Borohydride oxidation electrocatalysis at individual, shape‐controlled Au nanoparticles

Abstract

AbstractNanostructured materials are frequently employed as active components in electrochemical devices for energy conversion and storage. Unfortunately, the complexity of nanostructured materials, which can exhibit significant heterogeneities in morphology and/or composition within a macroscopic sample, makes it difficult to generate fundamental insights into their operation using traditional experimental techniques. Analytical methods that can probe the behavior of individual, discrete reactive entities, such as nanoparticles (NPs), may serve as powerful tools for the study of complex, heterogeneous systems, but remain experimentally challenging. Here, the application of probe‐based electroanalytical methods is demonstrated to be a powerful, high‐throughput strategy for the characterization of electrocatalytic systems. A pipet‐based approach, Targeted Electrochemical Cell Microscopy (TECCM), was applied to characterize the electrocatalytic properties of individual, shape‐controlled Au NPs toward the borohydride oxidation reaction (BOR), a model fuel cell reaction. Using TECCM, the BOR could be quantitatively interrogated at individual NPs in a high‐throughput fashion, directly revealing significant NP‐to‐NP variations in reactivity and stability. BOR kinetics were found to exhibit a significant shape dependence, generally increasing in the order Triangles < Spheres Octahedra < Rods, and prominent voltammetric features were observed that could be attributed to surface deactivation/reactivation process occurring at individual NPs. Together, these results demonstrate the large degree to which catalytic behavior varies at the single NP level and the power of applying single NP analytical techniques to the study of these systems.