Table 1. Summary of the Efficiency Metrics of the Graphene-O₂:N₂-4 Pa VRFBs Using Nafion 115 or Nafion XL^a.

Nafion	current density (mA cm–2)	CE (%)	VE (%)	EE (%)
115	25	97.1	96.7	93.9
	50	97.1	93.4	90.8
	75	97.8	90.3	88.3
	100	98.0	86.9	85.2
XL	100	97.1	88.2	85.64
	200	97.7	79.4	77.57
	300	98.8	70.3	69.45

^aThe values have been extrapolated from the galvanostatic CD measurements at various current densities and correspond to the second CD cycle.