(569ap) Exploring Bi-Metallic Oxygen Reduction Electrocatalysts with Open Catalyst Project Screening

Hydrogen, an energy dense green fuel, can be directly converted to electricity through proton exchange membrane fuel cells and offers a compelling alternative to fossil fuels. However, the efficiency of fuel cells is limited by the oxygen reduction reaction because of linear scaling relationships of oxygen-metal bond energies. Palladium is a less expensive metal than platinum with a high affinity for proton adsorption. This affinity inspires investigation into a novel oxygen reduction mechanism in which protons and oxygen groups are simultaneously adsorbed on the catalyst surface. The aim of this work is to ascertain whether linear scaling relationships can be bypassed with this novel dual site mechanism on bi-metallic palladium catalysts. This work compares bi-metallic nano particle oxygen reduction rates to platinum and other single metal catalysts through rotating disk electrode linear sweep voltammetry and cyclic voltammetry. Oxygen-metal bond strengths predicted by machine learning models from the Open Catalysis Project were used to screen bi-metallic alloys. Additionally, hydrodynamic and kinetic modelling is presented to better understand the reaction schemes. Of the bi-metallic catalysts screened and tested, palladium-gold alloys are found to have higher activity (+0.2 mA/cm^-2) and less negative onset potentials (+0.075V at 0.1mA/cm^2) than single metal counterparts indicating that electronic or mechanistic changes occur on the alloy surface. This could present a novel, less expensive catalyst for oxygen reduction in fuel cells.