Synergies of Atomically Dispersed Mn/Fe Single Atoms and Fe Nanoparticles on N-Doped Carbon toward High-Activity Eletrocatalysis for Oxygen Reduction

Abstract

PGM-free (platinum group metal) electrocatalysts are intensively investigated and used as low-cost catalysts for the oxygen reduction reaction (ORR) in the field of fuel cells, but further studying their performance improvement methods and actual reaction mechanism is still a big a challenge. In this work, a novel eletrocatalyst containing atomically dispersed Mn/Fe single atoms (SAs) and Fe nanoparticles (NPs) on N-doped carbonaceous (nanosheet/nanotube hybrids) is fabricated via a simple pyrolysis method. This high-activity ORR electrocatalyst has higher half-wave potential (E 1/2 = 0.91 V) and superior long-term durability in alkaline solutions and outperforms Pt/C catalysts, which can be ascribed to the synergetic interaction between Mn/Fe SAs and Fe-NPs. FeNPs/MnFeSAs-NC-25 has stronger reactant adsorption ability and a lower dissociation energy barrier than FeNPs/FeSAs-NC, which is conducive to breaking the O–O bond and accelerating ORR kinetics. This work presents a method to synthesize carbon-based electrocatalysts with high ORR activity and stability and shows that a variety of active sites encapsulated in N-doped carbonaceous materials can be a class of competitive candidates for PGM-free electrocatalysts.

Rational Regulation of Reducibility and Acid Site on Mn–Fe–BTC to Achieve High Low-Temperature Catalytic Denitration Performance

“…To uncover the influence of Mn, Fe, and the synergy Mn and Fe on de-NO x performance, the partial density of states (PDOS) of different optimized geometry structures was analyzed in detail (Figures –). By comparing the PDOS of T1, T2, and T3, it is found that the synergistic of Mn and Fe made the PDOS peaks of Mn–Mn and Fe–Fe shift positively (Figure a and b), which endows Mn–Fe–BTC with enhanced surface molecular adsorption capacity . At the same time, the PDOS of the catalyst active sites and the adsorbate elements connected to active sites in adsorption configurations (Figure ) were investigated.…”

“…By comparing the PDOS of T1, T2, and T3, it is found that the synergistic of Mn and Fe made the PDOS peaks of Mn−Mn and Fe−Fe shift positively (Figure 8a and b), which endows Mn−Fe−BTC with enhanced surface molecular adsorption capacity. 67 At the same time, the PDOS of the catalyst active sites and the adsorbate elements connected to active sites in adsorption configurations (Figure 7) were investigated. For NH 3 adsorption (Figure 9), d-sp hybridization occurred between N and Mn elements (Figure 9a, c, e, and g), which can establish a channel for electron transport between NH 3 and the active sites, enhance the transfer of charges, and promote further diffusion and reaction of NH 3 .…”

Co2P-Assisted Atomic Co–N4 Active Sites with a Tailored Electronic Structure Enabling Efficient ORR/OER for Rechargeable Zn–Air Batteries

“…Co 2 P/Co-NC had a d-band center of −2.06 eV, which was 0.41 eV lower than that of Co-NC (−1.65 eV). The downshift of the d-band center of Co 2 P/Co-NC means reduced binding between the oxygen species and the catalyst, which optimized the rate-determining step. ,,− Therefore, the presence of Co 2 P effectively regulated the electronic structure of the Co–N 4 centers. Combined with XPS analysis results, it could be concluded that the electrons transferred from the Co–N 4 center to the peripheral carbon matrix due to the adjacent Co 2 P nanoparticle, which would regulate the density distribution of states in the Co–N 4 center. , The possible ORR mechanism is summarized in Figure S13.…”

Design of advanced aerogel structures for oxygen reduction reaction electrocatalysis

“…Some of the proposed solutions focus on lowering the PGM content by using Pt alloys or eliminating Pt by completely replacing it with other, more abundant metals, mostly PGM‐free that consist of first‐row transition metals 12 . These catalysts are either NPs or atomically dispersed metal sites, usually transition metal–nitrogen–carbon (M–N–C) sites 13–20 . So far, it has been difficult to find PGM‐free ORR catalysts without paying a high penalty in activity and/or durability 21–25 …”

“…12 These catalysts are either NPs or atomically dispersed metal sites, usually transition metal-nitrogencarbon (M-N-C) sites. [13][14][15][16][17][18][19][20] So far, it has been difficult to find PGM-free ORR catalysts without paying a high penalty in activity and/or durability. [21][22][23][24][25] Catalysts' supports also play an important role in the ORR catalytic activity and durability through surface interactions.…”