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The Dynamic Plasma-based Electrochemical Interface for the Synthesis of Chemicals and Materials
February 26, 2021 from 11:00 am — 12:00 pm
Zoom Webinar with R. Mohan Sankaran
Department of Nuclear, Plasma, and Radiological Engineering
University of Illinois at Urbana-Champaign
Low-temperature plasmas have played a critical role in materials processing for the etching and deposition of thin films. Typically in these systems, non-equilibrium reactions occur at the interface of a gas and solid phase with species created in the plasma interacting with a substrate or a film that is “hard.” The recent development of low-temperature plasmas that operate at atmospheric pressure enables systems where non-equilibrium reactions occur at the interface of a gas and a “soft” phase such as a liquid or a polymer film. The resulting interfacial physics and chemistry is complex, but also offers new opportunities for applications.
In this talk, I will present my group’s recent efforts to understand the interfacial reactions between plasmas and soft phases such as liquids and polymers from the perspective of electrochemistry, and develop applications of these systems in chemical and materials synthesis. The majority of the talk will focus on an electrolytic system very similar to conventional electrochemistry in which a direct-current, atmospheric-pressure plasma jet is formed in contact with the surface of a solution and current flows from the plasma to the solution. In such a configuration, the plasma serves as an electrochemical electrode and redox reactions are carried out at a plasma-solution interface, which is distinct from a metal-solution interface. For example, in the absence of a solid electrode, metal salts can be reduced to zero-valent metal, and instead of producing a thin film or coating, form dispersed nanoparticles. This approach can be extended to thin films, to fabricate either nanocomposites composed of a polymer matrix with dispersed metal nanoparticles, or metallized patterns. In addition, unlike a metal electrode, the plasma generates energetic electrons which can be injected into solution to produce solvated electrons, one of the strongest chemical reducing species. We have applied this chemical effect to the reduction of nitrogen gas to produce ammonia. The formation of ammonia at near ambient conditions using only electricity offers an alternative to the well-known Haber-Bosch process that is potentially sustainable and distributed.
R. Mohan Sankaran received his B.S. in Chemical Engineering from the University of California Los Angeles in 1998 and his Ph.D. in Chemical Engineering from the California Institute of Technology. He began his independent academic career in the Department of Chemical and Biomolecular Engineering at Case Western Reserve University as an Assistant Professor in 2005, was promoted to Associate Professor in 2010, then promoted to Professor in 2014. In 2020, he moved to the Department of Nuclear, Plasma, and Radiological Engineering at the University of Illinois at Urbana-Champaign and is currently the Donald Biggar Willet Professor in Engineering. His research program focuses on developing atmospheric-pressure plasmas as a chemical platform for the synthesis of novel materials and small molecules with applications in emerging electronics, medicine, and energy conversion. He has co-authored over 100 peer-reviewed journal articles, edited one book, and contributed several book chapters. He has been recognized for his research achievements by the Camille and Henry Dreyfus Teacher-Scholar Award and the AVS Peter Mark Memorial Award. He currently serves as an Associate Editor of the Journal of Vacuum Science and Technology and a member of the Editorial Board of Plasma Chemistry Plasma Processing, Scientific Reports, and Plasma Research Express and the Advisory Board of the Journal of Physics D.
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