Pt-Ni Octahedra as Electrocatalysts for the Ethanol Electro-Oxidation Reaction

Alloying Pt electrocatalysts with late transition metals (e.g., Ni, Co, and Fe) is an effective strategy to lower the catalyst cost and improve their tolerance toward CO in the anode of direct ethanol fuel cells. In this study, shape-controlled octahedral Pt-Ni/C nanocrystals with uniformly exposed (111) facets and an average edge length of 10 nm were synthesized. The octahedral Pt-Ni/C nanocatalyst was at least 4.6 and 7.7 times more active than conventional Pt-Ni/C and commercial Pt/C catalysts, respectively. In situ infrared spectroscopic results showed that the acetic acid/CO2 absorbance peak intensity on octahedral Pt-Ni/C was 7.6 and 1.4 times higher as compared to commercial Pt/C and conventional Pt-Ni/C, respectively, at 0.75 V. This result suggests that ethanol oxidation on octahedral Pt-Ni produces more acetic acid than on other surfaces. The synergistic electronic and facet effects may explain the superior ethanol oxidation reaction activity of octahedral Pt-Ni/C. Further surface modification with Ru significantly lowered the onset potential for CO, production by-100 mV and resulted in a higher selectivity on CO, as compared to unmodified surface, which further boosted the ethanol utilization efficiency.