Electrochemical characterization of benzenesulfonamide
I'd change the solvent to acetonitrile (don't forget the quarternary ammonium salt) and give a glassy carbon electrode a try. 

It should be possible to observe the (irreversible) reduction of the sulfonamide.

And once you have optimized the conditions, please perform a final run with ferrocene as an internal reference.


Edit:
Let me explain the last suggestion. The literature is full of electrochemical data of organic compounds measured in non-aqueous solvents, mostly acetonitrile. 

It was once common (bad) practise to report the potentials vs SCE (saturated calomel electrode), although the latter, an aqueous(!) reference electrode, was atually never used in the measurement. Often rather exotic conditions plus a shaky conversion of data turned good experimental work into a pile of data of limited value.

Using an internal standard is the obvious solution to obtain solvent-independent electrochemical data for publication.

Note that the use of ferrocene as such a standard isn't my idea! It was originally proposed by GRITZER and KUTA in Pure Appl. Chem. and is a IUPAC recommendation nowadays.