| Summary: | 博士 === 國立清華大學 === 工程與系統科學系 === 100 === A silicon-based and fully integrated micro proton exchange membrane fuel cell (μ-PEMFC) system is introduced in this paper, which carry out high efficient catalyst utilization and outstanding cell performance. The system size is comparable to an AA battery and consumes a very low fuel requirement (20 ml/min of hydrogen at the anode, and 40 ml/min of oxygen at the cathode). The novel design integrates micro- and nano-structures that leads to higher reaction rate due to larger surface areas, reduced impedance of fuel diffusion due to micro-patterned radial type reaction chamber incorporating a spinning-in proces that creates extra three-phase zones, and improved interfacial strength and reduced ohmic impedance due to micro-interlocks of a single cell. The best performance in the current study is 26 mW/cm2 with only 0.69 mg/cm2 of Pt catalyst; namely, a catalyst utilization ratio of 38 W/g, and is superior to the present micro-fuel cells.
New technologies being developed in this study include the design and fabrication of micro-electrodes, micro-system package, micro-electrodes testing and the integration of a micro-fuel cell system. The processes being employed in this study include micro-lithography, silicon wet and dry etching, thin metal film deposition, chemical vapor deposition, electro-less Pt deposition and micro-fluidic manipulation. Electrochemical cyclic voltammetery (CV) and electrochemical impedance spectrum (EIS) were employed to verify the cathodic efficiency. Half cell testing results indicate the best cathodic performance corresponds to the 3000 rpm liquid NafionR spinning-in condition, which shows a 42.5 mA/cm2 cathodic efficiency and an oxygen diffusion impedance and charge transfer impedance of 2.32 Ω-cm2 and 4.49 Ω-cm2 , respectively. Polarization curves also perform a best power density of 26 mW/cm2, which also corresponds to the 3000 rpm liquid NafionR spinning-in condition. As a result, the integrative micro-silicon base cathoidc electrode could be adopted by whether the direct methanol fuel cells, proton exchange membrane fuel cells or reforming type direct methanol fuel cells. Finally, the study possesses a high potential for the realizing of the commercial mobile micro-power generators in the future.
|
|---|
