Novel structure for passive CO2 degassing in uDMFC

A new flowfield design enabling fully passive CO2-gas bubble removal from the anode of a micro direct methanol fuel cell (DMFC) is presented. The flowfields channels have an upside down T-shaped cross-section with defined opening angles along their axis and cross-section. The angles create an intrinsic transport mechanism removing growing gas bubbles from the electrode by capillary forces only. Applicable opening angles and are 5° and 1.5° respectively. The experimental verification has been done based on a transparent flowfield and by a fully operational DMFC delivering a power density output of up to 8 mW/cm2 without the need of external pumps. Although the fuel cell supply can be operated both passively and pump assisted, the passive operation shows the highest efficiency.