Recent advances in our understanding of alternative active sites for oxygen reduction has provided for the basis of its molecular design. This presentation put these developments in the context of more than two decades of effort devoted to engendering such nonnoble metal electrocatalysts. In this presentation we will present our latest data on the most active analogs which comprise of a FeNx coordinated active site in close concert with Fe nano-particles either present in some polymer composite or more ideally as edge defects close to the Fe-Nx coordinated structure. We will show how these active sites evolve on carbon supports as graphene defect structures. Such active site determinations are made with the use of a special in situ synchrotron X-ray absorption method using the near edge spectra referred to as X-ray absorption near edge structure (XANES), in a subtractive mode wherein the signal contribution from the bulk is successfully subtracted from the effect ofthe surface adsorbed species. When combined with our ability to simulate the same signatures using models with specifically adsorbed moieties, a powerful tool emerges to study electrochemical interfaces under actual in situ and operand conditions. This technique, commonly called the ‘Delta Mu (∆μ) Technique’ has been applied to a wide variety of transition metal surfaces and alloys (1-2) including non-Pt based metal electrocatalysts with element specificity. EXAFS data taken concurrently provide information on the changes in short range atomic order around the absorber atom thereby providing structural information such as bond distances and coordination numbers (thereby information on average cluster size, homogeneity and surface segregation etc.).
In this presentation among other things we will provide a picture of the electrocatalytic pathways in aqueous (at both the extreme edges of the pH scale) and non-aqueous environments. The technological consequence of such materials in power generation, electrolysis and energy storage will be described.
- J.M. Ziegelbauer, D. Gatewood, A.F. Gulla, M.J.F. Guinel, F. Ernst, D.E. Ramaker, S. Mukerjee, J. Phys. Chem. C, 113 (2009) 6955-6968.
- S. Mukerjee, T. Arruda, Mod. Aspects Electrochem., 50 (2010) 503-572.
Electrocatalysis, Charge Transfer in Electrified Interfaces, Materials Design and Synthesis, In-situ Synchrotron Spectroscopy
Awards and Honors:
- Fellow of the Electrochemical Society (2013)
- Northeastern University Award for Research Excellence and Creativity (2013)
- University Professorship from Ford Motor Company (2013)
- Massachusetts Clean Energy Council Catalyst Award (2013)