Graphene Oxide Enhanced Proton Exchange Membrane Fuel Cell
Gen Yuan (Bill) Chen
Prince of Wales Secondary
Floor Location : S 086 E
Hydrogen fuel cells emerged as a promising area of development with high theoretical efficiency limits and practically zero emission. However, costs of manufacturing and poor actual performance have rendered operation costs higher than other types of energy sources.
We hope to address the problem of fossil fuel over-consumption by improving the technology to a point of naturally driving down the energy price through upgrading the performance of Proton Exchange Membrane Fuel Cell (PEMFC). PEMFC is a type of fuel cell applicable to various everyday energy needs due to its low operation temperature and its polymer electrolyte’s excellent mechanical stability. PEMFC presents a set of challenges, namely its demand for extremely high purity fuel source and difficulty in proper hydration of the membrane. Its need for high purity fuel stems from the well-known poisoning phenomenon of the Platinum (Pt) catalyst by carbon monoxide (CO). CO concentrations as low as 10ppm can significantly reduce the efficiency of the fuel cell by adsorbing to Pt catalysts and occupying its active sites. The polymer electrolyte also requires proper hydration to achieve full performance as its proton conductivity is greatly affected by dehydration.
We hypothesize that graphene oxide can improve the performance of fuel cells due to its excellent water uptake potential, proton conductivity and theorized CO oxidation potential.
Nano Graphene Oxide (GO) Powder was purchased and dissolved in various solvents (Methanol/DI water, Isopropanol/DI water, DMF). The solutions were sonicated, stirred overnight and further sonicated before use. We made attempts to obtain the isothermal curve for each solution using the Wilhelmy plate method on LB trough but the pressure failed to build due to GO flakes’ tendency to sink beneath the subphase surface. However, we were able to maintain the surface pressure at 1mN/m and coated the NafionTM 117 membranes at 1mN/m target surface pressure. We then tested the membranes in H-tech PEMFC kit with open air environment at the cathode, fed pure Hydrogen into the anode, and collected Polarization curves and Power-Current curves. The comparison reveals that fuel cells coated with graphene oxide dissolved with isopropanol to have the best performance with as much as 81% improvement in maximum power output over control (Fig.1). We hypothesized that the performance increase was a result of the GO coating oxidizing CO into CO2 and preventing the catalyst poisoning phenomenon.
We tested the hypothesis of CO elimination through catalyzed oxidation mechanism by replacing the open air environment at the cathode with high purity oxygen. An improvement of more than 27% (Fig.2) in the absence of CO indicates that the improvement was not due to the elimination of CO alone. We also investigated the durability of the fuel cell was through the use of an industrial test station (Fuel Cell Technologies, INC) at the current density of 0.6A/cm2. We found the coated fuel cell to have a significantly lower operating voltage drop after 5 hours of continuous operation. Examinations of other theories in the future is imperative to confirm the exact mechanism of the improvement.