Electrodes used for fundamental electrochemical studies and for applications (e.g. in electrocatalysis, energy storage and sensor technologies) show heterogeneity and complexity on a range of lengthscales. However, the intrinsic activity of these electrodes is often characterized by old classical macroscopic electrochemical techniques that provide an average response of an electrode and are unable to detect and analyze spatially heterogeneous fluxes that ultimately govern the electrode response. We have developed new approaches to study electrochemical and electrocatalytic phenomena, whereby the activity of an electrode is visualized by electrochemical microscopy in the form of “activity maps” and “activity movies”, and these quantitative data are then related to co-located electrode structure from complementary high-resolution microscopy and spectroscopy techniques applied to the same area of the electrode. This new era of correlative electrochemical multi-microscopy seeks to relate electrode structure to activity clearly and unambiguously. This contribution will discuss the use of nanoscale scanning electrochemical cell microscopy (SECCM), scanning ion conductance microscopy (SICM) and combined scanning electrochemical microscopy (SECM)-SICM for the acquisition of electrochemical activity-electrode topography maps, coupled with a wide range of microscopy techniques, spanning electron microscopy and electron backscatter diffraction, micro-Raman spectroscopy and atomic force microscopy to pinpoint particular active sites in the same area. This is a general platform for investigating electrochemical interfaces, and illustrative examples of this approach will include: layered materials (2D and 3D), structurally and/or compositionally heterogeneous surfaces such as polycrystalline metals, and ensemble electrodes comprising of nanoparticles on an electrode support, with applications in electrocatalysis and energy storage (batteries). A key thesis of our work is that complex electrode surfaces can be broken down and studied as set of simpler “single entities” (e.g., individual steps, terraces, defects, crystal facets, grain boundaries, single particles), and the nanoscale understanding of reactivity that results can then be used to create scalable models for electrochemical interfaces that will ultimately facilitate the rational design of functional (electro)materials.

Structure-activity relationships at complex electrodes from correlative electrochemical multi-microscopy

2019 Fall National Meeting

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