Characteristics of Nafion Membranes with Pd Thin Films Deposited by DC Magnetron Sputtering Technique

Modified polymer electrolyte membranes were fabricated by the applying dc magnetron sputter-deposited Pd thin layers on the surface of the $Nafion^{TM}$ membranes in argon atmosphere. The Pd thin films were characterized by investigating its morphology, methanol permeability, and protonic conductivity. The performance of a direct methanol fuel cell(DMFC) with the modifed polymer electrolyte membrane was also tested by the measurement of its currents and voltages under flowing methanol. The Pd thin film could be a barrier layer to methanol crossover, but the protonic conductivity of the modified polymer membrane was reduced. By using the modified polymer eletrolyte membranes, both the methanol permeability and the protonic conductivity were decreased with increasing the thickness of Pd thin film. However, the performances of DMFC were almost independent on the thickness of Pd thim films. The efffcts of methanol concentration in a feeding fuels on the protonic conductivity and the cell performance were also investigated.

DC마그네트론 스퍼터링으로 Pd박막 입힌 Nafion막의 특성

상용 고분자 전해질인 Nafion 115 및 Nafion 117막 위에 do magnetron sputtering방법으로 Pd박막을 다양한 두께로 증착한 다음, 개질된 고분자 전해질 막의 morphology, proton 전도도(conductivity), 메탄을 투과도(permeability)를 측정하였으며, membrane and electrode assemblies(MEA)를 구성하여 DMFC 단위전지 성능을 측정하였다. Pd 박막은 Nafion막이 지니고 있는 단점인 메탄을 crossover에 대한 barrier로서 작용하였지만, 동시에 Nafion막의 고유 특성인 proton전도도의 감소를 가져왔다. Pd박막에 의하여 개질된 Nafion막의 메탄올에 대한 투과도와 proton전도도는 Nafion 막 상에 증착된 Pd 박막의 두께가 증가할수록 직선적으로 감소하는 경향을 나타냈다 개질된 Nafon 막을 사용하여 제작한 direct methanol fuel cell(DMFC)단위전지의 성능은 전체적으로 약간 저하되었다.