Weak Electric Fields Can Profoundly Influence Chemical Physics Phenomena

The Science

Electric fields that exist within and outside of materials can affect their chemical-physics properties. These properties can be leveraged to enhance catalysis or tune material behavior, but quantifying the fields and their effects is necessary to make this control a reality. New research delivered an integrated quantum-mechanical and experimental perspective on the effects of both intrinsic and externally applied electric fields at atomic-scale interfaces. Researchers recognized the importance of the lightning rod effect, which amplifies applied fields at nanoparticle tips in chemical reactivity and impact on intrinsic fields.

The Impact

External fields offer another route to precisely tuning the chemical physics related properties of materials. Explorations of field-centric orbital tuning from intrinsic and applied field amplification holds the promise of opening new doors in chemical physics in general, and catalytic pathways in particular. This view is fundamentally based upon the idea that intrinsic quantum electric potentials/fields and geometry-driven enhancements alter reaction energetics at atomic-scale interfaces. By understanding electric-field effects, researchers can more effectively design catalysts that exploit field tuning (e.g., catalytic transistors or plasmonic hot spots) for lower-temperature, energy-efficient processes with implications for the synthesis of commodity chemicals and the conversion of products previously deemed to be waste.

Summary

Understanding how weak applied electric fields influence condensed phase and interfacial molecular processes is relevant to both fundamental and applied sciences. Controlling interfacial fields can enable scientists to exploit chemical interactions at ever finer scales. But the intrinsic and response electric fields must be accurately characterized and quantified before fields can be precisely engineered. Researchers used the triple bond dissociation of nitrogen on a ruthenium nanoparticle with and without applied fields as a case study to demonstrate the role of measurement and theory in understanding the fundamental role of fields in chemical reactions. They quantified the electric potentials, fields, and changes in orbital energetics through quantum mechanical calculations, coupling the results with electron holography/tomography measurements and additional calculations. They highlighted that the spatial resolution of the interfacial fields relevant to local chemical interactions is beyond what is currently achievable with high-resolution electron holography/tomography. These intrinsic fields are many orders of magnitude greater than typical applied fields. The system exhibits a lightning rod effect where the inducing field is amplified by a factor of 3 above the tip of a Ru nanoparticle. These considerations call for a reinterpretation of how weak applied fields can have such a profound influence on chemical physics phenomena.

Contact

Shawn Kathmann, Pacific Northwest National Laboratory, shawn.kathmann@pnnl.gov 

Greg Schenter, Pacific Northwest National Laboratory, greg.schenter@pnnl.gov 

Funding

The authors were supported by the Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences and Biosciences Division, Condensed Phase and Interfacial Molecular Science Program and Separation Science Program.