Investigation of formate oxidation on effective palladium based electrocatalysis in direct alkaline formate fuel cells

Abstract

As the necessity for alternative energy technologies increases due to the energy problems such as depletion of fossil fuels, pollution, and global warming, electrochemical technology including battery and fuel cell has been in the limelight. In particular, fuel cell technology has higher specific energy compared with other electrochemical technology and higher efficiency due to the direct energy conversion compared with combustion of conventional engine. Even though proton exchange membrane fuel cell is taking the lead to commercialization, its drawbacks are also being regarded seriously: hydrogen utilization, sluggish cathodic reaction, extremely corrosive environment and cross-over due to its acidic atmosphere. In this regard, formate (HCOO–) as a liquid fuel based on the anion exchange membrane fuel cell can overcome these disadvantages because of higher theoretical potential, facile utilization, carbon neutral, and less corrosive environment. Furthermore, the oxidation kinetics of HCOO– is relatively faster than other small organic molecules (SOMs) as a liquid fuels such as methanol or ethanol. In the oxidation of HCOO–, palladium (Pd) shows much higher catalytic activity than platinum which is a conventional anode catalyst for the oxidation of SOMs. Thus, there have been some literatures for the oxidation of HCOO–, but the application of a practical system for the developed or modified catalyst is still insufficient. For this reason, in this dissertation, synthesis of outstanding Pd based anode catalyst as well as its physicochemical and electrochemical characterization including the application of practical system are mainly investigated, based on the understanding of the oxidation reaction of HCOO– on Pd in alkaline media. Through a series of studies on this dissertation, first, we tried to understand the origin of the adsorbed hydrogen as a site-occupying species using kinetic isotope effect. Furthermore, we tried to investigate an observation whether carbon monoxide is formed or not when the oxidation of HCOO– occurs, using in-situ surface enhanced infrared absorption spectroscopy in the attenuated total reflection mode. Based on the understanding of the reaction, we investigated the morphological effect and electronic effect of hydrogen incorporated palladium catalyst in direct alkaline formate fuel cell (DFFC). Finally, we synthesized boron incorporated palladium catalyst, and tried to investigate its modified electronic structures and its effect on the oxidation activity of HCOO–. Understanding for the oxidation reaction of HCOO–, synthesis of modified anode catalyst and application will be helpful to lift up the possibility of the development of DFFC as the alternative energy technology further.