Corrosion: Fundamentals and Experimental Methods When: June 5-10, 2016 Where: Penn State University Park Campus Registration is open for the annual Penn State University Corrosion Short Course being held at Penn State University Park Campus June 5-10th. Now in its 20th year, the course will cover the fundamentals of corrosion and various electrochemical techniques. Lectures Read more about 20th Annual Penn State University Corrosion Short Course[…]
Take two different metals, place an ion transporting medium between them, wire them up to be connected outside the electrolyte solution (perhaps to a voltmeter or potentiostat) and you’ve made a battery. With the ever-increasing demand for portable power, batteries are becoming more and more important. As demands on battery performance increase, so do demands Read more about Potentiostats for Battery Research Testing[…]
In the previous post (Electrochemical Corrosion Measurements Primer) we pointed out that Icorr cannot be measured directly. In many cases, you can estimate it from current versus voltage data. You can measure a log current versus potential curve over a range of about one half volt. The voltage scan is centered on Eoc. You then fit the measured data to a theoretical model of the corrosion process.
The model we will use for the corrosion process assumes that the rates of both the anodic and cathodic processes are controlled by the kinetics of the electron transfer reaction at the metal surface. This is generally the case for corrosion reactions. An electrochemical reaction under kinetic control obeys Equation 1-1, the Tafel Equation.
Using Digital Staircase Voltammetry
Cyclic Voltammetry (CV) is unarguably the most popular electrochemical technique. It owes its well deserved reputation to its ability to deduce reaction mechanisms with relatively low cost equipment and quick experimentation. Since the very highly cited paper by Nicholson and Shain1 the technique has been the centerpiece of any electrochemical study.
CV involves sweeping the potential linearly between two limits at a given sweep rate while measuring current. The sweep rate chosen can be varied from few microvolts per second to millions of volts per second.
Electrochemical instrumentation has evolved vastly since the days of Nicholson and Shain. Currently, most manufacturers (including Gamry) make digital instruments with digital signal generators. These signal generators approximate the linear sweep with a staircase of variable step sizes and durations.
Cyclic Voltammetry and Leakage Current
Purpose of This Note
This application note is the first part of an overview of electrochemical techniques used to test electrochemical capacitors (ECs). Electrochemical capacitors that are commercially available were tested to explain and discuss the theoretical background of cyclic voltammetry and leakage current measurement.
This application note is part one of 3. Part 2 of this note discusses techniques that are also familiar to battery technologists. Part 3 describes theory and practice of EIS measurements on capacitors.
In contrast to batteries, ECs generally store energy by highly reversible separation of electrical charge while batteries use chemical reactions. ECs consist of two high-surface electrodes immersed in a conductive liquid or polymer called the electrolyte. The electrodes are separated by an ionic-conducting separator that prevents shorts between the two electrodes.