Design Concepts for Directed Exit Flow in Micro Fuel Cells

Miniature and micro fuel cells continue to advance as promising alternatives for efficient and portable electric power. This paper presents a study of experimental modifications to the exit flow configuration of microchannels used in small proton-exchange-membrane fuel cells. New concepts for exit geometry are presented, which promote effective water removal and provide reactant back-pressure in an efficient and self-contained manner. Cell assembly is designed such that reactants must necessarily flow laterally through the gas diffusion electrodes near the exit, rather than simply pass over the free backside surfaces of these electrodes. Multiple prototypes were produced using microfabrication techniques with channel sizes of 100 and 200 microns, and performance was tested using a hydrogen-air test station with programmable electronic load. One of the new concepts in particular showed a marked improvement from 28 mW/cm2 peak power density under baseline conditions to 37 mW/cm2 for the modified design under similar operating conditions. The design offers an opportunity for higher performance in miniature fuel cells with low gas consumption and no additional cost.