Electrochemical selectivity and electro-osmosis in direct methanol fuel cell electrolytes

While much progress has come in the development of direct methanol fuel cells (DMFCs), one specific barrier that still limits the performance of DMFCs is the excessive permeation of methanol through the present polymer electrolytes.; While proton conductivity is essential to these membranes, the role of methanol permeability has been less studied. A quantitative basis for evaluating the electrolyte in terms of DMFC performance has been established. This basis, electrochemical selectivity, allows evaluation of potential DMFC electrolytes. A number of polymers have been characterized in terms of this basis.; Electro-osmosis and related phenomena were studied in an attempt to determine the factors that influence electrochemical selectivity in different polymer media. Model systems were investigated chosen due to differences in chemical and physical properties.; Composite membranes were investigated as a source of improved performance in DMFCs. These experiments provided justification of our choice of electrochemical selectivity as a basis for evaluating DMK electrolytes, and also demonstrated the importance of operating conditions on cell performance.; The results of this work allow polymers to be evaluated as potential DMFC electrolytes, and targets polymer systems for improved DMFC performance.