Single‐atom Iron Catalyst with Biomimetic Active Center to Accelerate Proton Spillover for Medical‐level Electrosynthesis of H₂O₂Disinfectant

Abstract

Electrosynthesis of H2O2 has great potential for directly converting O2 into disinfectant, yet it is still a big challenge to develop effective electrocatalysts for medical‐level H2O2 production. Herein, we report the design and fabrication of electrocatalysts with biomimetic active centers, consisting of single atomic iron asymmetrically coordinated with both nitrogen and sulfur, dispersed on hierarchically porous carbon (FeSA‐NS/C). The newly‐developed FeSA‐NS/C catalyst exhibited a high catalytic activity and selectivity for oxygen reduction to produce H2O2 at a high current of 100 mA cm−2 with a record high H2O2 selectivity of 90 %. An accumulated H2O2 concentration of 5.8 wt.% is obtained for the electrocatalysis process, which is sufficient for medical disinfection. Combined theoretical calculations and experimental characterizations verified the rationally‐designed catalytic active center with the atomic Fe site stabilized by three‐coordinated nitrogen atoms and one‐sulfur atom (Fe‐N3S‐C). It was further found that the replacement of one N atom with S atom in the classical Fe‐N4‐C active center could induce an asymmetric charge distribution over N atoms surrounding the Fe reactive center to accelerate proton spillover for a rapid formation of the OOH* intermediate, thus speeding up the whole reaction kinetics of oxygen reduction for H2O2 electrosynthesis.

Surface Redox Chemistry Regulates the Reaction Microenvironment for Efficient Hydrogen Peroxide Generation

“…The high-resolution Fe 2p spectra of the Fe-n-CNTs can be deconvoluted into five peaks at 702.1, 714.9, 704.9, 717.7, and 708.1 eV (Figure S4a), corresponding to Fe(II) 2p 3/2 , Fe(II) 2p 1/2 , Fe(III) 2p 3/2 , Fe(III) 2p 1/2 , and satellite peaks, respectively. 25 The binding energies are relatively lower than those of standard Fe(II) and Fe(III), suggesting metal coordination interactions between Fe atoms and SO 3 − anions, as well as with electronegative F atoms. 24 In contrast, Fe-PTFE-CNTs, lacking SO 3 − groups for chemical bonding with Fe atoms, exhibited a negligible peak in the Fe 2p XPS spectrum (Figure S4b).…”

Regulating the Local Microenvironment of an Fe−N4 Single-Atom Catalyst for Enhanced Oxygen Reduction Reaction

“…Two distinct infrared peaks at 1205 and 927 cm −1 on Fe-SA/NSC are clearly discerned, and their peak intensities gradually enhance with applied potentials (Figure c). These peaks could be attributed to the stretching vibrations of *OOH and *O, respectively. , By comparison, a notable IR peak is observed at 1323 cm −1 of Fe-SA/NC (Figure S26), which can be assigned to the emergence of the *HOOH intermediate, suggesting an unsatisfactory four-electron ORR efficiency of Fe-SA/NC. − Additionally, the intensity of *OOH intermediates for Fe-SA/NC is significantly lower than that of Fe-SA/NSC as the working potential increases (Figure d). This demonstrates that the unfavorable ORR activity and undesired two-electron product of HO 2 − for Fe-SA/NC can be attributed to the weak adsorption of *OOH.…”

Carbon-Based Single-Atom Nanocatalysts for Electrochemical Energy Applications

“…111 They discovered that it was possible to customize the catalytic performance of the Co−N 4 compounds by precisely adjusting its adjacent atomic structure to mimic the structural dependency reactive characteristics observed in metalloenzymes. Recently, Hou et al 112 reported monatomic iron catalysts with asymmetric nitrogen and sulfur coordination, and the unsymmetrically coordinated Fe−N 3 S 1 moieties served as active sites with superior performance in a two-electron path EORR, achieving an impressive current density of 100 mA cm −2 . This process also demonstrated an unmatched selectivity for H 2 O 2 of 90% coupled with a content of 5.8 wt %, making it optimal for applications in medical sanitation (Figure 3g and 3h).…”

“…(h) Recorded electrolyzer cell voltage over time at a constant current density of 100 mA cm –2 with O 2 flow. (i) DFT-calculated free energy landscapes for optimized FeN 2 S 2 , FeN 3 S 1 , and FeN 4 models . Reproduced with permission from ref .…”

“…(i) DFT-calculated free energy landscapes for optimized FeN 2 S 2 , FeN 3 S 1 , and FeN 4 models . Reproduced with permission from ref . Copyright 2023 Wiley-VCH Verlag GmbH.…”