Fuel Cell Polarization Curve.

The performance of the fuel cell is characterized through its output voltage (blue, left axis) and power density (red, right axis) as functions of output current density. A 2 mm² device exhibits an open-cell voltage of 192 mV and achieves maximum power output of more than 180 µW cm⁻² when sourcing 1.5–1.85 mA cm⁻².