all ORR catalysts ever reported. (5-7) Due to the substantial difference of standard reduction potentials between Pt and RE metals as well as the extremely high oxophilicity of RE metals, alloying of the two metals as nanoparticles meets great challenges by usual chemical routes.

Here we report a simple method of synthesizing Pt-RE alloy catalysts by one-step heat-treatment of common precursors. A long series of Pt-RE alloy catalysts with single alloy phases, e.g., Pt3Y, Pt2Gd, Pt2Sm, Pt5Ce, or Pt5La, have been successfully synthesized, which exhibit narrow particle size distributions and excellent ORR performance. The highest ORR activities, achieved as far, are around 6 times (by Pt surface area) and 3 times (by Pt mass) higher than the start-of-the-art Pt/C catalysts. Several alloy catalysts such as Pt5Ce/C and Pt5La/C have showed also excellent stabilities by the standard accelerated stability tests. Furthermore, the synthesis mechanism has been clarified by investigation of intermediate products of the synthesis. The synthesis scale has been increased to 5-10 per batch for specific catalysts. As such, fuel cell tests with this type of catalysts become feasible, which have yielded promising results.

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Molecular-Level Design and Synthesis of M-N-C Non-Precious Metal Catalysts Derived from Transition Metal-Coordinated Bis(imino)-Pyridine Based Polymers for Highly Efficient Oxygen Reduction
Authors: Tian ZhiQun
Published: February 2020

Molecular-Level Design and Synthesis of M-N-C Non-Precious Metal Catalysts Derived from Transition Metal-Coordinated Bis(imino)-Pyridine Based Polymers for Highly Efficient Oxygen Reduction

Zhi Qun Tian*, Xiaoran Zhang, Dandan Lyu, and Pei Kang Shen

Collaborative Innovation Center of Sustainable Energy Materials, Guangxi Key Laboratory of Electrochemical Energy Materials, State Key Laboratory of Processing for Non-ferrous Metal and Featured Materials, Guangxi University, Nanning，53004, China.

（E-mail:tianzhiqun@gxu.edu.cn）

Abstract: Transition-nitrogen-carbon (M-N-C) materials as the most promising non-precious metal catalysts for oxygen reduction reaction (ORR) to replace Pt-based catalysts are in high demand for large scale application of fuel cells. However, their activity and durability are still critical issues. Development of M/N/C-containing precursors is a straightforward strategy for obtaining advanced M-N-C ORR catalysts to address these issues. Herein, we report a new strategy for synthesizing a highly efficient and robust M-N-C catalyst for oxygen reduction reaction (ORR) via the pyrolysis of bis(imino)-pyridine metal-ligand based polymers. A series of Fe-N-C, Co-N-C and Mn-N-C catalysts prepared by the new presucors displays an excellent electrochemical performance for ORR with onset and half-wave potentials of >0.95 V, 0.84 V vs. RHE, respectively, in acidic media, and >1.0 V, 0.9 V vs. RHE, respectively, in alkaline media. These values are comparable to commercial Pt/C catalyst in acidic media and even more superior to commercial Pt/C in alkaline media. And a low H2O2 yield (< 2%) in the diffusion-limiting current region and a high electron transfer number (3.97-3.99) were achieved in our catalysts, indicating the occurance of direct 4 e- process for ORR. Meanwhile, the catalyst shows remarkable cycle stability at high potential range of 0.6-1.35V both in alkaline and acidic media, outperforming Fe-N-C catalysts reported previously, which is important for practical application of ORR catalysts in fuel cells. This feature makes it among most efficient non-precious catalysts in alkaline/acidic media for ORR. We believe this novel approach may open a new way of synthesizing highly efficient and robust noble metal-free catalysts for ORR.

References

[1]X. Zhang, Y. B. Mollamahale, D. Lyu, L. Liang, F. Yu, M. Qing, Y. Du, X. Zhang, Z. Q. Tian and P. K. Shen, J. Cata. 2019,372, 245-257.

[2]D. Lyu, Y. B. Mollamahale, S. Huang, P. Zhu , X. Zhang, Y. Du, S. Wang, M. Qing, Z. Q. Tian and P. K. Shen, J. Cata. 2018, 368, 279-290.

[3]X. Zhang, D. Lyu, Y.B. Mollamahale, F. Yu, M. Qing, S. Yin, Z. Q. Tian, and Shen, PK, Electrochim. Acta 2018, 281, 502-509
Pt3co Nanoalloys Decorated Graphene Electrocatalyst for the Oxygen Reduction, Methanol Oxidation, and Detoxification of Alkyl Halides
Authors: Ingole Pravin Popinand , Jha Shwetambara
Published: February 2020

Platinum has attracted a lot of attention from decades because of their high activity towards electrocatalytic applications. However, the high cost of Platinum due to less abundance is a limiting factor for materialistic applications in the energy conversion devices. So, lowering the cost of platinum-based electrocatalysts has been a thrust research area. Herein, we report multifunctional electrocatalyst by alloying of platinum with cobalt supported over 2D carbon framework, graphene oxide (GO). Polycrystalline Pt3Co alloys supported on GO have been synthesized via a hydrothermal route with a varying molar ratio of platinum and cobalt in presence of GO. Uniform distribution of Pt3Co nanoalloy over GO sheets with particle size ⁓10 nm was confirmed by the TEM. The elemental analysis and phase determination of alloys were studied by a XPS, and XRD. The ORR has been studied by using the RDE voltammetry in 0.1M HClO4 electrolyte. The as-synthesized 1:1 molar ratio of Pt and Co in GO composite electrocatalyst were found to exhibit better onset potential (1.04V) and current density (0.1 mA cm-2) as compared to commercial 20% Pt-C alongwith greater durability. The specific ORR activity observed was six times higher than 20% Pt/C in 0.1M HClO4. Besides, the catalyst shows similar trend towards methanol oxidation reaction, and detoxification of environmental pollutants like methyl iodide.

Keywords: Graphene oxide (GO), Platinum-cobalt nanoalloys, Oxygen reduction reaction (ORR), Methanol oxidation reaction (MOR), Halocarbons.

Figure 1
Recent Advances in Low and Pt-Free Loading in Anion Exchange Membrane Fuel Cells
Authors: Neyerlin Ami , Strasser Derek , Antunes Christopher M , Owczarczyk Zbyslaw R. , Meek Kelly M , Pivovar Bryan S.
Published: February 2020

Anion exchange membrane (AEM) fuel cells have seen tremendous advances in recent years.[1] Power densities have now been obtained reaching over 3 W/cm2.[2] The advances in the field have been enabled by new AEM materials that have improved properties and durability as well as advances in electrode processing and performance. While the potential advantages of AEM fuel cells have been widely reported to be around the area of enabling non-precious electrocatalysis (and lower cost system materials), most of the results reported to date have focused on Pt containing electrocatalysts, often with high loadings to improve power density.[1] Now that exceptionally high-power densities have been achieved, it has become more important to focus on the performance and durability of AEM fuel cells at low loadings.

At the National Renewable Energy Laboratory (NREL), we have investigated a number of different polymer systems and have demonstrated the ability to greatly improve performance through electrode processing techniques. We have also demonstrated durability greater than 500 hours with a wide range of different membrane compositions. We have found that electrodes play a much more critical role in determining performance and durability. Recently, we have demonstrated the ability to achieve high performance with a variety of different ionomeric electrode materials. Most of our initial work had focused on Pt at high loadings, but we have also explored low Pt and Pt-free catalysts. In this talk we will discuss the role of different polymers, different electrode fabrication techniques, and the impact of loading on observed fuel cell performance and durability. With the issue of power density largely demonstrated our efforts have focused on areas including increased robustness (operating under dynamic conditions particularly at different RH), low Pt group metal loading, impacts of carbon dioxide exposure, and durability.

References

[1] D. Dekel, J. Power Sources, 375 (2018) 158-169.

[2] G. Huang, M. Mandal, X. Peng, A. Yang-Neyerlin, B. Pivovar, W. Mustain, and P. Kohl, Achieving 3.4 W/cm2 Alkaline Polymer Fuel Cell: Composite Cross-linked Poly(norbornene) Anion Conducting Membranes for High Power, Durability and Water Management, submitted.
Electrochemical Behavior of Plutonium in Molten Fluoride Medium
Authors: Claquesin Julien , Lemoine Olivier , Massot Laurent , Gibilaro Mathieu , Bourges Gilles , Chamelot Pierre
Published: February 2020

A pyrochemical process for slag recycling containing trapped actinide particles into a CaF2-CaO matrix is currently in progress. Since the process requires to melt the slag (melting point above 1300°C), an additional amount of CaCl2 must be used to decrease the operating temperature below 1000°C. Then, a reducing agent (calcium) is added into the molten medium to remove the actinides in a stable metallic form after decantation. The clean salt product meets the radiological requirements to be discarded to the dedicated way (ANDRA).

However, the extraction process is operated in a molten chloro-fluoride salt which is complex and quite unknown. Pu investigation in simplified media, chloride and fluoride, must lead to understand the mechanism of Pu reduction in chloro-fluoride media. Pu behavior has already been investigated in molten chloride media via electrochemical techniques by J. Serp et al. [1], O. Shirai et al. [2] and Lambertin et al. [3]. Nevertheless, data regarding this actinide behavior in molten fluoride media are incomplete [4].

Consequently, a detailed electrochemical study was carried out on plutonium in fluoride salt. The selected solvent is a mixture of two well-known salts, LiF and CaF2, melted in a crucible made of vitreous carbon in an oxygen free atmosphere (argon). Plutonium ions were introduced into the melt in the form of PuF4 powder. The setup consisted of a three electrodes assembly: tungsten as working electrode, vitreous carbon as auxiliary electrode and the potentials were referred to a platinum electrode. Cyclic voltammetry, square wave voltammetry and chronopotentiometry were coupled with thermodynamic calculations (potential-oxoacidity diagram) to investigate the electrochemical system. The acquired data will be used for a better understanding of Pu extraction from the melt.

[1] J. Serp, R.J.M. Konings, R. Malmbeck, J. Rebizant, C. Scheppler, J.-P. Glatz, Electrochemical behaviour of plutonium ion in LiCl-KCl eutectic melts, J. Electroanal. Chem., 561 (2004) 143.

[2] O. Shirai, T. Iwai, Y. Suzuki, Y. Sakamura, H. Tanaka, Electrochemical behavior of actinide ions in LiCl-KCl eutectic melts, J. Alloys Compd., 271-273 (1998) 685.

[3] D. Lambertin, S. Ched’homme, G. Bourgès, S. Sanchez, G. Picard, Plutonium chemical properties in NaCl-KCl and CaCl2 at 1073 K, J. Nucl. Mater., 341 (2005) 124.

[4] C. Hamel, Séparation actinides-lanthanides (neodyme) par extraction électrolytique en milieux fluorures fondus, vol. 3, 2005. Thesis, Toulouse.
Proton-Coupled-Electron Transfer Enhances the Electrocatalytic Reduction of Nitrite to NO in a Bioinspired Copper Complex
Authors: Symes Mark , Cioncoloni Giacomo , Roger Isolda , Wilson Claire , Senn Hans , Wheatley Paul , Sproules Stephen , Morris Russell
Published: February 2020

The selective and efficient electrocatalytic reduction of nitrite to nitric oxide (NO) is of tremendous importance, both for the development of NO-release systems for biomedical applications and for the removal of nitrogen oxide pollutants from the environment. In nature, this transformation is mediated by (amongst others) enzymes known as the copper-containing nitrite reductases. The development of synthetic copper complexes that can reduce nitrite to NO has therefore attracted considerable interest. However, there are no studies describing the crucial role of proton-coupled-electron transfer during nitrite reduction when using such synthetic complexes. In this talk, I will describe a system for the electrocatalytic reduction of nitrite to NO in which the role of proton-relaying units in the secondary coordination sphere of the metal can be probed for the first time (ACS Catal.
2018, 8, 5070–5084). Our results suggest that positioning a pendant carboxylate group in close proximity to the copper centre gives an electrocatalyst that is twice as effective for nitrite reduction than the analogous compound that lacks such a proton-relaying moiety. These results highlight the critical role of proton-coupled-electron transfer in the reduction of nitrite to NO and have important implications for the design of biomimetic catalysts for the selective interconversions of the nitrogen oxides.

Figure 1
Inorganic Phototropic Growth of Nanoscale Semiconductor Deposits
Authors: Meier Madeline Claire , Carim Azhar I , Yalamanchili Sisir , Cheng WenHui , Thompson Jonathan R , Atwater Harry A , Lewis Nathan S
Published: February 2020

A uniform, incoherent, uncorrelated beam of light can exert control over the morphology and growth direction of an evolving, inorganic semiconductor deposit in three-dimensional space at the nanoscale. No laser source, photomask nor structured light field is necessary nor utilized. Such evolution is similar to natural phototropism exhibited by many photosynthetic plants, including palm trees and sunflowers, wherein the physical extension of the biological system proceeds preferentially towards the time-averaged position of the sun while being influenced by competition from neighboring organisms. In analogy, during inorganic phototropic growth, the shape and growth direction of the deposited structures with respect to the substrate can be defined by controlling the angle of incidence of the light; mass is spontaneously added most preferentially to the localized regions capturing the maximal light flux. Optical coupling between neighboring features can result in further complexity and the emergent growth of highly ordered and complex film morphologies. Computer simulations of light absorption in deposits generated by inorganic phototropic growth, based on modeling of the fundamental interfacial light-material interactions, indicates that this growth process does in fact proceed in a manner reminiscent of the natural process of phototropism.