Toward highly efficient bifunctional electrocatalysts for zinc–air batteries: from theoretical prediction to a ternary FeCoNi design

3d Transition-metal nitrogen–carbon nanocomposites (T–N–C, T = Fe, Co, Ni, etc.) with highly active M–Nx sites have received much attention in the field of rechargeable zinc–air battery research. However, how to rationally dope metallic elements to decorate T–N–C catalysts and enhance their electrocatalytic performances remains unclear. Herein, we demonstrated that cobalt-doped Fe-rich catalysts are effective in improving ORR performances by density functional theory (DFT) calculations. On this basis, we reported a kind of novel bifunctional electrocatalyst of hollow nitrogen-doped carbon tubes with coexisting M–N–C single atoms and alloy nanoparticles (denoted FexCoyNiz@hNCTs). Benefiting from the synergistic effect between different components, the as-prepared Fe4Co1Ni2@hNCT catalyst exhibited a small overpotential difference of 0.75 V between an OER potential at 10 mA cm−2 and an ORR half-wave potential, as well as an excellent zinc–air battery performance, when serving as the air cathode. This work provided a scalable design concept for multi-metal doping toward high-performance T–N–C electrocatalysts.