bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polybenzimidazole Supported Monolayer Graphene Membrane for Inexpensive PEM Fuel Cells
Authors: Sahoo Madhumita , Kalangi Vasu , Perez-page Maria , Nair Rahul Raveendran , Holmes Stuart 
Published: February 2020

One atom thick structure of the two dimensional single layer graphene has distinguished itself as a very promising material due to its unique properties. Excellent in-plane electron conductivity and permeability to proton but barrier to other kinds makes it a very tempting and cost effective membrane material for environment friendly alternative energy devices-proton exchange membrane (PEM) fuel cells. Expensive Nafion and Pt are the commonly used membrane and catalyst for fuel cells, covering 50 % of the total amount of the fuel cell cost [1]. To make them commercially viable, the overall cost needs to be reduced or the performance has to be enhanced at the expense of the same cost.
Our work showed that incorporation of monolayer graphene into the membrane electrode assembly with the Nafion enhances the direct methanol fuel cell power density by 45 %, owing to the graphene’s methanol barrier properties [2]. In this work we report inexpensive polybenzimidazole (PBI) membrane as mechanical support for the monolayer graphene substituting Nafion. The composites are tailored with different degrees of graphene coverage. The influence of these ‘defects’ are studied with respect to the fuel cell operation in different conditions. Further functionalization of the composition demonstrated to be a cost effective solution, showing a good prospect as an alternative to Nafion.
References:
1. US Department of Energy Hydrogen and Fuel cells programs record, 2017
2. Stuart M. Holmes, Prabhuraj Balakrishnan, Vasu. S. Kalangi, Xiang Zhang, Marcelo Lozada-Hidalgo, Pulickel M Ajayan, Rahul R. Nair., 2D Crystals Significantly Enhance the Performance of a Working Fuel Cell. Advanced Energy Materials 7 (2017) 1601216.
Synergistic bifunctional catalytic effect at metal oxide-based catalyst for oxygen electrodes: influence of support and investigation in DMSO
Authors: Amin Hatem M.A. , Soltani Mohammad , Bondue Christoph , Zan Lingxing , Baltruschat Helmut 
Published: February 2020

Li-air batteries are one of the most promising candidates for rechargeable systems.[1] Within the context of elucidating the possibilities of aqueous Li-air batteries, developing a cost-effective bifunctional catalyst for oxygen reactions is a key issue. Metal oxides including spinels and perovskites have been shown as efficient catalysts for OER,[2] while Ag is known as a good catalyst for ORR. We have recently shown that a mixture of Ag particles with Co3O4 nanoparticles has superior bifunctional activity than its own components.[3] Here, we will demonstrate that such effect can also be observed when other support materials than Ag are used. Therefore, this effect could partially be due to a conductivity effect. However, experiments using smooth electrodes suggest that there is a synergistic effect. We will further demonstrate that this effect is also observed for various perovskites loaded on Ag. XPS analysis has shown that the presence of Ag+ in contact with Co3O4 facilitates the redox switching of Co3O4, which might be the reason for the enhanced catalytic activity of the mixture.[4]

Moreover, the mechanism underlying OER on Co3O4 and mixed Ag+Co3O4 catalysts is further studied using differential electrochemical mass spectrometry together with 18O-isotope labelling experiments.[4-5] The results revealed that the lattice oxygen of the oxide takes part in OER and that the amount of oxygen exchange on the mixed catalyst is larger than that on Co3O4. The active surface area is also estimated from these measurements and is compared to that obtained from a simple ball model and BET data.[6]

Investigation of the catalytic activity of Co3O4 catalyst towards oxygen reactions in aprotic electrolytes, namely DMSO, is also presented.
Literature:
[1] K. M. Abraham, Z. Jiang, J. Electrochem. Soc.
1996, 143, 1-5.
[2] A. Bergmann, E. Martinez-Moreno, D. Teschner, P. Chernev, M. Gliech, J. F. de Araújo, T. Reier, H. Dau, P. Strasser, Nature Communications
2015, 6, 8625.
[3] H. M. A. Amin, H. Baltruschat, D. Wittmaier, K. A. Friedrich, Electrochim. Acta
2015, 151, 332-339.
[4] H. Amin, C. J. Bondue, S. Eswara, U. Kaiser, H. Baltruschat, Electrocatalysis
2017, 8, 540-553.
[5] S. Fierro, T. Nagel, H. Baltruschat, C. Comninellis, Electrochem. Commun.
2007, 9, 1969-1974.
[6] H. M. A. Amin, H. Baltruschat, Phys. Chem. Chem. Phys.
2017, 19, 25527-25536.
Electronic and Ionic Conductivity of Nanocrystalline Sodium Peroxide
Authors: Philipp Martin , Lunghammer Sarah , Hanzu Ilie , Wilkening Martin 
Published: February 2020

The development of advanced electrochemical energy storage systems is considered as one of the most important steps to drive the shift from fossil to renewable energies forward. Among the few alternatives to Li-ion batteries that would exceed significantly their specific energy, Li-oxygen and Na-oxygen batteries have attracted significant interest. In order to fully understand their electrochemical properties and to identify potential failure mechanisms, electrochemical properties and charge carrier transport of their discharge products (e.g. Na2O2) need to be known in detail. Here, we investigated the overall and electronic conductivity of nanocrystalline Na2O2 that was prepared by mechanical treatment of coarse-grained Na2O2 in a high-energy ball mill. The powder obtained is expected to be rich in defects and structural disorder. Thus, we expect that the sample investigated would be at the upper limit of reachable conductivities. Impedance measurements and DC-polarization experiments show that the overall conductivity is rather poor; it is in the order of 10−13 S/cm yielding diffusion coefficients in the order of 1.8 × 10−23 m2/s at approximately 300 K [1]. At room temperature the partial electronic conductivity ranges between 7.6 and 9.5 × 10−14 S/cm. Thus, the total conductivity in Na2O2 is largely influenced by electronic contributions rather than ionic conduction [2]. Furthermore, we also anticipate a strong coupling between ionic and electronic charge carrier transport. We measured the electronic conductivity at different temperatures to calculate the underlying activation energy. It turned out that electronic conductivity is governed by an activation energy as high as 0.95 eV while for overall charge transport values range from 0.85 and 1.03 eV depending on the samples exact properties and measurement conditions.

Acknowledgement:

Financial support by the Deutsche Forschungsgemeinschaft (DFG Research Unit 1277, grant no. WI3600/2-2 and 4-1 and HA6996/1-2) as well as by the Austrian Federal Ministry of Science, Research and Economy, and the Austrian National Foundation for Research, Technology and Development (CD-Laboratory of Lithium Batteries: Ageing Effects, Technology and New Materials) is greatly appreciated.

References:

[1] Dunst, A.; Sternad, M.; Wilkening, M.: Overall conductivity and NCL-type relaxation behavior in nanocrystalline sodium peroxide Na2O2 – Consequences for Na-oxygen batteries. Mat. Sci. Engin. B 211 (2016) 85-93.
[2] Philipp, M.; Lunghammer, S.; Hanzu, I.; Wilkening, M.: Partial electronic conductivity of nanocrystalline Na2O2. Mater. Res. Express 4 (2017) 075508.
The Preparation of NaCrO2 and Biomasss-Derived Hard Carbon for Sodium-Ion Batteries
Authors: Liu Xin , Sun Wanda , Mao Jing , Shao Guosheng 
Published: February 2020

Among all components in battery, cathode material is one of the most crucial parts, for cathode material contributes a lot to a battery’s good performance. Sodium-ion batteries (SIBs) have attracted more and more attention for large-scale electrical energy storage due to the abundance and wide distribution of Na resources. Recently, researchers focus on layered transition metal oxide, for its stable structure. NaCrO2 is one of the most promising sodium layered transition metal oxides as cathode material in SIBs, because of its excellent thermal stability and compatibility with non-aqueous electrolyte. Furthermore, certain remarkable advantages of NaCrO2 have been reported, including a high theoretical capacity of about 250 mAh g-1, although its practical reversible capacity is approximately 100 mAh g-1.
Hard-carbon are considered as one of the most promising anode materials for sodium-ion batteries (SIBs), but there are still two main disadvantages of high cost and low initial coulombic efficiency to be overcomed for practical SIBs.
Herein, we report preparation of layered NaCrO2 as sodium-ion battery cathode material using a gel-combustion method and a cheap pinecone derived biomass-bassed hard carbon (PHC) using a simple carbonization method as anode material for SIBs.
The electrochemical performance of layered NaCrO2 is greatly affected by the calcination temperature due to difference microstructure and carbon content. The NaCrO2 calcined at 850℃ shows the best electrochemical performance with a reversible capacity of 90 mAh g-1 at a current density of 20 mA g-1, along with a high initial coulombic efficiency and good cycling performance. To further study the microstructure of NaCrO2, XRD and FESEM are used to study the structure and morphology of NaCrO2.
The performance of PHC is greatly affected by the carbonization temperature due to different microstructure and impurity. The PHC carbonized at 1400℃ shows the best electrochemical performance with a reversible capacity of 345 mAh g-1 at a current density 30 mA g-1, along with a high initial coulombic efficiency of 85.4% and good cycling performance. To further study the microstructure of PHC, the amorphous structure is demonstrated by X-ray diffraction (XRD), Raman spectroscopy as well as high-resolution transmission electron microscopy (HRTEM).
We make a full cell using NaCrO2 as cathode material and PHC1400 as anode material. The initial coulombic efficiency is 93%. The initial charge specific capacity based on anode material is 311 mAh g-1, and the initial discharge specific capacity was 289 mAh g-1 at a current density 30 mA g-1. The specific capacity based on anode is 150 mAh g-1 after 200 cycles. The full cell shows excellent electrochemical performance benefited by well-prepared cathode and anode materials.
A Novel Sulfonated Aromatic Polymer Membrane with Different Pendant Groups for Vanadium Redox Flow Batteries (VRFBs)
Authors: Wang Tongshuai , Han Junyoung , Kim Kihyun , Lee Jannice , Bae Chulsung , Kim Sangil 
Published: February 2020

Vanadium redox flow batteries (VRFBs) have received extensive attention due to its attractive features for the large-scale energy storage because of their design flexibility, high energy efficiency, absence of intercalation/deintercalation and stress build-up in electrodes, and safe operation. One of the most critical components in VRFB is an ion exchange membrane (IEM) which can prevent cross mixing of the multivalence vanadium ions, while it still allows the transport of protons (or anions) to complete the circuit. However, the trade-off relationship of proton exchange membrane (PEM) limits the energy efficiency (EE) of the VRFB due to low coulombic efficiency (CE) caused by vanadium ion cross over through the membrane or high membrane resistances. Anion exchange membrane (AEM) suffers from poor chemical stability and low voltage efficiency due to low ion conductivity.
In this study, we synthesized a series of novel sulfonated aromatic polymer membranes having high proton conductivity as well as proton selectivity. Vanadium/hydronium ion permeability, proton conductivity, area resistance, and ion exchange capacities of the membranes were measured. The single cell VRFB performance with the prepared membranes was evaluated and compared with the one using a commercial Nafion 212 membrane. The effect of the pendent group structure on the membrane ion selectivity and battery performance was also discussed.
It was found that the incorporation of aromatic structures on the pendent groups effectively improved the ion selectivity of membranes which can overcome the limitations of the trade-off relationship between the proton conductivity and selectivity. The membrane with aromatic pendent groups (BP-Ar-SH) shows 7 times higher vanadium/proton ion selectivity than that without aromatic groups (BP-SH) (5.18 vs. 0.75) and 3 times higher than Nafion 212 (5.18 vs. 1.78). As a result, the VRB single cell equipped with the BP-AR-SH membrane shows significantly better performance in comparison to the cell with Nafion membranes, as high as 90.05% EE (vs. 73% EE of Nafion) at 20 mA/cm2. The cycle stability test shows that efficiencies of the membrane remain almost unchanged after running more than 50 cycles. Our results strongly suggest that the BP-Ar-SH membrane may provide a breakthrough toward the development of high-efficiency VRFB systems.
(Invited) Surface Hydrogen Bonding Effects. The Use of Redox Probes to Induce the Reversible Reorganisation of Electrografted Films
Authors: González Felipe J. , Morales-Martínez Daniel 
Published: February 2020

The electrochemical oxidation of tetrabutylammonium carboxylates on carbon surfaces is typically performed following a global non-Kolbe mechanism [1], whose reactive intermediates allow the grafting of carbon surface with organic moieties [2]. Several characterisation strategies have been used to obtain information about the properties of the grafted film, among them is the use of reversible redox probes [3]. In this case, it has been observed that that the behaviour of the redox probe on the grafted surface is not stable and varies during cycling procedures in cyclic voltammetry [4]. Therefore, in this work, grafted carbon surfaces bearing alkyl-ester, alkyl-ketone, alkynyl and saturated chains were prepared to demonstrate that the variability in the behaviour of 1,4-benzoquinone as redox probe is due to a reversible reorganization effect of the grafted film [5]. The voltammograms of the first reduction wave of the redox probe on the different modified electrodes change during cycling procedures. However, the stand time of these modified electrodes in the electrolyte solution allows the recovery of the initial voltammograms. The changes observed between cycling and stand time are cyclical and can be understood through a reversible reorganization effect of the grafted film, which is attributed to hydrogen bonding interactions between the functional groups present in the structure film and the water present in solvent.
References
[1] H.J. Schaeffer, Topics in Current Chemistry, 1990, 152, 90
[2] C.P. Andrieux, F. González, J.M. Savéant, J. Am. Chem. Soc., 1997, 119 4292
[3] A.C. Cruickshank, E.S.Q. Tan, P.A. Brooksby, A.J. Downard, Electrochem. Commun., 2007, 9 1456-1462.
[4] A.O. Solak, L.R. Eichorst, W.J. Clark, R.L. McCreery, Anal.
Chem., 2003, 75, 296
[5] D. Morales-Martínez, F.J. González, Electrochem.
Commun., 2016, 62, 21
Peroxynitrite Detection and Quantification on Selenide-Based Grafted Interfaces
Authors: Kalil Haitham , Fouad Farid , Bayachou Mekki 
Published: February 2020

Peroxynitrite (PON) is a reactive oxygen-nitrogen metabolite that has been linked with both oxidation and nitration reactions in biological systems. PON is a major cytotoxic agent that is implicated in a host of pathophysiological conditions. It is the primary product of the reaction of superoxide anion-radical and nitric oxide radical under oxidative stress, inflammatory reactions, and other related conditions. Some literature reports highlight the deleterious physiological reactivity of PON with different cellular targets including DNA, proteins, and lipids in cell membranes. On the other hand, other reports identify counterintuitive cytoprotective roles of this species under certain conditions. The balance of deleterious reactivity versus potential cytoprotective roles of PON is apparently driven by its dynamic concentration.
Accurate determination of PON concentration is inherently difficult due to its high reactivity and the low target concentration range that is relevant to biological systems. Various methods for PON determination have been reported including indirect spectroscopic assays and, recently, direct electrochemical methods. In this regard, viable electrochemical probes for PON detection, including catalytic interfaces for PON detection, are still lacking, and work in this area is still in its early stages.
In this work, we prepared an interface grafted with a selenium-based compound for sensitive electrochemical determination of PON. First, we describe the preparation and grafting of 4,4' diaminodiphenyl selenide on graphite and indium-tin oxide electrodes. We characterized the modified interfaces using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). We will present and discuss these findings as well as results on the performance of the selenide-based grafted electrodes as peroxynitrite sensing interfaces using voltammetry and dose-response amperometry. The modified electrodes showed a significant enhancement in peroxynitrite oxidative current compared to controls. We will show that the enhancement in peroxynitrite signal is the result of an electrocatalytic mechanism where the grafted selenide compound at the oxidized state mediates the oxidation of peroxynitrite at the electrode surface. To the best of our knowledge, this is the first time a selenium-based compound electrochemically grafted at an electrode surface is used for catalytic detection and quantification of peroxynitrite.
(Invited) The Impact of Polyelectrolyte Dynamics on the Electrochemical Reactivity of Soluble Redox-Active Polymers
Authors: Rodriguez-Lopez Joaquin 
Published: February 2020

In this presentation, I will discuss recent findings regarding the impact of polyelectrolyte dynamics on the charge percolation and electrolysis efficiency of soluble Redox-Active Polymers (RAPs). RAPs[1] and their colloidal form (RACs)[2] are a new class of materials for energy storage in fluid dispersions for a novel concept in size-exclusion flow batteries.[3] Despite RAPs displaying excellent charge storage properties, their complex electrochemical reactive pathways are just becoming elucidated. RAPs and RACs rely on intra-particle electron transfer to yield quantitative charge accessibility and high rate in order to achieve full electrolysis.[4] Charge mobility via inter-pendant electron hopping combines with their polyelectrolyte nature to exhibit a rich electrochemical behavior that is strongly modulated by specific and non-specific interactions with the electrolyte. In this talk, I will highlight the impact of several variables on the electrochemical signatures created by RAPs and RACs.
The mechanistic characterization of RAPs and RACs requires a spectrum of powerful electrochemical techniques, ranging from bulk methods to single-particle analysis. I will describe how the application of nano-resolved electrochemical microscopy techniques and Raman spectroscopy has helped us understand the mechanisms of individual electrochemical entities.
These experiments provide us with unprecedented versatility to identify kinetic bottlenecks, such as charge trapping, and to determine the maximum current densities attainable in flow devices. Altogether, the combination of novel structural motifs, the identification of structure-reactivity relationships, and the use of advanced electrochemical techniques, results in new directions to make better polymers for a new concept in redox flow batteries.
[1] J. Am. Chem. Soc. 2014, 136, 16309.
[2] J. Am. Chem. Soc. 2016, 138, 13230.
[3] Acc. Chem. Res. 2016, 49, 2649.
[4] Chem. Mater. 2016, 28, 7362.
*This work was supported as part of the Joint Center for Energy Storage Research, an Energy Innovation Hub funded by the U.S. Department of Energy, Office of Science, Basic Energy Sciences.
(Invited) Understanding and Predicting Transitions in Proton Coupled Electron Transfer
Authors: Frontana Carlos Eduardo 
Published: February 2020

Proton Coupled Electron Transfer (PCET) mechanisms include all kinds of reactions where concurrent/stepwise processes are involved. Unraveling the distinctive character of a given mechanism is therefore a issue of importance, as concerted mechanisms lead to formation of products, avoiding the formation of high energy intermediates and are important for catalysis, while stepwise steps allow explaining the reactivity where radical species (either neutral or charged), can be invoked. Therefore, studies are not only directed to distinguish between both mechanistic alternatives, but to rationalize their significance in the reactivity of molecules and aggregates. For this purpose, simple trends using model organic compounds have been studied and allow to identify the structural characteristics that a given species must bear to induce any path. Within the workgroup, systematic analysis with series of nitro aromatic compounds [1,2] where Electron Transfer Controlled Hydrogen Bonding (a specific type of PCET process), show the influence of both the basicity of the electrogenerated anion radical and the acidity of the proton donor, describing the trends using descriptors of reactivity derived from changes in the local density of the molecule [3]. Using this approach, we have been able to analyze critical parameters where Hydrogen Bonding can lead to Proton Transfer, thus probably becoming concerted proton transfers. Results are therefore discussed in this work, along with the theoretical analysis described, its own limitations and some recent extensions for multiple-bodies approaches. Also, experimental changed where self-protonation occurs are presented, where we have been able to identify the "non-innocent" character of hydrogen bonding donors within the structures, leading to prior of forward hydrogen bonding interactions. Finally, some results of the influence of hydrogen bonding in the changes in electron transfer entropy are presented.
[1] Martínez-González, E.; C. Frontana, J
.
Org
.
Chem
. 2014, 79, 1131-1137
[2] Martínez-González, E.; Armendáriz-Vidales, G.; Ascenso, J. R.; Marcos, P. M.; Frontana C. J. Org. Chem. 2015, 80, 4581-4589
[3] Gázquez, J. L.; Cedillo, A.; Vela, A. J. Phys Chem. A. 2007, 111, 1966-1970

Figure 1