Name: probing and mapping electrode surfaces in solid oxide fuel cells
Uploaded: 2012-09-20T13:00:00
Description: Watch this Scientific Journal Video about Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells at JoVE.com

This work was supported by the HeteroFoaM Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences (BES) under Award Number DE-SC0001061.

1. Fabrication of a YSZ-embedded Mesh Anode Cell
<ol>
	<li>Weigh out two batches of 0.2 g of YSZ powder.</li>
	<li>Compress one batch YSZ powder in a cylindrical stainless steel mold (13 mm in diameter) with a uniaxial dry press at a pressure of 50 MPa for 30 sec.</li>
	<li>Cut a &lt;1-cm piece of Ni mesh and place it onto the surface of YSZ disc inside the mold.</li>
	<li>Add the other 0.2 g of YSZ powder on top of the Ni-mesh inside the mold and flatten the surface of the powder using a ram.</li>
	<li>Uniaxially pres...

<ol>
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P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coke+formation+and+performance+of+an+intermediate-temperature+solid+oxide+fuel+cell+operating+on+dimethyl+ether+fuel.">Coke formation and performance of an intermediate-temperature solid oxide fuel cell operating on dimethyl ether fuel.</a> Journal of Power Sources. 196, 1967 (2011).</li><li>Cheng, Z., Abernathy, H., Raman Liu, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spectroscopy+of+Nickel+Sulfide+Ni3S2.">Spectroscopy of Nickel Sulfide Ni3S2.</a> Journal of Physical Chemistry C. 111 (49), 17997 (2007).</li><li>Yang, L., Choi, Y., Qin, W., Chen, H., Blinn, K., Liu, M., Liu, P., Bai, J., Tyson, T. A., Liu, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Promotion+of+water-mediated+carbon+removal+bynanostructured+barium+oxide/nickel+interfaces+in+solid+oxide+fuel+cells.">Promotion of water-mediated carbon removal bynanostructured barium oxide/nickel interfaces in solid oxide fuel cells.</a> Nature Communications. 2, 357 (2011).</li><li>Kumar, A., Ciucci, F., Morzovska, A., Kalinin, S., Jesse, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Measuring+oxygen+reduction/evolution+reactions+on+the+nanoscale.">Measuring oxygen reduction/evolution reactions on the nanoscale.</a> Nature Chemistry. 3, 707 (2011).</li><li>Kumar, A., Arruda, T. M., Kim, Y., Ivanov, I. N., Jesse, S., Bark, C. W., Bristowe, N. C., Artacho, E., Littlewood, P. B., Eom, C. B., Kalinin, S. V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+Surface+and+Bulk+Electrochemical+Processes+on+the+LaAlO3-SrTiO3+Interface.">Probing Surface and Bulk Electrochemical Processes on the LaAlO3-SrTiO3 Interface.</a> ACS Nano. 6 (5), 3841 (2012).</li><li>Katsiev, K., Yildiz, B., Balasubramaniam, K., Salvador, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electron+Tunneling+Characteristics+on+La0.7Sr0.3MnO3+Thin-Film+Surfaces+at+High+Temperature.">Electron Tunneling Characteristics on La0.7Sr0.3MnO3 Thin-Film Surfaces at High Temperature.</a> Applied Physics Letters. 95 (9), 092106 (2009).</li><li>Jesse, S., Kumar, A., Arruda, T. M., Kim, Y., Kalinin, S. V., Ciucci, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrochemical+strain+microscopy:+Probing+ionic+and+electrochemical+phenomena+in+solids+at+the+nanometer+level.">Electrochemical strain microscopy: Probing ionic and electrochemical phenomena in solids at the nanometer level.</a> MRS Bulletin. 37 (7), 651-65 (2012).</li><li>Datta, S. S., Strachan, D. R., Mele, E. J., Johnson, A. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+Layers+and+Layer+Charge+Distributions+in+Few-Layer+Graphene+Films.">Surface Layers and Layer Charge Distributions in Few-Layer Graphene Films.</a> Nano Letters. 9, 7 (2009).</li><li>Coffey, D. C., Ginger, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Time-resolved+electrostatic+force+microscopy+of+polymer+solar+cells.">Time-resolved electrostatic force microscopy of polymer solar cells.</a> Nature Materials. 5 (9), 735 (2006).</li><li>Nakamura, M., Yamada, H., Morita, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Roadmap of Scanning Probe Microscopy. , (2007).</li><li>Girard, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrostatic+force+microscopy:+principles+and+some+applications+to+semiconductors.">Electrostatic force microscopy: principles and some applications to semiconductors.</a> Nanotechnology. 12, 485 (2001).</li><li>Rasmussen, J. F. B., Hagen, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+effect+of+H2S+on+the+performance+of+Ni-YSZ+anodes+in+solid+oxide+fuel+cells.">The effect of H2S on the performance of Ni-YSZ anodes in solid oxide fuel cells.</a> Journal of Power Sources. 191 (2), 534 (2009).</li><li>Zha, S. W., Cheng, Z., Liu, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sulfur+poisoning+and+regeneration+of+Ni-based+anodes+in+solid+oxide+fuel+cells.">Sulfur poisoning and regeneration of Ni-based anodes in solid oxide fuel cells.</a> Journal of The Electrochemical Society. 154 (2), B201 (2007).</li><li>Liu, M. F., Ding, D., Blinn, K., Li, X., Nie, L., Liu, M. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Enhanced+performance+of+LSCF+cathode+through+surface+modification.">Enhanced performance of LSCF cathode through surface modification.</a> International Journal of Hydrogen Energy. 37 (10), 8613 (2012).</li><li>Park, H., Li, X., Blinn, K. S., Liu, M., Lai, S., Bottomley, L. A., Liu, M., Park, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+coking+resistance+from+nanoscale:+a+study+of+patterned+BaO+nanorings+over+nickel+surface.">Probing coking resistance from nanoscale: a study of patterned BaO nanorings over nickel surface.</a> , (2012).</li></ol>

Sulfur Poisoning Analysis
The impedance spectra shown in Figure 5 suggest that sulfur poisoning is a surface or interfacial phenomenon rather than one that affects the bulk of the material. Specifically, the quick poisoning of the Ni mesh electrode (Figure 6) might result from the direct exposure of Ni electrode to the fuel gas and subsequent sulfur adsorption; gas diffusion would not limit the rate of this process as much as in the case of a thick porous Ni/YSZ ...

<table border="1">
	<tbody>
		<tr>
			<td>Name of Reagent/Material</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Nickel mesh</td>
			<td>Alfa Aesar</td>
			<td>CAS: 7440-02-0</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Ni Foil</td>
			<td>Alfa Aesar</td>
			<td>CAS: 7440-02-0</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>YSZ powder</td>
			<td>TOSOH</td>
			<td>Lot No:S800888B</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Ag paste</td>
			<td>Heraeus</td>
			<td>C8710</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Barium oxide</td>
			<td>Sigma-Aldrich</td>
			<td>1304-28-5</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Silver wire</td>
			<td>Alfa Aesar</td>
			<td>7440-22-4</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Acetone</td>
			<td>VWR</td>
			<td>67-64-1</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td>Alfa Aesar</td>
			<td>64-17-5</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>UHP H2</td>
			<td>Airgas</td>
			<td>&nbsp;</td>
			<td>99.999% purity</td>
		</tr>
		<tr>
			<td>100 ppm H2S/H2</td>
			<td>Airgas</td>
			<td>&nbsp;</td>
			<td>Certified custom mix</td>
		</tr>
		<tr>
			<td>n-type Si AFM tip</td>
			<td>MikroMasch</td>
			<td>NSC16</td>
			<td>10 nm tip radius</td>
		</tr>
		<tr>
			<td>Au coated AFM tip</td>
			<td>MikroMasch</td>
			<td>CSC11/Au/Cr</td>
			<td>20-30 nm tip radius</td>
		</tr>
		<tr>
			<td>Raman Spectrometer</td>
			<td>Renishaw</td>
			<td>RM1000</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Ar Ion laser</td>
			<td>ModuLaser</td>
			<td>StellarPro 150</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>He-Ne laser</td>
			<td>Thorlabs</td>
			<td>HPL170</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Atomic Force Microscope</td>
			<td>Veeco</td>
			<td>Nanoscope IIIA</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Moving Raman Stage</td>
			<td>Prior Scientific</td>
			<td>H101RNSW</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Optical Microscope</td>
			<td>Leica</td>
			<td>DMLM</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Scanning Electron Microscope</td>
			<td>LEO</td>
			<td>1550</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Tube Furnace</td>
			<td>Applied Test Systems</td>
			<td>2110</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Polisher</td>
			<td>Allied High Tech Products</td>
			<td>MetPrep</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>6 &mu;m Grinding media</td>
			<td>Allied High Tech Products</td>
			<td>50-50040M</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>3 &mu;m Polishing media</td>
			<td>Allied High Tech Products</td>
			<td>90-30020</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>1 &mu;m Polishing media</td>
			<td>Allied High Tech Products</td>
			<td>90-30015</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>0.1 &mu;m Polishing media</td>
			<td>Allied High Tech Products</td>
			<td>90-32000</td>
			<td>&nbsp;</td>
		</tr>
		<tr>
			<td>Raman chamber</td>
			<td>Harrick Scientific</td>
			<td>HTRC</td>
			<td>&nbsp;</td>
		</tr>
	</tbody>
</table>

probing and mapping electrode surfaces in solid oxide fuel cells

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen 1-7. The performance of SOFCs and the rates of many chemical and energy transformation processes in energy storage and conversion devices in general are limited primarily by charge and mass transfer along electrode surfaces and across interfaces. Unfortunately, the mechanistic understanding of these processes is still lacking, due largely to the difficulty of characterizing these processes under in situ conditions. This knowledge gap is a chief obstacle to SOFC commercialization. The development of tools for probing and mapping surface chemistries relevant to electrode reactions is vital to unraveling the mechanisms of surface processes and to achieving rational design of new electrode materials for more efficient energy storage and conversion2. Among the relatively few in situ surface analysis methods, Raman spectroscopy can be performed even with high temperatures and harsh atmospheres, making it ideal for characterizing chemical processes relevant to SOFC anode performance and degradation8-12. It can also be used alongside electrochemical measurements, potentially allowing direct correlation of electrochemistry to surface chemistry in an operating cell. Proper in situ Raman mapping measurements would be useful for pin-pointing important anode reaction mechanisms because of its sensitivity to the relevant species, including anode performance degradation through carbon deposition8, 10, 13, 14 ("coking") and sulfur poisoning11, 15 and the manner in which surface modifications stave off this degradation16. The current work demonstrates significant progress towards this capability. In addition, the family of scanning probe microscopy (SPM) techniques provides a special approach to interrogate the electrode surface with nanoscale resolution. Besides the surface topography that is routinely collected by AFM and STM, other properties such as local electronic states, ion diffusion coefficient and surface potential can also be investigated17-22. In this work, electrochemical measurements, Raman spectroscopy, and SPM were used in conjunction with a novel test electrode platform that consists of a Ni mesh electrode embedded in an yttria-stabilized zirconia (YSZ) electrolyte. Cell performance testing and impedance spectroscopy under fuel containing H2S was characterized, and Raman mapping was used to further elucidate the nature of sulfur poisoning. In situ Raman monitoring was used to investigate coking behavior. Finally, atomic force microscopy (AFM) and electrostatic force microscopy (EFM) were used to further visualize carbon deposition on the nanoscale. From this research, we desire to produce a more complete picture of the SOFC anode.

Sulfur Poisoning Analysis
Shown in Figure 4 are typical I-V and I-P curves of a cell with a Ni mesh electrode under H2 and 20 ppm H2S condition. Clearly, the introduction of even just a few ppm of H2S can poison the Ni-YSZ anode and cause considerable performance degradation.
In order to more intensively understand the poisoning behavior of the Ni-YSZ anode, AC impedance spectroscopy of the cell was performed under open...

Watch this Scientific Journal Video about Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells at JoVE.com

Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

We present a unique platform for characterizing electrode surfaces in solid oxide fuel cells (SOFCs) that allows simultaneous performance of multiple characterization techniques (e.g. in situ Raman spectroscopy and scanning probe microscopy alongside electrochemical measurements). Complementary information from these analyses may help to advance toward a more profound understanding of electrode reaction and degradation mechanisms, providing insights into rational design of better materials for SOFCs.

Solid oxide fuel cells (SOFCs) are potentially the most efficient and cost-effective solution to utilization of a wide variety of fuels beyond hydrogen ...

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Fabrication of Nano-engineered Transparent Conducting Oxides by Pulsed Laser Deposition

Nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas allows the deposition of metal oxides with tunable morphology, structure, density and stoichiometry by a proper control of the plasma plume expansion dynamics. Such versatility can be exploited to produce nanostructured films from compact and dense to nanoporous characterized by a hierarchical assembly of nano-sized clusters. In particular we describe the detailed methodology to fabricate two types of Al-doped ZnO (AZO) films as transparent electrodes in photovoltaic devices: 1) at low O2 pressure, compact films with electrical conductivity and optical transparency close to the state of the art transparent conducting oxides (TCO) can be deposited at room temperature, to be compatible with thermally sensitive materials such as polymers used in organic photovoltaics (OPVs); 2) highly light scattering hierarchical structures resembling a forest of nano-trees are produced at higher pressures. Such structures show high Haze factor (&gt;80%) and may be exploited to enhance the light trapping capability. The method here described for AZO films can be applied to other metal oxides relevant for technological applications such as TiO2, Al2O3, WO3 and Ag4O4.

We describe the experimental method to deposit nanostructured oxide thin films by nanosecond Pulsed Laser Deposition (PLD) in the presence of a background gas. By using this method Al-doped ZnO (AZO) films, from compact to hierarchically structured as nano-tree forests, can be deposited.

Nanosecond Pulsed  Laser Deposition (PLD) in the presence of a background gas allows the deposition  of metal oxides with tunable morphology, structure, ...

Monolayer Contact Doping of Silicon Surfaces and Nanowires Using Organophosphorus Compounds

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra shallow and sharp doping profiles at the nanometer scale. In MLCD process the dopant source is a monolayer containing dopant atoms.
In this article a detailed procedure for surface doping of silicon substrate as well as silicon nanowires is demonstrated. Phosphorus dopant source was formed using tetraethyl methylenediphosphonate monolayer on a silicon substrate. This monolayer containing substrate was brought to contact with a pristine intrinsic silicon target substrate and annealed while in contact. Sheet resistance of the target substrate was measured using 4 point probe. Intrinsic silicon nanowires were synthesized by chemical vapor deposition (CVD) process using a vapor-liquid-solid (VLS) mechanism; gold nanoparticles were used as catalyst for nanowire growth. The nanowires were suspended in ethanol by mild sonication. This suspension was used to dropcast the nanowires on silicon substrate with a silicon nitride dielectric top layer. These nanowires were doped with phosphorus in similar manner as used for the intrinsic silicon wafer. Standard photolithography process was used to fabricate metal electrodes for the formation of nanowire based field effect transistor (NW-FET). The electrical properties of a representative nanowire device were measured by a semiconductor device analyzer and a probe station.

A detailed procedure for surface doping of Silicon interfaces is provided. The ultra-shallow surface doping is demonstrated by using phosphorus containing monolayers and rapid annealing process. The method can be used for doping of macroscopic area surfaces as well as nanostructures.

Monolayer Contact Doping (MLCD) is a simple method for doping of surfaces and nanostructures1. MLCD results in the formation of highly controlled, ultra ...

Writing and Low-Temperature Characterization of Oxide Nanostructures

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions. Oxide interfaces exhibit a wide range of properties that can be controlled include conduction, piezoelectric behavior, ferromagnetism, superconductivity and nonlinear optical properties. Recently, methods for controlling these properties at extreme nanoscale dimensions have been discovered and developed. Here are described explicit step-by-step procedures for creating LaAlO3/SrTiO3 nanostructures using a reversible conductive atomic force microscopy technique. The processing steps for creating electrical contacts to the LaAlO3/SrTiO3 interface are first described. Conductive nanostructures are created by applying voltages to a conductive atomic force microscope tip and locally switching the LaAlO3/SrTiO3 interface to a conductive state. A versatile nanolithography toolkit has been developed expressly for the purpose of controlling the atomic force microscope (AFM) tip path and voltage. Then, these nanostructures are placed in a cryostat and transport measurements are performed. The procedures described here should be useful to others wishing to conduct research in oxide nanoelectronics.

Oxide nanostructures provide new opportunities for science and technology. The interfacial conductivity between LaAlO3 and SrTiO3 can be controlled with near-atomic precision using a conductive atomic force microscopy technique. The protocol for creating and measuring conductive nanostructures at LaAlO3/SrTiO3 interfaces is demonstrated.

Oxide nanoelectronics is a rapidly growing field which seeks to develop novel materials with multifunctional behavior at nanoscale dimensions.  Oxide ...

Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently ...

Iridium Oxide-reduced Graphene Oxide Nanohybrid Thin Film Modified Screen-printed Electrodes as Disposable Electrochemical Paper Microfluidic pH Sensors

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use integrated paper microfluidic electrochemical pH sensor for resource-limited settings. Taking advantages from both pH meters and strips, the pH sensing platform is composed of hydrophobic barrier-patterned paper micropad (&#181;PAD) using polydimethylsiloxane (PDMS), screen-printed electrode (SPE) modified with IrO2-graphene films and molded acrylonitrile butadiene styrene (ABS) plastic holder. Repetitive cathodic potential cycling was employed for graphene oxide (GO) reduction which can completely remove electrochemically unstable oxygenated groups and generate a 2D defect-free homogeneous graphene thin film with excellent stability and electronic properties. A uniform and smooth IrO2 film in nanoscale grain size is anodically electrodeposited onto the graphene film, without any observable cracks. The resulting IrO2-RGO electrode showed slightly super-Nernstian responses from pH 2-12 in Britton-Robinson (B-R) buffers with good linearity, small hysteresis, low response time and reproducibility in different buffers, as well as low sensitivities to different interfering ionic species and dissolved oxygen. A simple portable digital pH meter is fabricated, whose signal is measured with a multimeter, using high input-impedance operational amplifier and consumer batteries. The pH values measured with the portable electrochemical paper-microfluidic pH sensors were consistent with those measured using a commercial laboratory pH meter with a glass electrode.

The study demonstrates the growth of iridium oxide-reduced graphene oxide (IrO2-RGO) nanohybrid thin films on irregular and rough screen-printed carbon substrate through a green electrochemical synthesis, and their implementation as a pH sensor with a patterned paper-fluidic platform.

A facile, controllable, inexpensive and green electrochemical synthesis of IrO2-graphene nanohybrid thin films is developed to fabricate an easy-to-use ...

Non-aqueous Electrode Processing and Construction of Lithium-ion Coin Cells

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational analysis. Testing of lithium-ion batteries in an academic setting has taken on several forms, but at the most basic level lies the coin cell construction. In traditional LIB electrode preparation, a multi-phase slurry composed of active material, binder, and conductive additive is cast out onto a substrate. An electrode disc can then be punched from the dried sheet and used in the construction of a coin cell for electrochemical evaluation. Utilization of the potential of the active material in a battery is critically dependent on the microstructure of the electrode, as an appropriate distribution of the primary components are crucial to ensuring optimal electrical conductivity, porosity, and tortuosity, such that electrochemical and transport interaction is optimized. Processing steps ranging from the combination of dry powder, wet mixing, and drying can all critically affect multi-phase interactions that influence the microstructure formation. Electrochemical probing necessitates the construction of electrodes and coin cells with the utmost care and precision. This paper aims at providing a step-by-step guide of non-aqueous electrode processing and coin cell construction for lithium-ion batteries within an academic setting and with emphasis on deciphering the influence of drying and calendaring.

Non-aqueous electrode processing is central to the construction of coin cells and the evaluation of new electrode chemistries for lithium-ion batteries. A step-by-step guide to the basic practices needed as an electrochemical engineer working with batteries in an academic experimental setting is furnished.

Research into new and improved materials to be utilized in lithium-ion batteries (LIB) necessitates an experimental counterpart to any computational ...

Combustion Characterization and Model Fuel Development for Micro-tubular Flame-assisted Fuel Cells

Combustion based power generation has been accomplished for many years through a number of heat engine systems. Recently, a move towards small scale power generation and micro combustion as well as development in fuel cell research has created new means of power generation that combine solid oxide fuel cells with open flames and combustion exhaust. Instead of relying upon the heat of combustion, these solid oxide fuel cell systems rely on reforming of the fuel via combustion to generate syngas for electrochemical power generation. Procedures were developed to assess the combustion by-products under a wide range of conditions. While theoretical and computational procedures have been developed for assessing fuel-rich combustion exhaust in these applications, experimental techniques have also emerged. The experimental procedures often rely upon a gas chromatograph or mass spectrometer analysis of the flame and exhaust to assess the combustion process as a fuel reformer and means of heat generation. The experimental techniques developed in these areas have been applied anew for the development of the micro-tubular flame-assisted fuel cell. The protocol discussed in this work builds on past techniques to specify a procedure for characterizing fuel-rich combustion exhaust and developing a model fuel-rich combustion exhaust for use in flame-assisted fuel cell testing. The development of the procedure and its applications and limitations are discussed.

A protocol for creating a model fuel-rich combustion exhaust is developed through combustion characterization and is applied for micro-tubular flame-assisted fuel cell testing and research.

Combustion based power generation has been accomplished for many years through a number of heat engine systems. Recently, a move towards small scale power ...

Preparation of Janus Particles and Alternating Current Electrokinetic Measurements with a Rapidly Fabricated Indium Tin Oxide Electrode Array

This article provides a simple method to prepare partially or fully coated metallic particles and to perform the rapid fabrication of electrode arrays, which can facilitate electrical experiments in microfluidic devices. Janus particles are asymmetric particles that contain two different surface properties on their two sides. To prepare Janus particles, a monolayer of silica particles is prepared by a drying process. Gold (Au) is deposited on one side of each particle using a sputtering device. The fully coated metallic particles are completed after the second coating process. To analyze the electrical surface properties of Janus particles, alternating current (AC) electrokinetic measurements, such as dielectrophoresis (DEP) and electrorotation (EROT)- which require specifically designed electrode arrays in the experimental device- are performed. However, traditional methods to fabricate electrode arrays, such as the photolithographic technique, require a series of complicated procedures. Here, we introduce a flexible method to fabricate a designed electrode array. An indium tin oxide (ITO) glass is patterned by a fiber laser marking machine (1,064 nm, 20 W, 90 to 120 ns pulse-width, and 20 to 80 kHz pulse repetition frequency) to create a four-phase electrode array. To generate the four-phase electric field, the electrodes are connected to a 2-channel function generator and to two invertors. The phase shift between the adjacent electrodes is set at either 90&#176; (for EROT) or 180&#176; (for DEP). Representative results of AC electrokinetic measurements with a four-phase ITO electrode array are presented.

In this article, a simple method to prepare partially or fully coated metallic particles and to perform AC electrokinetic property measurements with a rapidly fabricated indium tin oxide (ITO) electrode array is demonstrated.

This article provides a simple method to prepare partially or fully coated metallic particles and to perform the rapid fabrication of electrode arrays, ...

Experimental Methods for Spin- and Angle-Resolved Photoemission Spectroscopy Combined with Polarization-Variable Laser

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser (laser-SARPES), and demonstrate a power of this technique for studying solid state physics. Laser-SARPES achieves two great capabilities. Firstly, by examining orbital selection rule of linearly polarized lasers, orbital selective excitation can be carried out in SAPRES experiment. Secondly, the technique can show full information of a variation of the spin quantum axis as a function of the light polarization. To demonstrate the power of the collaboration of these capabilities in laser-SARPES, we apply this technique for the investigations of spin-orbit coupled surface states of Bi2Se3. This technique affords to decompose spin and orbital components from the spin-orbit coupled wavefunctions. Moreover, as a representative advantage of using the direct spin detection collaborated with the polarization-variable laser, the technique unambiguously visualizes the light polarization dependence of the spin quantum axis in three-dimension. Laser-SARPES dramatically increases a capability of photoemission technique.

Here, we combine polarization-variable 7-eV laser with spin- and angle-resolved photoemission technique to visualize the spin-orbital coupling effect in solid states.

The goal of this protocol is to present how to perform spin- and angle-resolved photoemission spectroscopy combined with polarization-variable 7-eV laser ...

Scalable Stamp Printing and Fabrication of Hemiwicking Surfaces

Hemiwicking is a process where a fluid wets a patterned surface beyond its normal wetting length due to a combination of capillary action and imbibition. This wetting phenomenon is important in many technical fields ranging from physiology to aerospace engineering. Currently, several different techniques exist for fabricating hemiwicking structures. These conventional methods, however, are often time consuming and are difficult to scale-up for large areas or are difficult to customize for specific, nonhomogeneous patterning geometries. The presented protocol provides researchers with a simple, scalable, and cost-effective method for fabricating micro-patterned hemiwicking surfaces. The method fabricates wicking structures through the use of stamp printing, polydimethylsiloxane (PDMS) molding, and thin-film surface coatings. The protocol is demonstrated for hemiwicking with ethanol on PDMS micropillar arrays coated with a 70 nm thick aluminum thin-film.

A simple protocol is provided for the fabrication of hemiwicking structures of varying sizes, shapes, and materials. The protocol uses a combination of physical stamping, PDMS molding, and thin-film surface modifications via common materials deposition techniques.

Hemiwicking is a process where a fluid wets a patterned surface beyond its normal wetting length due to a combination of capillary action and imbibition. ...