Poisoning Effect of CO: How It Changes Hydrogen Electrode Reaction and How to Analyze It Using Differential Polarization Curve

The hydrogen electrode reaction (HER) on Pt electrode in a H2SO4 solution when CO gas was injected/stopped was studied using polarization resistance curve. In order to elucidate and confirm the CO poisoning effect, a few curve techniques were proposed. Applying them, the kinetic parameters such as the number of electrons transferred (z) and the cathodic transfer coefficient (alpha(c)) were determined. The HER in a 0.5 mol dm(-3) H2SO4 solution saturated with H-2 was confirmed as a reversible reaction having z = 2. When the above solution was injected with CO, the reversible HER changed to an irreversible reaction having z = 1 and alpha(c) approximate to 0.6. Once we stopped the CO injection, alteration from the irreversible to quasireversible reaction was gradually made after several cyclic polarizations. The proposed curve techniques can provide a reliable way to determine the kinetic parameters changing among reversible, irreversible, and quasireversible reactions.

Automated summary

The study investigated the effect of CO gas injection/cessation on the hydrogen electrode reaction (HER) on a Pt electrode in H2SO4 solution, with the use of polarization resistance curves to determine kinetic parameters. The results showed that CO led to a transition from reversible to irreversible HER, which gradually shifted back to quasi-reversible after CO injection was stopped. The proposed curve techniques provide a reliable method to determine kinetic parameters in reversible, irreversible, and quasi-reversible reactions.