The energy density delivered by the vanadium oxide anode
fuel cells after shutting the fuel supply off ranged from 8 to 140
mJ cm−2, as shown in Figure 2c. The highest energy density
measured was 140 mJ cm−2 for the 27 nm thick VOx/Pt anode
cell at 360 °C at a current density of 7.8 mA cm−2. The energy
density increased with the current density up to the current
density at which the fuel cell operates at maximum power
density.