UC Berkeley

The corrosion kinetics of metals in the presence of polymer electrolyteswhich are frequently used in devices for the electrochemical production of hydrogen, hydrocarbons, and alcoholsis convoluted by transport and ill-defined reactive interfaces that mask the fundamental reaction kinetics. Underpotential-deposited monolayers of Cu at Au(111) surfaces provide a structurally well-defined active site for interfacial ion transfer with a fixed number of sites available for adsorption. Here, we investigate the adsorption behavior of Cu at Au(111) surfaces across a series of sulfate and sulfonate electrolytes to understand how anion structure influences the kinetics of elementary interfacial ion-transfer reactions. The influence of anion structure is most significant at high adsorbate coverage, with similar adsorption isotherms and kinetics observed for sulfates and two molecular sulfonates. In contrast, a suspended perfluorosulfonic acid ionomer reduced both the equilibrium coverage of Cu and the standard exchange rate at Au(111) at low coverages of Cu. These results suggest that electrocatalyst corrosion is inhibited for metal nanoparticles supported at polymer electrolytes due to changes in adsorbate coverage, as well as suppressed kinetics for interfacial ion transfer.