Current density distribution in air-breathing microfluidic fuel cells with an array of graphite rod anodes

Abstract Scale-up is required in the practical application of microfluidic fuel cells. Using an array of electrodes is demonstrated as a promising way. However, the non-uniform current density distribution in array anodes will significantly limit the power output. In this study, current density distribution in air-breathing microfluidic fuel cells with an array of graphite rod anodes is tested under acidic and alkaline conditions. The array anode is divided into four layers according to their distance to cathode. Current density of each layer is recorded individually. The cell performance under alkaline media is better than that under acidic media and various current density distributions are found under different media. When the air-breathing microfluidic fuel cell is operated under acidic media, at current densities lower than 50 mA cm−3, current densities of two-layer anodes far from the cathode are higher than that of the other layers, while the reverse happens at current densities higher than 50 mA cm−3. This is mainly due to the enhanced fuel transport caused by CO2 bubbles and the lower ohmic resistance. Moreover, the generated CO2 bubbles lead to fluctuation of discharging densities especially at low voltages. However, for the air-breathing microfluidic fuel cell operated under alkaline media, two-layer anodes far from the cathode are main contributor to the total current density at all operation voltages.