Over the past 15+ years, we have been developing and investigating homogeneous catalytic aerobic oxidation reactions that proceed via two sequential half-reactions: (1) oxidation of the organic substrate (SubH2) by an oxidized catalyst (catox), followed by (2) oxidation of the reduced catalyst (catred) by O2. This general mechanism closely resembles the two redox half-reactions in fuel cells, and we have recently begun developing and investigating independent electrochemical half-reactions that employ soluble electrocatalytic mediators. Examples include the use of organic nitroxyls and NOx-based cocatalysts for O2 reduction, and organic nitroxyl catalysts and Cu/nitroxyl-cocatalysts for alcohol oxidation. The emerging results highlight substantial synergies among the fields of homogeneous catalysis, organometallic chemistry and electrocatalysis. For example, the insights from homogeneous catalysis have led to significant lowering of the "overpotential" and enhancement of rates in challenging electrocatalytic reactions, while electrochemical studies of independent half-reactions have provided unprecedented insights into the mechanisms of important homogeneous catalytic reactions.
Shannon S. Stahl is a Professor of Chemistry at the University of Wisconsin-Madison. His research focus is catalysis, with an emphasis on development and mechanistic characterization of catalytic aerobic oxidation reactions for chemical synthesis. Additional efforts focus on the chemistry of molecular oxygen related to energy conversion, including fuel cells and solar energy conversion. He was an undergraduate at the University of Illinois at Urbana–Champaign, and his subsequent training took place at Caltech (Ph.D., 1997, Advisor: Prof. John E. Bercaw) and MIT (postdoc, 1997-1999; Advisor: Prof. Stephen J. Lippard), before he started his independent position in 1999.