Surface Modifications of a Carbon Anode Catalyst by Control of Functional Groups for Vitamin C Fuel Cells Ye Eun Kim & Mi-Young Kim & Jae Kwang Lee & Sunghyun Uhm & Gon Seo & Jaeyoung Lee Published online: 17 May 2011 # Springer 2011 Abstract We report that electro-oxidation treatment of carbon paper generates specific functional groups, and controllable coating of metal oxide films on carbon surface alters capacitive behaviors. Electrochemical char- acteristics, I–V curves in fuel cells, and a structural analysis of XPS represent that the carboxyl group is the most effective functional group in an electro-oxidation of L-ascorbic acid. The appropriate film thickness of titania on electro-oxidized carbon electrode further increases fuel cell performance and electrostatic capacitance by facili- tating electron transfer reaction. An excessive amount of titania on carbon reduces contribution of carboxyl groups to electro-oxidation of L-ascorbic acid resulting in decline of catalytic effects since they prohibit L-ascorbic acid molecules from access to the adsorption sites on the carbon surface. Keywords L-ascorbic acid . Electro-oxidation . Functional groups . Fuel cells . Capacitance . Metal oxides Introduction Portable polymer electrolyte fuel cells (PEFCs) as a substitute for fossil fuels and secondary batteries have been attracted due to its high power density and compact size at relatively low operating temperatures. Fuels for PEFCs have been reported based on oxidation of small organic compounds, such as methanol, ethanol, and formic acid. However, the fuels mentioned above limit their applications in human-implantable medical devices because they are often toxic, evaporable, burnable, and require noble catalysts [1–15]. L-ascorbic acid(L-AA), known as vitamin C, may be an alternative source as eco- and bio-friendly fuels since it could be oxidized by donating two electrons the same as its metabolic conversion. The oxidation of ascorbic acid has been studied on various types of electrode materials [16– 21] including platinum group metals, glassy carbon, and conducting polyaniline. However, the high cost of noble metals and their low performance, as well as that of polyaniline and glassy carbon blocked direct ascorbic acid fuel cells (DAAFCs) from being applied in PEFCs. Among them, activated carbon is the most promising anode catalysts because of its large surface area and reactive functional groups. We reported that a modified carbon paper improved its wettability and capacitance, resulting in the higher performance of DAAFCs. In this work, we tried to elucidate how metal oxides could enhance the oxidation kinetics of L-ascorbic acid and investigate what the most effective functional group is for oxidation of L-AA. Metal alkoxides offer a higher and more uniform surface coverage of functional groups and a better control over the surface properties of the resultant Y. E. Kim : J. Lee Electrochemical Reaction and Technology Laboratory/SESE, Gwangju Institute of Science and Technology, Gwangju 500–712, South Korea Y. E. Kim : J. K. Lee : S. Uhm : J. Lee (*) Ertl center for Electrochemistry and Catalysis/RISE, Gwangju Institute of Science and Technology, Gwangju 500–712, South Korea e-mail: jaeyoung@gist.ac.kr M.-Y. Kim : G. Seo School of Applied Chemical Engineering and The Research Institute for Catalysis, Chonnam National University, Gwangju 500–757, South Korea Electrocatal (2011) 2:200–206 DOI 10.1007/s12678-011-0055-0