Electrochemical Screening of Metallic Oxygen Reduction Reaction Catalyst Thin Films Using Getter Cosputtering.

Current commercial fuel cells operate in acidic media where Pt-containing compositions have been shown to be the best oxygen reduction reaction (ORR) electrocatalysts, due to their facile reaction kinetics and long-term stability under operating conditions. However, with the development of alkaline membranes, alkaline fuel cells have become a potentially viable alternative that offers the possibility of using Pt-free (precious metal-free) electrocatalysts. However, the search for better electrocatalysts can be very effort-consuming, if we intend to test every potential bi- or trimetallic combination. In this work, we have explored the application of physical vapor deposition using a custom-built getter cosputtering chamber to prepare catalyst thin films on glassy carbon electrodes, enabling catalyst compositions to be screened in a combinatorial fashion. The activity of combinations containing Au, Cu, Ag, Rh, and Pd as binary metal catalysts, in alkaline media, was studied using rotating disk electrode (RDE) voltammetry with an exchangeable disk electrode holder. Subsequently, we investigated a composition gradient of Pd-Cu, the best performing bimetallic catalyst thin film identified in the initial screening tests. Our results show the viability of using metal getter cosputtering as a rapid and effective tool for preliminary testing of ORR fuel cell electrocatalysts.