Simultaneous integration of Fe clusters and NiFe dual single atoms in nitrogen-doped carbon for oxygen reduction reaction

Atomically-dispersed iron-based electrocatalysts are promising substitutes for noble metal electrocatalysts because of excellent performance in oxygen reduction reaction(ORR).Rationally modulating the local coordination environment of the Fe site and optimizing the binding energy of oxygen reduction intermediates are effective strategies to optimize ORR activity.Herein,we report a new method in which Ni is introduced to construct NiFe dual single atoms and iron nanoclusters loaded on the nitrogen-doped carbon with a highly porous structure.This design plays a synergistic role of dual single atoms and clusters,optimizes the 3d orbital and Fermi level of Fe,breaks the symmetrical structure of Fe-N_(4),and effectively improves the adsorption/desorption behavior of the oxygen-containing intermediates.Electrochemical tests show FeNCs/NiFeSAs-NC has an excellent intrinsic activity.Theoretical calculations show the oxygen-containing species on the Ni active site will move to the middle of NiFe(bridge site connection)after optimization and that the key step is OH desorption,with a reaction energy of 0.27 eV.The electron exchange between NiFe-N6 and Fe-cluster is very strong,further indicating the introduction of Ni species and Fe clusters has a regulatory effect on the electronic structure of Fe-N_(4).

Atomically dispersed dual Fe centers on nitrogen-doped bamboo-like carbon nanotubes for efficient oxygen reduction

Interfacial atomic configuration between dual-metal active species and nitrogen-carbon substrates is of great importance for improving the intrinsic activity of catalysts toward oxygen reduction reaction(ORR).Thus,from the atomic-scale engineering we develop a high intrinsic activity ORR catalyst in terms of incorporating atomically dispersed dual Fe centers(single Fe atoms and ultra-small Fe atomic clusters)into bamboo-like N-doped carbon nanotubes.Benefiting from atomically dispersed dual-Fe centers on the atomic interface of Fe-Nx/carbon nanotubes,the fabricated dual Fe centers catalyst exhibits an extremely high ORR activity(E_(onset)=1.006 V;E_(1/2)=0.90 V),beyond state-of-the-art Pt/C.Remarkably,this catalyst also shows a superior kinetic current density of 19.690 mA·cm^(−2),which is 7 times that of state-of-the-art Pt/C.Additionally,based on the excellent catalyst,the primary Zn-air battery reveals a high power density up to 137 mW·cm^(−2) and sufficient potential cycling stability(at least 25 h).Undoubtedly,given the unique structure–activity relationship of dual-Fe active species and metal-nitrogen-carbon substrates,the catalyst will show great prospects in highly efficient electrochemical energy conversion devices.

Synthesis, structure and magnetic properties of a decanuclear Fe(Ⅲ)/oxo cluster

An iron(Ⅲ) cluster,namely [Fe10(μ3-O)8L8(NO3)6](1),has been synthesized by treatment of Fe(NO3)3·9 H2O with 3,5-dimethyl-l-(hydroxymethyl)-pyrazole(HL) under ambient temperature.The core skeleton of {FeⅢ10) can be regarded as a pear-like cage with eight triangular {FeⅢ3(μ3-O)} units,in which each three FeⅢ centers is held together by one μ3-O2- group with FeⅢ centers as corner-sharing triangle units.Importantly,{FeⅢ10} cluster is not only stable in solid state but also in solution,which is confirmed by powder X-ray diffraction(PXRD) pattern and electrospray ionization mass spectrometry(ESI-MS),respectively.Furthermore,1 shows anti ferromagnetic exchange behavior arising from the interactions between the iron(Ⅲ) centers.

Micro-vial Synthesis,Structure,Magnetic Properties and Hirshfeld Surface Analysis of a Penta-nuclear Fe(Ⅲ) Cluster

A new penta-nuclear Fe^Ⅲ cluster,[HN(C2H5)3]·[Fe5(timb)4(ATZ)4(μ3-O)2]·(H2O)5(1),(H2timb is 4-bromo-2-[(1H-tetrazol-5-ylimino)-methyl]-phenol;HATZ is 5-amino-1,2,3,4-tetrazole),was synthesized through micro-vial synthesis methods,which was characterized by elemental analysis,FT-IR spectra,X-ray single-crystal diffraction,thermogravimetric analysis.The single crystal belongs to the tetragonal system,space group √42d with a=0.19735(1),b=0.19735(1),c=0.26118(2)nm,Mr=1904.04,V=10.1724(10)nm^3,Z=4,Dc=1.118 g/cm^3,F(000)=3356,μ=2.314 mm^–1,R=0.0500 and wR=0.1151.The magnetic properties and Hirshfeld surface analysis of 1 were investigated and discussed in detail.