COOH on carbon surface

For some product we are developing, we need to create carboxylic groups on some carbon electrode surface. Since I am not a chemist, I
was wondering if some can give me some suggestions on how to acheive this. I prefer a wet chemistry (soaking and/or washing in certain chemicals) approach rather than an electrochemical approach (applying potential to the carbon electrode in certain electrolyte).
Any information is greatly appreciated.
David Wang
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