Paul Ridgway

Design of an Electrochemical Cell Making Syngas (CO + H2) from CO2 and H2O Reduction at Room Temperature

An electrolysis-cell design for simultaneous electrochemical reduction of CO 2 and H 2 O to make syngas (CO + H 2 ) at room temperature (25°C) was developed, based on a technology very close to that of proton-exchange-membrane fuel cells (PEMFC), i.e., based on the use of gas-diffusion electrodes so as to achieve high current densities. While a configuration involving a proton-exchange membrane (Nafion) as electrolyte was shown to be unfavorable for CO 2 reduction, a modified configuration based on the insertion of a pH-buffer layer (aqueous KHCO 3 ) between the silver-based cathode catalyst layer and the Nafion membrane allows for a great enhancement of the cathode selectivity for CO 2 reduction to CO [ca. 30 mA/cm 2 at a potential of -1.7 to -1.75 V vs SCE (saturated-calomel reference electrode)]. A CO/H 2 ratio of 1/2, suitable for methanol synthesis, is obtained at a potential of ca. -2 V vs SCE and a total current density of ca. 80 mA/cm 2 . An issue that has been identified is the change in product selectivity upon long-term electrolysis. Results obtained with two other cell designs are also presented and compared.

Mathematical Modeling of CO2 Reduction to CO in Aqueous Electrolytes I. Kinetic Study on Planar Silver and Gold Electrodes

A cell design for CO 2 (and H 2 O) reduction to CO (and H 2 ), similar to a proton-exchange-membrane fuel cell but with a silver or gold catalyst at the cathode and a pH buffer layer (aqueous KHCO 3 ) between the cathode catalyst layer and the membrane, is evaluated. The cell can operate at a CO current density as high as -135 mA/cm 2 (on supported Au catalyst). The general framework for treating equilibrated reactions and equilibrated interfacial mass transfer in a multiphase medium is derived and used to set forth a mathematical model of the electrolysis cell. At low current density, the model accounts for the experimental data pretty well, using rate constant values obtained on flat Ag and Au electrodes. The model is further used to understand some of the cell features, such as the effect of CO 2 partial pressure in the cathode gas channel and KHC0 3 concentration in the buffer layer, the resistance increase and the CO efficiency decrease at high current density, and the decay in CO efficiency upon operation. Finally, the model is used to predict the behavior of a cell design based on a porous anion-exchange membrane instead of the aqueous buffer layer.

Effect of Vinylene Carbonate on Graphite Anode Cycling Efficiency

Effect of Vinylene Carbonate on Graphite Anode Cycling Efficiency Paul Ridgway, Honghe Zheng, Gao L i u , Xiangun Song, Philip Ross, Vincent Battaglia Advanced Energy Technologies Department, Lawrence Berkeley National Laboratory, Berkeley, C A 94720 Vinylene Carbonate ( V C ) was added to the electrolyte in graphite-lithium half-cells. W e report its effect on the coulombic efficiency (as capacity shift) o f graphite electrodes under various formation cycling conditions. Cyclic voltammetry on glassy carbon showed that V C passivates the electrode against electrolyte reduction. The dQ/dV plots o f the first lithiation o f the graphite suggest that V C alters the SEI layer, and that by varying the cell formation rate, the initial ratio o f ethylene carbonate to V C in the SEI layer can be controlled. V C was found to decrease first cycle efficiency and reversible capacity (in ongoing cycling) when used to excess. However, experiments with V C additive used with various formation rates did not show any decrease in capacity shift. Introduction Carbonaceous materials, graphite formulations in particular, are the current standard for battery anodes in electric vehicle lithium-ion batteries (1). To attain performance suitable for plug-in hybrid and all-electric vehicles, improvement i n longevity o f the graphite anode is needed. Electrolyte additives have proven useful for this purpose. For example, vinylene carbonate ( V C ) added to Propylene Carbonate/LiPF6 electrolyte forms a Solvent-Electrolyte Interphase (SEI) layer on graphite anodes, preventing P C intercolation and reduction (and subsequent graphite exfoliaton) [2]. The addition o f V C to EC-based LiPF6 electrolytes is reported to improve performance o f graphite anodes by reducing irreversible capacity, suppressing gas formation, and improving cycling behavior [3-7]. A n important aspect o f anode performance is the effectiveness o f the SEI layer in inhibiting the side reactions which form it. The continuation o f these side reactions reduces cycling efficiency and consumes electrolyte which reduces the lifetime o f the cell. We probe the effect o f V C and various rates o f formation on these continuing side reactions by measuring the fractional capacity shift (8). HydroQuebecs SNG-12 anode graphite was chosen for this study because its relatively high capacity shift is a performance problem i n need o f a solution. In the results section, we begin by studying the effect of V C on the electrochemistry o f glassy carbon in EC-based L i P F 6 electrolyte. Then we determine a basis for choosing the concentration o f V C in the cell. This leads to our measurements o f the reversible capacity o f graphite in lithium half-cells as a function of V C concentration, followed by an examination o f the effect o f V C on the dQ/dV curves o f the first lithiation o f graphite.

Laser ultrasonic in‐process inspection of paper for elastic properties

A laser‐ultrasonic (LUS) sensor has been developed that allows measurement of the bending stiffness (BS) and shear rigidity (SR) of paper and paperboard as it is being made on the papermaking machine. A prototype system was recently tested in a paper mill at web speeds up to 5000 ft/min with excellent precision and accuracy. The LUS technique performs well on paper and board with basis weights up to 130 g/m2. Several laboratory methods exist for measuring the bending stiffness in small samples of paper and board. Currently, no commercial method exists for nondestructively measuring this property on the papermaking machine at production speeds. Commercial instruments using contact transducers measure ‘‘tensile strength orientation’’ (TSO) on heavier boards, where marking of the sheet by the contact transducers is not of concern. Unlike contact ultrasonic techniques, LUS does not visibly mark even the lightest grade papers. Contact ultrasonic measurements correlate approximately to the tensile strength of t...

Laser Ultrasonic Measurement of Elastic Properties of Moving Paper: Mill Demonstration

An automated sensor has been developed for use during paper manufacture that can measure flexural rigidity (bending stiffness). Based on laser ultrasonic technology, this sensor provides continuous noncontact on‐machine measurements on paper having area densities from 35 to 205 g/m2, moving at commercial manufacturing speeds, at any angle in the plane of the sheet. It was demonstrated on a high speed printing paper grade machine during commercial production. For that demonstration, the sensor was integrated into an existing scanning sensor system. Cross‐direction profiles of flexural rigidity had the expected shape, and compared well with traditional bending stiffness measurements on samples collected for that comparison.

A Laboratory Laser‐Ultrasonic Instrument for Measuring the Mechanical Properties of Paper Webs

For the paper industry, stiffness properties are an important parameter for producing more efficiently a fibrous material like paper. Some stiffness properties of paper webs can be obtained in a non‐contact fashion using two lasers. The authors have developed an automated laboratory laser‐ultrasonics instrument for paper, described here. The results of non‐contact laser generation and detection of ultrasound are also presented. The paper grades investigated were heavy grades like linerboard, as well as copy paper.

Sodium/Phosphorus‐Sulfur Cells II. Phase Equilibria

Equilibrium open-circuit cell voltage data from a sodium/{beta}{double_prime}-alumina/phosphorus-sulfur cell utilizing P/S ratios of 0, 0.143, and 0.332 and a sodium atom fraction ranging from 0 to 0.4 were interpreted to construct ternary phase diagrams of the Na-P-S ternary system at 350 and 400 C.

Laser Ultrasonics at 20 m/s in the production environment and on a budget: from dream to reality

A laser-based ultrasonic system for non-contact and non-destructive measurement of the elastic properties of paper was demonstrated on a paper manufacturing machine during commercial operation with paper moving around 20 m/s. We believe this to be the highest sample traveling speed reported to date for a commercial application of laser ultrasonics. Ultrasonic waves were generated in the paper with a pulsed Nd:YAG laser at 1064 nm wavelength and detected with a Mach-Zehnder interferometer coupled with a scanning mirror/timing system to compensate for paper motion. Measurements of the flexural rigidity (FR) and out-of-plane shear rigidity (SR) of the paper web were done automatically by fitting the frequency dependence of the phase velocity of Ao mode Lamb waves to a model wave propagation equation. Variation in FR and SR across the width of the paper sheet (cross-direction profiles), effects of changes in paper manufacturing process variables on measured FR and SR, comparisons with traditional mechanical stiffness tests are presented. The sensor head is fully optical and thus measures the web properties without any contact. This laser-ultrasonics system combines a very reasonable cost with a relatively small footprint and low power consumption due to the low power output of the lasers that are used. Finally, laboratory data indicate that this technology is directly transferable to measurements on sheet metals and possibly other opaque web materials

Final Technical Report of project: "Contactless Real-Time Monitoring of Paper Mechanical Behavior During Papermaking"

The early precursors of laser ultrasonics on paper were Prof. Y. Berthelot from the Georgia Institute of Technology/Mechanical Engineering department, and Prof. P. Brodeur from the Institute of Paper Science and Technology, both located in Atlanta, Georgia. The first Ph.D. thesis that shed quite some light on the topic, but also left some questions unanswered, was completed by Mont A. Johnson in 1996. Mont Johnson was Prof. Berthelots student at Georgia Tech. In 1997 P. Brodeur proposed a project involving himself, Y. Berthelot, Dr. Ken Telschow and Mr. Vance Deason from INL, Honeywell-Measurex and Dr. Rick Russo from LBNL. The first time the proposal was not accepted and P. Brodeur decided to re-propose it without the involvement from LBNL. Rick Russo proposed a separate project on the same topic on his side. Both proposals were finally accepted and work started in the fall of 1997 on the two projects. Early on, the biggest challenge was to find an optical detection method which could detect laser-induced displacements of the web surface that are of the order of .1 micron in the ultrasonic range. This was to be done while the web was having an out-of-plane amplitude of motion in the mm range due to web flutter; while moving at 10 m/s to 30 m/s in the plane of the web, on the paper machine. Both teams grappled with the same problems and tried similar methods in some cases, but came up with two similar but different solutions one year later. The IPST, GT, INL team found that an interferometer made by Lasson Technologies Inc. using the photo-induced electro-motive force in Gallium Arsenide was able to detect ultrasonic waves up to 12-15 m/s. It also developed in house an interferometer using the Two-Wave Mixing effect in photorefractive crystals that showed good promises for on-line applications, and experimented with a scanning mirror to reduce motion-induced texture noise from the web and improve signal to noise ratio. On its side, LBNL had the idea to combine a commercial Mach-Zehnder interferometer to a spinning mirror synchronized to the web speed, in order to make almost stationary measurements. The method was demonstrated at up to 10 m/s. Both teams developed their own version of a web simulator that was driving a web of paper at 10 m/s or higher. The Department of Energy and members of the Agenda 2020 started to make a push for merging the two projects. This made sense because their topics were really identical but this was not well received by Prof. Brodeur. Finally IPST decided to reassign the direction of the IPST-INL-GT project in the spring of 1999 to Prof. Chuck Habeger so that the two teams could work together. Also at this time, Honeywell-Measurex dropped as a member of the team. It was replaced by ABB Industrial Systems whose engineers had extensive previous experience of working with ultrasonic sensors on paperboard. INL also finished its work on the project as its competencies were partly redundant with LBNL. From the summer of 1999, the IPST-GT and LBNL teams were working together and helped each other often by collaborating and visiting either laboratory when was necessary. Around the beginning of 2000, began an effort at IPST to create an off-line laser-ultrasonics instrument that could perform automated measurements of paper and paperboards bending stiffness. It was widely known that the mechanical bending tests of paper used for years by the paper industry were very inaccurate and exhibited poor reproducibility; therefore the team needed a new instrument of reference to validate its future on-line results. In 1999-2000, the focus of the on-line instrument was on a pre-industrial demonstration on a pilot coater while reducing the damage to the web caused by the generation laser, below the threshold where it could be visible by the naked eye. During the spring of 2000 Paul Ridgway traveled to IPST and brought with him a redesigned system still using the same Mach-Zehnder interferometer as before, but this time employing an electric motor-driven spinning mirror instead of the previously belt-driven mechanical spinning mirror. For testing we chose to use a 1 foot-wide paper loop running on IPSTs large scale web handler which could reach a web speed of 2,000 feet/min (10.16 m/s). This was more representative of the conditions encountered of a pilot coater, than on a table-top scale web simulator.