The Waterloo Institute for Nanotechnology (WIN) presents a seminar by Dr. Nenad Markovic, Senior Chemist at the Materials Science Division, Argonne National Laboratory, United States.
Electrochemical Interfaces, Electrocatalysis and Green Energy
In recent years, improvements in the fundamental understanding of electrochemical interfaces and their role in electrocatalytic processes have started to revolutionize the development of alternative energy systems for clean energy production, storage and conversion. In this presentation, we describe how a synergistic interaction between fundamental science and technological progress has resulted in the development of a greatly enhanced understanding of electrocatalytic systems, as well as the development of materials that can efficiently transform chemical energy into electricity and synthesize chemicals that can be stored and reused in energy conversion systems. We begin by discussing oxygen electrochemistry in aqueous-based environments, focusing on the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) on well-characterized metal, metal/metal-oxide and complex oxide materials. Then, by addressing functional links between the activity and stability of electrode materials, we define the landscape of parameters that control the efficiency of the “water energy cycle” that is the result of a complex series of bond making and breaking events between hydrogen, oxygen and water molecules. We also propose key descriptors that control the reactivity of electrochemical interfaces during the ORR and OER in fuel cells and electrolyzers.
In the second part, we explore the subject of dioxygen electrochemistry in organic solvents, which is much less advanced than the corresponding understanding of interfaces in aqueous systems. This is due to the long-standing difficulty associated with developing in situ methods that are capable of characterizing interfaces at atomic-/molecular levels in organic solvents. One prime example is Li-O2 electrochemistry that has been studied on ill-defined, polycrystalline and/or high surface area cathode materials in organic solvents containing trace levels of water and other impurities that, even in ppm levels, can dominate interfacial properties. Not surprisingly, then, it has been very difficult to reproduce many claims of high re-chargeability and reversibility of the Li-O2 battery systems. This intrinsic disparity in the understanding of water-based and organic-based solvents, however, has a tendency to mask the inherently close ties that may exist between interfacial phenomena in aqueous and organic environments. In this lecture, we build a bridge between dioxygen electrochemistry in alkaline and ether-based environments in order to yield unique insights into the synergistic nature of double layer interactions and provide an integrated, stepwise link between the inherently multicomponent electrochemical interfaces in aqueous alkaline and nonaqueous Li-O2 systems. We conclude that understanding the complexity (simplicity) of electrochemical interfaces would open new avenues for the design and deployment of alternative energy systems.
Dr. Nenad Markovic
Nenad M. Markovic received his BSc, MsD and PhD at the University of Belgrade. His academic carrier started in 1978 as Research Associate at Institute of Electrochemistry, University of Belgrade. As a junior scientist he spend two years in Prof. Yeager's laboratory at the CWRU in Cleveland, OH. He returned at the University of Belgrade in 1984 and a year latter he become a Group Leader in the Department for Surface Electrochemistry. In 1991, he got a Staff Scientist position at Lawrence Berkeley National Laboratory, where he stayed fourteen yeas. In 2005, he joined ANL in Material Sciences Division as a Senior Chemist. He is a Group Leader of the Energy Conversion and Storage Group. His major research interest is understanding surface processes at the electrified metal-solution interfaces. Utilizing ex-situ (AES, LEED, UPS, XPS) and in-situ (SXS, STM/AFM) surface sensitive probes in combination with vibrational spectroscopy (FTIR, ATR) and classical electrochemical methods he established relations between the microscopic surface atomic/electronic structures of mono-metallic and multi-metallic single crystal surfaces and the macroscopic kinetic rates of (electro)chemical reactions. The knowledge obtained by studying model single crystal surfaces he used for both understanding the activity pattern of metal nanoparticles employed in energy conversion and storage systems as well as for finding relationships between the reaction rate, selectivity and stability with the characteristic dimension of a metallic catalysts. He is the author of more than 190 papers in the field of catalysis and surface electrochemistry.