Tyler Mefford (UCSB): "Oxygen Reduction on Organic Mixed Ionic-Electronic Conducting Polymer Electrodes"

Tyler Mefford received his B.S. in Chemistry in 2012 from Stanford University and Ph.D. in Chemistry in 2016 from the University of Texas at Austin where he worked with Prof. Keith Stevenson. He then moved back to Stanford to do a postdoc with Prof. William Chueh in the Materials Science & Engineering department and stayed on as a Senior Staff Scientist until joining the Department of Chemical Engineering at UCSB as an Assistant Professor in January 2024. His lab works at the intersection of engineering, chemistry, and materials to understand and control electron and ion transfer at electrified interfaces. With an emphasis on utilizing the increasingly low-cost of electrons generated from renewables, his lab develops novel redox-active polymers and inorganic electrode materials for applications in electrochemical energy conversion, storage, and chemical separations. Understanding of the non-equilibrium properties of electrochemical systems and reaction mechanisms across time and length scales is aided by a focus on device development, operando spectroscopy, microscopy, and scattering techniques, and computational methods.

Abstract: Organic mixed ionic-electronic conductors (OMIECs) are a class of conjugated polymers with tunable electronic and ionic transport properties enabled through polaron-forming ion insertion redox reactions. The energy to form these conductive polaronic states can be controlled through rational design of the polymer backbone to enable predominantly electron/cation (n-type) or hole/anion (p-type) transport. Simultaneously, electrolyte uptake into the bulk of the electrode can be controlled through incorporation of polar/non-polar sidechains. The ability to tune the energy of the redox-active states, the majority charge carrier, and the local reaction environment offers an opportunity to independently optimize activity and selectivity in electrochemical energy conversion processes with a single-phase electrode.

In this talk, I will discuss our efforts to develop these polymers as electrocatalysts for the oxygen reduction reaction. The electronic and chemical origins of reactivity are interrogated through pH-dependent electroanalytical characterization, operando spectroscopy, charge-transport measurements, and ab initio/microkinetic simulations. The nature of the polaronic states provide a generalized framework to understand pathway selectivity towards the 2-electron H2O2 or 4-electron H2O product and serve as a design principle in developing this emerging class of metal-free electrocatalysts.