The parathiocyanogen electrode

Stable, yellow anodic films of parathiocyanogen (SCN), were formed on a pla tinum electrode from 2.8 M KSCN in methanol at 45 degrees C at a constant c urrent of 20-40 mA cm(-2) for 15-30 min. Loosely bound orange crystals of a more amorphous character were removed by rinsing to leave an adherent yell ow film with sharp Raman bands under 647.1 nm laser excitation at 627 cm(-1 ) (nu CS), 1152 cm(-1) and 1236-1261 cm(-1) (nu NN and nu CN). The lack of electroactivity and short-lived photocurrents pointed to an insulating film at potentials up to 1.0 V (SHE). At more positive potentials, longer-lasti ng photocurrents were obtained, consistent with breakdown of the insulating film. XPS scans confirmed N:C:S ratios close to 1:1:1, with a deficiency o f S of some 10% due to S lost as sulfate at the film surface. Oxidation of SeCN- in neutral aqueous solution led to the formation of a less-stable ora nge paraselenocyanogen film with a Raman band at 1256-1267 cm(-1), which de composed within a day to grey selenium.