bluuebunny/crossref_metadata_2025_split huggingface dataset:
An ORR Identical Location STEM Investigation of the Stability of Pt3-Ni Octahedra Supported in Hollow Graphitic Spheres
Authors: Paciok Paul , Knossalla Johannes , Göhl Daniel , Ledendecker Marc , Jalalpoor Daniel , Pizzutilo Enrico , Heggen Marc , Schüth Ferdi , Mayrhofer Karl , Dunin-Borkowski Rafal E. 
Published: February 2020

The activity of a catalyst towards the oxygen reduction reaction (ORR) is determined by its surface composition and structure. Although careful synthesis strategies have managed to improve the ORR activity of Pt by a factor of 40 in recent years, the long-term stability of supported catalysts still poses a challenge.[1] One approach that can be used to supress degradation phenomena, such as particle migration and agglomeration, is incorporation of the active metal species in the pores of a conducting, porous graphitic matrix, in order to hinder the motion of the alloy particles. [2-4]

Here, we describe the synthesis, characterization and stability of octahedral Pt3NiMo nanoparticle catalysts supported in hollow graphitic spheres. By combining electrochemically active surface area (ECSA) measurements, identical location scanning transmission electron microscopy (STEM) and measurements performed using an in situ electrocatalytic scanning flow cell coupled to an inductively coupled plasma mass spectrometer (SFC-ICP-MS), we demonstrate the stabilizing effect of the hollow graphitic spheres on the PtNi octahedra. After 10800 cycles, the octahedra are found to have retained their shape, with only a small loss of ECSA.
In summary, we demonstrate the successful incorporation of shaped bimetallic nanoparticles into a porous support. This design strategy can be used for other catalytic reactions and opens new ways for achieving space confinement of faceted Pt alloy particles.
References:
[1] P. Strasser, Science
2015, 349, pp 379-380.
[2] C. Galeano, J. C. Meier, V. Peinecke, H. Bongard, I. Katsounaros, A. A. Topalov, A. Lu, K. J. J. Mayrhofer, F. Schüth, J. Am. Chem. Soc.
2012, 134, pp 20457– 20465.
[3] S. Mezzavilla, C. Baldizzone, A.-C. Swertz, N. Hodnik, E. Pizzutilo, G. Polymeros, G. P. Keeley, J. Knossalla, M. Heggen, K. J. J. Mayrhofer, F. Schüth, ACS Catal., 2016, 6 (12), pp 8058–8068.
[4] E. Pizzutilo, J. Knossalla, S. Geiger, J. P. Grote, G. Polymeros, C. Baldizzone, S. Mezzavilla, M. Ledendecker, A. Mingers, S. Cherevko, F. Schuth, K. J. J. Mayrhofer, Adv. Energy. Mater.
2017, 7(20).
Imidazolium-Based Grafted Anion Exchange Membranes: Interplay between the Morphology and Anion Transport Behavior
Authors: Zhao Yue , Yoshimura Kimio , Hiroki Akihiro , Kishiyama Yoshihiro , Shishitani Hideyuki , Yamaguchi Susumu , Tanaka Hirohisa , Maekawa Yasunari 
Published: February 2020

Anion-exchange membranes (AEMs) have been regarded as an alternative to proton-exchange membranes (PEMs) in energy conversion devices, due to the advantage of saving expensive platinum catalysts. However, neither the molecular design nor the property understanding is sufficient for developing AEMs capable of practical fuel cell applications. It is crucial to thoroughly study the current AEMs in terms of microphase structures and conducting properties. Recently, we developed a new graft type of AEMs by radiation-induced grafting method, where imidazolium and styrene monomers were grafted into poly(ethylene-co-tetrafluoroethylene) (ETFE) base films under a dose of 80 kGy from the 60Co γ-ray source (QST, Takasaki), followed by alkylation and ion exchange reactions. These AEMs exhibit well-balanced properties of high ion conductivity (> 100 mS/cm at 80oC) and good stability, which are believed to be controlled by the microphase structure of the membrane. In this report, we investigate the memrbane structure and reveal the relationship between structure and properties, using small-angle neutron scattering (SANS) method.
Fig. 1 shows typical SANS intensity profiles, I(q), of pristine ETFE films (profile 1), grafted-ETFE membranes (profile 2), dry AEM (profile 3) and AEM equilibrated in D2O (profile 4) as a function of scattering vector q. The different morphologies which can be deduced from the SANS profiles are also shown in the figure. The experiments confirm the semi-crystalline feature of AEM conserved from the original ETFE base film, which is the key factor for the high membrane mechanical stability, and show the dependence of the structure on hydration. Contrast variation experiments performed on AEM equilibrated in water mixtures of H2O and D2O, further show that graft polymers and water consist the hydrophilic ion channels [1]. Since graft polymers distribute randomly in AEM, well-connected hydrophilic ion channels are feasibly formed, which is the key factor for the high membrane conductivity.
Above all, the interplay between the morphology and properties can be characterized as follows: 1) semi-crystalline base film offers good mechanical properties; 2) graft polymers and water form ion channels to promote the conductivity.

Figure 1
Metal Organic Frameworks Based Catalysts for ORR: The Effect of the Transition Metal on the Catalytic Activity
Authors: Elbaz Lior , Gonen Shmuel , Lori Oran 
Published: February 2020

Fuel cells are promising alternative energy conversion devices. Their high energy density and efficiency in addition to the consumption of environmentally-friendly fuels such as hydrogen, drew a lot of attention in recent years. However, there are still some challenges to overcome. The most common cathode catalyst used to expedite the oxygen reduction reaction is platinum, which is relatively scarce and expensive. Many attempts to replace the platinum with precious group metal-free (PGM-free) catalysts were made, most of them are metal-nitrogen complexes in which iron and cobalt exhibit the best activity. One of the most prominent PGM-free catalyst family now-days are metal organic frameworks (MOFs).
Owing to their unique chemistry and physical properties, metal-organic Frameworks (MOFs) are an interesting class of materials which can be utilized for a wide array of applications. MOFs have been proposed to be used as catalysts for fuel cells, but their low intrinsic electronic conductivity hampered their utilization as-is. In this work, we present the synthesis and application of MOF-based PGM-free catalysts for oxygen reduction based on a unique metal-organic framework-carbon composite material. Benzene tricarboxylic acid-based MOFs were synthesized inside activated carbon (AC) with four different, first row transition metals: Mn, Fe, Co, and Cu. The MOFs@AC were analyzed electrochemically to measure their catalytic activity. Further physical and chemical characterizations were performed to measure the materials properties. The MOFs@AC are found to be conductive and active catalysts for oxygen reduction reaction in alkaline environment. Surprisingly, the Mn-based MOF@AC exhibits the best performance with onset potential of 0.9 V vs. RHE and almost four-electron mechanism, as opposed to most other known PGM-free catalysts, which show that Fe and Co as the most active metal. In this talk, we will share our most recent findings from studying these unique materials.
Durable Oxygen Evolution Catalysts for Alkaline Membrane Water Electrolysis
Authors: Xu Hui , Zhao Shuai , Wu Gang 
Published: February 2020

The utilization of renewable energy has substantially driven more attention into electrolysis technologies. An electrolyzer can utilize “off peak” electricity from solar or wind farms to produce hydrogen or other fuels. These chemicals can then be operated in a fuel cell mode to generate electricity when needed or used for other industrial applications. However, current hydrogen production from electrolysis comprises only a small fraction of the global hydrogen market due to the high costs that results from expensive materials even if “free” electricity from renewable energy can be acquired.
Alkaline membrane water electrolysis enables to use non-precious metals (or oxides) as the catalysts for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). This is very meaningful as the commercial OER catalyst IrOx for proton exchange membrane (PEM) electrolysis is very expensive; more importantly, the global storage and production of iridium is very scarce, tremendously limiting the mass production and deployment of PEM electrolyzers. However, there have rarely reported active and durable OER and HER catalysts for alkaline membrane water electrolysis, particularly in a membrane and electrode assembly (MEA) level; most previous studies on the OER and HER catalysts were focused on the rotating disk electrodes (RDEs).
We have investigated a series of OER catalysts including Co3O4 supported on carbon nanotubes (Co3O4/CNTs), binary transitional metal oxides (nickel cobalt oxide, NiCo2O4), and nanocarbon composites (FeCoNiMn-derived N-doped graphene tube, NC-FeCoNiMn4). These catalysts have first demonstrated remarkable durability in the RDE tests, subject to extensive voltage cycling from 0.0 V to 1.9 V. These catalysts have been integrated with other components including alkaline membrane and ionomer to test their MEA performance. It was discovered that both membrane and ionomers have a significant impact on the MEA performance and durability. The alkaline membrane and ionomer can quickly degrade upon high-voltage operations, leading to rapid MEA performance decay. However, the decayed performance can be restored after the introduction of diluted hydroxide solution (e.g, 0.1 M KOH) to the electrolyzer cell.
Therefore, this work can provide insightful guidance on the MEA design for alkaline membrane water electrolysis. Most importantly, the interaction between the catalyst and the ionomer will be investigated.

Acknowledgement: The project is financially supported by the Department of Energy’s Fuel Cell Technology Office under the Grant DE-EE0006960.
Theoretical Modeling of the Electrochemical Lithiation Processes of Lithium-Sulfur Battery Cathodes Based on Sulfur/Graphene-Nanosheets Composites
Authors: Perez-Beltran Saul , Balbuena Perla B 
Published: February 2020

The theoretical energy density of 2.5 kWh/kg of sulfur, plus its low-cost availability and environmentally friendliness, makes of lithium-sulfur (Li-S) batteries one of the most promising alternatives to fulfill the need of energy storage devices for high energy-demanding applications such as electric vehicles and smart grids. However, the successful commercialization of Li-S batteries is still challenged by the low utilization of sulfur, linked to its poor electronic/ionic conductivity and its continuous irreversible dissolution into the electrolyte in the form of long-chain lithium-polysulfides. So far, the mixing of sulfur with carbon has led to its better physical confinement and chemical sequestration in the cathode. However, the details of the sulfur-carbon interaction and its effects on the electrochemical lithiation processes during battery cycling are still largely unknown.
Here we aimed at characterizing the structure of sulfur/graphene-nanosheets composites (SC composite) and understand its effects on the electrochemical lithiation processes during battery cycling. Reactive molecular dynamics (ReaxFF) calculations provided information on the cathode microstructure and the bulk reduction products upon lithiation. Ab initio molecular dynamics simulations (AIMD) along with density functional theory (DFT) optimizations, yield details of the effects of different electrolyte compositions on the SC composite capabilities for retention of sulfur and the polysulfide formation paths.
We elucidated that a stronger sulfur-carbon interaction not only contributes to a better electronic conductivity but also leads to an alternative sulfur reduction path without the formation of long-chain polysulfides, which might help to explain the improved cycling stability observed in sulfurized polyacrylonitrile composites reported in the literature. In addition, we observed that different electrolyte compositions might be beneficial too by allowing an easier recovery of S-C bonds upon charging. We believe the results from this work can contribute to improving the synthesis methodologies of sulfur-carbon composites leading to a more rapid commercialization of lithium-sulfur batteries.
An Organic Electrolyte Additive for the Suppression of Li Dendrite in Li Metal Based Batteries
Authors: Kim Hee-Sang , Didwal Pravin N. , Park Chan-Jin 
Published: February 2020

Li metal has been known as an ideal anode material for high performance batteries due to its high theoretical specific capacity and lowest working potential. However, Li metal is thermodynamically unstable in polar aprotic electrolytes: it reacts with the electrolytes to form a solid electrolyte interface (SEI) layer. This layer, when a stable SEI layer is formed, it can prevent the direct contact between Li metal and liquid electrolyte and further decomposition of the electrolyte. Nevertheless, the non-uniform chemical composition of the SEI layer can induce an uneven current distribution on the Li surface, which causes Li dendrite growth and resulting electric short circuit. Thus far, approaches focused on making the stable and uniform SEI layer to prevent Li dendrite formation from modulating the electrolyte component and preventing the use of electrolyte additives.
In the present work, we suggest the use of an electrolyte additive for forming a uniform and stable SEI layer on Li surface for suppressing the growth of Li dendrite. The base electrolyte of 1 M LiTFSI in TEGDME was used for tests. The Li symmetric cell containing the electrolyte additive was galvanostatically cycled over 500 cycles for each charge and discharge time of 2 h at a current density 1 mA cm-2, which was >50 times longer than that of the Li symmetric cell without additive in electrolyte. This electrolyte additive helps to make a stable and uniform SEI layer, leading to effectively suppressing the growth of Li dendrite. Further, the electrolyte additive can be used in the Li metal based batteries such as a Li-O2 battery. The Li-O2 cell containing the additive was cycled for longer than 200 cycles at a current density of 0.1 mA cm-2 under the limited capacity mode of 1000 mAh g-1, which was >4 times longer than that of the Li-O2 cell without the additive in electrolyte. This electrolyte additive remarkably improved the electrochemical performance, especially cyclability of Li-O2 batteries.

Figure 1
Singlet Oxygen in Non-Aqueous Battery Chemistries
Authors: Mourad Eléonore , Mahne Nika , Schafzahl Lukas , Petit Yann K , Schafzahl Bettina , Renfrew Sara E , Kramer Denis , Fontaine Olivier , Wilkening Martin , Slugovc Christian , McCloskey Bryan D. , Borisov Sergey M. , Freunberger Stefan A 
Published: February 2020

The redox chemistry of O2 moieties has come into the focus of much of the forefront battery research such as metal-O2 batteries and Li-rich layered oxides (1, 2). O2 evolution is in either case a critical yet not fully understood phenomenon (1, 3). For example, operation of the rechargeable metal-O2 batteries depends crucially on the reversible formation/decomposition of metal (su)peroxides at the cathode on discharge/charge. The greatest challenge facing progress arises from severe parasitic reactions that decompose the electrolyte as well as the porous electrode. These processes have serious consequences. So far these parasitic reactions have been ascribed to the reactivity of superoxide and peroxide. Yet, their reactivity cannot consistently explain the observed irreversible processes. Unsurprisingly, strategies to mitigate the irreversibilities proved only partially successful. Therefore, only better knowledge of parasitic reactions may allow them to be inhibited.
Here we discuss our recent insights into irreversible parasitic reactions caused by the highly reactive singlet oxygen (1O2) during cycling of non-aqueous batteries that have so far been overlooked. They account for the majority of the parasitic products on discharge and nearly all on charge in Li-O2 and Na-O2 cells (4-6). Moreover, singlet oxygen forms upon oxidizing Li2CO3 above 3.8 V vs Li/Li+ (7). Li2CO3 is a universal passivating agent in Li-ion battery cathodes and decisive in interfacial reactivity. It is also a common side product in Li-O2 cathodes, as well as the targeted discharge product in Li-O2/CO2 batteries. We will further discuss work on open question with respect to 1O2 non-aqueous battery chemistries such as catalysts, electrolytes, mediators, quenchers and other additives as well as the formation mechanism and the implications for metal-O2 cells and intercalation chemistries. Awareness of the highly reactive singlet oxygen gives a rationale for future research towards achieving highly reversible cell operation in a broad range of cell chemistries.
References
(1) Bruce, P. G.; Freunberger, S. A.; Hardwick, L. J.; Tarascon, J.-M. Nature Mater.
2012, 11, 19.
(2) McCalla, E. et al.. Science
2015, 350, 1516.
(3) Luo, K; et al. JACS
2016, 138, 11211
(4) Mahne, N., et al. Nature Energy
2017
, 17036.
(5) L. Schafzahl, et al, Angew. Chem. Int. Ed., 2017, 56, 15728.
(6) N. Mahne, O. Fontaine, M. Thotiyl, M. Wilkening & S. A. Freunberger, Chem. Sci., 2017, 8, 6716.
(7) N. Mahne, S.E. Renfrew, B.D. McCloskey & S.A. Freunberger, Angew. Chem. Int. Ed., doi: 10.1002/anie.201802277.
Structural Transformations Leading to the Oxygen Evolution Active Phase for Fe Containing Layered Double Hydroxides
Authors: Dionigi Fabio , Zeng Zhenhua , Sinev Ilya , Merzdorf Thomas , Sarodnik Hannes , Drnec Jakub , Greeley Jeffrey , Roldan Beatriz , Strasser Peter 
Published: February 2020

NiFe based (oxy)hydroxides have been identified among the most active catalysts for the oxygen evolution reaction (OER) in alkaline electrolytes.1 Their crystal structure is known as layered double hydroxide (LDH) and is composed of layers of edge sharing metal oxygen octahedra that are intercalated with water molecules and charge balancing anions (Figure 1, insert).2 The incorporation of Fe3+ ions in Ni(OH)2 layers is considered to be responsible for the formation of this structure and its activity enhancement.3 Similarly, incorporation of Fe3+ into Co(OH)2 leads to CoFe LDH. This catalyst has also superior OER activity respect to Fe-free Co(OH)2.4 Despite their structure is well characterized, there are evidences that the OER active structure of LDH catalysts during OER is different than the one of the as prepared materials.3 In particular, oxidative deprotonation and the electrocatalytic reaction might lead to reversible structural differences that are only observable with in operando or in situ methods. More investigations are necessary, since the identification of the OER active structure of a catalyst is important for designing more active and stable catalysts. Theoretical predictions based on density functional theory (DFT) can guide this process, however so far different atomic models have been used in DFT calculations due the lack of clear structural information concerning the crystalline phase of Fe containing LDH under OER active conditions.
In this presentation we will discuss the results of an in operando X-ray absorption spectroscopy and diffraction study on crystalline NiFe and CoFe LDH nanostructured catalysts. We identified the structure of the catalytically silent and active catalyst state and observed that for both catalysts the interlayer distance contracts under operating conditions to a similar value (figure 1). Our results show structural modifications under operating conditions which correlate with the electrochemical activity in alkaline electrolyte. Thus they provide new insights into the structure of the active catalysts state which will help to understand the processes under catalytic conditions.
Figure 1. Shift of the (003) diffraction peak associated to the interlayer distance for NiFe LDH catalysts between the resting state (black) and OER active state (red) (unpublished). 3D structural model of the as prepared NiFe LDH with intercalated water and carbonate ions shown in the insert.

Figure 1
(Invited) Domino Killing Isomerization of Azobenzene Embedded in Rigid Polymer Gel
Authors: Watanabe Toshiyuki , Matsumoto Masaya , Karube Tamami , Isozaki Masatsugu , Misawa Kazuhiko 
Published: February 2020

Photoisomerization reactions of azobenzene derivatives have become the most common power source for molecular machines and photoresponsive polymers. Among photomechanical polymeric materials, a large response has been achieved exclusively using azobenzene-containing liquidcrystalline elastomers (azo-LCEs) and networks (azo-LCNs). Thus, although a number of efforts have been done to develop polymeric materials capable of transducing light to mechanical work, successful examples of bottom-up direct photomechanical transduction are still limited. Here we demonstrate that azobenzene containing rigid polymer networks, which consist of aromatic poly(amide acid) or polyimide backbones, show remarkable macroscopic deformation in response to blue (405 nm) and visible light (>532 nm) irradiation.
The bending motion of the cantilever was recorded by a video camera and analyzed on a computer. Although, the centimeter-long cantilever of PAA gel rapidly bends and forms a 90° angle within 4 s upon 405nm laser irradiation at one point, that of PI gels deflect 90 degree within 1.5 s. The bent cantilever cannot smoothly return to a straight shape upon visible light (> 532 nm) irradiation at one point. Surprisingly, in order to return the polymer rod of PI gels to the upright state, it is necessary to irradiate the entire rod with visible light. We believe that this is because trans-cis isomerization of azobenzene at the light irradiation site induces domino killing isomerization of the polymer gel at the non-irradiated site. In this research, we discuss the possibility that domino killing isomerization of azobenzene is induced by laser irradiation from various evidence.