Saudi Universities Theses & Dissertations
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Item Restricted Unsteady state performance of porous gas-diffusion electrodes in alkaline fuel cell(Saudi Digital Library) Abu Ibrahim InamahThe unsteady state method of employing exponential decay current was used to determine the performance of the hydrogen electrode of the alkaline fuel cell. A triangular wave technique was also carried out in a separate investigation in order to compare the results with that of the exponential decay current. The study was undertaken in a half-cell. The fuel was pure hydrogen and the electrolyte was a 25% solution KOH. The electrode used was a Raney-Nickel supplied by DLR of Germany. The experiments were carried out for the temperature range of 30$spcirc$C-65$spcirc$C. In the exponential current technique, the input currents were generated from the discharge of capacitors of different sizes. The responses of the fuel cell to the input currents were then analysed to determine the intrinsic parameters such as the exchange current densities i$sb{rm o}$, and the double layer capacitances C$sb{rm T}$. The activation energy and the surface roughness factors were also determined. The ranges of values obtained for the exchange current densities and the double layer capacitance were (1.05-11.9) $times$ 10$sp{-6}$ A/cm$sp2$ and (91-104) $times$ 10$sp{-3}$F respectively for the temperature range of the investigation. The activation energy was found to be 4.15 kcal/gmol and the surface roughness factor at 65$spcirc$C was 34 $times$ 10$rm sp{-4}cmsp2/cmsp2$. It was realised that both the exchange current density and the surface roughness factor were high while the activation energy was low compared to that reported earlier in the literature. These results showed that the electrodes have better performance due to the improved preparation techniques. An increase in temperature also promoted more electrochemical reactions to lake place resulting in the increase of the performance of the fuel cell.0 0Item Restricted An enhanced convex-elastic net technique for solving E-TSP(Saudi Digital Library) Abu Ibrahim InamahThe unsteady state method of employing exponential decay current was used to determine the performance of the hydrogen electrode of the alkaline fuel cell. A triangular wave technique was also carried out in a separate investigation in order to compare the results with that of the exponential decay current. The study was undertaken in a half-cell. The fuel was pure hydrogen and the electrolyte was a 25% solution KOH. The electrode used was a Raney-Nickel supplied by DLR of Germany. The experiments were carried out for the temperature range of 30-C-65-C. In the exponential current technique, the input currents were generated from the discharge of capacitors of different sizes. The responses of the fuel cell to the input currents were then analysed to determine the intrinsic parameters such as the exchange current densities I and the double layer capacitances C. The activation energy and the surface roughness factors were also determined. The ranges of values obtained for the exchange current densities and the double layer capacitance were (1.05-11.9) x10⁻⁶ A/cm² and (19-104) x10⁻³F respectively for the temperature range of the investigation. The activation energy was found to be 4.15 kcal/gmol and the surface roughness factor at 65⁰C was 34x10⁻⁴CM²/CM². It was realised that both the exchange current density and the surface roughness factor were high while the activation energy was low compared to that reported earlier in the literature. These results showed that the electrodes have better performance due to the improved preparation techniques. An increase in temperature also promoted more electrochemical reactions to take place resulting in the increase of the performance of the fuel cell.3 0