| Summary: | 碩士 === 國立成功大學 === 工程科學系 === 102 === In the present study, we demonstrated the fabrication of an energy conversion microchip using the standard microelectromechanical technique. This device was constructed using two microchannels connecting with Nafion junction, which performed cation selectivity fabricated by the process of surface patterned. According to the theory of reverse electrodialysis, when a concentrated salt solution and a diluted salt solution are separated by an ion-selective membrane, cations and anions would diffuse at different rates depending on the ion selectivity of the membrane; the difference of positive and negative charges at both ends of the membrane would produce a potential, called the diffusion potential. The experiment was conducted using Ag/AgCl electrodes and KCl solution, and the highest diffusion potential and diffusion current measured was 90.7mV and 54.1pW, respectively. To understand the properties of Nafion junction better, we used electrolytes at different pH values (4.0, 6.4, and 10.0). The results indicated that Nafion junction showed the maximum diffusion potential at pH 6.4and the lowest diffusion potential at pH 4.0. This finding implies that ion selectivity of Nafion decreased when additional H+ and OH-existed in the solution, as these ions would associate with water molecules and weaken the –SO3- groups of Nafion. Moreover, as the mobility of H+ is higher than that of OH-, H+ reduced the surface charge to a greater extent than OH-.
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