We utilize a Au electrode of 200 micrometer wide as working electrode to generate electric field on solution. The Au electrode is evaporated on SiO2 wafer. Its thickness is 3000A. There is 500A Ti-W between the wafer and Au. For experiment, the AU electrode is merged in tris buffer (PH=8.1, KCl 5mM) and then voltages more than 1.2V is applied on it. But, after several seconds, the electrode is burned, and becomes black. I have noted that in some publications, votages of several volts are utilized to control the Au electrode in Tris buffer, and no burning occurs. Is there anyone who has the same experience can tell me how to improve it?Furthermore, Is there any tip to deal with electrolysis happens?
At pH 8, you will observe gold anodic oxidation at potentials around 1 V (irrespective the potential of the reference electrode already mentioned by Ioannis above) - the change in colour seems to support that! What about the currents you are measuring? Do they increase as well? kind regards, Dirk
If 1.2 V is vs SCE, this potential will cause particial Au oxidation to form Au Oxide film on the electrode surface. If the time Applied at this potential is long enough, then the Au film could be completely destroyed. The suggestions are: 1) you should run a CV first in the electrolyte solution used to see the available (safe) potential window, 2) Instead of fixed at potential, you might use potential pulse to shorten time. On the other hand, Au might not be a good material for generating the Electric fileld at high voltage. Why donot you use much cheaper and wider potential window graphite materials?
When specifying a field strength, you will have voltage/distance. It is possible to apply 10s or 100s of volts/cm without actually applying that voltage to the electrodes by spacing the electrodes at some fraction of a cm e.g., 100mV applied to electrodes that are 100 microns apart will create a field of 10V/cm. Also, your pH at the electrode surfaces will not stay constant even in your buffered solution.
You should avoid the presence of chlorides in your electrolyte, because gold dissolves anodically in chloride solutions forming [AuCl4]-.
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