(6dn) Electrodeposition and Activity of Electrocatalysts in Ionic Liquids

Applications of electrocatalysts can be found in  sensors, electro-organic synthesis, waste-water treatment and energy conversion devices. The activity and selectivity of the electrocatalysts can be fine-tuned by applying potential or current. In addition, the electrochemical devices employing the electrocatalysts are not limited by Carnot efficiency. The requirement for triple-phase boundary for electrochemical reactions to occur in these devices necessitate that the electrocatalysts be deposited in a site-specific manner for maximum utilization. Electrodepostion of the catalysts meets this requirement. However, in traditional aqueous system, electrodeposition is limited by the narrow electrochemical window of water (1.2 V). In ionic liquids (ILs), the electrochemical window can be as high as 6 V and the metals having reduction potential negative than that of H₂ evolution could be reduced. Moreover, product selectivity and reaction efficiency can be enhanced in ILs for reactions such as CO₂ reduction. However, studies in these fields are limited. My graduate work in nitrogen-doped ordered mesoporous carbon (NOMC) supported Pt for oxygen reduction reaction (ORR) and my postdoctoral work in electrodeposition of fission platinoids (Pd, Rh, Ru) in ILs puts me in a favorable position to advance these fields.

My graduate work focused on creating strong metal-support interaction (SMSI) between carbon and Pt. Although various types of advanced carbon supports such as carbon black, carbon nanotubes, aerogels, carbon fibers and graphene have been investigated as the support, none have been shown to increase intrinsic ORR activity of Pt. To overcome this, I explored nitrogen-doped carbon supports. Nitrogen has been shown to change electronic and microstructural properties of carbon. However, there had been few works on Pt-supported nitrogen-doped carbon for ORR and most of it was limited to model systems such as highly oriented pyrolytic graphite (HOPG).  In my work, NOMC was synthesized by templating on SBA-15 with pyrrole as the precursor. Pt nanoparticles were deposited on the NOMC by electroless reduction in ethylene glycol. I showed how pore-order, graphiticity and nitrogen content plays a role in ORR activity of the Pt. This has provided guidance for designing of high-performing nitrogen-doped carbon supports.

Currently, I am working on recovery of fission platinoids (Pd, Rh, Ru) through electrodeposition in ionic liquids. Current processes for recovery of fission products is based on extraction in highly flammable volatile organic solvents (VOCs) such as kerosene and dodecane. ILs provide safer alternative to the VOCs because of their negligible vapor pressure. ILs also have complexing ability, hence metals could be dissolved in ILs without introducing additional complexing agents. Also the metals solvated could be recovered directly through electrodeposition in ILs. I am studying electrochemical and electroreduction behavior of Pd in many ILs previously not studied. The ILs affect the electroreduction behavior by controlling speciation, electrolyte/electrode interface, and the mass-transfer which in turn affect the thermodynamics, kinetics and morphology of the deposits. This work will expose fundamental underpinnings of electrodeposition of Pd, Rh and Ru in ILs.

In my poster, I will summarize my graduate and postdoctoral work and talk about how I will exploit them to develop the field of electrodeposition of catalysts and their activity in ILs for applications in low temperature fuel cells and CO₂ utilization.