Modulated FeWO4 electronic structure via P doping on nitrogen-doped porous carbon for improved oxygen reduction activity in zinc–air batteries

Abstract

As a catalyst of the air cathode in zinc–air batteries, tungstic acid ferrous (FeWO₄), a nanoscale transition metal tungstate, shows a broad application prospect in the oxygen reduction reaction (ORR). While FeWO₄ possesses favorable electrochemical properties and thermodynamic stability, its intrinsic semiconductor characteristics result in a relatively slow electron transfer rate, limiting the ORR catalytic activity. In this work, the electronic structure of FeWO₄ is significantly modulated by introducing phosphorus (P) atoms with abundant valence electrons. The P doping can adjust the electronic structure of FeWO₄ and then optimize oxygen-containing intermediates' absorption/desorption efficiency to achieve improved ORR activity. Furthermore, the sodium chloride template is utilized to construct a porous carbon framework for anchoring phosphorus-doped iron tungstate (P–FeWO₄/PNC). The porous carbon skeleton provides numerous active sites for the absorption/desorption and redox reactions on the P–FeWO₄/PNC surface and serves as mass transport channels for reactants and intermediates. The P–FeWO₄/PNC demonstrates ORR performance (E_1/2 = 0.86 V vs. RHE). Furthermore, the zinc–air batteries incorporating the P–FeWO₄/PNC composite demonstrate an increased peak power density (172.2 mW·cm⁻²), high specific capacity (810.1 mAh·g⁻¹), and sustained long-term cycling stability lasting up to 240 h. This research not only contributes to the advancement of cost-effective tungsten-based non-precious metallic ORR catalysts, but also guides their utilization in zinc–air batteries.

Graphical abstract