Ultrahigh-Loaded Fe Single Atoms and Fe₃C Nanoparticle Catalysts as Air Cathodes for High-Performance Zn–Air Batteries

Abstract

Fe-based materials containing Fe-Nx sites have emerged as promising electrocatalysts in the oxygen reduction reaction (ORR), but they still suffer structural instability which may lead to loss of catalytic activity. Herein, a novel electrocatalyst Fe 3 C-FeSA@3DCN with the coexistence of Fe 3 C nanoparticles and Fe single atoms (FeSA) in a three-dimensional conductive network (3DCN) is prepared via lattice confinement and defect trapping strategies with an Fe atomic loading of as high as 4.36%. In the ORR process, the limiting current density of Fe 3 C-FeSA@3DCN reaches 5.72 mA cm −2 , with an onset potential of 0.926 V and a Tafel slope of 66 mV/decade, showing better catalytic activity and stability than Pt/C catalysts. Notably, its assembled aqueous and solid-state Zn−air batteries (ZABs) achieve peak power densities of 166 and 56 mW cm −2 , respectively, with a long service life of up to 200 h 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 Fe 3 C and FeSA in the material for ORR activity to boost the electron transfer and mass transfer is demonstrated by a simple selective poisoning experiment.

Recent advances in Fe‐N‐C single‐atom site coupled synergistic catalysts for boosting oxygen reduction reaction

“…60 Notably, the relatively larger apertures of this benzimidazole-based ZIF (with a cage aperture of 14.6 Å), when compared to imidazole-based ZIF-8 and ZIF-67, rendered it suitable for hosting MPc, thereby facilitating the uniform dispersion of metal atoms during pyrolysis. Recently, Yang et al 78 employed a lattice confinement and defect trapping approach, resulting in the creation of a 3D conductive network formed by amino-carbon nanotubeinterconnected structures derived from ZIF-90. This network integrated FeSA and Fe 3 C nanoparticles.…”

“…The construction began with triethylamine deprotonated imidazole dicarbaldehyde to form the ZIF-90 precursor, which was then blended with Fe 3þ and NaCl (to facilitate uniform dispersion of Fe atoms) salts, followed by the carbonization process. 78 Besides ZIF-based precursors, Huang et al 75 employed an Fe-MOF for ACs coupled SACs preparation by precipitating potassium hexacyanoferrate and polyvinylpyrrolidone. As obtained Fe-MOF was subsequently coated with PDA and carbonized under an NH 3 atmosphere to achieve the desired nitrogen content, which yielded Fe nanoparticle-associated Fe SACs (Fe-NPSA@NC, Figure 2F).…”

“…This network integrated FeSA and Fe 3 C nanoparticles. The construction began with triethylamine deprotonated imidazole dicarbaldehyde to form the ZIF‐90 precursor, which was then blended with Fe 3+ and NaCl (to facilitate uniform dispersion of Fe atoms) salts, followed by the carbonization process 78 …”

Electrospinning-derived transition metal/carbon nanofiber composites as electrocatalysts for Zn-air batteries

“…Noble metal catalysts, characterized by d-band centres in proximity to the Fermi level, ensure an optimal adsorption energy towards oxygen intermediates, thereby manifesting efficient catalytic performance. [78][79][80][81][82] In the context of TMs/CNF composites, various strategies such as hybridization with other atoms, interface engineering, and defect engineering can be employed to modify the electronic structure of the active centre. These modifications enable the active centres to possess a suitable adsorption energy towards oxygen intermediates.…”