You are here

INVESTIGATION OF NANOCERIA-MODIFIED PLATINUM-GOLD COMPOSITE ELECTRODES FOR THE ELECTROCHEMICAL REDUCTION OF OXYGEN IN ALKALINE MEDIA

Download pdf | Full Screen View

Date Issued:
2011
Abstract/Description:
Platinum-gold and nanoceria-modified platinum-gold electrodes were prepared on a platinum surface via electrochemical reduction of solutions of platinum and gold salts in the dispersion of nanoceria. The molar ratios of Pt and Au were varied in both PtAu and PtAu/CeO2 electrodes while the total concentration of the metals was maintained at 2 x 10-3M and the concentration of nanoceria was maintained constant at 5 x 10-3M. The electrodes were characterized by their cyclic voltammetry curves in 0.5M sulfuric acid solution. The electrochemically active area of the electrodes was determined using the copper underpotential deposition method. The linear sweep voltammograms of the PtAu and PtAu/CeO2 electrodes were plotted from -1V to 0V vs. Ag/AgCl, 3M KCl reference electrode using the rotating disk electrodes for the rotation speeds from 200 to 3600rpm in an oxygen saturated 0.1M sodium hydroxide solution. The values of the kinetic controlled current density were determined from the rotating disk voltammetry. The values of the limiting current density for each rotation speed were used to plot the Koutecky-Levich plots for the electrodes. The rate constants were obtained from the Koutecky-Levich plots for each composition of the electrode. The values of kinetic current density and the rate constants indicated that the addition of Au enhances the ORR rates in both the PtAu and the PtAu/CeO2 electrodes. The values of the kinetic current densities of the PtAu/CeO2 were lower than that of the PtAu electrodes owing to the poor electrical conductivity of ceria. The Koutecky-Levich plots for the PtAu and the PtAu/CeO2 electrodes are linear for the four-electron reduction of oxygen in the alkaline media, which indicates that the overall reaction follows the first order kinetics. The electron transfer rate constants obtained from the Koutecky-Levich plots for the PtAu and the PtAu/CeO2 electrodes both were found to increase in values with the addition of Au. The Tafel plots were plotted for the PtAu and PtAu/CeO2 electrodes and the values of Tafel slopes were found to be in a small range for lower amounts of Au which indicated that the ORR rates were enhanced in lower amounts of Au. The values of Tafel slopes were found to be much higher for the ceria-modified PtAu electrodes as compared to the PtAu electrodes, which indicate the lower rates of ORR after the modification with ceria. Also, the ORR rates for the electrodes with smaller amounts of Au in PtAu/CeO2 were higher than those in the larger amounts of Au.
Title: INVESTIGATION OF NANOCERIA-MODIFIED PLATINUM-GOLD COMPOSITE ELECTRODES FOR THE ELECTROCHEMICAL REDUCTION OF OXYGEN IN ALKALINE MEDIA.
0 views
0 downloads
Name(s): Hegishte, Rahul, Author
Diaz, Diego, Committee Chair
University of Central Florida, Degree Grantor
Type of Resource: text
Date Issued: 2011
Publisher: University of Central Florida
Language(s): English
Abstract/Description: Platinum-gold and nanoceria-modified platinum-gold electrodes were prepared on a platinum surface via electrochemical reduction of solutions of platinum and gold salts in the dispersion of nanoceria. The molar ratios of Pt and Au were varied in both PtAu and PtAu/CeO2 electrodes while the total concentration of the metals was maintained at 2 x 10-3M and the concentration of nanoceria was maintained constant at 5 x 10-3M. The electrodes were characterized by their cyclic voltammetry curves in 0.5M sulfuric acid solution. The electrochemically active area of the electrodes was determined using the copper underpotential deposition method. The linear sweep voltammograms of the PtAu and PtAu/CeO2 electrodes were plotted from -1V to 0V vs. Ag/AgCl, 3M KCl reference electrode using the rotating disk electrodes for the rotation speeds from 200 to 3600rpm in an oxygen saturated 0.1M sodium hydroxide solution. The values of the kinetic controlled current density were determined from the rotating disk voltammetry. The values of the limiting current density for each rotation speed were used to plot the Koutecky-Levich plots for the electrodes. The rate constants were obtained from the Koutecky-Levich plots for each composition of the electrode. The values of kinetic current density and the rate constants indicated that the addition of Au enhances the ORR rates in both the PtAu and the PtAu/CeO2 electrodes. The values of the kinetic current densities of the PtAu/CeO2 were lower than that of the PtAu electrodes owing to the poor electrical conductivity of ceria. The Koutecky-Levich plots for the PtAu and the PtAu/CeO2 electrodes are linear for the four-electron reduction of oxygen in the alkaline media, which indicates that the overall reaction follows the first order kinetics. The electron transfer rate constants obtained from the Koutecky-Levich plots for the PtAu and the PtAu/CeO2 electrodes both were found to increase in values with the addition of Au. The Tafel plots were plotted for the PtAu and PtAu/CeO2 electrodes and the values of Tafel slopes were found to be in a small range for lower amounts of Au which indicated that the ORR rates were enhanced in lower amounts of Au. The values of Tafel slopes were found to be much higher for the ceria-modified PtAu electrodes as compared to the PtAu electrodes, which indicate the lower rates of ORR after the modification with ceria. Also, the ORR rates for the electrodes with smaller amounts of Au in PtAu/CeO2 were higher than those in the larger amounts of Au.
Identifier: CFE0003639 (IID), ucf:48860 (fedora)
Note(s): 2011-05-01
M.S.
Sciences, Department of Chemistry
Masters
This record was generated from author submitted information.
Subject(s): catalysis
fuel cell
PEMFC
oxygen reduction reaction
Pt
Au
ceria
electrochemistry
voltammetry
Koutecky-Levich plots
Tafel plots
Persistent Link to This Record: http://purl.flvc.org/ucf/fd/CFE0003639
Restrictions on Access: public 2011-04-01
Host Institution: UCF

In Collections