bluuebunny/crossref_metadata_2025 huggingface dataset:
(Invited) Active Carbon Supports for Pt Cathode Catalysts in PEM Fuel Cells
Authors: Chen Mengjie , Wang Xiaoxia , Wu Gang
Published: February 2020

Polymer electrolyte membrane fuel cells (PEMFCs) have been widely considered one of environmentally friendly and highly efficient electric power sources for a wide variety of power applications ranging from portable and stationary power supplies to transportation. However, some of the most critical barriers to their commercialization are the intrinsic high cost and insufficient long-term performance durability. Among others, the spherical carbon black particle support used for Pt catalyst in MEAs have a number of intrinsic structural disadvantage. It is partially responsible for current insufficient performance and durability of MEAs. They include (1) inefficient O2 transport due to significant tortuosity in carbon black-based cathode, (2) non-uniform distribution of ionomer due to significant microporosity of carbon blacks, (3) catastrophic corrosion during start-up/shut-down events due to low corrosion resistance, (4) low electrical conductivity, and (5) weak binding sites with Pt nanoparticles.

We has developed a new type of high-surface areas (up to 850 m2/g) and large size nitrogen-diped graphene tubes (NGT) in a highly controlled manner and at high yields. The diameters of these graphene tubes can be tuned from 50 to 500 nm, which is much larger than conventiona carbon nanotubes (20 nm). It should be noted that the graphene tube is low cost using inexpensive dicyandiamide as precursors ($1-2/kg) and the synthesis method is easily scaled up. Apart from the obvious advantage of high electronic conductivity and enhanced corrosion resistance, the large tube size provided better Pt nanoparticle dispersion and more facil mass transfer including O2 and H2O. Importantly, the NGT exhibited oxygen reduction reaction (ORR) activity in acidic media comparable with state of the art PGM-free catalsyts. Thus, the novel ORR active nitrogen-doped graphene tubes are able to not only offer remarkable support effects by geometrically and electronically modifying the deposited Pt nanoparticles, but also provide a large amount of complementary nonprecious ORR active sites, thereby significantly improving the overall activity and durability of the Pt catalysts. Thus, relative to conventional carbon blacks, the highly graphitized and active N-GT is an ideal support for low-PGM catalysts for high-performance MEAs with enhanced mass transport and durability along with ideal interfaces with ionomer.
(Invited) The Interplay of Oxygen Electrochemistry, Electrocatalysis, and Anionic Redox Processes in the Development of Electrochemical Energy Storage Technology for Vehicular Applications
Authors: Faguy Peter William
Published: February 2020

The importance of lithium batteries to both energy and environmental security and to economic development in the global marketplace has been well recognized by the United States Department of Energy. Beginning in 2002, the Vehicle Technologies Office within the Office of Energy Efficiency and Renewable Energy has directed and funded a significant R&D program across the national lab complex, academia, and industry specifically targeting lithium-based batteries. This family of electrochemical energy storage cell chemistries was seen as, and has been proven to be, foundational to the widespread electrification of the US vehicle fleet. Unlike previous major battery chemistries, for example lead acid and nickel metal hydride, viable lithium batteries have been developed with a chemically and structurally diverse set of active anode materials (AAMs): lithium metal, graphite, intermetallic alloy (Si- and Sn-containing) coupled to an even more diverse set of active cathode materials (ACMs): transition metal oxyanions, molecular sulfur, and molecular oxygen.

In the shorter term, ~< 10 years, transition metal oxyanions are and will continue to be the focus of intense R&D efforts. Two critical characteristics in need of improvement in these so-called next generation Li-ion cathodes are electrode specific capacity and electrode and electrolyte stability under high voltage operating conditions. The limit in capacity—in electrochemical energy stored—for lithium intercalating oxyanionic materials used in practical devices may well have already been reached. In the longer term, only with cell chemistries beyond lithium ion will batteries achieve the energy densities necessary for future applications such as autonomous electric vertical takeoff and landing (VTOL) aircraft. Next generation ACMs (NG-ACMs) will not provide the requisite specific capacity. On that horizon, lithium-air batteries have received a great deal of attention. Molecular oxygen-based cathodes are a critical class of beyond Li-ion ACMs (BLI-ACMs).

Considering this backdrop of technology development and the birth of a trillion dollar industry, there exists a pressing need for understanding the physicochemical processes at advanced electrodes involving oxygen electrochemistry, electrocatalytic oxygen reduction and evolution in BLI-ACMs and anionic redox processes in NG-ACMs. This interplay of oxygen electrochemistry and promising electrochemical energy storage devices will be the central theme of the presentation. What are the central issues in understanding structure and activity involving oxygen electrochemistry in energy storage materials. Examples of scientific progress from projects supported in national laboratories, academia, and industry will be presented and future directions of R&D discussed.
(Invited) Analysis of the Oxygen Evolution Reaction on M-IrO2 (M=Ni, Co) Surfaces
Authors: Balbuena Perla B , Camacho-Forero Luis E , Godinez-Salomon Fernando , Rhodes Christopher
Published: February 2020

Electrolysis of water to produce hydrogen using proton exchange membranes (PEM) is of great interest especially if the production can be coupled to a source of renewable energy, where the renewable hydrogen cycle could be achieved. The oxygen evolution reaction (OER) takes place at the anode of a PEM water electrolyzer and it is known to be the rate-determining step in the overall electrolysis process. Therefore, the catalytic activity for the OER must be improved, which only can be accomplished with a better knowledge and understanding of the OER mechanism. In this work, density functional theory calculations are used to analyze the OER reaction pathways on RuO2, IrO2, and M-doped Ir oxides (with M= Ni, Co) in order to get a deeper insight of the importance of each of these stages in the water electrolysis process. The DFT studies are used to interpret and complement experimental synthesis, characterization, and electrochemical evaluation studies of novel Ir-Ni oxy-hydroxide 2-dimensional nanoframe electrocatalysts.
(Invited) Kinetic Characterization of Ir, Pt, and Irpt-Alloy Nanocatalysts for Ammonia Oxidation Reaction
Authors: Wang Jia X. , Song Liang , Liang Zhixiu , Zhang Yu , Adzic Radoslav R.
Published: February 2020

Direct ammonia fuel cells (DAFC) is an attractive alternative of hydrogen fuel cells because of lower cost in storage and distribution of liquid fuel than hydrogen gas. A drawback is the sluggish kinetics of ammonia oxidation reaction (AOR). Based on previous DAFC studies and measurements using rotating disk electrodes (RDEs), Ir, Pt, and IrPt-alloy nanoparticles are considered as the most active AOR catalysts. However, many questions remain open in correlating RDE results obtained at ambient temperature with the catalysts’ performance in DAFC at elevated temperatures. This is due to low sustainable AOR currents at sufficiently low potentials at ambient temperature and complicated temperature effect on AOR kinetics.

Here, we report an AOR study using gas diffusion electrode (GDE) in 1 M KOH solution at temperatures up to 60 oC. We kept ammonia concentration constant with time at temperatures higher than the boiling point of ammonia by saturating the solution with argon gas that bubbled through concentrated ammonia before entering the electrochemical cell. Three commercial nanocatalysts, Ir, Pt, and PtIr 1:1 alloy particles with 40 wt% metal on carbon support, were used to establish test protocol and to benchmark the platinum group metal (PGM) mass activity. The three catalysts exhibited distinct kinetic behaviors in terms of onset potential, maximum current, and activity enhancement factor with increasing temperature.

Clearly characterized AOR kinetic behavior can be explained using the reaction pathways proposed based on previous DFT calculations. We’ll discuss in detail why Ir has lower onset potential, but lower peak current than Pt does, why temperature enhancement factor is higher for Ir than Pt, what are the inactive intermediates and how catalysts deactivated due to increased coverage of less active AOR intermediates at potentials above and below 0.6 V. New insights can help developing advanced AOR catalysts and making effective DAFCs. The method and concepts developed are generally applicable for studying oxidation of other liquid fuels, such as, methanol and ethanol as their oxidation reactions also involve multiple intermediates and pathways.

Acknowledgements

This research was funded by the Advanced Research Projects Agency-Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000805 and by the Division of Chemical Sciences, Geosciences and Biosciences Division, US Department of Energy under contract DE-SC0012704.
Pt Acts As a Catalyst to Activate RuO2: The Active Sites of RuO2 Co-Catalyst for the CO Oxidation
Authors: Sugimoto Wataru , Olu Pierre-Yves , Mochizuki Dai
Published: February 2020

RuO2 has been suggested to act as stable co-catalysts for CO oxidation on Pt. However, little is known on how the oxide functions to oxidize nearby CO. In this work, we use model rotating disk electrodes composed of RuO2 nanosheets (RuO2(ns)) deposited on the surface of polycrystalline Pt, polycrystalline Au and glassy carbon. A new co-catalytic mechanism regarding the Pt/RuO2 interface towards the electro-oxidation of CO is proposed. Two distinct synergetic effects were identified, decreasing the bulk CO electro-oxidation onset potential compared to bare Pt by 50 mV (the ‘high potential’ synergetic effect at 0.85 V vs. RHE) and 250 mV (the ‘low potential’ synergetic effect at 0.65 V vs. RHE). We discuss the later with a new mechanism, involving an activated surface of RuO2(ns) generated by a partial reduction catalyzed by Pt.

The peculiar ‘low potential’ synergetic effect decays upon potential cycling in CO-saturated electrolyte where Pt is poisoned with COad, but can be reactivated by COad-free Pt in HUPD potential region. These results were resolved considering the formation of ‘Ru metal-like’ sites on RuO2(ns) which are generated from a partial reduction of the RuO2(ns) surface catalyzed by a Pt surface that is not poisoned by CO (spill-over hydrogen). Therefore, this ‘low potential’ synergetic effect interestingly differs from the customary bifunctional mechanism and shows a highly interdependent relationship where Pt-catalyzed activated surface of RuO2(ns) provides oxygenated species for the removal of CO adsorbed on Pt.

Acknowledgments

This work was supported in part by the ‘Polymer Electrolyte Fuel Cell Program’ from the New Energy and Industrial Technology Development Organization (NEDO), Japan.
Modulating Selectivity in CER and Oer through Doped RuO2
Authors: Pala Raj Ganesh , Saha Sulay , Kishor Koshal
Published: February 2020

Electrochemical chlorine evolution reaction (CER) is one of the most important electrochemical reactions due to widespread importance of Cl2 as an industrial chemical. However, electrochemical CER is bridled with parallel of oxygen evolution reaction (OER) reducing the performance of anode towards Cl2 production. In this context, the guiding principles of enhancing the selectivity of CER is investigated experimentally and computationally in RuO2 doped with first-row-transition-metals. Computational studies suggest that low-valent dopant (Cu, Zn) tend to surface segregate and they tend to weaken the interaction of adsorbates with the surface. Further, doping of metals having higher d-electrons than Ru in RuO2 tend to lower the binding strength of OER intermediates (e.g. HO-, O-, HOO-) thereby increasing its overpotential . However, doping have less effect on the binding strength of monovalent CER intermediates (e.g. ClO-, Cl-) resulting in higher CER selectivity. Computational studies suggest that Cu (d9)-doped RuO2 would show maximum CER selectivity and this has been corroborated by experiments with electrodeposited doped RuO2. The electrodeposited Cu-doped RuO2 (2% dopant concentration) has been found to show 95% CER selectivity at acidic medium. However, doping of d-enriched metals also lower the bridge-oxygen vacancy formation energy which activates lattice-oxygen-vacancy aided water dissociation pathway and aid the selectivity of OER. This may result in an optimum doping concentration wherein maxima of CER selectivity is observed as in case of for Cu- and Zn-doped RuO2 electrocatalysts experimentally. The present work offers insight on catalyst design taking account of selectivity of CER and OER during electrochemical Cl2 production.
(Keynote) Synthetic Protection Matrices for Integration of Redox Proteins in Fuel Cells and Photovoltaic Cells
Authors: Plumeré Nicolas
Published: February 2020

Various redox proteins such as hydrogenases or photosynthetic proteins can be integrated in devices to produce electricity or chemical fuels. Redox hydrogels are among the best strategies to immobilize and electronically contact proteins to electrodes. The redox potentials and the solvation properties of viologen or Os-complex modified polymeric matrices can be tuned to enable benchmark current densities (300 μA cm-2 for photosystem 1 [1] and up to 400 μA cm-2 for photosystem 2 [2]) at low overpotential [3]. However, deactivation process of photosystems [4] and hydrogenases [5] limit their technological applications. We proposed the use of redox matrices for the protection of hydrogenases [6, 7] to open the possibility of utilizing these highly active but also highly sensitive enzymes in devices for energy conversion. The mechanism of protection relies on the redox buffering capacity of the matrix and the film properties can be adjusted to protect hydrogenases quasi-infinitely [8]. The main limitations are (i) the overpotential imposed by mediated electron transfer within the hydrogel, (ii) the film thickness required for protection which implies the need for a significant amount of enzyme that is not involved in the bioelectrocatalytic process and (iii) the inefficiency of the protection when the bioelectrodes are operated in a cathodic mode such as H2 production. However, recent progresses in bioelectrode and redox hydrogel design, in particular with respect to electron transfer properties, mitigate the compromise between protection and performance in hydrogenase based energy conversion.

[1] T. Kothe, S. Pöller, F. Zhao, P. Fortgang, M. Rögner, W. Schuhmann, N. Plumeré Chem. Eur. J.,
2014, 20, 11029 – 11034.

[2] K. Sokol, D. Mersch, V. Hartmann, J. Z. Zhang, M. M. Nowaczyk, M. Rögner, A. Ruff, W. Schuhmann, N. Plumeré, E. Reisner. Energy Environ. Sci., 2016, 9, 3698-3709.

[3] V. Hartmann, T. Kothe, S. Pöller, E. El-Mohsnawy, M. M. Nowaczyk, N. Plumeré, W. Schuhmann, M. Rögner Phys.
Chem. Chem. Phys., 2014, 16, 11936 - 11941.

[4] M. M. Nowaczyk, N. Plumeré. Nature Chemical Biology
2016, 12, 990-991.

[5] A. Kubas, C. Orain, D. De Sancho, L. Saujet, M. Sensi, C. Gauquelin, I. Meynial-Salles, P. Soucaille, H. Bottin, C. Baffert, V. Fourmond, R. Best, J. Blumberger, C. Leger, Nature Chem.
2017, 9, 88-95.

[6] N. Plumeré, O. Rüdiger, A.A. Oughli, R. Williams, J. Vivekananthan, S. Pöller, W. Schuhmann, W. Lubitz, Nature Chem. 2014, 6, 822.

[7] A. A. Oughli, F. Conzuelo, M. Winkler, T. Happe, W. Lubitz, W. Schuhmann, O. Rüdiger, N. Plumeré, Angew. Chem. Int. Ed.
2015, 54, 12329.

[8] Fourmond, V.; Stapf, S.; Li, H.; Buesen, D.; Birrell, J.; Rüdiger, O.; Lubitz, W.; Schuhmann, W.; Plumeré, N.; Léger, C. J. Am.
Chem. Soc.,
2015, 137, 5494

Acknowledgement. Financial support by the Cluster of Excellence RESOLV (EXC 1069) and by the ERC Starting grant REDOX SHIELDS is gratefully acknowledged.
Surface Recognition and Electron Transfer in Electroactive Bacterial Biofilms: Principal Component Analysis
Authors: Lebedev Nikolai , Yates Matthew , Tender Leonard M
Published: February 2020

Bacterial electroactive biofilms attract researchers’ attention due to their ability for generation of electric current when electrons travel for very long, up to several tens microns, distance. It was demonstrated that this electron transfer (ET) ability correlates with the accumulation in the BF huge amounts of a c-type cytochrome (Cyt), but molecular nature of this Cyt, its spatial localization, interaction with the environment, regulation and the controlling factors are not completely understood. Bacterial cell polarity is an internal cell asymmetry that correlates with the cell ability to sense energy and metabolite sources, chemical signals, quorum signals, toxins, and movement in the desired directions. This ability also plays central role in cell attachment to various surfaces and biofilm formation. Biochemical analysis and molecular imaging demonstrate that sensing of energy and nutrients by the cell correlates with asymmetric protein, lipid and other molecule distributions within the cell. In the present work, we develop a new experimental approach for analyzing redox potential spatial distribution within individual bacterial cells and use this approach for identification how attachment to inorganic mineral, mica affects redox state inside individual G. sulfurreducens cells. The approach is based on confocal Raman microscopy allowing for precise estimation of redox state and localization of subcellular cytochromes. Applying Gaussian deconvolution and principal component analysis we are able to identify spectral signatures of cytochromes in different redox states and intracellular locations. Our results give a new tool for quick identification of internal and surface exposed cytochromes and their localization at bacterial cell sides facing the substrate and the solution. They open up the possibility for analyzing electrochemical potentials inside individual bacterial cells and indicate that Cyt redox state might be a driving force switching cell metabolic activity that leads to irreversible cell attachment to electrode, cell-to-cell association, and biofilm formation.
(Keynote) Covalent and Non-Covalent Functionalization of Carbon Nanostructures for Designing Biological Fuel Cells
Authors: Krishnan Sadagopan
Published: February 2020

In this presentation, my objective is to share my research exposure on carbon nanomaterial-pyrenyl surface chemistry for designing scalable enzyme electrocatalysis and enzymatic fuel cells. I was introduced to this exciting and rapidly growing field of biological fuel cells by my postdoctoral advisor, Prof. Fraser Armstrong. Later, my own research group at Oklahoma State explored some aspects of the nanostructure-pyrenyl chemistry for enzyme bioelectrode designs. One of our current studies focuses on bucky paper-based biocathode designs with insights into direct electron transfer kinetics and electrocatalytic oxygen reduction to water. In summary, although the synthesis, optical, mechanical, and electronic properties of carbon nanomaterials are established, our understanding on the functioning of these materials in enzyme electrocatalysis is still at a primitive stage. As a result, the topic of nano-bioelectrocatalysis research has received a significant attention among electrochemists, who are now positioned to uncover the properties of these nanomaterials in an electrochemical environment.
Ion Migration in Organometal Trihalide Perovskite Solar Cells
Authors: Lee Seokwon , Ilhwan Oh
Published: February 2020

Recently, organometal trihalide perovskites (OTPs) are very prospective photovoltaic materials because of its low-cost, easy fabrication and high power conversion efficiency (PCE). However, the low stability of perovskite solar cell is one of the important problems to be solved for their commercialization. Among all those factors that affect the stability of OTPs, ion migration can be important. The presence of ion migration has received widespread attention since the report of photocurrent hysteresis of OTPs. According to experimental data, the ion migration must be an important factor for many unusual phenomena in OTP materials and device, such as current-voltage hysteresis. The direction of the diode polarity and photocurrents can be reversed repeatedly by applying a small electric field. Here we show that how ion migrates and what the effect of ion migration is.
(Invited) Lithium Ion Conductors – between Model Systems and Battery Materials
Authors: Heitjans Paul
Published: February 2020

Lithium ion conductors continue to attract huge attention mainly due to the need for improved Li ion batteries, although “post-Li” energy storage systems are also being explored. In any case, basic research dealing with, e.g., the elementary ion jump process, the dimensionality of diffusion or the influence of structural disorder – besides being a field in its own right – is indispensable for those applications, too.

Here, exemplary results of our group on Li ion conductors are reviewed. Interestingly, materials used as model systems for basic questions quite often are also potential battery materials, i.e. solid electrolytes or electrodes, and vice versa.

An early example of a cathode material has been the intercalation compound LixTiS2 which turned out to be a model system for two-dimensional Li diffusion, involving a unique jump process over many decades, as was proven by a combination of nuclear magnetic resonance (NMR) techniques. Besides the layer-structured also the cubic modification as well as nanocrystalline and amorphous forms were examined with respect to dimensionality and disorder effects.. Anode materials studied by us primarily from a fundamental point of view have been Li
x
C6 (0<x≤1), Li4+x
Ti5O12 (0<x<3) and, as one of the silicides, Li12Si7. In Li12Si7 very fast quasi one-dimensional Li diffusion was detected. Among the potential electrolytes for all-solid-state Li ion batteries, Li7La3Zr2O12 was investigated in some detail also with respect to the influence of doping and defects on Li diffusivity.

The examples to be presented extensively involve NMR, which now is an established materials science method for Li ion dynamics [1, 2], but also impedance spectroscopy [3], mass spectrometry [4] and neutron reflectometry [5] have been applied in the Li ion transport studies.

[1] C. V. Chandran, P. Heitjans, Solid-State NMR Studies of Lithium Ion Dynamics Across Materials Classes, Annual Reports on NMR Spectroscopy 89 (2016) 1-102.

[2] K. Volgmann, V. Epp, J. Langer, B. Stanje, J. Heine, S. Nakhal, M. Lerch, M. Wilkening, P. Heitjans, Solid-State NMR to Study Translational Li Ion Dynamics in Solids with Low-Dimensional Diffusion Pathways, Z. Phys. Chem. 231 (2017) 1215–1241.

[3] J. Rahn, E. Hüger, L. Dörrer, B. Ruprecht, P. Heitjans, H. Schmid, Li Self-Diffusion in Lithium Niobate Single Crystals at Low Temperatures, Phys. Chem. Chem. Phys. 116 (2012) 2427–2433.

[4] A.-M. Welsch, H. Behrens, I. Horn, S. Roß, P. Heitjans, Self-Diffusion of Lithium in LiAlSi2O6 Glasses Studied Using Mass Spectrometry, J. Phys. Chem. A 116 (2012) 309–318.

[5] F. Strauß, E. Hüger, P. Heitjans, T. Geue, J. Stahn, H. Schmidt, Li Permeation through Thin Lithium-Silicon Films for Battery Applications Investigated by Neutron Reflectometry, Energy Technology 12 (2016) 1582–1587.
(Invited) Electrocatalytic Activity Towards ORR and Stability of Binary and Ternary Catalysts Based on Pt and Cu
Authors: Coutanceau Christophe , Lankiang Styven , Baranton Stève
Published: February 2020

The catalytic activity of platinum can be enhanced by modifying Pt-NPs with transition metal atoms such as Ni, Fe, Co, Cr, Cu [1,2]. But, it has also been proposed that the addition of non-noble transition metals could involve a lower stability than pure platinum due to their dissolution [3,4] leading further to a loss of performances in PEMFC. Other authors have shown that the dealloying of the nanoparticle surface, leading to a core-shell structure having a Pt rich surface, could enhance the catalytic activity of binary or ternary Pt-based systems.

On the one hand, gold was proposed to prevent platinum dissolution by raising the Pt oxidation potential [5,6], a property which could be interesting to enhance the stability of core-shell Pt-based catalysts with Pt rich surface. Moreover, it has also been shown that PtAu-based catalysts could exhibit similar or even higher catalytic activity towards ORR than pure platinum [7–9]. On the other hand, recent DFT calculation identified that copper containing Pt-based catalysts, such as PtAuCu core-shell structures, as displaying high expected ORR activity and also a stabilizing effect from the Au-Cu interaction [10].

For these reasons, PtxCu1-x/C and ternary PtxAuyCuz/C catalysts were synthesized by a microemulsion method and characterized by TGA, TEM, XRD, AAS, XPS and cyclic voltammetry in order to assess their metal loading, their microstructure and their bulk and surface compositions. The electrocatalytic activity towards ORR, the selectivity and the stability of catalysts were studied in acidic electrolyte using the rotating disc and the rotating ring disc electrode techniques.

Acknowledgement:

The financial support of the European Commission under the FP7 Fuel Cells and Hydrogen Joint Technology Initiative grant agreement FP7-2012-JTI-FCH-325327 for the SMARTCat project is gratefully acknowledged.

References:

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2- N. Neergat, A.K. Shukla, K.S. Gandhi, J. Appl. Electrochem. 31 (2001) 373–378.

3- M. Watanabe, K. Tsurumi, T. Mizukami, T. Nakamura, P. Stonehart, J. Electrochem. Soc. 141 (1994) 2659–2668.

4- C.F. Yu, S. Koh, J.E. Leisch, M.F. Toney, P. Strasser, Faraday Discuss. 140 (2009) 283–296.

5- J. Zhang, K. Sasaki, E. Sutter, R.R. Adzic, Science 315 (2007) 220–222.

6- K. Sasaki, H. Naohara, Y. Cai, Y.M. Choi, P. Liu, M.B. Vukmirovic, J.X. Wang, R.R. Adzic, Angew. Chem. Int. Ed. 49 (2010) 8602–8607.

7- P. Hernández-Fernández, S. Rojas, P. Ocón, J.L.G. Fuente, J.S. Fabián, J. Sanza, M. A. Peña, F.J. Carcía-García, P. Terreros, J.L.G. Fierro, J. Phys. Chem. C 111 (2007) 2913–2923.

8- D.F. Yancey, E.V. Carino, R.M. Crooks, J. Am. Chem. Soc. 132 (2010) 10988–10989.

9- S. Lankiang, M. Chiwata, S. Baranton, H. Uchida, C. Coutanceau, Electrochim. Acta 182 (2015) 131–142.

10- P. C. Jennings, S. Lysgaard, H. A. Hansen, T. Vegge, Phys. Chem. Chem. Phys. 18 (2016) 24737–24745.
Deciphering the Oxygen Reduction Reaction on Platinum: A Theoretical Framework
Authors: Huang Jun , Zhang Jianbo , Eikerling Michael Hermann
Published: February 2020

The conversion of oxygen into water is crucial to the operation of polymer electrolyte fuel cells and other emerging electrochemical energy technologies. Chemisorbed oxygen species play a central role in this reaction, since they necessarily act as intermediates but also as site-blockers. Any attempt to decipher the oxygen reduction reaction must relate the formation of oxygen intermediates to basic electronic and electrostatic properties of the catalyst surface and, on the other hand, link it to effective parameters of the electrode activity. An approach that accomplishes this feat will be of great utility in guiding design and development of catalyst materials and developing predictive models of electrode operation. Here, we present a theoretical framework for the multiple interrelated surface phenomena and processes involved. It correlates the formation of chemisorbed oxygen intermediates, metal surface charging phenomena, ion density and potential distribution in electrolyte, field-dependent ordering of interfacial water molecules, and effective kinetic parameters of the ORR. Parameterized with density functional theory results and rotating disk electrode data, the model sheds light on the double-edged roles of oxygen intermediates; it produces as output the Tafel slope and exchange current density as continuous functions of electrode potential and presents a new perspective on the volcano relation the ORR. The optimal oxide coverage is a result of two oppositely-headed trends upon increasing coverage by oxygen intermediates, viz, the intuitive site-blocking effect and the increasing protophilicity of the surface.
(Invited) Stability of Palladium Electrocatalysts in Alkaline Solutions
Authors: JIA Sitong , Shao Minhua
Published: February 2020

It has been found that the durability of Pt/C in alkaline solutions is worse than in acidic medium during potential cycling.1 The durability of Pd/C, which shows even higher activity toward oxygen reduction reaction than Pt/C in alkaline solutions, has not been systematically studied. In this study, the commercial Pt/C (46%, TEC10E50E, TKK) and Pd/C (30%, TECPdE30, TKK) were chosen to evaluate the durability during potential cycling in various potential windows and cycling patterns. The potential decay in terms of half-wave potential was compared after 2500, 5000 and 10000 cycles. It was found that the Pd/C had a much better durability than Pt/C under the same conditions. The dissolution of metal nanoparticles was detected by utilizing an electrochemical cell directly coupled to an inductively coupled plasma mass spectrometer (ICP-MS) to understand the origins of the higher stability of Pd/C.

References

Anicet Zadick, Laetitia Dubau, Nicolas Sergent, Gregory Berthome, and Marian Chatenet. Huge instability of Pt/C catalysts in alkaline medium[J]. ACS Catalysis, 2015, 5(8): 4819-4824.
Ligand-Regulated ORR Activity of Au Nanoparticles in Alkaline Medium: The Importance of Surface Coverage of Ligands
Authors: Lu Linfang
Published: February 2020

The functionalization of organic ligands on nanoparticles (NPs) to create metal-organic interfaces can tune the activity and selectivity of catalytic reactions. Comparing to well-documented electronic and steric contribution of organic ligands, the coverage of ligands is also a significant factor but has been rarely investigated. Herein, we employ two methods, potential cycling (Figure 1c) and thermal annealing, to judiciously remove the surface ligands from gold nanoparticles (AuNPs) and systematically investigate the influence of surface coverage of ligands on the catalytic performance. Potential cycling enables a mild removal of ligands without changing the size of AuNPs (Figure 1a and Figure 1b) and thus provides ideal models to identify the intrinsic influence of surface coverage of ligands on oxygen reduction reaction (ORR). The ORR activity and selectivity is quantitatively evaluated by plotting half potential and transferred electron number versus the surface coverage of ligand. Thermal annealing at different temperatures produces different sized AuNPs with various surface ligand coverage. However, it is suggested that the surface coverage of ligand plays a more significant role on ORR than the particle size of AuNPs. Capping AuNPs with oleylamine and sodium citrate and the reverse poisoning clean AuNPs with thiol, butylamine and CTAB further reveal the difference of ORR activity/selectivity of the capped AuNPs is directly related to the surface coverage of the ligands regardless the diverse chemical nature of these ligands (Figure 1d). This work highlights that the surface coverage of ligands should be considered to be an important factor accounting for metal-organic interfaces in addition to chemical nature of the ligand itself.

Figure 1
(Invited) Understanding ORR Reaction on Nitrogen Doped Carbon Materials: Insight from Experiments and Calculations
Authors: Ferre-Vilaplana Adolfo , Briega-Martos Valentín , Feliu Juan , Herrero Enrique
Published: February 2020

In this communication, we will present recent results on the oxygen reduction reaction (OOR) on nitrogen doped carbons. DFT calculations on nitrogen doped graphene systems will be used to understand the key elements that activate the reaction on these materials. The study is centered on the monodentate chemisorption of molecular oxygen as the first step of the process. It will be shown that carbon atoms are the active sites provided that several conditions are fulfilled. First, water should be included in the models, since it stabilizes the adsorption of the oxygen molecule with the characteristics of a superoxide species on the carbon atoms, which are the active sites. This carbon atom should be able to transition from a sp2 hybridization state to sp3 upon adsorption of the oxygen molecule to have a favorable interaction energy with the oxygen molecule. This transition is favored destabilized carbon atoms, that is, those neighboring a nitrogen dopant. Second, a significant charge transfer to this site should occur, so that charge can be concentrated on the adsorbed oxygen molecule. This charge transfer requires the presence of additional nitrogen dopants, which are charge donors, even when they are in distant positions. When the nitrogen dopant is located in an edge of the graphene structure, a clearly favorable chemisorbed state for molecular oxygen was found when nitrogen-dopant is hydrogenated and located at an armchair edge. The chemisorbed state is further favored by additional available charge from other nitrogen. By contrast, the chemisorbed state of oxygen is much less favorable when the hydrogenated pyridinic nitrogen-dopants are located at zigzag edges. To demonstrate the applicability of this approach, the ORR was experimentally studied on an aza-fused π-conjugated microporous polymer, which has a very well characterized structure. The experimental results using a rotating disk configuration indicate that hydrogen peroxide is almost exclusively produced at very low overpotentials on these materials. The DFT calculations indicate half of the nitrogen atoms of the material are hydrogenated at the potentials at which the reaction takes place. This hydrogenation process destabilizes some carbon atoms in the lattice and also provide a source of charge. On these carbon atoms, molecular oxygen could be chemisorbed with the aid of charge transferred from the hydrogenated nitrogen atoms and solvation effects, as in the previous cases. Due to the low destabilization of the carbon sites, the resulting molecular oxygen chemisorbed state is only slightly stable, promoting the formation of hydrogen peroxide.
Heterogeneous Iron-Containing Carbon Gels As Catalysts for Oxygen and Carbon Dioxide Electroreductions – Rotating Ring-Disk Voltammetric Studies
Authors: Dembinska Beata , Kiciński Wojciech , Kulesza Pawel J
Published: February 2020

There has been growing interest in the development of highly active catalysts for electroreduction of oxygen that could be effectively utilized in low-temperature fuel cells. The important practical issue is related to the need of lowering costs of catalysts by substituting the noble metals with inexpensive abundant elements. In this respect materials containing metallic moieties coordinated by nitrogen atoms embedded in the carbon matrix (M-N-C) are recognized as most suitable candidates to replace platinum catalysts. More recently, the approach of using such biomimetic centers has been considered for the carbon dioxide reduction, the reaction which permits generation of carbon-based chemicals, fuels or syngas. Since both reactions (O2 and CO2 reductions) are characterized by slow kinetics and may proceed through different pathways producing various products, their efficiency and selectivity still remain fundamental problems for practical applications.

It is well established that the best performing M-N-C catalysts (with high specific surface area and large fraction of micropores) are produced from nitrogen-containing polymeric precursors. In these study we present a new type of self-supporting M-N-C materials, namely nitrogen and sulfur co-doped iron containing highly porous carbon gels (obtained through pyrolysis of organic gels) as efficient non-precious metal catalysts for both the oxygen and carbon dioxide electroreductions. The precursors of the catalysts were prepared via the sol-gel polycondensation (induced with iron(III) cations) of resorcinol together with the mixture of two heterocyclic aldehydes containing nitrogen and sulfur. The role of S is to produce carbon gels with high specific surface areas (e.g. when compared to carbon gels containing solely N heteroatom).

It is commonly accepted that rotating ring(platinum)-disk(glassy carbon) electrode voltammetry can be effective diagnostic tool for elucidation of the performance and selectivity (towards water or hydrogen peroxide) of the oxygen electroreduction. We are going to demonstrate that a combination of the rotating ring-disk electrode methodology and stripping type voltammetry (at platinum ring) can be also used for the determination of the reaction mechanism, competitive formation (evolution) of hydrogen, and determination of CO-type adsorbates generated at the catalyst during the CO2 electroreduction.
Li-Birnessite Manganese Oxide Coated on Graphene Aerogel for High-Efficient Electrocatalyst Towards Oxygen Reduction Reaction
Authors: Kosasang Soracha , Sawangphruk Montree , Ma Nattapol
Published: February 2020

The sluggish kinetics of oxygen reduction reaction (ORR) is a critical challenge for metal-air batteries and fuel cells. To increase the reaction rate, the high-efficient electrocatalysts are needed. Among various catalysts, platinum and its alloys are investigated as the best catalyst for the ORR. However, the Pt-based catalysts suffer from many disadvantages, including excessive cost, scarcity, and poor stability. In this work, layered manganese oxides, Li-birnessite, Na-birnessite, K-birnessite and their composites with graphene aerogel were used as the ORR catalysts. The ORR catalytic activity of these materials has been studied using rotating disk electrode (RDE) in O2-saturated and Ar-saturated KOH solution. The linear sweep voltammogram (LSV) curves at scan rate of 10 mVs-
1 show that the Li-birnessite/graphene aerogel provided the best catalytic performance with an onset potential of 0.99 V (V vs. RHE), half wave potential of 0.66 V (V vs. RHE), limiting current density of 5.60 mA cm-
1 (at a rotation rate of 1600 rpm), and Tafel slope of 104.3 mV dec-
1, which is comparable to the Pt catalyst. Moreover, the electron transfer number per oxygen molecule (n) calculated by Koutechy–Levich (K–L) equation is ~ 4, indicating a 4-electron pathway for ORR and suggesting the Li-birnessite manganese oxide coated on graphene aerogel as a high-efficient ORR catalyst.
(Invited) Light Metal Hydride Nanocomposites As Room Temperature Solid Electrolytes
Authors: de Jongh Petra E. , Ngene Peter , Blanchard Didier
Published: February 2020

A central goal in current battery research is to increase the safety and energy density of Li-ion batteries. Electrolytes nowadays typically consist of lithium salts dissolved in organic solvents. Solid electrolytes could facilitate safer batteries with higher capacities, as they are compatible with Li metal anodes, prevent Li dendrite formation and sulphur shuttling, and eliminate risks associated with flammable organic solvents. Less than 10 years ago, LiBH4 was proposed as a solid state electrolyte. It showed a high ionic conductivity, but only at elevated temperatures. Since then strategies have been developed to extend the high ionic conductivity of LiBH4 down to room temperature, and other light metal hydrides have been explored as solid electrolytes [1].

Using LiBH4 as an example we will discuss how the properties of solid electrolytes can be modified by forming nanocomposites with metal oxides, leading to an enhancement of the room temperature ionic conductivity of more than three orders of magnitude[2]. DSC measurements combined with solid state NMR allow to identify how the nanoconfinement and presence of interfaces modify the phase stability and the Li+ mobility [3]. Systematic studies show how the ionic conductivity can be optimized by tuning the nanostructure and interfaces in these nanocomposites. Finally, promising results have been obtained in using these materials as solid-state electrolytes in next generation all-solid state lithium-sulphur batteries. [4]

[1] de Jongh et al. J. Appl. Phys. A (2016), 122:251.

[2] Blanchard et al., Adv. Funct. Mater. 25 (2015), 182.

[3] Verkuijlen et al., J. Phys. Chem. C 116 (2012) 22169.

[4] Blanchard et al, J. Electrochem. Soc. (2016).
A Way to New Smart Materials – Hierarchical 3D Structures Produced Via Self-Organization of Nanowires
Authors: Strukova Galina
Published: February 2020

Galina Strukova, Gennady Strukov

The beauty of these pictures is intriguing and fascinating by its asymmetric, exquisite and intricate pattern. What is it? Is it a product of a novel computer program or photographs of fine creations of nature? Neither statement is true. In fact, these are not pictures, but images of metal samples made with an electron microscope. Only some color is added to the images to emphasize their resemblance to natural objects of our macroworld: seashells, jelly-fish, leaves of exotic plants. The size of the samples is varied in micron scale. They are produced via self-organization of nano-sized (millionth of a millimeter) wires growing on porous membranes under the action of electric current pulses. This is how such volumetric (3D) sculptures are described in scientific journals [1- 3] along with the experimental conditions for their reproduction, i.e., the conditions of the process (electrolyte composition, porous membrane, pulsed current mode) are specified, when growing nanowires organize themselves in an inexplicable fashion into “sculptures” that show perfect resemblance to natural creations. The authors have managed to isolate and photograph them with a modern electron microscope. Besides, they have proved that the internal structure of this metallic “seashells” is a volumetric multilayer network woven by nano-sized wires. Such antenna-like samples are expected to find application in nanotechnology as new materials for different applications. Now we produce such “sculptures” from various metals “by order”, examine their magnetic properties, study their interaction with plasma and focused electron beam, look for a field of their application and admire their elegant forms. However, it is still a riddle. Why do they so closely resemble shells and leaves? Does this mysterious self-organization have anything in common with formation of plant leaves and seashells?

[1] J of Bionic Engineering 10 (2013) 368–376

[2] Materials Today 16 (2013) 98–99 ,

[3] Materials Letters, 128 (2014) 212-215.

Figure 1
Enhanced Capacitive Deionization of Graphene Nanoplatelet/Activated Carbon Composite Electrode
Authors: Ham Kahyun , Lee Jae Kwang , Lee Jaeyoung
Published: February 2020

Water treatment is an essential technology. Especially, some nations demand appropriate technology to produce fresh water with a low cost. Capacitive deionization (CDI) with low-energy consumption and no secondary waste is emerging as an innovative desalination technology. [1] It removes salts in the water by adsorbing ions onto electric double layer in surface of electrode. Hence, carbon with high surface area as well as high conductivity and chemical stability against corrosion is one of the candidates for CDI electrode material. [2]

Electrosorption ability of CDI electrode is related with such textural characteristics as the pore structure, size and the ratio of mesopore to micropore. [3] In the recent study, the micropore with size less than 1nm showed an anomalous increase in carbon capacitance for the electric double layer capacitor. [4] Meanwhile, the well-connected pore channels are accessible for ion mobility in pore structure, formed by ample micropore and mesopore via intercalation. Therefore, it is utmost approach to develop micro/mesoporous carbon structures to enhance electrosorption capacity and construct facile ion transfer pathway.

In this work, we reported the development of meporous/microporous carbon composite for fast ion infiltration with high electrosorption capacity using different ratio of graphene nanoplatelet to activated carbon as CDI electrode. The electrode was characterized by SEM, XRD, BET and contact angle. To confirm electrochemical performance, cyclic voltammetry and electrochemical impedance spectroscopy was investigated. Also, the fabricated electrode was conducted Langmuir isotherm adsorption experiment to compare adsorption kinetics among the electrodes and CDI performance test. We found that the composite electrode had the improved process efficiency, attributed to the high conductivity and adsorption kinetics of graphene nanoplatelet compared with the electrode exploiting only activated carbon.

[1] S. Seo, Investigation on removal of hardness ions by capacitive deionization (CDI) for water softening applications, Water Research, 2010, 44, 2267

[2] S. Porada, Direct prediction of the desalination performance of porous carbon electrodes for capacitive deionization, Energy Environ. Sci., 2013, 6, 3700

[3] P.M. Biesheuvel, Dynamic adsorption/desorption process model for capacitive deionization, Journal of Physical Chemistry C, 2009, 113, 5636

[4] J. Chmiola, Anomalous increase in carbon capacitance at pore sizes less than 1 nanometer, Science, 2006, 313, 1760