| Abstract
| - The catalytic activities of FexPt100-x alloy nanoparticles at different compositions (x = 10, 15, 42, 54, 58, and 63)in the electro-oxidation of formic acid have been investigated by using cyclic voltammetry (CV), chronoamperometry,and electrochemical impedance spectroscopy (EIS). It was observed that the electrocatalytic performance was stronglydependent on the FePt particle composition. In chronoamperometric measurements, the alloy particles at x ≈ 50showed the highest steady-state current density among the catalysts under study and maintained the best long-termstability. In addition, on the basis of the anodic peak current density, onset potentials, and the ratios of the anodicpeak current density to the cathodic peak current density in CV studies, the catalytic activity for HCOOH oxidationwas found to decrease in the order of Fe42Pt58> Fe54Pt46 ≈ Fe58Pt42> Fe15Pt85> Fe10Pt90> Fe63Pt37. That is, withinthe present experimental context, the alloy nanoparticles at x ≈ 50 appeared to exhibit the maximum electrocatalyticactivity and stability with optimal tolerance to CO poisoning. Consistent responses were also observed in electrochemicalimpedance spectroscopic measurements. For the alloy nanoparticles that showed excellent tolerance to CO poisoning,the impedance in the Nyquist plots was found to change sign from positive to negative with increasing electrodepotential, suggesting that the electron-transfer kinetics evolved from resistive to pseudoinductive and then to inductivecharacters. However, for the nanoparticles that were heavily poisoned by adsorbed CO species during formic acidoxidation, the impedance was found to be confined to the first quadrant at all electrode potentials. The present workhighlights the influence of the molecular composition of Pt-based alloy electrocatalysts on the performance of formicacid electro-oxidation, an important aspect in the design of bimetal electrocatalysts in fuel cell applications.
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