Recent progress in nitrogen-doped carbon and its composites as electrocatalysts for fuel cell applications

► Progress in N/C composites for the ORR in fuel cell applications. ► ORR mechanisms with nitrogen-doped carbon in acidic and alkaline media. ► Nanostructure effects on nitrogen-doped carbon and its composites in the ORR. ► Improvement in ORR activity and stability through use of metal oxides and N/C composites.