| Résumé | Using a simple thermal method, a non-noble metal electrocatalyst (Co-N-S/C) is successfully synthesized and its' composition is analyzed using EDX. The electrochemical activity of such a catalyst is also tested using surface electrochemical methods. Three one-electron transfer redox processes in the studied potential range are identified, where only one such a process is associated with the catalyst's ORR activity. The effect of KOH on the Co-N-S/C catalyzed ORR kinetics is investigated using the rotating disk electrode technique in a concentration range of 0.05 to 6.0M. Several ORR kinetic parameters such as overall electron transfer number (n), the product of electron transfer number and coefficient in ORR rate determining step (αnα), and the exchange current density (iO2/H2O°) are estimated. The results show that values of n at different KOH concentrations are close to 4.0, suggesting that Co-N-S/C catalyzed ORR is a 4-electron transfer process from O2 to H2O. KOH concentration has an insignificant effect on the value of n, however, a significant effect is observed on both values of αnα and iO2/H2O°. (αnα decreases while that of iO2/H2O° increases with increasing KOH concentration). |
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