NiFe-LDH loaded on N-doped Paulownia-derived carbon as a bifunctional oxygen electrocatalyst for rechargeable zinc–air batteries

Abstract

Rational design of low-cost and high activity bifunctional oxygen electrocatalysts is necessary for advancing the performance of rechargeable Zn–air batteries (RZABs). Herein, 2D NiFe layered double hydroxide (NiFe-LDH) nanosheets supported on 3D N-doped biomass-derived carbon (NBC) were prepared by pyrolysis and in situ electric field assisted deposition using green and renewable Paulownia wood as a precursor (NiFe-LDH/NBC), simultaneously, avoiding the use of toxic reagents and achieving the green synthesis of catalysts. The half-wave potential (E_1/2) of the oxygen reduction reaction (ORR) on NiFe-LDH/NBC is 0.85 V, with a maximum current density of 5.90 mA cm⁻². The potential of the oxygen evolution reaction (OER) at j = 10 mA cm⁻² (E_j=10) is 1.47 V. The potential difference (ΔE) between the E_1/2 value of the ORR and the E_j=10 value of the OER reaches 0.62 V, lower than those of most similar catalysts previously reported. Aqueous RZABs assembled with NiFe-LDH/NBC as cathode electrocatalysts show a high peak power density of 155.9 mW cm⁻² and an excellent durability of over 360 h. The hierarchical porous structure of the carbon support accelerates electron transfer and mass transport during the reaction, and the strong coupling interaction between NBC and NiFe-LDH enhances the overall catalytic performance. This work provides a new path in line with the concept of green chemistry for the design of efficient and environmentally friendly non-noble metal catalysts in RZABs through the sustainable utilization of biomass resources and green synthesis strategies.