Investigation of bubble effect in microfluidic fuel cells by a simplified microfluidic reactor

This study experimentally examines the influence of two-phase flow on the fluid flow in membraneless microfluidic fuel cells. The gas production rate from such fuel cell is firstly estimated via corresponding electrochemical equations and stoichiometry from the published measured current–voltage curves in the literature to identify the existence of gas bubble. It is observed that O2 bubble is likely to be generated in Hasegawa’s experiment when the current density exceeds 30 mA cm−2 and 3 mA cm−2 for volumetric flow rates of 100 μL min−1 and 10 μL min−1, respectively. Besides, CO2 bubble is also likely to be presented in the Jayashree’s experiment at a current density above 110 mA cm−2 at their operating volumetric liquid flow rate, 0.3 mL min−1. Secondly, a 1000-μm-width and 50-μm-depth platinum-deposited microfluidic reactor is fabricated and tested to estimate the gas bubble effect on the mixing in the similar microchannel at different volumetric flow rates. Analysis of the mixing along with the flow visualization confirm that the membraneless fuel cell should be free from any bubble, since the mixing index of the two inlet streams with bubble generation is almost five times higher than that without any bubble at the downstream.