Dear colleges,
After activation of pristine carbon felt by chemical oxidation, electrochemical activity increased 20 times, but contact angle remaining practically the same. By XPS increases of oxygen of 8% is detected, and content of C=C, C-C, C=O decreased, while C-O and COOH groups increased. Does anyone have idea for the such behavior. Some references will be favorable
Thanks in advances
Water droplet contact angle? And the felt has air pockets of microscale dimensions? First idea: Cassie-Baxter case, with a very large fraction of air, so the droplet contact angle is only changed to a minor extent by the carbon chemistry.
https://en.wikipedia.org/wiki/Wetting#Cassie%E2%80%93Baxter_model
or better E.Y. Bormashenko's book on wetting
It is more of a redox response than a change in the surface chemistry. Similar changes are reported in carbon materials when they undergo oxidation/over-oxidation. When the material undergoes oxidation, charges will be introduced, which will increase the redox activity of the material. In aerobic environments, oxygen reduction reaction will be the driver of the oxidation half of the redox reaction, which may account for the increase in O-content detected by XPS. Refer:
Article Molten salt carbon felt oxidation for VRFB electrode perform...
Electrochemical reduction in NO3- electrolyte was investigated for the hydrophily of carbon materials, which seem to be facile and effective. Please see Nanoscale, 2015, 7, 3581-3587; Journal of Power Sources, Volume 249, 1 March 2014, Pages 48-58.
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