Bimetallic CoSn nanoparticles anchored on N-doped carbon as antibacterial oxygen reduction catalysts for microbial fuel cells

Abstract

Sluggish oxygen reduction reaction (ORR) kinetics and biofilm formation limit the power generation and stability of microbial fuel cells (MFCs). Herein, bimetallic CoSn nanoparticles anchored on ZIF-derived N-doped carbon (CoSn@NC) were designed and synthesized as bifunctional catalysts to accelerate the ORR and improve the antibacterial activity. Sn modulated the electronic structure of bimetallic CoSn by drawing electrons from Co. Electron redistribution of CoSn@NC optimized the O₂ adsorption at Co sites for rapid ORR kinetics. The up-shifted d-band center of Co sites reduced the energy barrier of the rate-determining step for *O formation, resulting in efficient catalytic activity. Bimetallic CoSn nanoparticles were beneficial for the four-electron transfer process for more ˙OH species production. Sn²⁺ and ˙OH synergistically improved the antibacterial activity of CoSn@NC to inhibit the growth of the cathode biofilm and accelerate mass-charge transfer. CoSn@NC demonstrated superior oxygen reduction activity with a half-wave potential of 0.84 V and an onset potential of 0.90 V, respectively. The MFCs assembled with the CoSn@NC cathodic catalyst exhibited an excellent power density of 1380 mW m⁻² and long-term stability for 105 h. This work provides a strategy for the design of antibacterial ORR catalysts for improved catalytic activity and long-term stability.