Effect of Chloride on Platinum Dissolution

• 10 ppm of chloride significantly enhances Pt dissolution at higher potentials.
• 35 folds increase of Pt dissolution on addition of 100 ppm of chloride.
• Pt dissolves in Ptn+ and PtCl42− below 1.2 V and PtCl62− above 1.2 V.
• Electrochemically Pt chloro-complex forms during cathodic scan.
• Quantitatively, Pt dissolution has linear dependence with chloride concn.

The effect of chloride (from 10 ppm to 100 ppm) on platinum dissolution during potential cycling in 0.5 M H2SO4 solution at 25 °C is investigated using a channel flow double electrode. The dissolved platinum in the form of Ptn+ or a Pt chloro complex produced at the upstream electrode is reduced at the downstream electrode. The introduction of 10 ppm of chloride does not have a significant effect during potential cycling until 1.05 V in the anodic scan; however, above this potential even 10 ppm of chloride has a prominent effect. Higher chloride concentration has a negligible effect in a lower potential range; however, at a higher potential, the dissolution increases by 35-fold. Dissolution of Pt in the form of Ptn+ and PtCl42− is proposed below 1.2 V and that in the form of PtCl62− is proposed above 1.2 V in the anodic scan. Furthermore, a platinum chloro complex is formed electrochemically during cathodic scan. Quantitative analysis is performed and a linear dependence of platinum dissolution with chloride concentration is observed.