Effect of reduction conditions on electrocatalytic activity of a ternary PtNiCr/C catalyst for methanol electro-oxidation

The effect of reduction conditions on a Pt28Ni36Cr36/C catalyst was investigated by using two different reduction methods: hydrogen reduction and NaBH4 reduction. In hydrogen reduced catalysts, dissolution of metallic Ni and Cr was observed during cyclic voltammetry (CV) tests, and a larger amount of Ni and Cr was dissolved when reduced at higher temperatures. For methanol electro-oxidation, the highest specific current density of 1.70 A m(-2) at 600s of the chronoamperometry tests was observed in the catalyst reduced at 300 degrees C, which was similar to 24 times that of a Pt/C catalyst (0.0685 A m(-2)). In NaBH4 reduced catalysts, formation of an amorphous phase and a more Pt-rich surface was observed in X-ray diffraction and CV results, respectively, with increasing amounts of NaBH4. When reduced by 50 times of the stoichiometric amount of NaBH4, the PtNiCr/C catalyst (PtNiCr-50t) showed a current density of 34.1 A g(noble metal)(-1), which was 81% higher than the 18.8 A g(noble metal)(-1) value of a PtRu/C catalyst at 600 s of the chronoamperometry tests. After 13 h of chronoamperometry testing, the activity of the PtNiCr-50t (15.0 A g(noble metal)(-1)) was 110% higher than the PtRu/C catalyst (7.15 A g(noble metal)(-1)). The PtNiCr/C catalyst shows promise as a Ru-free methanol oxidation catalyst. (C) 2008 Elsevier Ltd. All rights reserved.