Over the last century, global economic growth has been enabled by fossil resources. Securing long-term prosperity requires the development of technologies that facilitate the sustainable production of fuels and commodity chemicals. Electrocatalysis is considered one of the most promising technologies in this regard. Two reactions of particular significance are the electrochemical reduction of carbon dioxide to fuels and other useful chemicals and the oxidation of water to dioxygen, which provides the electrons and protons consumed by reduction processes. At presently employed electrode/electrolyte interfaces, both reactions are slow at low overpotentials. Further, for carbon dioxide reduction, present electrocatalytic interfaces typically exhibit poor product selectivity. To design selective and efficient catalytic interfaces, it is essential to identify the molecular-level origins that are principally responsible for controlling the reaction path. In the first part of this talk, we will focus on how cations steer the competition between CO2-to-CO conversion and the hydrogen evolution reaction on polycrystalline gold electrodes. The mechanisms by which alkali metal cations can modulate the free energy landscapes of electrocatalytic processes are manifold and poorly understood. In this regard, it is essential to quantify the population of specifically adsorbed cations, that is, the cations that are in direct contact with the electrode. Using a novel infrared-spectroscopic approach, we probed the surface coverage of specifically adsorbed alkali metal cations. For the same bulk concentration of alkali metal cations, we found their propensity to specifically adsorb on Au electrodes during CO2-to-CO reduction correlates with their free energy of hydration, that is, the surface coverage follows the order Liads< Naads < Kads < Csads. Our observations indicate that the extent to which alkali metal cations partially shed their hydration shells plays a central role in their ability to act as promoters in CO2-to-CO reduction. The second part of this talk focuses on the water oxidation reaction. It has been recognized that the accumulation of oxidative charges (holes) on catalytically active sites and the chemical structure of these sites collectively determine activity. However, the hole distribution dynamics and the structure of the active sites are typically correlated; it has been challenging to independently change them, impeding the development of a deeper understanding of their relative importance. To address this challenge, we studied the oxidation of water on a heterogenized dinuclear Ir catalyst supported on different metal oxide supports. We found that the rate of water oxidation exhibits a remarkable dependence on the identity of the support. We rationalize this observation with the distinct abilities of the supporting substrates to redistribute surface holes. Our findings shine light on the key role that the support plays in determining the turnover at the active sites of heterogeneous water oxidation catalysts.

Dr. Matthias Waegele started his undergraduate studies in chemistry at the University of Tübingen, Germany, in October 2002. Two years later, he obtained a Visiting Graduate Student Fellowship from Indiana University, Bloomington, where he spent a year in Professor Bogdan Dragnea’s laboratory. During his time at Indiana University, he engaged in research on non-linear optics and light-induced conformational changes of proteins. He then returned to Germany to complete his undergraduate work and obtained his Bachelor of Science degree from the Technical University of Munich in 2006. Following this undergraduate work, he moved to the University of Pennsylvania, Philadelphia, where conducted his graduate work under the direction of Professor Feng Gai. In his PhD work, Dr. Waegele studied the conformation and dynamics of peptides and proteins, using infrared and fluorescence spectroscopies. Following his graduation in 2011, he assumed a postdoctoral position in Professor Tanja Cuk’s laboratory at the University of California, Berkeley. During his postdoctoral work, he studied the charge-transfer dynamics at the semiconductor/electrolyte interface under conditions of photocatalytic water oxidation. In July 2015, Dr. Waegele started his independent career in the Department of Chemistry at Boston College, where he is now an Associate Professor. His research group engages in spectroscopic investigation of catalytic interfaces that show potential for the synthesis of renewable fuels and high-value commodity chemicals. To this end, his team combines surface-enhanced infrared and Raman spectroscopies with mass spectrometric approaches. His group is particularly interested in the rich chemistry exhibited by electrified interfaces suitable for electrocatalytic carbon dioxide reduction, methane activation, and water oxidation.