Metal–organic framework–derived trimetallic particles encapsulated by ultrathin nitrogen-doped carbon nanosheets on a network of nitrogen-doped carbon nanotubes as bifunctional catalysts for rechargeable zinc–air batteries

[Display omitted] •The CoNiFe0.08-NC@p-NCNTs is synthesized by DBD plasma treatment.•NC encapsulated CoNiFe NPs constructed nanosheets distribute on the network of NCNTs.•The CoNiFe0.08-NC@p-NCNTs is demonstrated to be an excellent catalyst for ORR/OER.•It shows great potentials in improving the performance of rechargeable ZABs.•The assembled flexible all-solid-state ZAB exhibits a high OCV of 1.384 V. Economical oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) bifunctional catalysts with high activity aimed at replacing precious metal catalysts for rechargeable zinc-air batteries (ZABs) must be developed. In this study, a multiple hierarchical-structural material is developed using a facile dielectric barrier discharge (DBD) plasma surface treatment, solvothermal reaction, and high-temperature carbonization strategy. This strategy allows for the construction of nanosheets using nitrogen-doped carbon (NC) material-encapsulated ternary CoNiFe alloy nanoparticles (NPs) on a network of NC nanotubes (NCNTs), denoted as CoNiFe–NC@p–NCNTs. Precisely, the presence of abundant CoNiFe alloy NPs and the formation of M–N–C active sites created by transition metals (cobalt, nickel, and iron) coupled with NC can provide superior OER/ORR bifunctional properties. Moreover, the prepared NC layers with a multilevel pore structure contribute to a larger specific surface area, exposing numerous active sites and enhancing the uniformity of electron and mass movement. The CoNiFe0.08–NC@p–NCNTs show remarkable dual functionality for electrochemical oxygen reactions (ORR half-wave potential of 0.811 V, limiting current density of 5.73 mA cm−2 measured with a rotating disk electrode at a rotation speed of 1600 rpm, and OER overpotential of 351 mV at 10 mA cm−2), which demonstrates similar ORR performance to 20 wt% Pt/C and better OER performance than the commercial RuO2. A liquid ZAB prepared using the proposed material has excellent bifunctionality with an open-circuit voltage of 1.450 V and long-term cycling stability of 230 h@10 mA cm−2.