Effect of pre-treatment on the surface and electrochemical properties of screen-printed carbon paste electrodes

The effect of various electrochemical pre-treatment methods on the surface and electrochemical properties of screen-printed carbon paste electrodes (S PCE) prepared with three different commercial products was examined. It was observed that a positively charged redox couple, e.g., hexaammineruthenium (III), exhibited quasi-reversible behavior at the untreated SPCE. However, the cyclic voltammograms (CVs) of the SPCE prepared with general-purpose ca rbon inks did not exhibit clear redox peaks to other representative redox c ouples [e.g., hexacyanoferrate(III), hexachloroiridate(IV), dopamine, and h ydroquinone] without activation. Electrochemical pre-treatment methods were sought in four different aqueous solutions, i.e., sulfuric acid, potassium chloride, sodium hydrogencarbonate, and sodium carbonate, applying various activation potentials. It was found that the pre-treatment procedure in sa turated Na2CO3 Solution at 1.2 V provides a mild and effective condition fo r activating the SPCE. By measuring the water contact angles at the SPCE su rfaces and recording their SEM images, it was confirmed that the electroche mical pre-treatment effectively removes the organic binders from the surfac e carbon particles. A prolonged period of activation (> 5 min) or the use o f high potentials ( > 1.2 V) increased the capacitance of the electrode ove r 20 muF cm(-2). The pre-treated SPCE behaved like a random array microelec trode, exhibiting a sigmoidal-shaped CV at a slow scan rate. The short pre- anodization method in Na2CO3 solution was generally applicable to most SPCE prepared with general-purpose carbon inks.