Stacked and Core–Shell Pt:Ni/WC Nanorod Array Electrocatalyst for Enhanced Oxygen Reduction Reaction in Polymer Electrolyte Membrane Fuel Cells

In this study, we developed a stacked core–shell nanorod array electrocatalyst design to improve oxygen reduction reaction (ORR) kinetics and catalyst stability for polymer electrolyte fuel cell (PEMFC) applications. For this purpose, we fabricated two-layer stacked nanorod arrays with each layer consisting of a tungsten carbide (WC) core and a platinum–nickel (Pt–Ni) alloy shell. WC nanorods were grown by a glancing angle deposition (GLAD) method. Then, WC nanorods were coated with a Pt–Ni shell conformally by a high-pressure sputtering (HIPS) method. This process was repeated twice to form the second layer of the stack. We investigated three different Pt:Ni ratios including 3:7, 1:1, and 3:1. Cyclic voltammetry (CV) and rotating disk electrode (RDE) methods were used for electrochemical characterization of the Pt:Ni/WC electrodes in a 0.1 M HClO4 electrolyte solution. Morphological and crystallographic analyses were performed using scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Pt mass loading values were measured using a quartz crystal microbalance. Electrochemically active surface area (ECSA) values change in the order of 3:7 > 1:1 > 3:1 in the Pt:Ni ratio. Specific activity (SA) and mass activity (MA) were higher for the 3:7 composition after accelerated stability tests were comparable to those of other compositions.