کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
196069 | 459831 | 2007 | 7 صفحه PDF | دانلود رایگان |
The oxygen reduction reaction (ORR) was studied in KOH electrolyte on manganese oxides supported on Vulcan carbon (MnyOx/C). The oxides were prepared by thermal decomposition of manganese nitrate at different conditions. The oxides were characterized by X-ray diffraction (XRD) and in situ X-ray absorption near edge structure (XANES). The electrochemical studies were conducted using cyclic voltammetry (CV) and steady state polarization measurements carried out with a thin layer rotating ring/disk electrode. XRD results showed that the manganese oxide prepared at 200 °C in air is formed by a major phase of β-MnO2 and the polarization curves indicated the highest activity for this material. In situ XANES evidenced the occurrence of a redox process involving Mn(II)/Mn(III) and Mn(III)/Mn(IV) in the range of potentials of the CV measurements. The electrocalytic activity was related to the occurrence of a mediation process involving the reduction of Mn(IV) to Mn(III), followed by the electron transfer of Mn(III) to oxygen and by a disproportionation reaction of the HO2− species in the MnyOx sites. In situ XANES results showed that the Mn(IV) species is MnO2 and the Mn(III) is most likely MnOOH.
Journal: Electrochimica Acta - Volume 52, Issue 11, 1 March 2007, Pages 3732–3738