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 press the Ni mesh sandwiched between packs of YSZ powder at a pressure of 300 MPa for 30 sec.</li>
	<li>Extract the pressed Ni/YSZ pellet from the mold.</li>
	<li>Fire the pellet at 1440 &deg;C for 5 hr in a zirconia crucible using a horizontal tube furnace with a flowing reducing gas atmosphere (4% H2/bal. Ar).</li>
</ol>
2. Exposure, Polishing, and Modification of Ni Mesh Electrode
<ol>
	<li>Mechanically grind away one face of the sintered YSZ sample using 6 &mu;m diamond grit until the Ni mesh surface is revealed.</li>
	<li>Further polish the exposed Ni mesh surface using 3 &mu;m, 1 &mu;m, and 0.1 &mu;m diamond media in a water / ethylene glycol suspension for approximately 1 min at each polishing step.</li>
	<li>Ultrasonically clean the polished sample in acetone, ethanol, and DI water for 10 min each.</li>
	<li>Dry the sample under a clean compressed air stream.</li>
	<li>For Ni mesh with increased coking resistance, fire the sample at 1,200 &deg;C for 2 hr in reducing atmosphere in the presence of, but not in contact with, BaO powder.</li>
</ol>
3. Preparation and Electrochemical Testing of Full Cells
<ol>
	<li>Brush-paint Ag paste on the opposite surface of the YSZ sample from the Ni-mesh to act as a counter-electrode.</li>
	<li>Attach a coiled Ag wire to the counter-electrode using Ag paste.</li>
	<li>After drying the Ag paste on the sample at 120 &deg;C in an oven for 30 min, connect a 0.2-mm diameter Ag wire to the Ni-mesh using Ag paste on the tip.</li>
	<li>Dry the sample again at 120 &deg;C in an oven for 30 min.</li>
	<li>Seal the cell (Ni mesh down) on top of a 3/8 inch ceramic cell fixture tube using Aremco Seal 552 (Ceramabond).</li>
	<li>Allow the sealant to dry in air for 2-4 hr.</li>
	<li>Connect two insulated silver wires to each of the two electrode wires.</li>
	<li>Mount the cell fixture in a tubular furnace, connect the fixture to a gas line, and attach the wires to proper electrochemical testing equipment.</li>
	<li>Begin flowing ultra-high purity grade (99.999%) H2 gas through the cell fixture at a rate of 50 sccm; the gas should be bubbled through room-temperature water to humidify the gas to 3% vol. H2O prior to entering the cell fixture.</li>
	<li>Heat the furnace with the mounted cell to 100 &deg;C for 2 hr, followed by 260 &deg;C for 1 hour, and then finally 800 &deg;C at a ramping rate of 1 &deg;C with continued flowing of H2 during all heating to avoid oxidation of the Ni electrode. The first two heating steps are for curing the Ceramabond.</li>
	<li>Hold the cell in the furnace at 800 &deg;C for 2 hr to allow the Ag counter electrode to sinter.</li>
	<li>Cool the cell slightly to 767 &deg;C for electrochemical performance testing.</li>
	<li>After testing, carefully remove the cell fixture from the furnace for quenching at room temperature while continuing to flow humidified H2. (CAUTION: Use proper PPE for handling extremely hot ceramics, such as thermal gloves and mats!)</li>
	<li>Detach the cell from the fixture for post-characterization by detaching the electrode wires and carefully separating the cell from the Ceramabond sealant.</li>
</ol>
*Figure 1 presents a schematic of the YSZ-embedded Ni mesh cell, along with a typical photograph and optical micrograph of the embedded mesh.
*For our investigations, cells were electrochemically characterized with an EG&amp;G PAR potentiostat (model 273A) coupled with a Solartron 1255 HF frequency response analyzer using CorrWare and ZPlot softwares (Scribner and Associates). Linear sweep voltammetry and constant-voltage amperometry were used to characterize cell performance, and impedance spectra were acquired in the frequency range of 100 kHz to 0.1 Hz with an amplitude of 10 mV. For the sulfur poisoning study, a certified gas mixture of 100 ppm H2S in H2 was mixed into the fuel gas stream with pure H2 to obtain a 20 ppm H2S/H2 mixture.
4. Post-test Raman Spectromicroscopic Mapping
<ol>
	<li>Affix the cell sample with the mesh anode facing upward onto the Raman microscope stage plate with tape or adhesive to prevent sample movement during Raman analysis.</li>
	<li>Use the microscope and XYZ stage to locate an interface boundary between the Ni mesh and YSZ substrate.</li>
	<li>Bring the laser into focus by switching the microscope filters and finely adjusting the Z coordinate of the stage.</li>
	<li>Set the Raman spectrometer to obtain spectra at the nodes of a rectangular mesh overlaying the area of the interface with 2 &mu;m intervals separating the nodes. The spectra should be centered around the wavenumber(s) corresponding to the Raman mode(s) of the species or phase(s) of interest. In this case, 980 cm-1 is chosen for SOx.</li>
	<li>For each spectra, integrate the intensity across the Raman mode(s) of interest and divide the intensity by a flat baseline with the same spectrum. The relative intensity can then be plotted in a contour / color map with respect to its coordinates.</li>
</ol>
Raman spectromicroscopy was performed using a Renishaw RM1000 system equipped with a Modu-Laser StellarPro 514 nm Ar-ion laser (5 mW) and a Thorlabs HRP170 633 nm He-Ne laser (17 mW). The system is equipped with an X-Y-Z motorized stage (Prior Scientific H101RNSW) and a 50X objective lens, which together allow for ~2 &mu;m mapping resolution. Renishaw WiRE 2.0 software was used in conjunction with the hardware. Data was processed using MATLAB (MathWorks).
5. In situ Raman Monitoring of Coking8
<ol>
	<li>Attach an YSZ-embedded Ni mesh sample to the Raman chamber stage using Ag paste with the mesh facing upward.</li>
	<li>Heat the open chamber to 300 &deg;C for 1 hr to dry and eliminate the Ag paste suspension medium.</li>
	<li>Seal the Raman chamber's cap and affix it to the Raman microscope stage. Use the microscope to locate a Ni/YSZ interface as described in Protocol 4.2.</li>
	<li>Begin flowing 4% H2 / Ar gas humidified by water bubbler through the chamber at ~100 sccm.</li>
	<li>Heat the Raman chamber to 625 &deg;C.</li>
	<li>Bring the laser into focus and collect baseline Raman scans from spots on the Ni mesh and YSZ substrate in the 150-2000 cm-1 range.</li>
	<li>Introduce 3-5% C3H8 into the gas flow and collect Raman spectra from the Ni at regular intervals while the gas is flowing to observe the deposition of carbon on the surface over time (e.g. 15 hr).</li>
	<li>Cool the sample down slowly (5 &deg;C /min) in flowing 4% H2 / Ar.</li>
</ol>
*The in situ Raman analysis was performed with a custom-modified Harrick Scientific high-temperature reaction chamber.The chamber is equipped with a quartz window cap, gas connections, and a cooling line. A schematic and photograph is provided in Figure 2.
CAUTION: Cooling water should be used to protect the optical microscope on the Raman system from heating!
6. Nanoscale Visualization of Coking by AFM and EFM
<ol>
	<li>Polish one face of a 1 cm x 1 mm square nickel coupon down to the grade of 0.1 &mu;m as described in Protocol 2.2.</li>
	<li>In a quartz tube-lined furnace, expose the polished nickel coupon to flowing gas containing 10% C3H8 balanced by Ar at 550 &deg;C for 1 min; the gas should be bubbled through room-temperature water to humidify the gas to 3% vol. H2O prior to entering the quartz tube.</li>
	<li>Remove the sample from the furnace. Inspect the surface morphology by optical microscopy and SEM.</li>
	<li>Mount the sample onto a metal puck using copper conductive tape for AFM and EFM study.</li>
	<li>Collect a morphology image using AFM in Tapping Mode.</li>
	<li>Install an n-type Si based AFM tip (NSC16) or a conductive AFM tip (CSC11/Cr-Au) onto the electrical holder (MMEFCH).</li>
	<li>Scan the sample surface in "Lift Mode", in which the tip first collects the topographic information on its first trip across the sample surface and then senses the phase angle on its second trip for electrostatic force information. Set the lift height initially to 100 nm, and gradually decrease it to approximately the same value of the surface roughness (20-30 nm).</li>
	<li>Across a clear interface between the coked and clean region of nickel surface, collect a series of EFM linescans while changing the sample bias.</li>
	<li>By comparing the EFM linescans at different sample bias potentials, identify the voltage at which the phase angle contrast flips21.</li>
	<li>Collect an image with a sample bias that is 1-2V negative w.r.t. the switch point, and another image with sample bias that is 1-2V positive w.r.t. the switch point.</li>
	<li>By comparing the topography image, and the two sets of EFM images at different sample biases, obtain a distribution map of the carbon and nickel phase on the sample. *For our SPM analyses, a Veeco Nanoscope IIIA system was used. A schematic of the working principle of the EFM analysis23, 24 is shown in Figure 3.</li>
</ol>

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No conflicts of interest declared.

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...

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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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15.8K Views.  Georgia Institute of Technology. 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...

Video: Probing and Mapping Electrode Surfaces in Solid Oxide Fuel Cells

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 ...

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in industry. The wettability of the produced surface was analyzed by bouncing drop experiments and the topography was analyzed by confocal microscopy. In addition, we show various methodologies to measure its durability and anti-icing properties. Superhydrophobic surfaces hold a special texture that must be preserved to keep their water-repellency. To fabricate durable surfaces, we followed two strategies to incorporate a resistant texture. The first strategy is a direct incorporation of roughness to the metal substrate by acid etching. After this surface texturization, the surface energy was decreased by silanization or fluoropolymer deposition. The second strategy is the growth of a ceria layer (after surface texturization) that should enhance the surface hardness and corrosion resistance. The surface energy was decreased with a stearic acid film.
The durability of the superhydrophobic surfaces was examined by a particle impact test, mechanical wear by lateral abrasion, and UV-ozone resistance. The anti-icing properties were explored by studying the ability to repeal subcooled water, freezing delay, and ice adhesion.

We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in ...