Langmuir−Blodgett Thin Films of Fe₂₀Pt₈₀ Nanoparticles for the Electrocatalytic Oxidation of Formic Acid

Abstract

The electro-oxidation of formic acid catalyzed by Fe 20 Pt 80 nanoparticles was studied by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) where the particles were deposited onto a gold electrode surface by the Langmuir-Blodgett (LB) technique at varied film thickness/coverage. It was found that the particle assembly thickness strongly affected the electrocatalytic activity for HCOOH oxidation. For a single monolayer and two layers of FePt particles, extensive CO adsorption (poisoning) was observed in CV measurements, whereas with a four-layer assembly of the FePt particles, the tolerance to CO poisoning improved drastically. Furthermore, from the current density for formic acid oxidation, the electrodes functionalized with LB layers of nanoparticles exhibited higher activities than those with dropcast films of similar thickness, suggesting the importance of the ordering of the particle layers in the electrocatalytic performance. The reaction kinetics in the HCOOH oxidation on the three kinds of particle film-modified electrodes was then examined by EIS measurements. It was found that except within the potential range for CO oxidation, the impedance spectra behaved normally with the responses shown in the first quadrant for all three nanoparticle assemblies under study, indicative of only resistive and capacitive components in the electrochemical cell. In contrast, at potentials of CO electro-oxidation, the impedance spectra were found to migrate from the first quadrant to the second quadrant and then back to the first quadrant with increasing electrode potential, which suggests that the reaction kinetics evolve from resistive to pseudoinductive and then to inductive behaviors. The different EIS behaviors are ascribed to the different degree of tolerance to CO poisoning, consistent with the voltammetric results.

Preparation and characterization of DNA films using oleylamine modified Au surfaces

“…The energy minimization of an OLA single molecule adopting a fully extended chain conformation led to a value for the distance between the nitrogen atom and the furthest hydrogen (in the carbon terminal group) of 2.0473 nm (see Scheme 1), which is in agreement with that reported by Chen et al [25]. A final value of L = 2.2853 nm was obtained by the addition of 0.238 nm with respect to the Au-N distance [26,27].…”

Electrocatalytic Reduction of Oxygen by FePt Alloy Nanoparticles

“…Such voltammetric features have been observed with other Ptbased alloys such as CoPt, NiPt, and FePt, and they are ascribed to the formation of a "Pt skin" on the catalyst surface. [23][24][25][52][53][54]57,58 This Pt surface enrichment is caused by Pt dissolution from the alloys and then redeposition and rearrangement on the catalyst surface during potential cycling in acidic electrolytes. From these voltammetric measurements (Figure 1), the active (Pt) surface areas were then quantitatively evaluated on the basis of the charge for the oxidation of surface-adsorbed hydrogen by assuming that hydrogen desorption yields 210 µC per cm 2 of the Pt surface area.…”

Size-controlled synthesis and impedance-based mechanistic understanding of Pd/C nanoparticles for formic acid oxidation

“…Its ability to unravel complex reactive steps involving adsorbed species in different frequency domains provides advantages for getting kinetics information [14]. Therefore, EIS based technique, other than for the measurement of polymer membrane resistance at high frequency, has in recent years been increasingly used for the study of anodic reaction processes in fuel cells [15][16][17][18][19][20][21][22]. Using a kinetics-based impedance model, electrochemical impedance patterns of anodic oxidation of methanol and formic acid on Pt/C could be quantitatively interpreted and the information of such processes would lead to a better understanding of reaction pathways.…”