bluuebunny/crossref_metadata_2025_split huggingface dataset:
(Invited) Investigation of Hydrogen Oxidation and Evolution Reaction Activity on Iridium Metal in Alkaline Electrolyte
Authors: Gorlin Yelena , Herranz Juan , Durst Julien , Rheinländer Philipp Jan , Gasteiger Hubert A 
Published: February 2020

One of the challenges that currently impedes the commercialization of anion exchange membrane fuel cells (AEMFCs) is the development of suitable catalysts for the hydrogen oxidation reaction (HOR, H2 + 2 OH- → 2 H2O + 2 e-).(1) Because this challenge is unique to the alkaline environment of AEMFCs and is not present in the acidic environment of the proton exchange membrane fuel cells (PEMFCs), there has been renewed interest in quantifying hydrogen oxidation and evolution (HOR/HER) reaction kinetics and understanding the differences in activities of catalysts in acidic and alkaline environments. In these studies, a disagreement has emerged concerning the HOR/HER activity of iridium (Ir) metal in base, with researchers reporting that it is both higher(2, 3) and lower(4) than the corresponding activity of platinum (Pt) metal. In our study, we re-examine the electrochemical behavior of polycrystalline Ir in alkaline environment and find that the HOR activity of Ir depends on the electrochemical characterization procedure used in its quantification. In particular, we determine that subjecting the electrode to increasingly more cathodic potentials leads to a decrease in the HOR activity. Although this phenomenon could be argued to correspond to the adsorption of contaminants onto the catalyst surface, we demonstrate that the underlying reason for the drop in activity is likely not a surface contamination effect, but rather absorption of hydrogen into the sub-surface of the Ir electrode. Specifically, we find that exposure of the Ir surface to potentials that are lower than 0.10 V vs. the reversible hydrogen electrode (RHE) in H2-saturated environment leads to an appearance of an oxidation peak (Fig. 1) in a potential region in which surface contaminants are not expected to be oxidized (0.15-0.20 V vs. RHE), and that the size of this peak scales inversely with the HOR activity of the surface. Our results have important implications towards understanding of the HOR/HER kinetics and the development of improved catalysts for these reactions.

References

1. W. Sheng, H. A. Gasteiger and Y. Shao-Horn, J. Electrochem. Soc., 157, B1529 (2010).
2. N. Danilovic, R. Subbaraman, D. Strmcnik, K.-C. Chang, A. P. Paulikas, V. R. Stamenkovic and N. M. Markovic, Angewandte Chemie International Edition, 51, 12495 (2012).
3. D. Strmcnik, M. Uchimura, C. Wang, R. Subbaraman, N. Danilovic, V. van der, A. P. Paulikas, V. R. Stamenkovic and N. M. Markovic, Nat Chem, 5, 300 (2013).
4. J. Durst, A. Siebel, C. Simon, F. Hasche, J. Herranz and H. A. Gasteiger, Energ. Environ. Sci., 7, 2255 (2014).

Figure 1
(invited) Spectroscopic Techniques for the Identification of Fe and Co Coordination Chemistries in Fe(Co)-N-C Catalysts : Pristine Versus Degraded Catalysts
Authors: Jaouen Frederic , Goellner Vincent , Sougrati Moulay-Tahar , Zitolo Andrea , Fonda Emiliano 
Published: February 2020

While Proton Exchange Membrane Fuel Cells (PEMFCs) are already entering the portable sector and the market of materials handling vehicles, the long term economic growth of this technology remains subject to a further decrease in the platinum loading. Recent advances in non-precious metal catalysts for the oxygen reduction reaction (ORR) and synthesized from a transition metal (Fe, Co), a nitrogen and a carbon precursor are encouraging. The initial metal coordination in such catalysts is not yet fully understood, let alone that in the catalysts degraded in situ or ex situ.
The initial metal coordination in Fe(Co)/N/C catalysts as well as coordination changes following accelerated degradation in PEMFC or accelerated ex situ degradation by H2O2 will be discussed, and compared to the parallel decrease in their ORR activity and other structural changes. In PEMFC, accelerated degradation was achieved by applying a set number of short potential steps up to 1.4 V vs. RHE, while the extent of ex situ H2O2 degradation was controlled through the amount of moles H2O2 contacted per gram of catalyst. The two different modes of degradation lead to two completely different set of changes in the metal contents, coordination and morphological changes in the catalysts.
Coordination of the Fe atoms was experimentally investigated with both 57Fe Mössbauer and X-ray absorption spectroscopy while that of the Co atoms was investigated solely with X-ray absorption spectroscopy. These techniques are sufficiently sensitive to investigate powders with small metal contents (down to 0.1 wt %) or even initial and degraded electrodes with metal loadings of ca 50-150 mg cm-2. Full exploitation of these techniques and interpretation of the spectra is possible only when the pristine Fe(Co)/N/C catalysts are free of metallic, oxide or carbide by-products that are believed to be ORR inactive. If one or several of these phases are present, the spectroscopic signal related to the ORR active site(s) is obscured, which complicates or impedes analysis of the spectra. Catalysts free of such crystalline phases were obtained either by optimizing the metal content or the synthesis, allowing the recording of clean initial spectra and the tracking of coordinative changes occurring upon degradation. Furthermore, ab initio modeling of the X-ray absorption near edge structure spectra was performed and compared to experimental spectra, leading to a more precise concept of the metal coordination in Fe(Co)/N/C pyrolyzed catalysts.
Electrochemical Analysis and Density Functional Theory (DFT) Simulation to Investigate the Phosphoric Acid Adsorption on Pt3m (M = Fe, Co, Ni) Nanoparticles
Authors: Park Hee-Young , Lim Dong-Hee , Cha In Young , Chung Young-Hoon , Yoo Sung Jong , Kim Hyoung-Juhn , Henkensmeier Dirk , Kim Jin Young , Nam Suk Woo , Jang Jong Hyun 
Published: February 2020

High temperature-polymer electrolyte membrane fuel cell (HT-PEMFC) utilizing phosphoric acid doped polybenzimidazol membrane is a promising power supply for a number of stationary applications. At high operating temperature, significant enhancement in oxygen reduction reaction (ORR) kinetics is expected. However, typically the cell performance of HT-PEMFC is lower than that of conventional Nafion-based PEMFCs. One of important reason is the strong adsorption of phosphoric acid or anions, so called ‘phosphoric acid poisoning’, which blocks the active sites on Pt/C.
Alloying with transition metals have been suggested for an efficient way to improve the performance of HT-PEMFC as the alloying may provide enhanced intrinsic ORR activity and improved tolerance against the phosphoric acid poisoning. Experimental observation and computational simulations revealed that lowered adsorption energy of OH on alloy of Pt and transition metal nanoparticle catalysts (PtM/C) provided the enhanced ORR activity1.
However, there were few reports investigating effect of transition metal alloying on the phosphoric acid tolerance. Recently, He et al. demonstrated improved tolerance against the phosphoric acid poisoning in bulk PtSn2 and PtNi nanoparticle3 alloy surfaces. They postulated that ligand effect or geometric effect may be responsible for the tolerance of alloy surfaces. As a theoretical investigation of the alloying effect, Savizi and Janik calculated potential dependence of phosphoric acid adsorption free energy4 on Pt(111) surfaces, using density functional theory (DFT) simulations. However, there has been no further study, including PtM/C electrocatalysts.
In this research, we investigated the effect of transition metal alloying on the phosphoric acid poisoning in Pt3M (where, M = Fe, Co, Ni) nanoparticle catalyst (Pt3M/C) surfaces. Using the cyclic voltammetry, adsorption strength of phosphoric acid on Pt3M/C was analyzed. Also, the effect of transition metal alloying on the adsorption strength of phosphoric acid in Pt3M/C was analyzed based on the DFT simulations. Combination of electrochemical analysis and DFT simulations allowed investigating systematically the effect of alloying on the phosphoric acid adsorption in Pt3M/C surfaces.

References
1. I.E.L. Stephens, A.S. Bondarenko, U. Gronbjerg, J. Rossmeisl, I. Chorkendorff, Energy Environ. Sci., 5, 6744 (2012).
2. Q. He, X. Yang, W. Chen, S. Mukerjee, B. Koel, S. Chen, Phys. chem. Chem. Phys., 12, 12544 (2010).
3. Q. He, B. Shyam, M. Nishijima, D. Ramaker, S. Mukerjee, J. Phys. Chem. C, 117, 4877 (2013).
4. I. S. P. Savizi, M. J. Janik, Electrochim. Acta 56, 3996 (2011).
High Electrocatalytic Activity of the Pt-Based Catalyst Supported on Carbon Prepared Using a Plasma Torch and Natural Gas
Authors: Ribeiro Josimar , Evangelista Tereza Cristina Santos , Paganoto Giordano Toscano 
Published: February 2020

Physicochemical and electrochemical characterisations of Pt-based electrocatalysts supported on carbon (Vulcan® XC72, C1 and carbon produced using a plasma torch from natural gas vehicles, C2) toward ethanol electrooxidation were investigated. The Pt/C1 and Pt/C2 electrocatalysts were prepared by thermal decomposition of polymeric precursors at 350 ° C. The electrochemical and physicochemical characterisations of the electrocatalysts were performed by means of X-ray diffraction (XRD), Raman scattering, cyclic voltammetry and chronoamperometry tests. The XRD results show that the Pt-based electrocatalysts present platinum metallic which is face-centered cubic structure. The results indicate that the Pt/C1 electrocatalyst has a smaller particle size (10.1 – 6.9) compared with the Pt/C2 electrocatalyst; however, the Pt/C2 particle sizes are similar (12.8 – 10.4 nm) and almost independent of the reflection planes, which suggests that the Pt crystallites grow with a radial shape. Raman results showed that all the materials are composed of randomly oriented structural units varying from 50 to 80 Å in size. Cyclic voltammetry and chronoamperometry data obtained in this study indicate that the deposition of Pt on carbon plasma increases its electrocatalytic activity toward ethanol oxidation.
Acknowledgments
FAPES, CAPES, FINEP, PETROBRAS, LMC and CNPq.
Quantitative Study of Antioxidants and Their Reactivity in Various Tea
Authors: Perera Manori , Hocker Nathan , Rudd Lydia , Prochotsky Jennifer , Eppurath Atul 
Published: February 2020

Tea is known as one of the most popular beverage throughout the world. Lately it has also attracted consumers due to its health benefits through antioxidant properties. Research shows different methods to identify and quantify these antioxidant-polyphenols. But not much research has gone into (1) carefully quantifying what polyphenols are really active as antioxidants and (2) consumer products and their antioxidant content in consurmer products. In this project, various tea ranging from lose leaf tea to already brewed bottled tea are used to identify and quantify the polyphenols and measure how reactive these are as antioxidants. Polyphenol activity is measured using different potentiometric methods as well as a colorimetric method. These results will enable us to understand what content of antioxidants are present is each tea and are all antioxidants are active in presence of radicals.
Electroactive Polymers Prepared By Vapour Phase Polymerisation
Authors: Brooke Robert , Crispin Xavier , Murphy Peter J , Evans Drew 
Published: February 2020

Polymers are lightweight, flexible, solution-processible materials, which can possess insulating, semiconducting or metallic properties. Because of the high natural abundance of their constituting atoms, polymers are promising materials for low-cost printed electronics, mass produced and/or large-area applications. The conducting polymer poly(3,4-ethylenedioxythiophene), PEDOT, is one example material which displays (among others) high conductivity [1], and excellent thermoelectric properties [2]. Here, we report that when doped with tosylate and fabricated via vapour phase polymerization (VPP), the resulting PEDOT material is semi-metallic [2]. This material then forms the platform for a range of electrochromic applications.
Through the use of variations to the VPP process, a range of electroactive thin films are prepared. These cover complex multilayer structure, copolymerization of different conductive monomers, and spatial patterning. Performance data on the switching of electrochromic devices based upon these polymer films show stability upwards of 10,000 switches. Further enhancement of the electroactive polymers is achieved by incorporating within various 2D materials such as graphene [3]. In this extension, graphene- or MoS2-PEDOT-tosylate nanocomposite films, ca. 170 nm thick, have been prepared by dispersing sterically stabilised nanosheets throughout an oxidant solution containing a triblock copolymer, with the liquid-like properties of the oxidant film under typical VPP conditions transporting the 2D nanomaterials into the forming PEDOT-tosylate film. The resulting composite film of graphene-PEDOT-tosylate has a 65% larger in-plane modulus when compared to the polymer only film, and can be used to facilitate the oxygen reduction reaction, with efficiencies equivalent to or greater than that of Pt [3].
[1] M.V. Fabretto, D.R. Evans, M. Mueller, K. Zuber, P. Hojati-Talemi, R.D. Short, G.G. Wallace, P.J. Murphy, Polymeric material with metal-like conductivity for next generation organic electronic devices, Chem. Mater., 24, 3998-4003, 2012
[2] O. Bubnova, Z.U. Khan, H. Wang, S. Braun, D.R. Evans, M.V. Fabretto, P. Hojati-Talemi, D. Dagnelund, J.-B. Arlin, Y. Geerts, S. Desbief, D. Breiby, J.W. Andreasen, R. Lazzaroni, W. Chen, I. Zozoulenko, M. Fahlman, P.J. Murphy, M. Berggren, X. Crispin, Semi-metallic polymers for thermoelectricity, Nat. Mater., 13, 190-194, 2014
[3] N. Vucaj, M.D.J. Quinn, C. Baechler, S.M. Notley, P. Cottis, P. Hojati-Talemi, M.V. Fabretto, G.G. Wallace, P.J. Murphy, D.R. Evans, Vapor phase synthesis of conducting polymer nanocomposites incorporating 2D nanoparticles, Chem. Mater., 26, 4207-4213, 2014
Polymer Electrolytes for Electrochromic Devices
Authors: Silva M. M. , Leones R. , Alves R. , Pereira Rui F. P. , de Zea Bermudez V. 
Published: February 2020

Polymer electrolytes are currently the focus of much attention as potential electrolytes in electrochemical devices such as batteries, display devices and sensors [1,2]. Generically, solid polymer electrolytes (SPEs) are mixtures of salts with soft polar polymers. SPEs have many advantages including high energy density, no risk of leakage, no issues related to the presence of solvent, wide electrochemical stability windows, simplified processability and light weight. With the goal of developing a new family of environmentally friendly multifunctional biohybrid materials displaying high ionic conductivity we have produced in the present work, flexible films based on different polymers or hybrids incorporating different salts.
The polymer electrolytes studied here have been characterized by means of Differential Scanning Calorimetry, Thermogravimetric Analysis, X-ray diffraction, Polarized Optical Microscopy, complex impedance spectroscopy and cyclic voltammetry. An evaluation of the performance of the sample with the highest conductivity as electrolyte in all solid-state ECDs was performed [3].

Acknowledgments:This work is funded by FCT- Fundação para a Ciência e a Tecnologia, project references Project Pest-C/QUI/UIO686/2013, PEst-OE/QUI/UI0616/2014, POPH/FSE for a grant (SFRH/BPD/87759/2012) (R.F.P.P.), POPH/FSE for a grant SRFH/BD/90366/2012 (R.L), grant POPH/FSE for a grant SFRH/BD/97232/2013 (R. A) and COST Action MP1202 ‘‘Rational design of hybrid organic–inorganic interfaces.” M. M. Silva acknowledges CNPq, for the mobility grant provided by this institution.

REFERENCES

[1] F.M. Gray, in Solid Polymer Electrolytes: Fundamentals and Technological Applications, VCH Publishers, Inc. (1991).
[2] J.R. MacCallum, C.A. Vincent, Polymer Electrolyte Reviews, vol. 1, Elsevier, London, 1987.
[3] S. C. Nunes, V. de Zea Bermudez, M. M. Silva, M. J. Smith, D. Ostrovskii, R. A. Sá Ferreira L.D. Carlos and J. Rocha, A. Gonçalves, E. Fortunato “Sol-gel derived potassium-based di-ureasils for smart windows”, Journal of Materials Chemistry 17 (2007) 4239-4248.
Electrochromic Devices Incorporating Conducting Polymer or Novel Viologens
Authors: Deepa Melepurath , Sydam Rambabu 
Published: February 2020

Organic electrochromes such as conducting polymers and viologens (di-substituted-di-pyridinium salts) are attractive for electrochromic smart window applications due to high optical contrast, possibility of switching between multiple colors, ease of preparation and good write-erase efficiency. While conducting polymers are electrode bound species and undergo a color change via redox reactions at the electrode, viologens are typically colorless solution phase compounds, which form a reversible insoluble deeply colored film on the conducting electrode, upon application of an external bias (Figure 1). In this talk, the development of new viologen derivatives like the poly(cyclotriphosphazene-4,4′-bipyridinium) chloride, the effect of substituents on the electro-optical response, issues related to electrolytes and their compatibility with the electrochromic materials will be discussed. In the realm of conducting polymers, poly(3,4-ethylenedioxythiophene) (PEDOT), is a dual function material: it can serve as a transparent conducting electrode and a cathodically coloring electrochrome. In our lab, large area PEDOT films have been fabricated over plastic substrates and their ability to concurrently work as flexible conducting substrates while switching between the pale blue and dark blue hues is demonstrated. Concerns pertaining to scaling up of conducting polymer coatings and viologen based devices will also be discussed.

Figure 1
An Electrostatically Strong Polyviologen-Reduced Graphene Composite Film for Highly Stable Electrochromic Systems
Authors: Gadgil Bhushan , Damlin Pia , Kvarnström Carita 
Published: February 2020

Polyviologen (PV)-reduced graphene oxide (rGO) nanocomposite films were fabricated by simple, one step reductive electropolymerization of cyanopyridinium based precursor monomer in an aqueous dispersion of graphene oxide (GO). Since the polymer formation and reduction of GO occurs at the same potential window, electrocodeposition technique was chosen for obtaining nanostructured PV-rGO film. The cyclic voltammetry experiments of PV-rGO displayed two well resolved, highly stable one-electron redox processes typical of viologen. Being a redox polymer, incorporation of rGO further enhances the electroactivity of the PV in the composite films. FTIR, Raman, XRD and XPS analysis revealed structural changes occurred after composite formation. The PV-rGO nanostructured film exhibits a conspicuous electrochromism with low driving voltage and striking color changes. It was found that the PV-rGO film exhibit high coloration efficiency, fast response times and better cycling stability compared to pristine PV thin film. This performance can be attributed to the high stability of the electrochrome in the composite assembly induced by electrostatically driven non-covalent interactions between redox PV and rGO, high electrical conductivity and enlarged surface area through reinforced nanostructured graphene sheets for tethering PV molecules.

Figure 1
Syntheses and Applications of Inorganic Electrochromic Materials and Devices
Authors: Wang Jinmin 
Published: February 2020

Tungsten oxide (WO3) nanorods were synthesized by a hydrothermal process. Transparent film was fabricated by an aggregation-deposition process of WO3 nanorods on transparent conductive glass. The as-synthesized WO3 nanorods exhibit good electrochromic properties. WO3 nanopaltes were directly grown on transparent conductive glasses by a crystal-assisted hydrothermal process, showing enhanced response and coloration efficiency. These properties of WO3 nanostructures endow their promising application in large-area smart windows. Prussian blue films were fabricated and used in color-changeable betteries.
A bi-functional Prussian blue/Aluminium device has been demonstrated for self-powered electrochromic window and self-rechargeable transparent battery. Without applying any external bias, Prussian blue can be bleached to Prussian white by connecting the Prussian blue and Al electrodes. After bleaching, the blue colour of the device can be spontaneously recovered. In this regard, the designed device can be used as an energy-saving electrochromic smart window which requires no external power source. The as-prepared device can also be used as a battery with a high output voltage. Most importantly, after discharging, such a battery can automatically self-recharge. The as-prepared device exhibits promising applications in broad fields, for example, as a self-powered smart window to perform indoor light and heat management, and as a self-rechargeable transparent battery to power some delicate devices.
Conducting Polymers-Based Electrochromic Materials with Tunable Properties
Authors: Zhang Cheng 
Published: February 2020

Conducting polymers-based electrochromic (EC) materials have attracted wide interests on the applications of smart window, display and rearview mirror due to their better processability, the ease of color control, fast switching and high coloration efficiency.1-3And for EC polymers, multi-color showing is one of the most important factors for commercial applications. Changing the structure of the EC polymers at the molecular level is an effective way to tune polymers’ colors, such as introducing functional groups, constructing D-A structure and copolymertization. Up to now, we have synthesized a series of conducting polymers base on thiophene, carbazole and triphenylamine derivatives. Among them, five different colors (including red, green and blue) could be realized, the higher optical contrast could reach to 76% and the switching time could be less than 1 s (about 0.6 s). The excellent properties have already meet the requirement of the materials for the practical applications. In addition, we investigated the influence of different donor (or accepter) units and multi-active position on the performance of EC polymers, which could give some reasonable conclusion and explanation.

References

1. H. K. Song, E. J. Lee , S. M. Oh, Chemistry of Materials, 17, 2232 (2005).
2. P. M. Beaujuge, J. R. Reynolds, Chemical Reviews, 110, 268 (2010)
3. G. E. Gunbas, A. Durmus, L. Toppare, Advanced Materials, 20, 691 (2008).

Fig.1
t
he electropolymerization route, spectroelectrochemical spectra and electrochromic properties

Figure 1