Recently, impacts of ion transport and electrostatic potential in the electrical double layer (EDL) are turning out to be significant in various catalytic reactions. This study systematically evaluated the oxygen reduction reaction (ORR) activity of HCP and FCC cobalt core–shell cobalt/ N-doped carbon (Cobalt@NC) electrocatalyst via theoretical and experimental studies. Our electronic structure calculations using density functional theory (DFT) calculations revealed that the ORR activity of the N-doped carbon layer could be improved by i) switching the electrostatic potential of the ELD, due to the polarization induced at the carbon-cobalt interface and ii) modulating the electron population in the bonding orbital in the C-O bonds in an ORR. The results revealed that an O atom is bounded stronger to the outer NC shell with FCC Cobalt than HCP Cobalt, which hindered the desorption steps of OH*. Experimentally, plasma-engineered HCP Cobalt@NC also showed remarkably advanced performance towards ORR compared to that FCC Cobalt@NC. Specifically, HCP Cobalt@NC exhibited a half-wave ORR potential of 0.851 V vs. RHE and kinetic current density of 39.64 mA/cm2, and a similar peak power density (110 mW/cm2) as 20 wt.% Pt/C as a cathode catalyst in a practical Aluminum-air battery.