bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrochemical Palladium Deposition on Titanium Nitride, Ruthenium and Palladium Substrates for Nanoscale Device Fabrication
Authors: Sahin Asli , Cotte John M , Huang Qiang , Baker-O'Neal Brett 
Published: February 2020

With the advances in device fabrication, scaling of electrochemical techniques to molecular scale is becoming essential. Electrochemical deposition of metals in devices with nanoscale dimensions can play an integral role in reducing critical dimensions of such devices. This study focuses on electrochemical deposition of palladium on substrates such as titanium nitride, ruthenium and palladium that are commonly used in manufacturing of nanoscale devices such as nanochannels and nanopores.
Palladium is used in many applications ranging from electrochemical biosensors to catalysts in electronic and optoelectronic devices (1, 2). Electrochemical deposition of palladium is preferred in many of these applications as a result of ease of manufacturing, controllability and economics.
Cyclic voltammetry and hydrodynamic linear sweep voltammetry were used to understand the effects of electrolyte composition and operating conditions on palladium electrodeposition. Blanket samples of titanium nitride, ruthenium and palladium were plated to study nucleation of palladium on these substrates. It was observed that high nucleus densities could be achieved on all three substrates under optimal operating conditions and electrolyte compositions. Ruthenium and palladium substrates behaved similarly in the electrolytes used in this study whereas titanium nitrite behavior was different.
To study palladium plating in small openings two test vehicles were designed. The first test vehicle (panel A) had metal lines buried under oxide layers and the second test vehicle (panel B) had metal lines without the oxide capping layer. Transfer of knowledge from beaker-scale experiments on blanket samples and electroanalytical techniques to plating in these test vehicles will be presented.

References

1. M. Schlesinger, Modern electroplating, Wiley (2010).
2. L. Shaidarova, I. Chelnokova, A. Gedmina, G. Budnikov, S. Ziganshina, A. Mozhanova and A. Bukharaev, Journal of Analytical Chemistry, 61, 375 (2006).

Figure 1. Schematic of test vehicles for palladium plating.
Effect of Copper Particle Size on the Product Distribution of the Electrochemical Reduction of CO2
Authors: Ethier Jeffrey , Kalu Egwu Eric 
Published: February 2020

Electroless copper electrocatalyst is explored in the electrochemical reduction of carbon dioxide for renewable energy generation. Non-conductive carbon toray paper is made active for electroless plating with Pd-ink and is followed by the elctroless deposition method where copper particle size is varied with deposition time. The copper catalyzed toray paper is utilized as the cathode in the electrolytic reduction of carbon dioxide. The feasibility of using the electrocatalyst as prepared to electrochemically reduce carbon dioxide is first determined from cyclic voltammogram. The electroless copper particle size deposited on the working electrode for CO2 reduction is estimated via SEM. It was found that the electrocatalyst prepared by electroless deposition was active for the CO2electrochemical reduction reaction. Particle size is shown to have an effect on current measured from the reaction. Results will be presented on the product distributions resulting from use of different electroless Cu particle sizes for the reduction of carbon dioxide. Detailed characterization of the electrode material will also be presented.
Electroless copper electrocatalyst is explored in the electrochemical reduction of carbon dioxide for renewable energy generation. Non-conductive carbon toray paper is made active for electroless plating with Pd-ink and is followed by the elctroless deposition method where copper particle size is varied with deposition time. The copper catalyzed toray paper is utilized as the cathode in the electrolytic reduction of carbon dioxide. The feasibility of using the electrocatalyst as prepared to electrochemically reduce carbon dioxide is first determined from cyclic voltammogram. The electroless copper particle size deposited on the working electrode for CO2 reduction is estimated via SEM. It was found that the electrocatalyst prepared by electroless deposition was active for the CO2 electrochemical reduction reaction. Particle size is shown to have an effect on current measured from the reaction. Results will be presented on the product distributions resulting from use of different electroless Cu particle sizes for the reduction of carbon dioxide. Detailed characterization of the electrode material will also be presented.
Characterization of Micro-Porous Layer of Gas Diffusion Layer of a PEM Fuel Cell Via X-Ray Tomographic Microscopy
Authors: Odaya Silvia , Philips Ryan , Phillion Andre , Hoorfar Mina 
Published: February 2020

Abstract

The gas diffusion layer (GDL) performs key functions within the fuel cell, providing access for hydrogen and oxygen gas to flow to and from the catalyst layer, conducting electricity and heat, and removing water byproduct. The GDL is commonly treated with a micro-porous layer (MPL) on the catalyst side to minimize contact resistance by reducing the roughness of the contact surface. The MPL also reduces mass transport losses and hence improves water management in the cell operated at high current densities [1].
This paper describes a method to characterize the GDL/MPL porous structure and their interface using X-ray micro-computed tomographic (µ-CT) microscopy. µ-CT is a relatively new tool that is used for acquiring the internal three-dimensional structure of both fully dense and porous materials [2]. In this work, the structure of the MPL/GDL is evaluated via µ-CT for various GDL samples (such as Toray TGP060 and EP40) loaded with different MPL loadings. Figure 1 shows a 3D image of the EP40 T12 GDL without the MPL (CBT 18). While previous studies have also examined the MPL layer using this technique (e.g. [1,3]), this is the first to examine the GDL/MPL interface, as well as the surface characteristics of the MPL. A new method is presented for separating, or segmenting, various phases (GDL, PTFE, and MPL). Using this methodology, the surface roughness of the MPL, and the porosity within the GDL is identified. The results show that there is considerable overlap between the GDL and MPL. Also, while the MPL has a smooth surface in comparison to the GDL, it remains relatively rough. The correlation between PTFE content, thickness of the MPL, and porosity will be discussed.

References

1. Z. Fishman, A. Bazylak (2011). Journal of The Electrochemical Society, Vol. 158, B846-B851.
2. C. Puncreobutr, P.D. Lee, R.W. Hamilton, A.B. Phillion (2012). JOM, Vol. 64, pp:89-95.
3. A. Pfrang, S. Didas, G. Tsotridis (2013). Journal of Power Sources, Vol. 235, pp:81-86.

Figures

Figure 1: EP40 T12 GDL specimen without MPL (CBT18). The PTFE can be seen between the carbon strands.
Preparation of Porous Yttria-Stabilized Zirconia Ceramics By Thermal Removal of Potassium Iodide
Authors: Muccillo R. , Carvalho Sabrina Macedo 
Published: February 2020

Near to full skeletal density ZrO2:8 mol% Y2O3 polycrystalline ceramics with different pore content were prepared by mixing different amounts of KI and thermally removing them during sintering at 1400oC. That removal of the alkali halide was evaluated by thermogravimetric and dilatometric measurements from room temperature to 1500oC.
The sintered pellets were analyzed by X-ray diffraction and X-ray fluorescence (XRF) for structural phase identification and KI content, respectively. Images of the polished and thermally etched surfaces were obtained by scanning probe microscopy (SPM) and scanning electron microscopy (SEM) for evaluation of average pore content and distribution. Electrochemical impedance spectroscopy measurements were carried out in the 300-450oC range in the 5 Hz-10 MHz frequency range.
The thermal removal of KI starts at its melting point, ~ 680oC and ends at ~ 900oC. No traces of KI are found by XRF analysis in sintered pellets.
The final linear shrinkage value is higher for compositions without KI and the temperature of maximum shrinkage rate increases for increasing KI content.
The total oxide ion electrical resistivity, extracted from the impedance plots, also increases for increasing KI content.
The SPM images observed at polished and thermally etched surfaces of sintered pellets show that the larger is the amount of KI addition, the larger is the average pore size and the smaller is the average grain size.
The effect of KI addition before sintering leads, upon sintering, dense porous ceramics with high skeletal density. Moreover, grain growth is inhibited.
The impedance spectroscopy results allowed for the evaluation of the bulk and the grain boundary conductivities. The increase in both contributions with the increase in KI addition was correlated to the observation by scanning probe microscopy of the increase of intragranular as well as of intergranular porosity. Other parameters determined after the deconvolution of the impedance plots, namely, the blocking factor, the frequency factor and the descentralization angle showed that the impedance spectroscopy technique is an important tool for the characterization of porous ionic conducting solids.
Investigation of Borohydride Oxidation on Graphene Supported Gold-Copper Nanocomposites
Authors: Norkus Eugenijus , Baronaite Asta , Stankeviciene Ina , Vaiciuniene Jurate , Kondrotas Rokas , Juskenas Remigijus , Tamasauskaite-Tamasiunaite Loreta 
Published: February 2020

Graphene as catalyst support has incurred intense interest in fuel cell applications due to its unique, outstanding physicochemical properties. Pure gold and gold-based catalysts show an enhanced electrocatalytic activity towards the direct oxidation of borohydride. Combination of graphene and gold-based catalysts allows reducing the amount of noble metal and fabricating novel materials with high efficiency towards borohydride electro-oxidation.
In this study the graphene supported AuCu catalysts (denoted as AuCu/GR) with different Au:Cu molar ratio were prepared by microwave heating of Au(III) and Cu(II) salts in ethylene glycol (EG) solutions at 150 oC for 30 min. It has been determined that the composition of AuCu/GR catalysts depends on pH of reaction mixture. When the reaction mixture pH was 7.0, 10.1 and 12.2, the AuCu/GR catalysts having the Au:Cu molar ratio 37:1, 1:13 and 1:32, respectively, were synthesized. The morphology, structure and composition of the prepared catalysts were examined by transmission electron microscopy (TEM), X-ray diffraction (XRD) and inductively coupled optical emission spectroscopy (ICP-OES). The electrocatalytic activity of the synthesized catalysts was investigated towards the oxidation of borohydride by means of cyclic voltammetry and chronoamperometry.
It was found that Au nanoparticles were successively deposited onto the surface of graphene nanosheets. Au nanoparticles were uniform and well dispersed on the surface of graphene. The analysis of composition of the prepared AuCu/GR catalysts by means of ICP-OES confirms the presence of Au and Cu.
The Au loadings were 0.055 mg Au cm–2 in the Au/GR and 0.107, 0.091 and 0.088 mg Au cm–2 in the synthesized AuCu/GR catalysts having the Au:Cu molar ratio 37:7, 1:13 and 1:32, respectively. It has been determined that the graphene supported AuCu catalysts show an enhanced electrocatalytic activity towards the oxidation of BH4
– ions comparing with the graphene supported bare Au catalyst and graphene supported bare Cu catalyst. Furthermore, borohydride oxidation current densities at the graphene supported AuCu/GR catalysts having the Au:Cu molar ratio 1:12 and 1:32 are ~13 times higher than those obtained at the AuCu/GR catalyst with the Au:Cu molar ratio 37:1.

Acknowledgement

This research was funded by a Grant (No. ATE-08/2012) from the Research Council of Lithuania.
Advanced Electrocatalysts for Fuel Cells
Authors: Snyder Joshua David , Kang Yijin , Li Dongguo , Strmcnik Dusan , Markovic Nenad M , Stamenkovic Vojislav R 
Published: February 2020

The primary barrier to broad applications of electrocatalyst for electrolyzers, fuel cells and metal-air batteries is lack of fundamental understanding of processes that are taking place at solid-liquid interfaces. Moreover, the cost, performance and durability of the current state of the art electrocatalysts are still not at level that would warrant commercialization of these technologies. Major catalytic improvements have been accomplished for the oxygen reduction reaction in case of Pt bi/multi-metallic alloys. It has been demonstrated that tuning of surface properties such as surface and subsurface composition, surface structure, and hence, electronic properties are critical aspects toward novel materials with unique functional properties. For instance, an increase in activity of almost two orders of magnitude compared to conventional Pt/C catalyst was reported for single crystalline Pt-Skin surfaces. This finding inspired subsequent nanoscale catalyst design aiming to synthesize more active, but also more durable catalysts. A synergy between well-defined extended surfaces and practical electrocatalysts remains to be a potent approach in development of systems with advanced catalytic properties and it will be thoroughly discussed in this presentation.
[1] Stamenkovic et al. Science 315 (2007) 493.
[2] van der Vliet et al. Nature Mat. 11 (2012) 1051.
Characterisation of Anion Exchnage Membrane Fuel Cells
Authors: Smith Graham T. , Kucernak Anthony R. J. 
Published: February 2020

Alkaline membrane fuel cells (AMFC) offer an exciting route to reduce the material cost of low temperature fuel cells. In contrast to traditional proton exchange membrane fuel cells (PEMFC) hydroxide ions rather than protons carry charge [1]. The resulting rise in pH increases the stability and possibly reactivity of some oxygen reduction reaction (ORR) catalysts such as Ag and Ni [2]. Critically, unlike alkaline fuel cells with a liquid electrolyte AMFC are resistant to metal carbonate precipitation and can purge themselves of carbonate anions during operation [3].
We will report techniques to characterise the electrochemical surface area of silver fuel cell electrodes and carry out in-situ measurements of the extent of membrane carbonation. We believe these techniques to be widely applicable and essential in understanding AMFC.
As well as having exceptional conductivity, silver has been shown to have an ORR price activity (£/mA) similar to the archetypal PEM catalyst platinum when in contact with alkaline membranes [4]. It is an outstanding material for both transport layers and cathode catalysts and is used widely in AMFC [5,6]. Unlike platinum, it is not possible to accurately measure the specific surface area of a silver catalyst using hydrogen adsorption or oxide formation. We will show specific surface area measurements on both full silver electrodes and silver nanoparticles down to 10nm in size, using lead under potential deposition (UPD) [7]. Though UPD is a well-known technique, its use on nanoparticles has recently been the subject of increased attention [8]. Our work confirms that lead UPD on silver nanoparticles is possible for select electrolytes.
Anion exchange membranes exhibit their highest conductivity when hydroxide ions are the mobile anion. When membranes are exposed to air carbonate and bicarbonate ions form (carbonation) and conductivity is reduced. In an operating cell the reverse process occurs [3]. Previously this phenomenon has only been studied by online mass spectrometry. We will report a new electrode, which can be placed inside an operating cell, to monitor the extent of carbonation locally during both start-up and steady state operation. Using this technique we will show an optimised method for purging the membrane during start-up.

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Effect of Gas Diffusion Layer Structure on the Performance of Hydrogen Oxygen and Hydrogen Air Polymer Electrolyte Membrane Fuel Cell
Authors: Velayutham Guruviah , Sribollepalli Srinivas , Kalingamuthu P 
Published: February 2020

Gas diffusion layer (GDL) plays a very important role in the function of fuel cell performance. Therefore, the requirements of an ideal GDL include diffusion and distribution of reactants to the catalyst layers, good in plane and thro plane conductivity. Depending on the reactants and operating current densities, the GDL must provide an optimum hydrophobicity and hydrophilicity for gas distribution, water and thermal management (1-3). In order to improve the stability of fuel cell stack, a complete understanding of GDL properties are essential. In the present work, AvCarb MGL370 carbon paper and AvCarb 1071 carbon cloth is used as a substrate material. The effect of PTFE content on the substrate and micro-porous layer on the fuel cell performance is compared in both hydrogen/oxygen and hydrogen/air. The properties of GDL were characterized by experimental setup developed in house for the measurement of gas diffusion coefficient. The properties were also measured using Capillary Flow Porosity meter.
The percentage of PTFE on the substrate is varied for both carbon paper as well as carbon cloth ranging from 5 to 20%, however the concentration of PTFE in the micro layer is fixed. The experiments are conducted by keeping constant PTFE loading in the substrate while the concentration PTFE in the micro layer is varied from 15 to 30%. The PEMFC cells were tested at 65oC and at ambient pressure with relative humidity of hydrogen and air kept at 90% and 80%, respectively. The results were analyzed from the polarization curves. The long-term stability of the cell is evaluated by operating the cell at constant current density. PTFE content in the substrate as well as micro porous layer is important for the performance of fuel cell. The current density achieved in the hydrogen/oxygen is about 1.25A/cm2 at 0.6V, while the same electrode when operated with hydrogen air is 0.5A/cm2 at the same operating voltage (GDL1). Alteration of both substrate and micro-layer PTFE concentration improve the performance to 1.6A/cm2 and 0.7A/cm2 at 0.6V for hydrogen/oxygen and hydrogen/air respectively (GDL2),Fig.1. The effect of hot pressing condition on both carbon cloth as well as carbon paper is also discussed. The pressing pressure conditions varied from 40 to 120kg/cm2. In this paper the performance of both carbon paper and carbon cloth is discussed with respect to PTFE content and pressing conditions.
Fig.1: The effect of PTFE content in the substrate and micro layer, ambient pressure, temperature of operation 65oC, H2/O2 - 100/80%, flow rate H2/O2is 300/400cc
References:
1. G. Velayutham, J. Kaushik , N.Rajalakshmi , K.S.Dhathathreyan , Fuel Cell 7, 314-318 (2007)
2. G. Velayutham, International Journal of Hydrogen Energy 36(22), 14845-14850, (2011)
3. E.Passalacqua , G.Squadrito, F.Lufrano , A.Patti, L.Giorgi . J Appl Electrochem , 31, 449-54 ( 2001)
First-Principles Computational Studies on Li-Ion Battery Cathode Materials
Authors: Saavedra-Arias Jose J. , Chitturi Venkateswara Rao , Katiyar Ram S. , Ishikawa Yasuyuki 
Published: February 2020

First-principles computation methods play an important role in designing and developing new electrode materials for Li-ion batteries (LIBs). These methods are more useful to study phase transformations, electron and ion mobility processes, and transportation kinetics related to various Li-intercalated materials and investigate mechanisms underlying in the electrochemical/lithium intercalation processes [1-3].
We have examined the influence of Mn substitution by Ni on the structural, electronic, and Li-intercalation properties of LiMn2O4spinel and also identified potential layered cathode material for LIBs by performing first-principles computational studies. The calculations were performed in the local density aproximation (LDA) to density-functional theory (DFT) as implemented in the Vienna Ab Initio Simulation Package (VASP). In order to reduce the number of the plane waves required for simulating the interactions between ions and electrons, ultra-soft Vanderbilt pseusopotentials were used.
In the case of spinel cathode materials, Ni substitution was done systematically for up to 25% by replacing Mn in a Mn16O32 supercell configuration and then Li atoms were intercalated. The influence of Ni substitution on the lithium hoping pathways between the two stable Li positions was studied and Li+ diffusion pathway in the Ni-substituted Mn-O supercell structures was identified. The calculations revealed that Ni substitution for Mn in LiMn2O4 indeed improved Li ion mobility [4].
To identify potential layered cathode materials for LIBs, first-principles calculations in conjunction with alloy metal method were used to evaluate average voltage, phase stability, formation energy, and Li intercalation potential for a series of layered LiMO2 (M = Co, Ni, Mn, and W) systems. According to the negative formation energy (-0.0535 eV), average voltage (3.48 V), and similar phase stability upon lithium extraction compared to LiCoO2, we concluded LiNi0.66Co0.17Mn0.17O2as a promising layered cathode material for lithium-ion batteries [5]. Computational details and results on the spinel and layered cathode materials will be presented in detail.

References

1) G. Ceder, Y.-M. Chiang, D.R. Sadoway, M.K. Aydinol, Y.-I. Jang and B. Huang, Nature392 (1998) 694.
2) G. Ceder, MRS Bulletin35 (2010) 693.
3) Y.S. Meng and M. Elena Arroyo-de Dompablo, Energy Environ. Sci.2 (2009) 589.
4) R. Singhal, J.J. Saavedra-Arias, R. Katiyar, Y. Ishikawa, M.J. Vilkas, S.R. Das, M.S. Tomar and R.S. Katiyar, J. Renewable Sustainable Energy1 (2009) 023102.
5) J.J. Saavedra-Arias, C.V. Rao, J. Shojan, A. Manivannan, L. Torres, Y. Ishikawa and R.S. Katiyar, J. Power Sources 211 (2012) 12.
Fermi Potential across Working Solid Oxide Cells with Zirconia or Ceria Electrolytes
Authors: Jacobsen Torben , Chatzichristodoulou Christodoulos , Mogensen Mogens Bjerg 
Published: February 2020

A solid electrolyte will always possess a finite electronic conductivity, in particular electrolytes like doped ceria that easily get reduced and become mixed ionic and electronic conductors. This given rise too high leak currents through the solid oxide cell (SOC). Especially, problems have been observed for ceria based electrolytes, but also in case of solid oxide electrolyser cells (SOEC) with yttria stabilized zirconia (YSZ) big electronic leak currents have been observed for very high overvoltages on one or both electrodes.
Furthermore, it is important to realize that the potential gradient driving the O2-ions is not the Fermi potential, which is the potential of the electrons, but the Galvani potential (or inner potential) (1). The concepts of potentials describing the electrical situation of a solid electrolyte is shown i Fig. 1, and an example of the Fermi potential (π) and Galvani potential (φ) profiles are shown in Fig. 2. The Fermi potential will be affected directly by the Galvani potential, whereas the Galvani potential need not necessarily be affected by the Fermi potential because the concentration of “free” electrons may be very low.
The paper gives illustrative examples at various temperatures and operation conditions. Furthermore, the situation within cells based on gadolinia doped ceria (CGO) and on YSZ electrolytes are compared. Finally, it is discussed how the Fermi potential and electron conductivity will be affected by the various parameters including operation conditions.

Reference

[1] T. Jacobsen and M. Mogensen, ECS Transactions, 13 (no.26), 259 (2008).