Ultrahigh-loaded Fe single atoms and Fe₃C nanoparticle catalysts as air cathodes for high-performance Zn–air batteries

Qi Yang ^†, Rumeng Liu ^†, Yanan Pan ^†, Zheng Cao ^†, Jiabao Zuo ^†, Fan Qiu ^†, Jian Yu ^†, Haiou Song ^‡, Zhiwen Ye^†, Shupeng Zhang ^{†, *}

ABSTRACT

Fe-based materials containing Fe-Nx sites have emerged as promising electrocatalysts in the oxygen reduction reaction (ORR), but they are still suffering from structural instability which may lead to loss of catalytic activity. Herein, a novel electrocatalyst Fe₃C-FeSA@3DCN with coexistence of Fe₃C nanoparticles and Fe single atoms (FeSA) in a three-dimensional conductive network (3DCN) is prepared via lattice confinement and defect trapping strategies with a Fe atomic loading of as high as 4.36%. In the ORR process, the limiting current density of Fe₃C-FeSA@3DCN reaches 5.72mA cm^-2, with an onset potential of 0.926V and a Tafel slope of 66mV/decade, showing better catalytic activity and stability than Pt/C catalysts. Notably, its assembled aqueous and solid-state Zn-air batteries (ZAB) achieve peak power densities of 166 and 56 mW/cm², respectively, with a long service life of up to 200 hours at a current density of 5 mA cm^-2. In addition, the assembled ZAB can provide a constant voltage on activated carbon electrodes to perform capacitive deionization to adsorb different ions. The importance of the Fe species active sites generated by Fe₃C and FeSA in the material for ORR activity to boost the electron transfer and mass transfer is demonstrated by a simple selective poisoning experiment. 

CONCLUSIONS

In conclusion, we designed stable 3DCN structures by simple metal ion anchoring and hydrothermal treatment, and prepared Fe₃C-FeSA@3DCN catalysts by introducing abundant Fe species using lattice-confinement and defect-trapping strategies. Through characterization analysis, abundant Fe₃C nanoparticles and FeSA were uniformLy dispersed on the carbon layer and CNTs of Fe₃C-FeSA@3DCN. Using a simple selective poisoning experiment, the effect of Fe₃C nanocrystals and FeSA-generated active sites on ORR activity was elucidated. Comparing with the commercial Pt/C catalyst, Fe₃C-FeSA@3DCN showed good ORR activity and stability. When used as an air electrode, it provided a power density of 166 mW/cm² and exhibited long-term stability at different current densities. This finding provided a versatile and reliable method for designing high metal content nanoparticles and single atom catalysts for energy storage and conversion.

 原文链接：https://pubs.acs.org/doi/10.1021/acsami.2c21751