Chemical fabrication and synergistic mechanism of N-doped carbon modified with FeP as catalysts for flexible rechargeable Zn–air batteries

Low-cost and efficient electrocatalysts for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are vital for the applications of flexible rechargeable zinc–air batteries (ZABs). Herein, three-dimensional (3D) porous N-doped Paulownia-derived carbon modified with FeP nanoparticles (FeP@NPW) was used as a bifunctional catalyst for flexible rechargeable ZABs. The FeP@NPW electrocatalyst exhibits a first-class bifunctional activity for the ORR and OER. The descriptor ΔE between the half-wave potential of the ORR and the potential of the OER at 10 mA cm−2 was 0.65 V. The flexible rechargeable ZABs have a high open circuit voltage of 1.43 V and superior cycle stability (over 70 h). Coupling 3D hierarchical pores of NPW and FeP facilitates charge exchange, mass transfer, and electron transportation. A high concentration of FeP sites was available during the reaction because of the large specific surface area (798 m2 g−1) of FeP@NPW. The synergistic effects between N-doped biomass-derived carbon and FeP nanoparticles improve the catalytic activity towards the ORR and OER. This work paves the way for the conversion of abundant biomass into high-value engineering products and the application of transition metals in the energy conversion and storage field.