|M.Sc Student||Gaponenko Vladimir|
|Subject||High Surface Area Carbon Anode for Glucose Fuel Cells|
|Department||Department of Chemical Engineering||Supervisors||Professor Yachin Cohen|
|Professor Eyal Zussman|
|Full Thesis text|
Glucose fuel cells are among the most promising green energy suppliers. Glucose has several advantages over other fuels: it is safe, cheap, easy to transport, and renewable. This work focuses on an anode for alkaline fuel cells in which the fuel (glucose) is mixed with the electrolyte. The electrodes, fabricated using electrospinning, are based on polyacrylonitrile (PAN) and carbon nanotubes (CNT). They were coated with three metal catalysts: silver by sputter deposition, gold by electron beam deposition, and PtRu by dripping the PtRu on carbon -black dispersion. The solvents in the latter method were Nafion dispersion in water and propanol, and the same solvent without Nafion. The role of the polymer is to function as an adhesion promoter. As seen by scanning electron microscope (SEM), in the case of silver and gold, the electrode was totally coated by the catalyst. The silver coating was comprised of grains (~20 nm in diameter), while gold coated the electrode more evenly. In case of PtRu, when the suspension included Nafion, the electrode pores were totally blocked. When the suspension did not include Nafion, the carbon fibers were coated with clusters, consisting of metal catalyst and carbon black.
Gold and PtRu electrodes were activated in plasma before the metallization, which significantly increases the hydrophilicity of the electrode: in addition to removing the oily molecules it attaches polar oxygen groups onto the electrode surface. This was confirmed by X-ray photoelectron spectroscopy (XPS) study: the electrode surface oxygen concentration rises from 1% to 15%, altering the oxygen-to-carbon ratio from 0.01 to 0.2. These catalysts were tested in cyclic voltammetry: they showed high activity towards glucose electrochemical oxidation. After adding 0.6M glucose, the currents of existing peaks increased from 0.01 A/cm2 for blank to 0. 13 A/cm2; furthermore new peaks appeared around 0V vs. saturated calomel electrode (SCE), corresponding to glucose oxidation.
All the catalyst types were evaluated in the fuel cell. Polarization and power density curves were made. The open circuit voltage was 0.4, 0.59, and 0.89 V for silver, gold, and PtRu (without Nafion) catalysts. The maximum power density was 10.3, 157, and 643?W/cm2 respectively. Thus, carbonized PAN/CNT electrode, activated and then metallized may form a promising basis for glucose fuel cell anodes.