| Summary: | 碩士 === 國立高雄應用科技大學 === 機械與精密工程研究所 === 103 === The performance of air-breathing direct formate microfluidic fuel cells using the mixture of Potassium hydroxide and Potassium formate solution as fuel under various operating conditions, including the flow rates of fuel, operating temperature, catalyst loading, reactant concentration and Nafion content, was tested and investigated. Also, the performance comparison of the direct formate microfluidic fuel cells was also made between the fuel cells with 0.5-M H2SO4 and the fuel cells with 1.0-M or 2.0-M KOH as liquid electrolyte. Besides, flow visualization was also performed during the experiment. The Nafion content in the anode was 3.73 mg/cm2, 5.6 mg/cm2, and 7.46 mg/cm2 and the concentration of Potassium formate was 1.0 M and 2.0 M. The microfluidic fuel cells were operated with flow rate of fuel ranging from 0.1 to 0.6 mL/min at temperature of 300C, 400C and 500C.
The result suggests that the cell performance becomes higher as the operating temperature of the fuel cell gets higher. Because no gas bubble could be observed in the microchannel as the KOH solution was used as electrolyte, the cell output of the fuel cell using alkaline electrolyte would not significant increased with the increase of flow rate. Besides, the Nafion was used as binder in the anode which affected both the electrode reliability and cell performance. Although direct formate microfluidic fuel cells using 0.5-M H2SO4 as electrolyte had much higher open circuit potential, the electricity generation was so unstable because the numerous gas bubbles occupied the microchannel before electrochemical reaction.
As the Pd loading loading was 2.0 mg/cm2 with Pd/C ratio of 30% and Nafion content was 5.6 mg/cm2 in the anode, concentration of Potassium formate was2.0M, concentration of Potassium hydroxide electrolyte was 2.0M, and the volume flow rate was 0.1 mL/min, the maximum current density and power density of the air-breathing direct formate microfluidic fuel cells reached 469 mA/cm2 and 111 mW/cm2, respectively, at operating temperature of 500C with [KOH] = 2.0 M and [HCOOK] = 2.0 M as fuel and electrolyte.
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