Electrocatalytic performance of samples and related devices. (a) LSV and (b) Tafel slope of fabricated samples and 20% Pt/C in oxygen-saturated 0.1 M KOH electrolyte with 1600 rpm. (c) The HO2- yields of fabricated samples and 20% Pt/C derived from RRDE. (d) The schematic diagram of Zn-air battery. (e) The discharging plots of SA-Cu/NG-based battery as well as 20% Pt/C constructed one. (f) The total 82 h voltage curves as well as the enlarged 1-10 h and 75-82 h cycle voltage for SA-Cu/NG+IrO2 and contrast batteries.