Integrating Alternative Solvent Systems with Electrocatalysis for Energy and Environmental Applications

                Energy and environmental applications will remain main thrusts of interest in chemical engineering for the foreseeable future and are more-and-more becoming tied hand-and-hand with each other.  Resource type and uses, utilization efficiencies, and emissions and other wastes all need to be addressed.  All of these issues have to be addressed in a cost-effective and technically feasible manner.  I propose adding tools from my PhD and post-doctoral experiences to my intellectual “toolbox” to address these problems.  I have a background in electrocatalysis, heterogeneous catalysis and alternative solvent systems and will show how they can be integrated together to give a stronger tool set to tackle the difficult problems that lay ahead.

                In my PhD work at Ohio State, I investigated nitrogen-containing carbon nanostructures (CN_x) as alternatives to platinum for oxygen reduction reaction (ORR) electrocatalysts in PEM and direct methanol fuel cells. In this work, CN_x electrocatalysts were grown over removable oxide supports or unsupported metal catalysts.  The nanostructure growth catalyst and growth reactant gases were selected to control the nanostructure and nitrogen content of the resulting CN_x.  The nature of the active site for this class of ORR electrocatalysts has been heavily debated in the literature.  CN_x nanostructure, nitrogen-type and –content were tuned to examine the nature of the active site.  The catalysts were extensively characterized using traditional heterogeneous catalysis experimental techniques including X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), surface area analysis, thermogravimetric analyses and other temperature-programmed experiments.  The catalysts were electrochemically tested for activity and selectivity to correlate the catalyst properties with desired activity and selectivity to ORR.  Results of this work suggested that an active site containing nitrogen and not a metal ion existed on the graphitic edge plane of the active electrocatalysts. 

                During my post-doctoral experience at Georgia Tech, I have worked on using alternative solvent systems to reduce emissions, decrease process energy consumption, increase product separations and improve desired reaction pathways and kinetics.  In this poster, I will focus on the use of reversible ionic liquids (RevILs) as a tunable medium for separations.  The main application that will be highlighted with these RevILs is CO₂ capture from coal-fired power plants.  Here we use one-component silylamines as the RevIL.  In this system, the excess water typically used in amine-based CO₂ capture absorption systems is not required.  This results in the possibility of significantly reducing the energy of regeneration of the absorbant system while maintaining high CO₂ capture capacities.  The silylamines selected are a molecular liquid before CO₂ capture.  Upon reaction with CO₂, they form an ionic liquid with an ammonium cation and a carbamate anion.  With a moderate increase in temperature, the RevIL will reverse back to the molecular liquid, resulting in the release of a purified CO₂ stream.  The chemical structure of these silylamines can be altered to tune the desired properties of the absorption system including CO₂ capture capacity, energy of regeneration, viscosity and CO₂ release purity.  The modified silylamines have been studied to develop structure-property relationships.  With these established structure-property relationships, viable RevIL candidates for CO₂ capture absorption systems can be identified and further studied in the laboratory.

                The two research areas presented in the poster can be combined by using the alternate solvent systems in the pre-processing of reactants, post-processing of products or as the electrolyte itself in the electrochemical system.  Electrocatalysts will be developed that are both active and selective to the desired reaction.  The synergetic effects of use of the electrocatalysts with the solvent systems will be examined in the systems studied.