Journal of Power Sources, Vol.188, No.2, 427-432, 2009
Improvement of methanol electro-oxidation activity of PtRu/C and PtNiCr/C catalysts by anodic treatment
The effect of an anodic treatment on the methanol oxidation activity of PtRu/C (50:50 at.%) and PtNiCr/C (Pt:Ni:Cr = 28:36:36 at.%) catalysts was investigated for various potential limits of 0.9, 1.1, 1.3 and 1.4V (vs. reference hydrogen electrode, RIIE). NaBH4 reduced catalysts were further reduced at 900 C for 5 min in an argon balanced hydrogen flow stream. Improved alloying was obtained by the hydrogen reduction procedure is confirmed by X-ray diffraction results. In the PtRu/C catalyst, a decrease of irreversible Ru (hydrous) oxide formation was observed when the anodic treatment was performed at 1.1 V (vs. RHE) or higher potentials. In chronoamperometry testing performed for GO min at 0.6 V (vs. RHE), the highest activity of the PtRu/C catalyst was observed when anodic treatment was performed at 1.3 V (vs. RHE). The current density increased from 1.71 to 4.06 A g(eat) (-1) after the anodic treatment. In the PtNiCr/C catalyst, dissolution of Ni and Cr was observed when potentials >= 1.3 V (vs. RHE) were applied during the anodic treatment. In MOR activity tests, the current density of the PtNiCr/C catalyst dramatically increased by more than 13.5 times (from 0.182 to 2.47 A g(cat) (-1)) when an anodic treatment was performed at 1.4V. On an A g(noble metal) (-1) basis, the current density of PtNiCr-1.4V is slightly higher than the best anodically treated PtRu-1.3V catalyst, suggesting the PtNiCr catalyst is a promising candidate to replace the PtRu catalysts. (C) 2008 Elsevier B.V. All rights reserved.
Keywords:Methanol electro-oxidation;Direct methanol fuel cell;Anodic treatment;Cyclic voltammetry;Chronoamperometry