bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transport-Geometry Interactions in Li-Ion Cathode Materials Imaged Using X-Ray Nanotomograph
Authors: Nelson George J. , Ausderau Logan , Buckley Joseph , Mistry Aashutosh , Mukherjee Partha P. , De Andrade Vincent 
Published: February 2020

Layered Li-transition metal oxide compounds of the form LiMO2 serve as chemically stable, energy dense active cathode materials for Li-ion batteries. Among these materials Li(Ni1/3Mn1/3Co1/3)O2 (NMC) has received increased attention due to its improved rate capability compared to other LiMO2 cathode materials. Forging a stronger connection between complex mesoscale electrode geometry, material performance, and processing techniques can enable development of practical approaches for realizing electrode performance controlled by mesoscale geometry. To this end, 3D x-ray imaging, microstructural characterization, and computational modeling techniques have been applied to analyze the charge/discharge behavior of the active material in a set of NMC cathodes subject to varied processing approaches. For the present studies, the cathodes were produced using combinations of rapid or gradual drying process along with ball milling and calendaring prior to cutting into coin cell electrodes. Samples were extracted from pristine cathodes and imaged using x-ray nanotomography approximately halfway between the Co and Ni K-absorption edges. Imaging at this x-ray energy provided clear contrast between the NMC phase and the carbon/binder/pore regions within the samples. Particle geometry was characterized and compared for samples from four cathodes treated with distinct combinations of preparation steps. Geometric characteristics of the active cathode material include the particle size distribution, surface area, volume, and sphericity. Following characterization the tomographic data sets were applied as computational domains in multiphysics transport models to assess the effects of processing methodology on charge/discharge performance. Distinct variation in particle count and geometry is observed within the samples analyzed. The performance implications of this variation are discussed, particularly with respect to charge/discharge capabilities. A comparison is also made for particles with varied degrees of mechanical degradation.
Life Tests of Current Switched Oxygen Electrodes for Reversible Solid Oxide Cells
Authors: Railsback Justin , Hughes Gareth , Lu Matthew , Barnett Scott A 
Published: February 2020

Large scale energy storage is a necessary component of any electricity grid operating primarily on intermittent renewable power sources. Recent experimental and techno-economic studies on reversible solid oxide cell (ReSOC) technology suggest that this technology performs well compared to other available technologies in terms of round-trip efficiency, stable storage time, and cost per kilowatt-hour stored.[S.H. Jensen, Energy Environ Sci 2015 ,8, 2471-2479] However, SOCs are known to degrade by delamination at the oxygen electrode under electrolysis conditions; this must be better understood in order to operate SOCs over their desired lifetimes. Here we investigate the conditions that cause delamination and degradation by carrying out life tests of symmetric cells, observing electrochemical behavior by impedance spectroscopy and by post-test SEM analysis. Symmetric cells are subjected to switching current operation with a 12 hour period at current densities ranging from 0.5 to 2.0 A/cm2 – similar to that expected in a ReSOC energy storage application. Cells are typically operated for 1000 hours, long enough to detect degradation rates as low as 1 %/kh. Three types of symmetric cells are investigated: single phase (La0.6Sr0.4)(Co0.2Fe0.8)O3 (LSCF) on Ce0.9Gd0.1O2 (GDC), (La0.8Sr0.2)MnO3 (LSM) on Zr0.92Y0.08O2 (YSZ) and La2NiO4 wet infiltrated into (La0.9Sr0.8)(Ga0.8Mg0.2)O3 (LNO infiltrated LSGM) on LSGM. Degradation rates are determined for each current density and corresponding initial electrode overpotential. Degradation rates < 1%/kh are observed for LNO infiltrated LSGM on LSGM at 1.0 A/cm2 (0.20 V), and below ~0.9 A/cm2 (0.1 V) for LSCF on GDC. The results are also compared with prior results from similar experiments with (La0.8Sr0.2)MnO3 (LSM) on Zr0.92Y0.08O2 (YSZ). Changing the temperature by 50 °C from 800 to 750 °C for a previously stable current density (0.5 A/cm2) for LSM-YSZ results in a higher over potential (0.55 V) and fast degradation. Comparing the critical current densities and overpotentials where the degradation rates become measurable, and where structural damage can be observed in post-test SEM images, for this range of different electrode and electrolyte materials, suggests that degradation is controlled by overpotential rather than by current density.
Characterization of Ultra-Low Pt Loading Meas Prepared By Electrospray
Authors: Martinez-Vazquez Beatriz , Sanchez Daniel G , Martin Santiago , Castillo Jose Luis , Garcia-Ybarra Pedro Luis , Friedrich K. Andreas 
Published: February 2020

Ultralow Pt-loading electrodes with 0.02 mgPt cm−2and 0.04 mgPt cm−2 were prepared by electro hydrodynamic atomization (electrospray) of catalytic inks on carbon paper coated with a carbon micro-porous layer. MEAs of 25 cm2 active area were manufactured with this type of electrodes [1-3] and tested in a single-cell equipped with segmented bipolar plates to show in operando the local current density distribution throughout the electrode surface. From hydrogen & air as feeding gases, tests under different pressures, relative humidity and gas flow rates were performed using the segmented cell [4,5]. Moreover, electrochemical impedance spectroscopy (EIS) analyses were accomplished to determine the ohmic and charge transfer resistances in each of the test conditions. The best performance was achieved for a MEA with an overall loading of 0.06 mgPt cm−2 providing a platinum utilization of 3.8 kW gPt
−1 at 0.6 V and a maximum platinum utilization of 5.9 kW gPt
−1 when working at 70 ºC, 1.5 bar and stoichiometries of λH2=1.5 and λair= 2, At different test conditions, i.e. increasing the backpressure or the feeding flow rate, the cell behaviour improves significantly and maximum platinum utilizations of 9 kW gPt
−1 and 7 kW gPt
−1 were respectively reached. Additionally, short-term runs of about 100 hours of continuous operation were carried out to assess electrode durability.

References

[1] S. Martin, P. L. Garcia-Ybarra, J. L. Castillo, Method for the Uniform Nanostructured Deposition of Catalytic Particles by Means of Electrospray, WIPO Patent PCT Application No. WO 2013/144390 A1.
[2] S. Martin, P. L. Garcia-Ybarra, J. L. Castillo, Electrospray deposition of catalyst layers with ultra-low Pt loadings for PEM fuel cells cathodes, J. Power Sources, 195 (2010) 2443–2449.
[3] S. Martin, B. Martinez-Vazquez, P. L. Garcia-Ybarra, J. L. Castillo, Peak utilization of catalyst with ultra-low Pt loaded PEM fuel cell electrodes prepared by the electrospray method, J. Power Sources, 229 (2013) 179–184.
[4] B. Martinez-Vazquez, D. G. Sanchez, J. L. Castillo, K. A. Friedrich, P. L. Garcia-Ybarra, Scaling-up and characterization of ultralow-loading MEAs made up by electrospray, Int. J. Hydrogen Energy, 40 (2015) 5384-5389
[5] M. Schulze, E. Gülzow, S. Schönbauer, T. Knöri, R. Reissner, Segmented cells as tool for development of fuel cells and error prevention/prediagnostic in fuel cell stacks, J. Power Sources, 173 (2007) 19–27.
(Invited) 2-D Surface Phases for Energy-Related Applications
Authors: Luo Jian 
Published: February 2020

Nanoscale, impurity-based, surficial films with self-selecting or “equilibrium” thickness can form spontaneously as the thermodynamic equilibrium states in various oxide materials [Annu. Rev. Mater. Res. 38: 227 (2008)]. They can be considered as a unique class of 2-D surface phases (that are also called “complexions” to differentiate them from the 3-D bulk phases defined by Gibbs). Such surface phases can be utilized as a class of ideal nanocoatings (made by thermodynamics) to improve the performance of various functional materials for energy-related applications. This presentation will review a series of our recent studies to utilize this and other analogous types of spontaneously-formed 2-D surface phases to tailor battery cathode [APL 95: 211905 (2009); JCCP 16: 7786 (2014)] and anode [J. Power Source 245: 594 (2014)] materials, supported oxide catalysts [APL 91: 061909 (2007); Acta Mater. 56: 4702 (2008)] and photocatalysts [Mater. Lett. 98: 205 (2013)], nanowire-based fast oxygen-ion conductors [Nature Communications 6: 8354 (2015)], and supercapacitors [unpublished results]. A potentially-transformative scientific goal is to utilize such 2-D surface phases to achieve superior properties that are unattainable by conventional bulk phases.
Local pH Determines Lanthanum Accumulation on Electrodes in Aqueous Solution
Authors: Babauta Jerome T. , Medina Adan , Beyenal Haluk 
Published: February 2020

Electrochemical detection or accumulation of lanthanum and the lanthanides are typically investigated on modified electrodes such as carbon paste and mercury film electrodes.1-4 However, little data exists on lanthanum’s interaction with unmodified electrodes. Lanthanum deposition was characterized using an electrochemical quartz crystal microbalance (eQCM) in aqueous solution on unmodified carbon electrodes. We used a home-made pH microelectrode to directly measure a 10 pH unit variation in the local pH ~ 100 µm above a flat carbon electrode. The eQCM frequency response during voltammetric sweeps in the presence of lanthanum showed that the background current masked the dependence of lanthanum deposition on local pH and applied electrode potential. Lanthanum deposition in unbuffered LiCl solutions exhibited a stable deposited film until the anodic scan reached nearly 1.8 VAg/AgCl. The addition of 1 mM α-hydroxyisobutyric acid, a complexing ligand, decreased the deposition onset potential on the first scan. Subsequent scans showed the frequency response returning to that without added HIBA. Similar experiments with acetate-buffered solutions resulted in film stripping at -2VAg/AgCl on the anodic scan. The large variation in local pH is likely due to water electrolysis at the surface of the working electrode, which can impact form of the electroactive species. The formation of insoluble lanthanum hydroxides at high pH values contributes to the stable film in pH-controlled anodic sweeps. The frequency response on gold electrodes is also shown.
Refernces:
1. P. D. Schumacher, J. L. Doyle, J. O. Schenk and S. B. Clark, Rev. Anal. Chem., 2013, 32, 159-171.
2. P. D. Schumacher, K. A. Fitzgerald, J. O. Schenk and S. B. Clark, Anal. Chem., 2011, 83, 1388-1393.
3. P. D. Schumacher, N. A. Woods, J. L. Doyle, J. O. Schenk and S. B. Clark, Anal. Chem., 2011, 83, 4788-4793.
4. P. D. Schumacher, N. A. Woods, J. O. Schenk and S. B. Clark, Anal. Chem., 2010, 82, 5663-5668.
3D-Polypyrrole Hydro-Sponge Thin Films for Electrochemical Applications
Authors: Antonio Jadielson Lucas da Silva , Cordoba de Torresi Susana I. , Torresi Roberto M. 
Published: February 2020

Conducting polymers have been targeted as research interest in many publications and it is possible to find applications in drug delivery systems, artificial muscles, artificial neurons, tissue engineering, supercapacitors, etc. All this interest about conducting polymers comes from their unique properties such as, high conductivity, chemical stability, versatility and biocompatibility. At the present moment, not only the properties of the materials are important but also the ability to control their morphology is a goal, because this can lead to the improvement of the materials to be applied in different technologies. This work reports the controlled electrochemical synthesis of polypyrrole hydro-sponges (Ppy-HS) thin films nanostructured with methyl orange (MO) template.
The Ppy-HS thin film was synthesized on a gold surface using chronoamperometry. The synthesis was performed in 5 mmol L-1 MO aqueous solution to which 35 μL of distilled pyrrole (Py) were added to a final volume of 10 mL. The pH of the solution was adjusted to 2 by the addition of HCl. A three electrodes system was mounted using gold, Ag/AgCl/NaCl-3M electrode and platinum as work, reference and auxiliary electrodes, respectively. Different Ppy-HS thin films were synthesized at 0.6 V using different electrochemical charge of polymerization.
Scanning Electron Microscopy (SEM) characterization showed that the Ppy-HS presents a microfibrillar structure organized as a 3D material. However, it is possible to control the morphology of the Ppy-HS by the electrochemical charge of polymerization. Under the microfibrillar there is a compact layer with the typical granular structure of Ppy. After that, the increase of the electrochemical charge used in the polymerization results in the increase of the density of the microtubules to form a 3D structure.
The 3D porous structure makes the Ppy-HS a very interesting material for many technological applications. The material presents good elastic properties, high water uptake, and enhanced electroactivity. All these characteristics allows the application of PPy-HS in biosensors, drug delivery, tissue engineering and in other areas. In this work, the Ppy-HS is being explored in storage energy field. This material shows a specific capacitance of 800 F/g, which is much higher compared with no-strucutured Ppy and comparable to other materials applied in the field.
References:
Daí, T.; Lu, Y. J. Mat. Chem. 2007, 17, 4797.
Antonio, J. L. S.; Lira, L. M.; Gonçales, V. R.; Córdoba de Torresi, S. I. Electrochim. Acta 2013, 101, 216.
Experimental Study and CFD Model for Partial Oxidation of Methane over Self-Sustained Electrochemical Promotion Catalyst
Authors: Zhou Xiangyang , Huang Hao , Liu Hongtan 
Published: February 2020

The so-called self-sustained electrochemical promotion catalyst or SSEP catalyst is a micro-particulate material with solid-solid interfaces between the active catalyst phase, the oxygen ion conductor, and oxygen reduction phase forming multiple micro-electrochemical cells. We have demonstrated that electrochemical promotion can make the catalyst more effective than conventional transition metal (Ni, Co) based catalysts and precious metal based catalyst for partial oxidation (POX) reforming of hydrocarbons. A computational fluid dynamics (CFD) model will help quantify the effects of the components in the microscopic electrochemical cells and of detailed thermal-chemical processes on electrochemical promotion thereby allowing better understanding and further optimization of the catalyst system.
A multi-physical multi-scale CFD was developed for analyzing POX of methane (CH4) over a SSEP catalyst in a fixed-bed reformer. The model incorporates a conventional transport processes, heat transfer, and kinetics for POX of CH4 over the active components and the electrochemical processes occurring in the unique microstructure. The simulation results show that the temperature in the first reactor with the Ni based conventional catalyst is generally about 30 K lower than that in the second reactor with the Ni-based SSEP catalyst. This temperature difference is impossible to explain the huge difference in the conversion in these two reactors. The simulation results are compared with the experimental results. The good agreement can only be achieved by correctly describing the electrochemical processes and electrochemical promotion in the theoretical system. The validated model was used to predict the performance of the SSEP catalysts as a function of flow rate, O/C ratio, and the microstructure of the catalysts providing guidance for further optimization the SSEP catalyst.
Synthesis of Reduced Graphene Oxide-Supported PtAu Catalysts and Their Electrocatalytic Activity for Formic Acid Oxidation
Authors: Jeevagan Arockiam John , Gunji Takao , Tanabe Toyokazu , Kaneko Shingo , Matsumoto Futoshi 
Published: February 2020

In this paper, we demonstrate that, a one-pot synthesis of a reduced graphene oxide (RGO)-supported freely assembled binary alloy catalyst (PtAu/RGO) under alkaline conditions. The synthesized PtAu/RGO catalyst has been characterized by powder X-ray diffraction (pXRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). It was found that graphene oxide (GO) was successfully reduced to RGO and that the PtAu nanoparticles exhibited alloy structure about 3.60 ± 0.20 nm in diameter and uniformly distributed on RGO surface. Further, the electrocatalytic activity of the catalyst was examined toward formic acid (FA) oxidation, which exhibited better catalytic activity toward FA
The electrocatalytic activity of PtAu/RGO (Pt mass loading: 20%) was examined with the solution of 0.1 M H2SO4 + 0.5 M HCOOH. The catalytic activity of PtAu/RGO was compared with the Pt/RGO (Pt mass loading: 20%) and commercial Pt/CB (Pt mass loading: 20%). Figure 1 shows that the linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing 0.1 M H2SO4 aqueous solution. It could be observed from the Fig. 5, two oxidation peaks can be clearly observed, the peak I is related to the direct oxidation of HCOOH to CO2, whereas the peak II is correspond to the oxidation of the COads generated from the dissociative adsorption step. The peak I current densities are in the order of PtAu/RGO > Pt/RGO > commercial Pt/CB, which indicates that the RGO can effectively enhance the activity of PtAu and Pt catalysts, which may be due to the strong interaction between PtAu or Pt NPs and RGO surface. In contrast, the peak II current densities are in the order of PtAu/RGO < Pt/RGO < commercial Pt/CB, indicating that the presence of RGO in PtAu/RGO hold back the formation of poisoning intermediate COadsduring the FA oxidation. Based on the present and previously reported results, it can be considered that the uniform distribution of NPs and electronic interaction between PtAu NPs and RGO could enhance the catalytic activity.
To sum up, freely assembled PtAu/RGO nanocomposites were synthesized under alkaline conditions. On the basis of pXRD, TEM, STEM, XPS, the GO was converted to RGO and PtAu NPs were highly dispersed and uniformly distributed through out the surface. The PtAu/RGO catalyst exhibited higher catalytic activity for FA oxidation compared to the other catalysts Pt/RGO and commercial Pt/CB. This work provides a simple and fast approach to synthesize a novel RGO based catalyst with high electrocatalytic activity.

Figure 1. Linear sweep voltammograms of (a) Pt/RGO, (b) PtAu/RGO and (c) Pt/CB in 0.5 M HCOOH containing Ar-saturated 0.1 M H2SO4 aqueous solution at 2000 rpm.

Figure 1
Platinum Deposited on Carbon with Different Surface Properties for PEFC Application
Authors: Hayashi Akari , Noda Zhiyun , Sasaki Kazunari 
Published: February 2020

Electrocatalysts for PEFC, made of platinum deposited carbon materials, have an import role to govern PEFC performance. The surface properties of carbon materials influence on both PEFC performance and durability. Especially, considering stop/start cycles of fuel cell vehicles, carbon oxidation becomes a serious problem since the potential at the cathode becomes as high as 1.5 V vs RHE. Durability against carbon oxidation is mostly determined by surface properties of carbon.
In this study, Vulcan XC72, which is a common carbon black support, is used, and its surface properties are controlled by heat treatments. Oxygen reduction reaction activity and durability were evaluated for platinum on surface controlled carbon, electrochemically. Additionally, we introduce our method to accelerate degradation of electrocatalysts using Environmental TEM (Hitachi HF-3300). For carbon oxidation, the air is introduced into the specimen chamber, and the specimen holder is heated up to 200 oC to accelerate degradation instead of cycling to high potential many times.
Regarding to the temperature of heat treatments, 1600 oC worked best in our studies. The surface of carbon black particles was graphitized, and a few graphitic layers were observed in TEM images. Oxygen reduction reaction activity was not much changed by the heat treatment, but the durability was significantly increased.
In order to understand the degradation mechanism on different carbon surface, the method using Environmental TEM was introduced. A new phenomenon of platinum particles embedded into Vulcan carbon with almost no agglomeration was observed. However, on graphitized Vulcan carbon surface, agglomeration more occurred, and embedding of platinum was rather suppressed. Since platinum on graphitized carbon showed much improved durability though the electrochemical analysis, embedding is believed to be a more predominate factor than agglomeration on degradation of PEFC performance.
Reference: X. Zhao, A. Hayashi, Z. Noda, K. Kimijima, I. Yagi, K. Sasaki, Electrochim. Acta 97 (2013) 33.
Two-Dimensional Ni(OH)2@Pt Nanosheets: High Activity Fuel Cell Oxygen Reduction Reaction Electrocatalysts
Authors: Rhodes Christopher , Godinez-Salomon Fernando 
Published: February 2020

Oxygen reduction reaction (ORR) electrocatalysts with high activity, extended durability and lower cost are needed for proton exchange membrane fuel cells (PEMFCs). Compared with conventional nanoparticles, nanosheets composed of atomic-thin two-dimensional (2D) layers offer a higher relative concentration of catalytically active (111) surfaces. In contrast to many approaches that have investigated graphene-supported Pt ORR catalysts, we have explored Pt supported on Ni(OH)2 nanosheets (i.e. Ni(OH)2@Pt) for enabling high activity ORR electrocatalysts. Synthesis conditions were controlled to obtain Ni(OH)2 nanosheets with controlled sizes, phase, and aggregation. Temperature/atmosphere treatments were found to significantly affect the structure and morphology of the nanosheets. The effect of changing the Pt shell composition on the Ni(OH)2 nanosheets on the ORR activity was evaluated. The nanosheet structure and morphology with determined using x-ray diffraction and scanning electron microscopy, and the ORR activity was determined from rotating disc electrode experiments. Our initial results have shown that Ni(OH)2@Pt nanosheets provide significantly higher catalytic activities compared with Pt/C. The ability to control the structure and properties of 2D transition metal oxide nanosheets provides a route to develop electrocatalysts with high activity, extended durability, and lower cost.