Metallopolymer nanowalls were prepared through a simple wet-chemical process using reduced graphene oxides as heterogeneous nucleation aids, which also help to form conductive electron paths. The nanowalls grow vertically on graphene surface with 100 -200 nm in widths and ∼20 nm in thickness. The Fe-based metallopolymer nanowall-based electrode shows best performance as O2 cathode exhibiting high round-trip efficiencies and stable cycling performance among other transition metal containing metallopolymer counterparts. The electrode delivers discharge–charge capacities of 1000 mAh/g for 40 cycles and maintains round-trip efficiencies >78 % at 50 mA/g. The 1st-cycle round-trip efficiencies are 79%, 72%, and 65% at current densities of 50, 200, and 400 mA/g, respectively. The NMR analysis of the Fe-based metallopolymer based electrode after 40 cycles reveals slow formation of the side products, CH3CO2Li and HCO2Li.