Speaker
Patrick Unwin Ph.D.
Speaker's Institution
University of Warwick
Date
9/11/19
Time
4:00 PM
Location
Chemistry A101
Mixer Time
3:45PM
Mixer Location
B101E
Additional Information

About the Seminar:

Electrodes used in electrochemistry, with applications in electrocatalysis, energy storage, sensor technologies and corrosion, show heterogeneity and complexity on a range of lengthscales. The activity of these electrodes is often determined by old classical macroscopic electrochemical techniques that provide the average response of an electrode and are unable to detect and analyze spatially heterogeneous fluxes that govern the electrode response. We advocate 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 “potentiodynamic movies”. These quantitative data are then related to co-located electrode structure from complementary high-resolution microscopy and spectroscopy techniques applied in the same area of the electrode. This correlative electrochemical multi-microscopy approach seeks to relate electrode structure to activity clearly and unambiguously. In our work, scanning electrochemical cell microscopy (SECCM) and scanning ion conductance microscopy (SICM) are used primarily for the acquisition of electrochemical activity-topography maps at electrodes with nanoscale spatial resolution, 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 include: layered materials, structurally and/or compositionally heterogeneous surfaces such as polycrystalline metals, screen printed electrodes and conducting polymers, and ensemble electrodes comprising of nanoparticles on an electrode support surface, 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). The resulting nanoscale understanding of electrochemical reactivity can then be used to create scalable models for electrochemical interfaces that will ultimately facilitate the rational design of functional (electro)materials.

Many talented people at Warwick and elsewhere have contributed to our work in this area and will be acknowledged throughout.

 

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