Electrocatalytic Reduction of Oxygen at Au Nanoparticles–Manganese Oxide Nanoparticle Binary Catalysts

Abstract

The screening and testing of fuel cell electrocatalysts often involves comparisons under conditions that do not closely match their use in membrane electrode assemblies. We compared the activities of several commercial and homemade Pt and PtRu catalysts for electrochemical methanol oxidation by four different techniques; disk electrode linear sweep voltammetry in aqueous methanol/sulfuric acid solutions, optical fluorescence detection in aqueous methanol solutions containing a fluorescent acid-base indicator, steady-state voltammetry in a 25 electrode array fuel cell with a large common counter electrode, and steadystate voltammetry in a conventional direct methanol fuel cell. The fluorescence detection method, which is a high-throughput technique developed for large arrays of electrocatalysts, can distinguish active from inactive catalysts, but it does not accurately rank active catalysts. Both the disk electrode and array fuel cell methods gave a reliable ranking of the catalysts studied. The best agreement occurred between the array fuel cell and single electrode fuel cell catalyst rankings. A wide range of catalytic activities was found for PtRu catalysts of the same nominal composition that were prepared by different methods. © 2005 The Electrochemical Society. All rights reserved.