Liquid fuel crossover, experimental

The catalytic (supported or unsupported) interface in the vast majority of direct liquid fuel cell studies is realized in practice either as a catalyst coated membrane (CCM) or catalyst coated diffusion layer (CCDL). Both configurations in essence are part of the electrode design category, which is referred to as a gas diffusion electrode, characterized by a macroporous gas diffusion and distribution zone (thickness 100-300 pm) and a mainly mesoporous, thin reaction layer (thickness 5-50 pm). The various layers are typically hot pressed, forming the gas diffusion electrode-membrane assembly. Extensive experimental and mathematical modeling research has been performed on the gas diffusion electrode-membrane assembly, especially with respect to the H2-O2 fuel cell. It has been established fliat the catalyst utilization efficiency (defined as the electrochemically available surface area vs. total catalyst surface area measured by BET) in a typieal gas diffusion electrode is only between 10-50%, hence, flie fuel utilization eflfieieney can be low in such electrodes. Furthermore, the low fuel utilization efficiency contributes to an increased crossover rate through the membrane, which deteriorates the cathode performance. 

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