bluuebunny/crossref_metadata_2025 huggingface dataset:
Iodide Effect On the Conduction Band Edge of ZnO Nanomaterials
Authors: Chhetri Pushpa , Perera Neluni , Alpuche-Aviles Mario A
Published: February 2020

Abstract not Available.
Can Electron Tunneling Occur in a Hundred-Nanometer Thick Nafion Film and be Utilized to Image Nafion/Electrode Interfaces With An Angstrom Level Resolution?
Authors: Zhou Xiangyang
Published: February 2020

Abstract not Available.
Distance-Dependent Electron Transfer At Passivated Electrodes Decorated By Gold Nanoparticles
Authors: Barfidokht Abbas , Ciampi Simone , Luais Erwann , Darwish Nadim , Gooding John Justin
Published: February 2020

Abstract not Available.
Bromide Oxidation On a Polycrystalline Platinum Rotating Disk Electrode in Aqueous Solutions
Authors: Scherson Daniel A , Xu Jing
Published: February 2020

Abstract not Available.
Characterization of Flow-Through Porous Electrodes for Microfluidic Electrochemical Cells
Authors: Goulet Marc-Antoni , Kjeang Erik
Published: February 2020

Abstract not Available.
Heavy Metal Extraction and Electroseparation From Wastewater By Acidic Solutions
Authors: Addi Yassine
Published: February 2020

Abstract not Available.
Doping in Organic Semiconductors and Solar Cells
Authors: Gregg Brian
Published: February 2020

Abstract not Available.
Photooxidation of Chloride By Oxide Minerals: Implications for Perchlorate On Mars
Authors: Parkinson Bruce A
Published: February 2020

Abstract not Available.
Sacrificial dye electrode for non-gassing electro-osmotic pumps
Authors: Nagarale Rajaram K.
Published: February 2020

Abstract not Available.
Redox Mediators Coupled to Surfaces and Supports: Operation of Enzymatic Biofuel Cells in Physiological Buffers, Human Saliva and Blood
Authors: O Conghaile Peter , MacAodha Domhnall , Falk Magnus , Shleev Sergey , Gorton Lo , Leech Dónal
Published: February 2020

Abstract not Available.
(Invited) Cold Gas Sprayed Semiconductor-Based Electrodes For The Photo-Induced Water Oxidation
Authors: Herrmann-Geppert Iris , Gutzmann Henning , Bogdanoff Peter , Emmler Thomas , Hillebrand Philipp , Schieda Mauricio , Gaertner Frank , Klassen Thomas
Published: February 2020

Abstract not Available.
Influence of CO2 On the Stability of Discharge Performance for Li-Air Battery With Hybrid Electrolyte Based On the Graphene Sheet
Authors: Zhou Haosen , Yoo Eunjoo
Published: February 2020

Abstract not Available.
A Membrane-Free Lithium/Polysulfide Semi-Liquid Battery for Large-Scale Energy Storage
Authors: Yang Yuan , Zheng Guangyuan , Cui Yi
Published: February 2020

Abstract not Available.
A Reversible 3.88 V Single Plateau in Sodium-Ion Battery By Iso-Energetic Structural Rearrangement: Experiment and Theory
Authors: Lim Soo Yeon , Choi Jang Wook
Published: February 2020

Abstract not Available.
Comparative Electrochemistry of Sodium and Lithium Intercalation in Mixed-Alkali Transition Metal Oxide Cathodes: Insight Into Structure and Reactivity
Authors: Slater Michael D. , Dogan Fulya , Lee Eungje , Johnson Christopher
Published: February 2020

Abstract not Available.
High Energy Density Na-Ion Batteries Through Electrolyte Optimization
Authors: Ponrouch Alexandre , Dedryvère Rémi , Monti Damien , Johansson Patrik , Croguennec Laurence , Masquelier Christian , Palacín María Rosa
Published: February 2020

Abstract not Available.
New Sodium Ion Conducting Solid Electrolytes Based Upon Mixed Glass Formers
Authors: Martin Steve W , Bischoff Christian , Christensen Randilynn
Published: February 2020

Abstract not Available.
The Reaction of Sn and Cu6Sn5 As Na-Ion Anodes
Authors: Baggetto Loic , Jumas Jean-Claude , Meisner Roberta , Ganesh P. , Gorka Joanna , Bridges Craig A , Veith Gabriel M
Published: February 2020

Abstract not Available.
Stoichiometric Analysis of Li2O2stored in Li-O2 Batteries
Authors: Hase Yoko , Ito Emi , Shiga Tohru , Mizuno Fuminori , Nishikoori Hidetaka , Iba Hideki , Takechi Kensuke
Published: February 2020

Abstract not Available.
In-Situ Scanning Probe Microscopy for Observing Electrode Surfaces Under Operating Conditions
Authors: Kreidler Eric , Xu Qingmin , Omichi Kaoru , Brooks Christopher
Published: February 2020

Abstract not Available.
All Solid-State Iron-Air Redox Battery for Advanced Energy Storage
Authors: Zhao Xuan , Gong Yunhui , Xu Nansheng , Li Xue , Huang Kevin
Published: February 2020

Abstract not Available.
Olivine-Structured MgxFePO4: Cathode Material for Mg-Ion Batteries
Authors: Ranjan Rajeev
Published: February 2020

Abstract not Available.
Anti-Site Mixing Governs Electrochemical Performances of Olivine Type MgMnSiO4 for Magnesium Ion Battery Cathode
Authors: Mori Takuya , Masese Titus , Okado Tetsuya , Yamamoto Kentaro , Huang Zhen-Dong , Kim Jungeun , Orikasa Yuki , Minato Taketoshi , Uchimoto Yoshiharu
Published: February 2020

Abstract not Available.
Activated Carbon Synthesized From Banana Peel as Electrodes in Li-Ion Capacitors
Authors: Arie Arenst Andreas
Published: February 2020

Abstract not Available.
Dependence of Electric Double Layer Capacitance On Ionic Liquid Structure and Electrode Nanostructure and Polarity
Authors: Bedrov Dmitry , Vatamanu Jenel
Published: February 2020

Abstract not Available.
Hydroxide Ion Conductive Polymer Electrolytes for Electrochemical Supercapacitors
Authors: Gao Han , Li Jak , Lian Keryn
Published: February 2020

Abstract not Available.
Effects of Functionalities On Selfdischarge Process: A Step-Forward Study On Energy Retention of Single-Walled Carbon Nanotube Based Supercapacitors
Authors: Zhang Qing , Cai Chuan , Qin Jinwen , Wei Bingqing
Published: February 2020

Abstract not Available.
Carboxyl-Functionalized Graphene Oxide/Polyaniline Composite As a Promising Supercapacitor Material
Authors: LIU Yan
Published: February 2020

Abstract not Available.
Hierarchical Nanostructured Carbon Materials for Ultrahigh Electrical Charge Storage
Authors: Fang Baizeng
Published: February 2020

Abstract not Available.
Enhanced Supercapacitor Performance of Graphene/V2O5 Nanocomposites
Authors: Ramadoss Ananthakumar , Kim Sang Jae
Published: February 2020

Abstract not Available.
Improvements on Capacity Retention and Metal Dissolution of NCM Cathode Material By the Use of Alternative Conducting Salts
Authors: Gallus Dennis Roman , Wagner Ralf , Cekic-Laskovic Isidora , Winter Martin
Published: February 2020

Ni1/3Co1/3Mn1/3O2 (NCM) cathode material can be charged to different potentials. When using the standard salt LiPF6, elevated cutoff potentials lead to increased energy densities and better energy quality, but reduce the cycle life dramatically. Metal dissolution is catalyzed by acids, like HF, derived from deterioration of the salt. To exclude the influence of HF, next to LiPF6 the less hydrolysis sensitive LiBF4 and the fluorine-free conducting salt LiClO4 were investigated. To determine the metal dissolution behavior of NCM, these electrodes were stored in 1 M EC/DMC (1/1, by wt.) electrolyte containing different salts for 28 days at different states of charge. The measurement of metal ion content was carried out by inductively coupled plasma/optical emission spectrometry (ICP-OES) technique. Constant current cycling experiments were performed with different charge potential limits. In contrast to LiPF6, LiBF4 showed suppressed metal dissolution and superior cycling performance with low capacity fading even at high cutoff-potentials (4.6 V vs. Li/Li+). At low potentials, metal dissolution, as well as capacity fading, is rather low for LiClO4 but escalates at potentials above 4.4 V vs. Li/Li+.
Electrolyte Optimization of a Doped-LiCoPO4 Cathode
Authors: Allen Joshua L. , Allen Jan L. , Delp Samuel A. , Jow T. Richard
Published: February 2020

Advanced high voltage cathode materials can increase the energy density through increased charging voltage but this usually limits the cell’s cycle life and/or efficiency. This tradeoff is due to irreversible electrolyte decomposition or damage to the cathode structure that occurs at higher potentials. Furthermore, materials such as LiCoPO4 are naturally electronically insulating and thus may either require a constant voltage charging step or very high voltage constant current cutoff voltage( >5.0V) to ensure a full charge is obtained. This can lead to perpetual electrolyte decomposition on each cycle due to the increased time the cell is held at higher potentials. Many researchers have incorporated various transition metals as dopants to improve the cycle life of these cells while maintaining the same cutoff voltage, and subsequently achieving higher energy density and cycle life. This was demonstrated recently in our lab by Fe-doping LiCoPO4 (1). This is perhaps attributed to better electronic conductivity of Fe-doped LiCoPO4and stabilization of the cathode material.

An alternative approach involves the use of electrolyte additives for improved passivation layer formation (2-3). This approach, however, does not affect any structural changes that may occur within the cathode (i.e., additives are not as effective in stabilizing the cathode structure as doped metals). The use of additives can nevertheless improve the high-temperature performance of the cell and ensure a longer cycle life (4).

This study utilizes a joint cathode/electrolyte research approach. A next-generation LiCoPO4-doped cathode was used (developed by ARL) that is less insulating than traditional LiCoPO4, as indicated by a shorter CV step requirement. Various electrolyte additives were examined with the new cathode to further optimize the performance. These additives include tris(hexafluoro-iso-propyl)phosphate (HFiP), lithium difluoro(oxalato)borate (LiDFOB), lithium bis(oxalato)borate (LiBOB), fluoroethylene carbonate (FEC) and Trimethylboroxine (TMB). While investigating the properties of the new cathode material, the electrolyte mixture was optimized for high-capacity cycling. This study has yielded a high-efficiency cell with a long cycle-life that is stable at room temperature and elevated temperatures.

ACKNOWLEDGEMENT

The authors wish to express their gratitude to the DOE ABR program for partial financial support.

REFERENCES

J.L. Allen, T.R. Jow and J. Wolfenstine, J. Power Sources,
196, 8656 (2011).

R. Sharabi, E. Markevich, K. Fridman, G. Gershinsky, G. Salitra, D. Aurbach, G. Semrau, M.A. Schmidt, N. Schall and C. Bruenig, Electrochem. Commun., 28, 20 (2013).

M. Hu, J. Wei, L. Xing and Z. Zhou, J. Appl. Electrochem., 42, 291 (2012).

N.P.W. Pieczonka, L. Yang, M.P. Balogh, B.R. Powell, K. Chemelewski, A. Manthiram, S.A. Krachkovskiy, G.R. Goward, M. Liu and J.-H. Kim, J. Phys. Chem. C, 117, 22603 (2013).
Solid Polymer Electrolytes Based on Poly(vinylidene fluoride-trifluoroethylene) and the [N1 1 1 2(OH)][NTf2] Ionic Liquid for Energy Storage Applications
Authors: Leones R. , Costa C. M. , Machado A. V. , Esperança J.M. S.S. , Silva M. M. , Lanceros-Méndez S.
Published: February 2020

Rechargeable lithium-ion batteries take advantage of solid-state ionic conductors, such as solid polymer electrolytes (SPEs) [1, 2]. Despite the large technological potential of solvent-free SPEs, they suffer from a serious problem: a relatively low ionic conductivity. The addition of ionic liquids (ILs) to SPEs appears as a possible solution due to the enhancement of electrochemical stability (~4-6 V) and ionic conductivity (~10-3 – 10-2 S.cm-1) [3].

ILs has two important features for their specific use in battery applications: high concentration of ions and high ion mobility at room temperature. The use of PVDF polymer and its copolymers together with ILs as SPEs still has to be thoroughly explored.

This work shows the thermal and electrochemical properties of SPEs based on poly(vinylidene fluoride-co-trifluoroethylene), P(VDF-TrFE), and specific amounts (4wt% to 32wt%) of the ionic liquid N,N,N-trimethyl-N-(2-hydroxyethyl)ammonium bis(trifluoromethylsulfonyl)imide, [N1 1 1 2(OH)][NTf2]. The SPE was prepared by thermaly induced phase separation (TIPS).

The addition of ILs in P(VDF-TrFE) affects the microstructure, thermal stability and ionic conductivity of the polymer membrane.

The ionic conductivity increases as the ionic liquid (IL) content increases with a maximum value at room temperature of 1.7x10-5 S.cm-1for an IL composition of 32wt%. The temperature behavior of the ionic conductivity follows the Arrhenius equation and the electrical response of the membrane is well represented by a Randles modified equivalent circuit. The results prove that the developed SPEs are adequate for energy storage devices.

Acknowledgments

This work was supported by FEDER through the COMPETE Program and by the Portuguese Foundation for Science and Technology (FCT) in the framework of the Strategic Project PEST-C/FIS/UI607/2011, PEST-C/QUI/UI0686/2011, PEST-OE/EQB/LA0004/2011, projects PTDC/CTM-NAN/121274/2010 and PTDC/QUI-QUI/117340/2010, grants SFRH/BD/68499/2010 (C.M.C.) and SRFH/BD/90366/2012 (R.L.) and FCT Investigator grant (J.M.S.S.E.). The authors also thank funding from Matepro –Optimizing Materials and Processes”, ref. NORTE-07-0124-FEDER-000037”, co-funded by the “Programa Operacional Regional do Norte” (ON.2 – O Novo Norte), under the “Quadro de Referência Estratégico Nacional” (QREN), through the “Fundo Europeu de Desenvolvimento Regional” (FEDER). The authors thank Solvay for kindly supplying the high quality materials.

References

[1] P. Arora, Z. Zhang, Chemical Reviews
104(2004) (10) 4419.

[2] J.M. Tarascon, M. Armand, Nature
414(2001) (6861) 359.

[3] Y.-S. Ye, J. Rick, B.-J. Hwang, Journal of Materials Chemistry A
1 (2013) (8) 2719.
Ionic Conduction in CNFs Reinforced PMMA Based Nanocomposite Gel Polymer Electrolytes for Li-Ion Batteries
Authors: Sharma Rajni , Sil Anjan , Ray Subrata
Published: February 2020

Nanocomposite gel polymer electrolytes are gaining more and more attention among the researchers worldwide due to their possible applications in various electrochemical devices particularly in solid-state Li-ion batteries [1]. In the present work, the effect of carbon nanofibers (CNFs) reinforced in PMMA based gel polymer on the electrical properties has been investigated. The length and outer diameter of CNFs used are in the ranges of 5-50 µm and 200-600 nm, respectively. The electrolytes have been synthesized by solution casting technique with varying the CNFs content. The impedance spectroscopy analysis shows that the incorporation of CNFs into PMMA–(PC+DEC)–LiClO4gel polymer significantly enhance the ionic conductivity of the electrolyte system. The enhancement of ionic conductivity seems to be correlated with the fact that the dispersion of CNFs to PMMA prevents polymer chain reorganization due to the high aspect ratio of CNFs, resulting in reduction of polymer crystallinity, which gives rise to an increase in ionic conductivity. The decrease of crystallinity of PMMA due the addition of CNFs has been confirmed by X-ray diffraction study. The interaction of CNFs with various constituents of polymer electrolytes has been studied by Fourier transform infrared spectroscopy (FTIR). Transmission electron microscopy (TEM) results show that uniform distribution of CNFs in the polymer electrolytes and FESEM for morphological analysis. Moreover CNFs added gel polymer electrolytes offer better thermal stability as compared to that of electrolytes without CNFs as confirmed by thermal gravimetric analysis (TGA).

Keywords: Polymer electrolytes; CNFs; Ionic conductivity; XRD; FTIR; TEM; FESEM; TGA.

References

[1] F. Croce, G.B. Appetecchi, L. Persi, B. Scrosati, Nanocomposite polymer electrolytes lithium batteries, Nature (London), 394, 456, 1998.
Analysis of Impedance Spectrum By Electrochemical Approach
Authors: Haung Chih-Sheng , Lin Yang-Shan , Chen Kuo-Ching
Published: February 2020

Electrochemical impedance spectroscopy (EIS) and electrochemical approach are two major tools in analyzing the performance of a battery, where the former one is commonly used to measure frequency response of a battery. However, the impedance spectrum does not clearly reveal the information about the change in material parameters of electrochemical models like electrolyte conductivity, solid-phase diffusivity, and double-layer capacity. To gain more information about impedance spectrum, the link between the two methods should be established.

By constructing an isothermal one-dimensional electrochemical model of lithium iron phosphate (LFP) cell, we have simulated the discharge curve of a single 26650 LFP cell, which agrees well with the experimental data [1], as shown in the inset of Fig. 1. Figure 1 also shows that the simulation physical model can be further used to calculate the impedance spectrum. Although there exists slight difference between the experiment and the simulation, which could be caused by the use of distinct electrode materials, using the physical model to explore battery impedance still provides a new way to have a deeper understanding of discharge behavior.

It is known that double layer on the surface of solid electrodes significantly contributes to impedance spectrum, whereas it exerts little influence on the discharge curve whether it exists or not. Base on the electrochemical model, we find in Fig. 2 that there are few variations between the case which has double layer in cathode only and the other case which has double layer in both electrodes. This result shows an agreement with an experiment, which indicates that cathode contributes to impedance spectrum magnitude [2].

In spectrum analysis the irreversible resistance, coming from electrolyte conductivity and resistance between the porous electrode surface and the current collector [3], is frequently treated as a constant value. Figure 3 shows that decreasing electrolyte conductivity in the electrochemical model drives the impedance curve to the right. This proves that the difference in electrolyte conductivity will lead to a change in the real-part resistance. More detailed discussion on the electrochemical parameters in the impedance spectrum will be presented in this work.

REFERENCES

[1] M. Safari and C. Delacourt, J. Electrochem. Soc.,158, A562 (2011).

[2] G. Nagasubramanian, J. Power Sources, 87, 226 (2000)

[3] D. D. Macdonald, Electrochemica Acta, 51, 1376, (2006)
Modeling and Validation of Electrodeposition in Copper Plating and Electrowinning
Authors: Robison Mark , Free Michael L , Shukla Abhijeet
Published: February 2020

Modeling and simulations can be cost effective ways of predicting the behavior of an electroplating system, and many mathematical models have been developed to describe an electrolyte’s current distribution, however the models are usually restricted to specific simplified geometries such as flat panels, rotating discs, or triangular geometries. Various software packages have been developed that allow for three dimensional modeling, however very little information validating such models has been published in literature. In this study models of copper electrowinning and copper plating have been developed using Comsol Multiphysics software and have been validated using experimental plating and electrowinning cells. The Comsol Multiphysics models are also compared with empirical models in this study. The results show a good correlation between the models and the experimental data for a variety of cathode geometries and electrodeposition parameters.
Analytical Modeling of PEM Fuel Cell Gas Diffusion Layers Deformation Under Compression: Part 1 - Linear Behaviour Region
Authors: Norouzifard Vahid , Bahrami Majid
Published: February 2020

In the Proton exchange membrane PEM fuel cell stack, transport characteristics of the porous gas diffusion layer (GDL) change due to the GDL microstructural parameters variation in a result of compressive loading during the fuel cell assembly and operation. The GDL is a carbon fiber based highly porous media in the form of paper or cloth. In addition to the reactants and reactions products transportation, GDL provides mechanical support for the membrane assembly against the compressive loads imposed by bipolar plates. According to the results of compression tests, GDL mechanical behaviour can be divided into regions; nonlinear and linear. In the compressive loads smaller than a critical pressure, GDL has a nonlinear mechanical behaviour and its compressive modulus is a function of deformation level. After reaching the critical pressure, the compressive strain increases linearly with the applied stress. Using unit cell approach and assuming a simplified geometry for the complex and random microstructure of the GDL, a new mechanistic model is developed that can accurately predict the mechanical behaviour of GDL. The unit cell model covers salient microstructural parameters and properties of the fibrous porous medium including: carbon fiber diameter, elastic modulus, and pore size distribution. Bending of carbon fibers is proved to be the main deformation mechanism of GDL deformation in linear region. A comprehensive optical measurement study with statistical analysis was performed to determine the effective geometrical parameters of the model for a number of commercially available GDL samples. A comparison between the present model and the GDL stress-strain data shows that the model can predict accurately the mechanical behaviour of the GDL material. The nonlinear behaviour of GDL will be addressed in the second part of this study.

Keywords: Gas Diffusion Layer, Porous media, Fuel cell,analytical modeling, mechanical behaviour, compression
Analytical Modeling of PEM Fuel Cell Gas Diffusion Layers Deformation Under Compression: Part 2 - Nonlinear Behaviour Region
Authors: Norouzifard Vahid , Bahrami Majid
Published: February 2020

In the Proton exchange membrane PEM fuel cell stack, transport characteristics of the porous gas diffusion layer (GDL) change due to the GDL microstructural parameters variation in a result of compressive loading during the fuel cell assembly and operation. The GDL is a carbon fiber based highly porous media in the form of paper or cloth. In addition to the reactants and reactions products transportation, GDL provides mechanical support for the membrane assembly against the compressive loads imposed by bipolar plates. GDL mechanical behaviour can be divided into two regions; nonlinear and linear. In the compressive loads smaller than a critical pressure, GDL has a nonlinear mechanical behaviour and its compressive modulus is a function of deformation level. Using assumption of existing gap between the fibers in GDL micro-structure, the analytical model proposed in first part of this study for linear region, based on the unit cell approach, is extended to predict the nonlinear mechanical behaviour of GDL. The present unit cell model covers salient microstructural parameters and properties of the fibrous porous medium including: carbon fiber diameter, elastic modulus, pore size distribution, and gap size distribution between fibers. Bending of carbon fibers and closing the gaps between fibers are proved to be the main deformation mechanism of GDL deformation in nonlinear region. The statistical parameters of the gap distribution between carbon fibers in the GDL structure are calculated using experimental stress-strain data for a number of commercially available GDL samples. A comparison between the present model and the GDL stress-strain data shows that the model can predict accurately the mechanical behaviour of the GDL material. In addition to the mechanical behaviour, the proposed model provides useful information about the microstructural properties of the GDL during compression such as gap distribution between fibers that can be used in the GDL transport properties prediction.

Keywords: Gas Diffusion Layer, Porous media, Fuel cell,analytical modeling, mechanical behaviour, compression
Kinetics Analysis of Ammonia Electrolysis
Authors: Diaz Luis A. , Botte Gerardine G.
Published: February 2020

Introduction

When ammonia electro-oxidation in alkaline media is coupled with water reduction, in a process known as ammonia electrolysis [1], it is theoretically possible to produce hydrogen with just five percent of the energy required from water electrolysis [2,3]. However, the lack of understanding of the reaction mechanism and reaction kinetics has not allowed the full utilization and implementation of the technology in processes such as the removal of ammonia from wastewater [4].

In this work, it is discussed a methodology for the elucidation of a reaction mechanism and the kinetics parameters for ammonia electro-oxidation in a well characterized polycrystalline Pt electro-catalyst. Experimental data and mathematical modeling of a rotating disk electrode system were combined with parameter estimation to obtain information about the intrinsic kinetics of the ammonia electro-oxidation reaction. The validation of the reaction mechanism and kinetics parameters was supplemented by the analysis of a fluid cell electrolyzer.

Valuable information regarding operation conditions and catalyst deactivation were obtained from the mathematical model and corroborated with the fluid cell system. Finally it was possible to observe the scalability advantage of the developed methodology and the application of the calculated kinetic parameters for the ammonia electro-oxidation simulation and process design.

References

[1] G. G. Botte. (2010). U.S. Patent No. 7,803,264.

[2] F. Vitse, M. Cooper, G.G. Botte, J. Power Sources 142 (2005) 18.

[3] F. Vitse, M. Cooper, G.G. Botte, J. Power Sources 152 (2005) 311.

[4] L.A. Diaz, G.G. Botte, Ind. Eng. Chem. Res. 51 (2012) 12167.
Coupling of Heterogeneous Photocatalysis Process with Solar Photo Electro-Fenton Process to Improve the Mineralization of Salicylic Acid in a Solar 3L Flow Plant
Authors: Ruiz-Ruiz Edgar Jocsan , Garza-Campos Benjamin , Brillas Enric , Hernández-Ramírez Aracely , Ghenymy Abdellatif
Published: February 2020

Degradation of salicylic acid was performed coupling of the advanced oxidation processes: solar photo electro Fenton Solar (SPEF) and solar photocatalysis (SPC) using TiO2supported on glass spheres in a 3L flow plant.

Glass spheres (5mm in diameter) were covered with TiO2synthesized by the sol-gel route from titanium butoxide as precursor using the dip-coating method. Deposits were obtained layer by layer until obtain 10 layers of catalyst. The amount of photocatalyst on the glass beads that was used for the experiments was 0.25 g/L.

Degradation of salicylic acid (165 mg/L) was carried out in a 0.05M Na2SO4 solution with pH adjusted to 3 and adding 0.5 mM Fe2+ as Fenton reagent. The current density applied was 50 mA/cm2. The electrolytic cell consisted of Pt anode and an oxygen diffusion electrode as cathode.

It was performed the processes of SPC, anodic oxidation with platinum (AO), AO-SPC, electro-Fenton (EF), SPEF and SPEF-SPC to evaluate the degradation and mineralization of salicylic acid. The obtained results during the mineralization for these processes were 9, 16, 27, 29, 59 and 66%, respectively. Also a study was conducted by varying the applied current density (50, 100 and 150mA/cm2) for the process of SPEF and SPEF-SPC, the result mineralization for each current intensity was 59, 67, 78% for FEFS and 66, 76, 87% for FEFS-FC process .

The use of photocatalytic process with electrochemical processes to improve the mineralization of salicylic acid between 7-9% and this reduces energy costs and mineralization current efficiency.
Highly Active Pt-Sn/C Catalysts for Ethanol Electro-Oxidation Prepared By a Polyol-Alcohol Reduction Process
Authors: Gonzalez-Quijano D. , Pech-Rodríguez W.J. , Escalante-Garcia J.I. , Vargas-Gutierrez G. , Rodriguez-Varela F.J.
Published: February 2020

Introduction.

Fuel cells are very attractive devices as power source for mobile, stationary or portable applications. In a Direct Ethanol Fuel Cell, the fuel is directly feed into the cell anode compartment without any previous chemical modification. However, alcohols are very difficult and complex to electrooxidize completely to CO2, because of the need to break C-C bonds, which results in the formation of intermediates that poison the Pt active sites. In order to overcome these issues, the efforts are focused on developing new bimetallic catalysts with higher catalytic activity and tolerance to the presence of the intermediates, mainly CO, than Pt-alone. The most efficient alternative has been to add a second metal to the composition of the catalysts used as anodes for the electrooxidation of organic molecules. Therefore, this work presents the results of a study carried out to evaluate how different synthesis variables can have an effect on the chemical reduction process of the salts, and thus, on the chemical composition of PtSn/C catalysts. Then, the chemical composition has an effect on the performance of the PtSn/C materials for the ethanol oxidation reaction in acid media.

Methodology.

PtSn/C anodes with Pt:Sn atomic ratio of 1:1 were prepared by the polyol method, in the presence different concentrations of ethanol and water, which were used to dissolve the Sn precursor. The structural characteristics of the catalysts were studied by XRD analysis in a Philips X’Pert diffractometer using Cu Kα Kα (λ= 1.5406 Å) radiation operating at 40 kV. The chemical composition of the catalysts was analyzed by SEM-EDS and ICP-AES.

Results.

Through XRD analysis, the degree of alloying of the Pt-Sn/C catalysts is evaluated with Vegard’s law. Also, the average particle size is obtained with the Scherrer equation. The results show the formation of nanocatalysts having a particle size of 2-4 nm. Chemical analysis using SEM-EDS and ICP-AES indicate the actual Pt:Sn ratio, confirming the formation of Sn oxides as a function of the concentration of ethanol and water.

The electrochemical characterization indicates that the Pt-Sn/C with high degree of alloying and less Sn oxides is more active for the EOR than Pt-Sn/C anodes with a high Sn oxides formation and low degree of alloying. Moreover, the Pt-Sn/C anodes demonstrated a higher catalytic activity than Pt/C synthesized by the same method.
Characterization of Dealloyed Catalysts in PEMFC
Authors: Kongkanand Anusorn , Kukreja Ratan S , Moylan Thomas , Ziegelbauer Joseph M. , Theobald Brian , O'Malley Rachel , Gan Lin , Strasser Peter , Carlton Chris , Han Binghong , Shao-Horn Yang , Jia Qingying , Mukerjee Sanjeev , Caldwell Keegan M. , Ramaker David E.
Published: February 2020

Pt-alloy catalysts have attracted much attention because of their high activity for the oxygen reduction reaction compared to that of pure Pt catalysts. One variant of the Pt-alloy catalyst is the “dealloyed catalyst” made by first preparing an alloy precursor with a high base-metal-to-Pt ratio (≥1:1) and then removing most of the base metal, resulting in Pt-rich particles (M:Pt of ~1:3).1 Removal of the base metal (dealloying) by electrochemical voltage cycling or by acid leaching can result in a particle with Pt-rich skin covering a base-metal-rich core. It was suggested that lattice mismatch between the two layers induced strain in the surface Pt shell2 and that the near-surface structure was a driving factor in determining the initial activity3. We have generated a set of catalysts with very similar initial activity but vastly different durability under fuel cell testing.4

These catalysts were characterized using high-resolution TEM and extended X-ray absorption spectroscopy. In this talk we will summarize the factors that appear to have significant affects on their activities and durability. Electrode development using the improved catalysts will also be discussed.
Sonoelectrochemical Production of Nanosized Fuel Cell Electrocatalysts
Authors: Pollet Bruno G
Published: February 2020

For the first time, this study describes the sonoelectrochemical synthesis of Pt nanoparticles from solutions containing Pt salt, ionomer, solvent and water in the presence of ultrasound (20kHz, ~100W.cm-2) using a specially designed/constructed Glassy Carbon (GC) electrode acting as a Vibrating Working Electrode (VWE) [Fig.1]. From early studies, it was found that Pt mean nanoparticle sizes could be produced in the range [11 - 15nm] in the absence of surfactants and solvents [1,2]. In this investigation (undertook at the Birmingham Centre for Hydrogen and Fuel Cell Research laboratories, UK), the syntheses of Pt nanoparticles were performed galvanostatically at (298±1)K, at various ultrasonic and current pulses using several time managements and at a high cathode efficiency. Physical characterisations by TEM, SEM, XRD and SAED showed that Pt mean grain sizes and cluster sizes of up to ~20nm and ~100nn were obtained respectively. Non-ultrasonicated (silent) but high-shear mixed catalyst inks made of Pt/C(Vulcan XC-72R)/Nafion® were prepared using the method described by Curnick et al. [3,4]. Electrochemical characterisation (Cyclic and RDE voltammetry) data of the as-prepared catalyst inks showed low ECSA values (<~35 m2.gPt
-1). This finding was mainly attributed to: (i) the fairly ‘large’ Pt nanoparticle/cluster sizes, (ii) the ionomer acting as a ‘surfactant’ encapsulating the Pt nanoparticles thus preventing local electron transfer and (iii) poor dispersion of Pt nanoparticles/homogeneisation of the ink caused by the high-shear mixer (19,000rpm). However it was observed that the ionomer prevented Pt nanoparticles aggregation. It was suggested that the Nafion® content may play an important role on the activity of the Pt nanoparticles as previously observed [3,4]. It also possible that ultrasonication affects the composition and morphology of the electroanalyte/Pt nanoparticles/ionomer, mainly due to cavitation and sonolysis phenomena as recently shown by Pollet and Goh [5].

References

[1] V. Zin, B.G. Pollet, M. Dabala, Sonoelectrochemical (20 kHz) Production of Platinum Nanoparticles from Aqueous Solutions, Electrochem. Acta 54 (2009) 7201-7206

[2] B.G. Pollet, The Use of Ultrasound for the Fabrication of Fuel Cell Materials, Int. J. Hydrogen Energy 35(21) (2010) 11986-12004

[3] O.J. Curnick, P.M. Mendes, B.G. Pollet, Enhanced Durability of a Pt/C Electrocatalyst Derived from Nafion®-Stabilised Colloidal Platinum Nanoparticles, Electrochem. Comm. 12(8) (2010) 1017-20

[4] O.J. Curnick, B.G. Pollet, P.M. Mendes, Nafion®-stabilised Pt/C Electrocatalysts with Efficient Catalyst Layer Ionomer Distribution for Proton Exchange Membrane Fuel Cells, RSC Advances 2 (22), 8368-8374

[5] B.G. Pollet, J.T.E Goh, The Importance of Ultrasonic Parameters in the Preparation of Fuel Cell Catalyst Inks, Electrochim. Acta, in press
The Hybrid Bi-Cell Approach for Reducing Active Water Management in the Direct Methanol Fuel Cell
Authors: Grew Kyle N. , Chu Deryn
Published: February 2020

Direct methanol fuel cells (DMFCs) provide an avenue for developing high (specific) energy density, portable power sources. While the overall energy efficiencies that have been reported for DFMCs are rather modest (e.g., approximately 15-20%), interest in the technology stems from the specific energy methanol (6.1 kWhr/kg) which still enables very large system energy densities to be achieved (1, 2). Despite this key benefit, the size and cost of the DMFC technology remain key technical hurdles.

To date, many if not most efforts to develop DMFC technologies have used membrane electrolyte assemblies (MEAs) which utilize proton exchange membrane (PEM) electrolyte materials. These acidic PEM materials tend to be quite robust ; however, their use has relegated the DMFC systems to use of relatively large balance of plant (BoP) components for active water/fuel management (3, 4) and expensive platinum based catalyst materials (5).

In this talk, we review an approach which is intended to address the size of the BoP required for active water/fuel management as well as enable the removal of some of the platinum based catalysts. This approach uses a bi-cell, or pseudo-bipolar, configuration which has been previously shown to be well suited to portable power applications (6). The novelty of this approach is the combination of a first acidic MEA using PEM electrolyte materials and a second alkaline MEA using anion exchange membrane (AEM) electrolyte materials. This configuration naturally balances the water stoichiometry of the methanol oxidation and oxygen reduction reactions between the adjacent acid and alkaline MEAs, significantly improving the water balance within the system. The integration of alkaline AEM materials has the additional benefit of opening doors for alternatives to platinum based catalysts.

A multi-phase, multi-component transport model is used as the basis of this work, which is intended to demonstrate the technical feasibility of the approach for miniaturizing portable DMFC system. A previous study by Kim et al. has shown the compatibility of the materials (7). In this talk, focus will be placed on comparing standard and hybrid configurations and the relative water/fuel management requirements. Additional attention will be placed on the treatment of direct oxidation of methanol in an alkaline MEA and the effect of MEA properties.

1. D. Chu and R. Jiang, Electrochim Acta
51(26), 5829 (2006).

2. R. Jiang, C. Rong and D. Chu, J Power Sources
126(1-2), 119 (2004).

3. R. Jiang and D. Chu, J Electrochem Soc
155(8), B798 (2008).

4. R. Jiang and D. Chu, J Electrochem Soc
155(8), B804 (2008).

5. S. Wasmus and A. Kuver, J Electroanal Chem
461(1-2), 14 (1999).

6. R. Jiang and D. Chu, J Power Sources
93(1-2), 25 (2001).

7. H. Kim, M. Unlu, J. F. Zhou, I. Anestis-Richard and P. A. Kohl, J Power Sources
195(21), 7289 (2010).
In Situ Surface Enhanced Raman Spectroscopic Studies on Iridium Oxide
Authors: Pavlovic Zoran Miroslav , Ranjan Chinmoy
Published: February 2020

In oxygen electrocatalysis, hydrous oxides are common occurrence but less studied part of electrochemical literature. Most of these oxides naturally form in situ during the reaction.
The exact structure of hydrous oxide, its catalytic properties and its stability are very critical to understanding the nature of the real catalyst. This knowledge will allow us to develop better catalysts based on iridium and possibly reduce the amount of noble metal involved.

We have built a setup for in situ surface Enhanced Raman spectroscopy. We deposited hydrous iridium oxide on Au. We have followed the Ir-OH peaks and its behavior over various potentials to investigate the potentials dependent property of the oxide. We followed the dominant peak at 520 cm-1 over potentials ranging from 0.4 to 1.8V. The peak shows expected tuning in response to applied electric field. Potentials 1.6V and higher are potentials where considerable evolution of oxygen happens. The shifting of this peak to higher values (stronger bonds) can be linked to higher charge on the Iridium center. The differential tuning of Raman shifts with respect to the applied potential are used to establish the points of charge transfer.

DFT calculations were performed in conjunction with isotope substitution studies to interpret the experiments. The peak at 780 cm-1 appears at 1.4V and grows in intensity till 1.8V (beyond which the potential was turned off). This is the potential regime for oxygen evolution. This peak at only exists under applied potential regime of oxygen evolution and goes away as soon as the potential is removed and an open circuit is established. This experiment reiterates the importance of in situ studies in the context of electrocatalysis.
Electrochemical Studies on High Durable Carbon Supported Fuel Cell Catalysts
Authors: Sribollepalli Srinivas , Velayutham Guruviah , Kalingamuthu P
Published: February 2020

Fuel cell cost reduction demands improved catalyst performance and durability. Platinum (Pt) particle size, crystallite geometry, metal dispersion on carbon support, conductivity, and porosity of the catalyst layer are key features that determine the catalytic activity in fuel cell operating environment. These properties can be controlled by proper design of the catalyst synthesis process with suitable carbon support1. The fundamental properties of the carbon support can have great influence on fuel cell catalyst at low temperature PEMFC as well as high temperature PAFC systems. Pt catalysts supported on high surface area carbon supports result in smaller Pt crystallites with increased electrochemically active surface area but it results in lower durability due to carbon corrosion. The durability of Pt catalyst at cathode is considered as one of the key challenges for fuel cell system reliability. The major degradation in fuel cell performance is due to loss of electrochemical surface area of Pt catalyst due to carbon corrosion2. This phenomenon is attributed to Oswald ripening (Pt particles detached from carbon support to form larger aggregates), which contributes to the loss in fuel cell performance. In the present study we have prepared fuel cell catalysts with three high durable carbon (HDC) supports with varying surface areas and graphitization. The carbon corrosion behavior of catalysts was studied using cyclic voltammetry. With high durable carbon support, optimization of electrode structure with PTFE binder is crucial for improved performance and to mitigate carbon corrosion. The electrodes are prepared with different loadings of PTFE content and characterized by measuring electrochemical surface area and linear sweep voltammetry (Figure 1). The carbon corrosion experiments are conducted in 0.5M H2SO4 by sweeping the voltage from 0.4 to 1.0 using Ag/AgCl as reference electrode. After every 1000 cycles, electrochemical surface area is measured (Figure 2). An optimum surface area and graphitization is required to balance the performance and durability.

Reference:

Chunzhi He, Sanket Desai, Garth Brown, and Srinivas Bollepalli, The Electrochemical Society Interface, 41-45, Fall 2005.

R. Borup, J. Meyers, B. Pivovar, Y.S. Kim, R. Mukundan, N. Garland, D. Myers, M. WilSon, F. Garzon, and D. Wood, Chem. Rev., 107, 3904 (2007)
An In Situ TEM Liquid Cell for Imaging Electrode/Electrolyte Interactions
Authors: Leenheer Andrew Jay , Harris Charles Thomas , Jungjohann Katherine L , Sullivan John P , Zavadil Kevin R
Published: February 2020

The transmission electron microscope (TEM) has provided valuable insights about electrochemical processes in solid battery electrode nanostructures [1], and recent advances in microfabrication have enabled the encapsulation of volatile liquids in miniature, high-vacuum electrochemical cells [2]. Imaging the electrode/electrolyte interfaces in a standard liquid electrolyte environment will enable the study of electrolyte decomposition processes such as the formation and evolution of solid-electrolyte interphases (SEI) on Li-ion battery anodes. We have developed a custom TEM liquid cell platform that is well suited to quantitative electrochemical control on Li-ion battery materials and electrolytes. The liquid cell design incorporates a thin, electron-transparent liquid cavity (0.1-1 micron thick) between two silicon nitride membranes, multiple current-collector electrodes with minimal exposed area optimized for facile nanomaterial assembly, and sealable fluid fill ports which allows the cell to be electrochemically cycled either on or off the TEM holder.

To test the cell operation, we imaged Li electrodeposition on a nanopatterned Ti working electrode. The liquid electrolyte consisted of 1:1 ethylene carbonate:diethyl carbonate with 1M LiPF6, and a galvanostatic two-electrode charging experiment was performed to deposit Li from the electrolyte onto the working electrode. The TEM was operated in scanning mode (STEM) with a low electron dose to minimize beam effects on the liquid electrolyte. Upon application of a few pA of current, we acquired a characteristic chronopotentiometric curve and saw clear deposition of Li particles in the STEM images and movies (see Figure 1). Following Li deposition, a thick growth of SEI was evident near the Li nanoparticles, consistent with electrolyte decomposition in the presence of reactive Li. We also imaged electrodeposition/stripping of Cu nanoparticles in the same liquid environment and will explore battery-relevant materials such as LiFePO4 and Si nanostructures. Our TEM liquid cell provides a unique, high-resolution view of the electrode/electrolyte interfacial phenomena, and both the challenges in fabrication as well as the successes in imaging electrochemical processes will be presented.

1. Sullivan, J. P. et al. “Real-time Studies of Battery Electrochemical Reactions Inside a Transmission Electron Microscope.” Sandia Technical Report SAND2012-0103 (2012). doi:10.2172/1038174

2. de Jonge, N. & Ross, F. M. “Electron microscopy of specimens in liquid.” Nat Comms
6, 695–704 (2011).
Physical Properties of the Catalyst Layer in Proton Exchange Membrane Fuel Cell
Authors: Li Luyue , Sun Che-Nan , Zawodzinski Thomas A.
Published: February 2020

The catalyst layer (CL) in proton exchange membrane fuel cells (PEMFC) is a composite material comprised of carbon-supported Pt bonded with proton-conductive ionomer. Resistances associated with processes in the CL, e.g. proton conduction through the ionomer percolation within CL, contribute to the voltage loss during the fuel cell operation. In this study, we attempt to characterize CLs from several aspects [1].

A DSC study was carried out to investigate the possible component interactions in the CL. As shown in Fig.1, in a nitrogen environment, an endothermic peak appeared around 100ºC for a dried Pt/Vulcan and Nafion mixed catalyst ink and at 135ºC for a Pt/Nafion mixture. However, this peak was not observed in a Carbon/Nafion mixture implying distinct interactions between each component. TEM was also adopted to further investigate the microstructure of CLs.

Moreover, the proton conductivity of CL using Nafion and BPSH as ionomer were measured respectively via the method proposed by Liu et al[2]. The effects of ionomer/carbon ratio relative humidity and ionomer equivalent weight on CL proton conductivity, will be discussed.

Reference:

[1]H. Iden, A. Ohma, and K. Shinohara, “Analysis of Proton Transport in Pseudo Catalyst Layers,” Journal of The Electrochemical Society, vol. 156, no. 9, p. B1078, 2009.

[2] Y. Liu et al., “Proton Conduction and Oxygen Reduction Kinetics in PEM Fuel Cell Cathodes: Effects of Ionomer-to-Carbon Ratio and Relative Humidity,” Journal of The Electrochemical Society, vol. 156, no. 8, p. B970, 2009.
Sensitivity Analysis of a One-Dimensional SOFC Contaminant Degradation Model Using Dual Numbers Automatic Differentiation
Authors: Sezer Hayri , Celik Ismail Bektas , Pakalapati Suryanarayana Raju
Published: February 2020

Sensitivity analysis of a computational model with respect to a parameter is the derivative of the model outcome with respect to same parameter. In experimental studies, sensitivity of the experiment to the parameter is very crucial for the accuracy of the results. In this study, a one-dimensional contaminant performance degradation computational model for solid oxide fuel cells (SOFC) is utilized to study its sensitivity to changes in model parameters. Both finite difference (FD) method and dual numbers automatic differentiation (DNAD) are used to evaluate derivatives and compared to each other. The DNAD method uses dual number arithmetic to calculate the derivative of any mathematical functions or any numerical model with respect to a given parameter. Dual number arithmetic is a well-known strategy for automatic differentiation of computer codes which gives exact derivatives, to the machine accuracy, of the computed quantities with respect to any of the involved variables. The sensitivity to a model parameter calculated by DNAD is then verified and compared with finite differences. This technique can be used to evaluate the sensitivity of simulation results on changes in the critical parameters involved in the mathematical model. It is those parameters which have to be carefully calibrated and validated against experiments to confidence on predictions.