We develop emerging energy materials for applications in chemical and electrochemical catalysis, such as solid oxide fuel cells, electrolyzers, and hydrocarbon reformers. We focus on the reactions that occur at the “interfaces between ionic solids (oxides in particular) and gases” and improve in the high-temperature reaction kinetics.
Gas-Solid interface reaction kinetics
Electrochemically well-defined model interfaces
Highly active nanostructured gas/oxide interfaces
Fuel cells, and in particular solid oxide fuel cells (SOFCs) are expected to play a major role in a sustainable energy future. SOFCs are the most efficient devices known to convert chemical energy stored in a fuel to electrical energy. SOFCs can furthermore operate on many different fuels – they work very well on hydrogen, but also can operate nearly as well on methanol, ethanol, methane, propane, coal-derived syngas, or even diesel reformate.
Essential to the fuel cell energy conversion process is the electrochemical reactions at the electrodes - oxygen reduction at the cathode and fuel oxidation at the anode. Despite recognition of the importance of the electrochemical reactions and extensive research efforts towards their elucidation, the reaction pathways, and rate-limiting steps remain largely unknown. Here, we address these factors through micro-fabrication of simplified, well-defined structures and evaluation of materials with the well-known bulk defect and transport properties. We employ physical vapor deposition and micro-fabrication methods to prepare oxide-metal composite electrode structures with good impurity control. This geometry, in combination with selected in-situ and ex-situ characterization techniques, enables identification of the reaction pathways, facilitates measurement of the site-specific electro-catalytic activity, and reveals critical factors governing the overall electrode reaction rate.
Nature Materials 11 (2012) 155
Advanced synthesis and characterization
Strain-driven surface manipulation
in-situ growth of self-assembled metal nanocatalysts
Highly active complex catalysts
More energy from sunlight strikes the earth in one hour than all of the energy consumed on the planet in one year. Thus, the challenge modern society faces is not one of identifying a sustainable energy source, but rather one of capitalizing on the vast solar resource base. To enable effective solar utilization, several candidate storage solutions are being pursued in laboratories worldwide. However, large-scale energy storage remains elusive.
We pursue an alternative strategy that relies on the capacity of selected nonstoichiometric metal oxides to release and uptake oxygen in response to changes in temperature, where the thermal cycling is induced by exposure to solar radiation. The resulting stoichiometry changes can be directly utilized for fuel production when coupled with the introduction of appropriate reactant gases.
Science 330 (2010) 1797