The effect of concentration in electrochemical oxidation of thiocyanate on platinum electrode

Electrochemical oxidation of thiocyanate (SCN-) on platinum electrode in the sulfuric acid medium was studied using cyclic voltammetry, in situ UV-visible absorption measurement, rotating ring-disc electrode voltammetry, and electrical impedance spectroscopy. Two oxidation processes are involved in the electrochemical oxidation of SCN- in sulfuric acid medium. The adsorbed SCN- undergoes oxidation at potential values higher than 0.900 V versus saturated calomel electrode (SCE). Trithiocyanate,(SCN)(-)(3), is formed as a relatively stable product during the first oxidation process. The potential range of (SCN)(-)(3) formation increases with increase in concentration of SCN-, and it is exclusively produced in the potential range of 0.550 to 1.40 V versus SCE with 1.0 M NH4SCN solution. The second oxidation process does not produce any stable product, and the products of second oxidation passivate the electrode surface.