GLAD Cr Nanorods Coated with SAD Pt Thin Film for Oxygen Reduction Reaction

Vertically aligned chromium nanorod arrays were grown on glassy carbon electrodes by a dc magnetron sputtering glancing angle deposition (GLAD) technique. The Cr nanorods were used as low-cost, high surface area, metallic supports for a conformal Pt thin film, resulting in a potential low-loading electrocatalyst for the oxygen reduction reaction (ORR) in polymer electrolyte membrane (PEM) fuel cells. Conformal coatings of Pt on Cr nanorods were achieved using a dc magnetron sputtering small angle deposition (SAD) technique. The electrocatalytic ORR activity of SAD-Pt/GLAD-Cr electrodes was investigated using cyclic voltammetry and rotating-disk electrode techniques in a 0.1 M HClO4 solution at temperatures ranging from 20 to 60°C, and was compared to those of GLAD Cr nanorods coated with Pt thin film deposited at normal and large angles of incidence. The results show that SAD-Pt/GLAD-Cr nanorods exhibit higher values of electrochemically-active surface area (ECSA), area- and mass-specific activities, and better stability against loss of ECSA during potential cycling in the acidic electrolyte. The improved ORR activity and enhanced catalyst utilization of SAD-Pt/GLAD-Cr electrode might be attributed to a better Pt conformality, especially at the sidewalls of the nanorods, and a preferential exposure of certain crystal facets.