| AVS 57th International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF+SE-WeM |
| Session: | Glancing Angle Deposition (GLAD) I |
| Presenter: | W.J. Khudhayer, University of Arkansas at Little Rock |
| Authors: | W.J. Khudhayer, University of Arkansas at Little Rock A.U. Shaikh, University of Arkansas at Little Rock T. Karabacak, University of Arkansas at little rock |
| Correspondent: | Click to Email |
In this work, we have investigated the electrochemical properties of vertically aligned, single-layer, low loading, carbon-free and single crystal Pt nanorod arrays as a potential cathode material in polymer electrolyte (PEM) fuel cells. These nanorods of different lengths in the range of 20-600 nm were produced by glancing angle deposition (GLAD) technique with Pt loading values of 0.016-0.5 mg/cm2. Electrodes of conventional carbon supported Pt nanoparticles (Pt/C) were also prepared for comparison with Pt nanorods for their electrochemical properties. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were utilized to study the morphology and crystallography of Pt nanorods. SEM and XRD results reveal that Pt nanorods are well-isolated, vertically aligned, and single-crystal with atomically sharp tips. The single-crystal property allows enhanced electrochemical activity and reduced surface oxidation, while the isolated nature of the rods in lateral directions can provide a channeled porosity for effective transportation of gases in a PEM fuel cell. The electrochemical activity of Pt nanorods as well as Pt/C was evaluated using cyclic voltammetry (CV). CV results show that Pt nanorod electrocatalysts reduce oxygen to water at a more positive potential that of Pt/C, indicating that our catalyst has a lower oxygen overpotential due to the enhanced electrode porosity, single-crystal property, and the dominance of the preferred crystal orientation for oxygen reduction reaction (ORR). In addition, a series of CV scans show that our catalyst is more stable than Pt/C in the acidic environment. Finally, in order to get a fair comparison for high surface area catalysts, detailed thin-film rotating disk electrode measurements at room temperature were performed on 200 nm long Pt nanorods as well as Pt/C for comparison to calculate the most important kinetics parameters (Tafel slopes, exchange current density, Pt mass-specific activity and area-specific activity), which are the accepted measures of true catalysts activity towards ORR. These results reveal the enhanced mechanism and kinetics of ORR on Pt nanorods compared to Pt/C.