OXYGEN REDUCTION REACTION ELECTROCATALYSIS ON GRADED POROUS PALLADIUM-COPPER ALLOYS

Abstract

Hydrogen fuel cells, which can utilize either a proton- or an anion-exchanged membrane, are one of the most promising technologies for sustainable energy conversion. However, the slow kinetics of the ORR has hindered the devices’ applications to several real-world settings. One of the most successful strategies for improving the ORR activity has been to alloy a precious metal with 3d transition metals. In my study, I examine this enhancement in Pd-Cu bimetallic catalysts in a mesoporous structure format. My approach starts by creating a mesoporous Cu structure via electroless-plating on a self-assembled triblock terpolymer template. Then, I apply galvanic displacement in Pd2+ aqueous solution, where time and concentration variable were controlled to arrive at different Pd:Cu ratios. The catalysts were characterized by X-ray diffraction to confirm the structure of the alloy, while scanning electron microscopy and adsorption isotherm were used to characterize the morphology. Inductively coupled plasma atomic emission spectroscopy was further used to identify the atomic ratio. I optimized the heat treatment sequences as well as ink formulations and catalyst loadings to measure the intrinsic ORR activity of the bimetallic catalysts using a standard three-electrode rotating disk electrode cell. The results of the ORR activity, whether normalized by mass or by surface areas, are compared to standard palladium on carbon catalyst to gain new insights into the role of the Cu addition and how the confined porosity can benefit future catalyst design.