Technical description: The core hypothesis of this project is that colloidal particles can function as probes of local electrochemical current density. The essence of the innovation is using scattered light from colloidal particles during polarization of electrodes. In experiments, colloidal particles will be scattered across test electrodes used in electrochemical cells. Laser radiation introduced at an angle of incidence greater than a critical angle will create evanescent radiation proximate to the electrodes. The particles scatter these evanescent waves as visible light. The particles respond dynamically to local current density, which means that the particles transduce the local current density to light having an intensity that can be measured. Theory will convert the light intensity to a determination of current density. When ensembles of particles are used, the method creates an image of current density on the electrode. Imaging the scattering of a 2D ensemble of particles on a composition spread alloy working electrode during polarization of the film will reveal the regions of high electrochemical activity over the entire sample within minutes, with a resolution of areas as small, or perhaps smaller, than 100 microns on a side. This will mean that a library made from a sample one square centimeter in area will have 104 samples in its collection. The project focuses on oxygen evolution from aqueous solution as the test electrochemical reaction. This reaction is highly irreversible and has been of considerable interest for decades.
Broader significance and importance: There is broad interest in developing high throughput methods for accelerating research. This project focuses on development of a high throughput method for investigation of an electrochemical reaction that is critical to enabling the supply of hydrogen as a fuel. The project will make possible a thousandfold increase in productivity in the search for new electrode materials for carrying out the splitting of water to produce hydrogen and pure oxygen. The concept of imaging amperometry might be the best solution to this problem; if so, the method will be adopted at other laboratories and/or a scientific instrument will be developed by an electrochemical instrument company or a startup. The proposed research has the potential for a large payoff in capability in addition to the richness of its research in education.