| Summary: | 博士 === 國立聯合大學 === 材化博士學位學程 === 101 === The development of fuel cell is depending on many variables. Thisresearch studies in four different aspects of proton exchange membrane fuel cell (PEMFC).Part one is studied the source of fuel cell reactant gas,hydrogen production from ammonia decomposition by Cs-Ru catalyst. The effect of Cs-Ru catalyst on hydrogen production by ammonia decomposition was studied. By using reduction process and precipitation method, the Ru was precipitated on nitric acid treated carbon powder. The ammonia conversion percentage and hydrogen formation rate at different catalyst compositions and operating conditions were measured. Factors consider includes Cs-Ru composition, ammonia inlet flow, and reformer reaction temperature, converted, catalyst loading, and Cs promoter ratio. The catalyst was characterized by Fourier transform infrared spectroscopy (FTIR), contact angle meter (CA), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), and X-ray diffraction analyzer (XRD). The results show that higher Ru content catalyst can be obtained by precipitation method than by reduction process. Catalyst with high Cs promoter enhances reaction conversion effectively. The hydrogen formation rate reached 29.8 m mol/min-gcat and ammonia conversion rate reached 90 % when ammonia inlet flow rate at 6 mL/min with reaction temperature at 400 oC.
Part two is studied the fabrication process of membrane electrode assembly (MEA) for PEMFC. The effects of catalyst slurry composition on the slurry rheological behavior and Pt catalyst active surface area was measured and analyzed. The effect of hot-press temperature and pressure on fuel cell performance was then studied. The cell performance was measured by voltage-current curve, current-power curve, cyclic voltammetry, and AC impedance. Optimal processing condition for the MEA of PEMFC was found. As shown in the results, with ethylene glycol solvent addition, better dispersionand stability of Pt catalyst in slurry was obtained. The Pt catalyst effective active area was substantially increased. Single cell discharge performance reached up to 1428 mA /mg Pt. The MEA hot-pressing optimal conditions are at 1200psi, 135 oC for 90 seconds.
Part three is using experimental design to evaluate the PANI-Pt processing condition of MEA for direct methanol fuel cell (DMFC). Three methods including fractional factorial design (FFD), response surface method, and central composite design (CCD) were used. We foundthat PANI sediment extent and PANI growth temperature were the key conditions that affecting methanol oxidation current. Methanol oxidation currents were fitted by regression equation and results were plotted onto contour map. As shown in the contour map, the optimal methanol oxidation current 35 mA/cm2/mg Pt, can be obtained under conditions of PANI sediment extent at 0.130 C/cm2 and PANI temperature at 25 oC.
In part four, the MEA optimal process conditions of PEMFC are found by using the statistics tool. The main affecting conditions are: anode catalyst layer thickness, cathode catalyst layer thickness, MEA hot-pressing temperature and pressure. From the fractional factorial design results, cathode catalyst layer thickness and hot-press temperature are the key conditions that affecting PEMFC performance. The response surface method and central composite design results indicate that optimal processing conditions of MEA for PEMFC are: cathode catalyst layer thickness is 170 μm, hot-pressing temperature at 135 oC. Single cell has optimal current density of 3500 mA/mg Pt. The performance was enhanced almost twice as comparing to prior process conditions (1428 mA/mg Pt).
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