Markedly Enhanced Oxygen Reduction Activity of Single-Atom Fe Catalysts via Integration with Fe Nanoclusters

Abstract

Single-atom catalysts (SACs) have emerged as one of the most promising alternatives to noble metal-based catalysts for highly efficient oxygen reduction reaction (ORR). While SACs can offer notable benefits in terms of lowering overall catalyst cost, there is still room for improvement regarding catalyst activity. To this end, we designed and successfully fabricated an ORR electrocatalyst in which atomic clusters are embedded in an atomically dispersed Fe–N–C matrix (FeAC@FeSA–N–C), as shown by comprehensive measurements using aberration-corrected scanning transmission electron microscopy (AC-STEM) and X-ray absorption spectroscopy (XAS). The half-wave potential of FeAC@FeSA–N–C is 0.912 V (versus reversible hydrogen electrode (RHE)), exceeding that of commercial Pt/C (0.897 V), FeSA–N–C (0.844 V), as well as the half-wave potentials of most reported non-platinum-group metal catalysts. The ORR activity of the designed catalyst stems from single-atom active centers but is markedly enhanced by the presence of Fe nanoclusters, as confirmed by both experimental measurements and theoretical calculations.

Ultrasmall Co@Co(OH)2 Nanoclusters Embedded in N‐Enriched Mesoporous Carbon Networks as Efficient Electrocatalysts for Water Oxidation

“…The ultrasmall NCs and their assembly on the supramolecular N‐enriched graphitic structure was achieved by the controlled polymerization of melamine with blocking of some of the terminal amine groups by creating cobalt–melamine complexes under the optimal conditions without using any template or directing agents. Consequently, the unique texture of the hybrid material with multimodal porosity and open channels not only support the infiltration of electrolytes and/or charges but may also enhance the synergistic effect with NCs with nanoscale dimensions …”

“…Consequently, the unique texture of the hybrid material with multimodalp orosity and open channels not only support the infiltration of electrolytes and/orcharges but may also enhancethe synergistic effect with NCs with nanoscaled imensions. [24] Results and Discussion Synthesis and characterization of Co/Co(OH) 2…”

Emerging Metal Single Atoms in Electrocatalysts and Batteries

“…[54] The common strategy for preparing the Fe SAs entails the utilization of Fe-containing organic precursors, followed by pyrolysis under high temperature. So far, reported Fe-containing organic precursors include Fe-bipyridine, [55] Fe-phthalocyanine, [56] Fe-zeolitic imidazolate framework (ZIF)-8, [57][58][59] Fe-polypyrrole, [60][61][62] Fe-porphyrinic triazine, [63] Fe-imidazole-melamine, [64] Fe-1,3,5-tris(4aminophenyl)-benzene/terephthaldehyde, [65] Fe-1,10 phenanthroline, [66] Fe-pyrrole-thiophene copolymer, [67] Fe-histidine, [68] Fe-porphyrinic MOFs, [69] Fe-phthalocyanine/unsubstituted phthalocyanine, [70] Fe-formamide, [71] Fe-tetra(4′-vinylphenyl) porphyrin, [72] Fe-bis(imino)-pyridine, [73] Fe-phthalocyanine/ ZIF-8, [74] Fe-melamine/lipoic acid, [75] Fe-polydopamine, [76] Feguanine, [77] Fe-polyoxyethylene-polyoxypropylene-polyoxyethylene (pluronic F-127), [78] Fe-glucosamine hydrochloride, [79] Fe-porphyra, [80] and ferrocene-ZIF-8. [81] For instance, Li et al reported a novel pyrrole/thiophene copolymer pyrolysis approach to synthesize the Fe-isolated SAs on sulfur and nitrogen co-doped carbon frameworks.…”

Recent Advances in Non-Precious Transition Metal/Nitrogen-doped Carbon for Oxygen Reduction Electrocatalysts in PEMFCs

“…Overall speaking, this approach makes the preparation of single-atom M-N x C catalysts more facile and reliable. Apart from the fact that the monatomic catalysts have exhibited satisfactory activity towards ORR, recently Zeng's group [115] found that Fe single atoms together with Fe nanoclusters anchored on nitrogen-doped carbon support (Fe AC @Fe SA -N-C) displayed superior ORR catalytic activity ( Figure 13). Their work provides a novel insight and pathway to the catalysts design.…”