Core-shell catalysts are effective to improve the stability of Pt in the oxygen reduction reaction (ORR). Adding nitrogen (N) into transition metal (TM) core is a novel way for the substantial reduction in Pt loading while retaining high ORR activity. Core-shell electrocatalysts containing Pt shell with TM (TM =- Ti, V, Mn, Fe, Co, Ni, and Cu) and transition metal nitride (TMN) cores were investigated using density functional theory (DFT). The dissolution potential, binding energy of oxygen (BE-O) and hydroxyl (BE-OH), surface strain, and d-band center were calculated on TM13@Pt-134 and TM12N@Pt(134 )catalysts in oder to investigate the stability and ORR activity. The calculation results indicated that compared to the corresponding non-nitrogen nanoparticles, TMN cores resulted in higher dissolution potential and surface strain, lower BE-O, and downshift of d-band center. Among the investigated catalysts, Cu12N@Pt-134 showed a comparable activity with pure Pt catalyst. The former preferred a dissociative mechanism to an associated mechanism in the ORR pathway, with the Gibbs free energy change (Delta G) of 0.88 V in the rate-determining step. This study will contribute to the accurate identification and innovative design of promising core-shell electrocatalysts toward ORR in fuel cell applications. (C) 2018 Elsevier B.V. All rights reserved.