Air-breathing microfluidic fuel cells with a cylinder anode operating in acidic and alkaline media

•An air-breathing microfluidic fuel cell with a cylinder anode is proposed and tested.•The CO2 gas bubbles can be trapped between the anode and spacer.•The current production is well correlated with the dynamic behavior of CO2 bubbles.•CO2 bubbles improve the internal ohmic resistance by reducing the proton conduction.•The cell performance in the alkaline media is higher than that in the acidic media.

An air-breathing microfluidic fuel cell with a cylinder anode is fabricated and characterized in the acidic and alkaline media. The dynamic behavior of CO2 bubbles is visualized in the acidic media, and its impact on current production is discussed. The effects of electrolyte concentration, reactant flow rate and channel length on the cell performance are also evaluated in the alkaline media. The results show that most of the CO2 bubbles are trapped between the anode and spacer in the acidic media, and the corresponding chronoamperometry curve is well correlated with the bubble movement. Further analysis indicates that the gas bubble improves the internal ohmic resistance by reducing proton conduction. In the alkaline media, the fuel cell yields a much higher performance than the acidic case, and fuel transfer limitation and cathode potential reversal occur at combined low flow rate and high current density. The cell performance is found to be predominated by ohmic resistance at flow rates over 200 μL min−1.

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