04/05/2018
Hi ECS members,
In case anyone was deciding how to spend their Saturday evening and settled on reviewing characterization techniques used in electrochemistry… I thought I would point out that Akshay and Linnette’s presentations are now available on the chapter’s google drive.
The topics covered were:
Cyclic Voltammetry
- This included a discussion of the idea behind linear sweep voltammetry (as V increases, the reaction of interest bec.omes more favorable so a current develops and is eventually inhibited by diffusion limitations)
- Things got quantitative with the Randle-Sevcik equation.
- Differential voltage analysis was presented as a way to correlate dV/dQ peaks to phase transitions and investigate fading mechanisms.
- A general emphasis was placed on backing out species concentrations and diffusivities.
Electrochemical Impedance Spectroscopy
- We were introduced to several historical figures, such as Heaviside, Warburg, and Nernst.
- The idea of modeling electrochemical systems as equivalent circuits possessing resistors, capacitors, and impedance was posited.
- There was a discussion of frequency limits, such as kinetic limitations at high frequency.
- We were introduced to EIS figures of merit (Nyquist & Bode plots).
- The general merits of EIS were presented (simple to run, non-destructive, an ability to model situations, and an ability to extract parameters).
Other notable occurrences were your secretary vowing to wait over a week to send out un-proofread meeting minutes.
Hope everyone’s weekend is going well. See you Thursday!
02/28/2018
Dear UW ECS Members,
Yesterday marked the final installment of the critically acclaimed Intro to E Chem Series. Thanks and recognition are due to your very own Victor Hu for his role in organizing the series as well as to yesterday’s presenters, Keith Steele and Erica Eggleton. If you had the misfortune to miss yesterday’s seminar, a brief overview of the topics covered can be found below and the actual presentations will soon be made available on the community’s google drive.
Other noteworthy occurrences included a discussion of possible social events. The consensus was that the end of quarter is incredibly busy for most people and that we will reconvene once things die down, though Kate’s and the College Inn Pub were discussed as possibilities.
Yesterday’s seminar covered a review of electrostatics and a discussion of the double layer, some highlights are detailed below:
Review of Electrostatics
- The electric field and electric potential were formally defined (also, Griffiths was recommended as a resource)
- The behavior of the electric field in a conductor was reviewed.
- The term current coordinate came up in discussion to define an axis in a system diagram system diagram plotting electrochemical potential.
- The reason for a large electric field at a boundary between materials at two different potentials was discussed.
- Note that thermodynamics requires the electrochemical potential only change at an interface.
Double Layer (a brief history)
- Hermann von Helmholtz observed positive species in solution migrated to negative surface of metal electrode, this resembles a capacitor!
- Trouble on the horizon! Louis Georges Guoy and David Leonard Chapman showed that we can’t just consider charges on the electrode as some charges may be spread out in dilute system. Not a capacitor, need Debye Huckle theory.
- Stern claimed a species could only get so close to the interface surface.
- Topography near electrode: Metal, Inner Helmholtz Plane, Outer Helmholtz Plane, diffuse layer, diffusion layer, bulk
- Three take aways: true rate and exchange current depends on potential and concentration of electrolyte. GCS model for predicting capacitance and something else I was not fast enough to type. Erica launched a career in stand-up comedy.
- Finally, the reason for specifically adsorbed anions was deemed a mystery. I am sure there are those in our community who know more than I or can do a better literature search, but, for those curious, here are the articles I found during my brief google search and mentioned at the meeting (should they prove useful):
o “On the specific adsorption of anions in the electrical double layer” by M. A. V. Devanathan and B. V. K. S. R. A. Tilak.
o “Unravelling the electrochemical double layer by direct probing of the solid/liquid interface” by M. Favaro, et al.
o “Influence of an electrostatic potential at the metal/electrolyte interface on the electron binding energy of adsorbates as probed by X-ray photoelectron spectroscopy.” by W. Zhou, et al.
Sincerely,
Evan Jahrman
02/07/2018
Hello electrochemistry enthusiasts!
Today marked the installment of Intro to Electrochemistry, part deux. The topics spanned kinetics and transport, the event was organized by your very own Victor Hu, and the material was presented by himself and Elena Pandres. A big thanks to both of them!
For those who were unable to attend, here is a quick overview along with discussions that arose. Should it spark your interest, the presentation (as well as these notes) will be available in the group’s google drive tomorrow and can be found at:
ttps://drive.google.com/drive/u/0/folders/1ospoDeHSrTXAuJ1D_D4g1aeVhlOF9HoK
Kinetics Highlights
- A review of the Butler Volmer equation
- Faraday’s law of electrolysis dictating a reaction rate proportional to current
- Asymmetric impact of charge transfer coefficient on anodic/oxidic current (reaction rate)
- I believe Tafel was mentioned a few times, not sure, looked tough-el.
Transport Highlights
- There is exactly one form of transport in electrochemistry. Diffusion, migration, and convection. Good times.
- These factors are accounted for in the Nernst-Planck equation.
- Various boundary conditions were discussed.
- Also, if you were unable to attend, never fear, the double layer was tabled for next time.
Other Discussions
- Can electrons be lost from a system?
o This led to a discussion of charge conservation (and what would lead to the continuity equation in electromagnetism). We also threw in some caveats of nuclear/particle processes for giggles/completeness/pedantry (these would include electron capture/pair production/pair annihilation).
- One electron processes were highlighted as the only processes necessary for kinetics as the others would be too slow (note that multielectron transitions and processes are observed at meaningful rates in various spectroscopies or under extreme conditions where large perturbations or sudden changes in nuclear screening exist. Why am I bringing this up? Is it because I am on a paper investigating these? Is it a shameless act of self-promotion? You bet.)
- Ample discussion into the specifics of a salt bridge in preventing charge build-up. The details of the ions in the salt bridge were also discussed and the need for chemical inertness and high ion mobility. Note that a buffer could play the same role as the salt bridge.
- A transference number is a measure of how quickly the charge moves and is always positive.
Have a great rest of your week,
Evan Jahrman
01/24/2018
Today’s meeting marked our chapter’s first “Introduction to Electrochemistry” talk. For those unlucky souls who were unable to join our discussion, rest easy. Below you will find a brief synopsis of the topics covered and the presentation elsewhere on this drive. Should it spark your interest, a copy of Newman is available elsewhere on this chapter’s drive for your perusal.
Today’s discussion was divided into two subjects with the following subdivisions:
Thermodynamics
- A brief definition of Electrochemistry
- Example cell diagrams and how to formally write them
- An overview of terms culminating in a discussion of spontaneity
- Examples of how to calculate cell potentials
- Finally, the Nernst equation and a remark that Nernstian behavior is achieved when activities are approximated by concentrations, but that many research areas (such as batteries and fuel cells) concern Non-Nernstian behavior
Kinetics
- A discussion of Faradaic/Non-Faradaic currents and Faraday’s law of electrolysis
- The Butler-Volmer Equation and simplifications available in the limiting cases of high and low overpotentials
- The three types of transport: Diffusion, migration, and convection as dictated by the Nernst-Planck Equation
12/04/2017
Summary of the December 4th, 2017 meeting of the student chapter of the Electrochemical Society at the University of Washington
In fair Seattle, where we lay our scene, a scorching high of 42 °F drove a gaggle of grad students to seek shelter from the oppressive heat. Collectively shrinking from the heat and our relatives’ Thanksgiving Day inquiries into “how much time we have left at UW,” these brave souls convened and commiserated, announcing a new, singular purpose: to jovially consume more pinwheel sandwiches and coffee than is arguably healthy. After appropriate indulgence, our trope of protagonists embarked on a quest of edification, discovering applications of electrochemistry in neural interfaces, water purification, and rare earth mining (these presentations were prepared and facilitated by Brian Gerwe, Jon Witt, and Evan Jahrman, respectively). As the hour drew to a close, we welcomed Dr. Elizabeth Biddinger for a discussion spanning the future directions of our student chapter. This:
“Is now the two hours’ traffic of our stage;
The which if you with patient ears attend,
What here shall miss, out toil shall strive to mend.”
Below is a significantly abridge overview:
Neural Interfaces- can simulate electrical stimulation in the nervous system of biological systems. These devices have numerous applications, including neuroprosthesis, which connects the brain with mechanical limbs, but may also enhance cognitive function and connect human minds. Considerations include: biocompatibility, size, and insulation requirements for microelectronic devices. A challenge is that nerve bundles instead of individual fibers are currently stimulated and this represents a front for future research endeavors.
Water Purification- is needed to aid nearly a billion indiviuals without access to clean/safe drinking water. One resource, the aqueduct water risk atlas, outlines a surprisingly high risk of exposure to water-related risks around the world. In this field quick analytical methods which are deployable and easy use (such as indicator organisms) are in dire need. Finally, fracking spikes contaminant concentrations in water. As a potential method for purification, specific metals may be introduced to remove impurities via electrocoagulation or electroflotation, yet the utilized metal should then be removed.
Rare Earth Metals- have extremely similar physical and chemical properties. Extracting and purifying rare earth ores ideally involves a chemical separation from other constituents, reduction to form a metallic product, and removal of impurities (such as by zone refining and solid state electrotransport). Current mining operations and research efforts are nearly nonexistent in the U.S., however, rare earth production infrastructure is extensively established by the world’s primary source of rare earths, China.
Speaker:
Dr. Bidding gave several recommendations for our community.
First, if applying for ECS travel grants, be sure to follow directions! This includes pursuing a personalized faculty letter.
Another discussion topic was the ECS conference in Seattle this spring. It was remarked that there may be an opportunity for student/chapter involvement at the national level. This could include seeking a collaboration with the program out of Ohio for a hydrogen fuel cells for cars demonstration for local schools.
In addition, potential electrochemistry resources were discussed (note that the spelling of all following names are merely a guess). In addition to Bard, a text by Jeffrey Prentice was recommended for its discussion of overpotentials. An electrocatalysis text by Brokis was recommended. It was also remarked that a new text would soon be published by Harb. Finally, Case Western has an electrochemistry encyclopedia online. Again, Case Western has an electrochemistry encyclopedia online.
As a future direction, it was proposed that a collaboration with car dealerships to present a hybrid and electric vehicle panel may be possible.
With regard to research conducted by Biddinger, she not only studies ionic liquids, but is pursuing electrocatalysis research as well. Specifically, electrocatalysis for CO2 electroreduction where there exists a selectivity problem as one substrate, Cu, yields 18 possible products and leads to massive costs associated with separation needs.
As a final inspirational thought for this summary, please consider the words of Wernher von Braun, who once remarked, “research is what I’m doing when I don’t know what I’m doing.”