Download How to measure the electrochemical properties of metals

Haonan Zhou How to measure the electrochemical properties of metals 1. Introduction Corrosion is a common reaction, which appears almost everywhere at any time. Metals and alloys will normally be oxidized, form new substance with different structure and cause terrible damage. Therefore, it is necessary for you to measure the electrochemical properties of a metal you have chosen. By understanding these properties, you can design a much stronger structure. The measurements used to determine electrochemical properties are Potentiodynamic technique, Electrochemical Impedance Spectroscopy, Linear polarization, Cyclic Voltammetry and SEM. “Cyclic Voltammetry is an electrochemical technique which measures the current that develops in an electrochemical cell under conditions where voltage is in excess of that predicted by the Nernst equation.” [1] The system used for experiments is three electrodes system, which contains a reference electrode, a working electrode and a counter electrode. The test has the following steps: electrodes pre-­‐treatment, electrochemistry system setup, main procedures and analyzing. Depending on how many test you want to finish, the time of the whole experiments may vary. But it will at least take 2 hours. All the tests should be performed in a safety lab with at least two people in that lab. 2. Materials needed 1. The metal you want to measure 2. Reference electrode 3. Counter electrode 4. AUTOLAB Potentiosat 5. Nova software 6. Chemicals 7. Bakes 8. Ar gas and plastic tubes 1 WARNING: 1. YOU MUST WEAR GLOVES AND SAFETY GLASSES TO CONTINUE THE FOLLOWING STEPS! 2. NEVER TOUCH ACETONE WITH YOUR EXPOSED SKIN! 1 http://chemwiki.ucdavis.edu/Analytical_Chemistry/Instrumental_Analysis/Cyclic_Voltammetry 3. Electrodes pre-­‐treatment: 1. All the electrodes and the metal were cleaned by acetone first to remove all the dirt on the surface. 2. Then they were cleaned with deionizing water to remove extra acetone. 4. Electrochemistry system set up As shown below, you need to setup the system before you start the experiments. 1.
After filling the solutions, this special
beaker needs to be fixed horizontally and tightly.
2.
Then put the working electrode in the left.
Make sure the metal is submerged in the solution
but the copper clip doesn’t touch the solution.
3.
Put the reference electrode in the middle. It
also needs to at least touch the liquid.
4.
Put the counter electrode in the right. And
make sure the grid’s most area is submerged in the
liquid.
5. Connect the front two vent holes with two
plastic tubes.
One is submerged in the liquid to flow
the Ar gas. The other one is placed above the liquid
surface.
6.
Following the sign on the wires, you can
connect the AUTOLAB Potentiosat and the system
easily.
7.
On the right wire, a small yellow sign with
characters “CE”, which means counter electrode, is
connected with counter electrode.
8.
Other wires can be connected the same
way.
5. Main procedures: (make Na2SO4 solution as an example) 1. 1M Na2SO4 solution (in double distilled water) will be prepared as electrolytic solution. 2. Working electrode, reference electrode and counter electrode were connected with the AUTOLAB Potentiosat. 3. Argon gas was flowed through the system for at least 10 minutes to make sure no gas would be involved in the reaction. 6. Analyzing with NOVA software 1. Nova, the advanced electrochemical software was used for the following measurements: A. Open circuit potential B. Electrochemical Impedance Spectroscopy to Plot 50 points C. Cyclic Voltammetry 1.
Setting the potential range 2.
Setting the scanning rate 3.
Choosing cycling times D. Linear polarization You can select the measurement under the procedures section shown on the left. And you can change the parameters under the commands section on the right. 2. After measuring procedure, you need to collect your figure and data. Here’s an example about how to collect data. A. Select right click B. Find save figure as or export data as button C. Browse the folder you want to save in D. Name the files, which help you find it easily E. Finally click save button 7. Troubleshooting tips What should I do if I touch Acetone? If the concentration of Acetone isn’t too high, you can rinse your skin with a large amount of water. If the concentration is high and you start to feel hurt, call 911 and the person in charge of the lab. They will provide professional treatment. What should I do if the software doesn’t work? Make sure you open the Autolab first. Then check if all the wires are connected correctly. Finally, check the setting parameters. What should I do with useless liquids? Never pour them out directly washbasin. Find an empty bottle, pour your liquid in it and label the name and date of your liquid. Also, you should sign your name. And place the bottle in a proper place. 8. Glossary of key terms and definitions Cyclic Voltammetry An electrochemical technique, which measures the current that develops in an electrochemical cell under conditions where voltage is in excess of that predicted by the Nernst equation Three electrodes system A system contains a reference electrode, a working electrode and a counter electrode, and always used for electrochemical experiments. AUTOLAB Potentiosat
An equipment help simulate different electrochemical environments. Nova software Software works with AUTOLAB Potentiosat to help analyze different properties.