Single-atom dispersed Co–N–C catalyst: structure identification and performance for hydrogenative coupling of nitroarenes

Wang, Xinyang; Zhang, Leilei; Yan, Wensheng; Liu, Xiaoyan; Yang, Xiaofeng; Miao, Shu; Wang, Wentao; Wang, Aiqin; Zhang, Tao

doi:10.1039/c6sc02105k

Cited by 601 publications

(473 citation statements)

References 48 publications

(40 reference statements)

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“…In addition, the FT of Ni-NHGF also reveals a minor signal at 2.01 Å, which overlaps partially with the Ni-Ni peak at 2.18 Å for bulk Ni. The same observations can be made in Fe-NHGF and Co-NHGF with the minor peaks located at 2.03 and 1.92 Å, respectively, which are shifted to the lower R direction compared with the corresponding Fe-Fe (2.20 Å) and Co-Co (2.17 Å) peaks of bulk Fe and Co. We note that such an EXAFS-FT profile, featuring the co-presence of the Gaussian-like main peak and the minor satellite peak, has never been observed in previously reported M-N-C materials 26,41 , which turns out to be a key characteristic of the MN x C y atomic structure adopted by M-NHGFs and will be discussed later. EXAFS wavelet transform (WT) analysis is powerful for discriminating the backscattering atoms even when they overlap substantially in R-space, by providing not only radial distance resolution but also k-space resolution 42 .…”

Section: Resultsmentioning

confidence: 74%

“…4c-e), atomic structures within single-layer graphene can be clearly resolved and the observed coordination configurations of the atomic metals apparently match well with the MN 4 C 4 moieties derived from XAFS studies. In addition, the arrangement of the light elements near the metal site and the overall graphene honeycomb lattice structure remain largely undistorted, which further excludes the existence of the porphyrinic structure or pyridinic-N-based structure in M-NHGFs, since they can only form in strongly disordered graphene lattice or between graphene zigzag edges 26,41 .…”

Section: Nature Catalysismentioning

confidence: 99%

“…We first evaluated a previously identified porphyrin-based FeN 4 C 12 moiety 26 and a pyridinic-N-based CoN 4 C 8 moiety 41 . XANES calculations performed on the porphyrin-based MN 4 C 12 moieties, with various axial oxygen or nitrogen ligands considered , show that all simulated spectra are drastically different from the experimental spectra above 50 eV above the absorption edge.…”

Section: Nature Catalysismentioning

confidence: 99%

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General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities

et al. 2018

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E fficient and cost-effective electrocatalysts play critical roles in energy conversion and storage [1][2][3] . Homogeneous and heterogeneous catalysts represent two parallel frontiers of electrocatalysts, each with their own merits and drawbacks 4,5 . Homogeneous catalysts are attractive for their highly uniform active sites, tunable coordination environment and maximized atom utilization efficiency, but are limited by their relatively poor stability and recyclability. Heterogeneous catalysts are appealing for their high durability, excellent recyclability, and easy immobilization and integration with electrodes, but usually have rather low atom utilization efficiency due to the limited surface sites accessible to reactants. To this end, considerable efforts have been devoted to developing nanoscale heterogeneous catalysts that can increase the exposed surface atoms 3 . However, the inhomogeneity in the distribution of particle sizes and facets poses a serious challenge for controlling active sites and fundamental mechanistic studies 6,7 . In contrast, homogeneous catalysts typically exhibit the well-defined atomic structure with tunable coordination environment that is essential for deciphering the catalytic reaction pathway and rational design of targeted catalysts with tailored catalytic properties 8 . Single-atom catalysts (SACs) with monodispersed single atoms supported on solid substrates are recently emerging as an exciting class of catalysts that combine the merits of both homogeneous and heterogeneous catalysts [9][10][11][12][13][14] . However, most SACs studied to date employ metal oxides (for example, TiO 2 , CeO 2 and FeO x ) as supporting substrates to prevent atom aggregation [15][16][17][18] , which cannot be readily applied in electrocatalytic applications due to their low electrical conductivity and/or poor stability in harsh liquid-phase electrolytes (for example, strong acid or base). Atomic transitionmetal-nitrogen moieties supported in carbon (M-N-Cs) represent a unique class of SACs with high electrical conductivity and superior (electro)chemical stability for electrocatalytic applications 19 . In particular, Fe-based M-N-Cs have been extensively studied as electrocatalysts towards the oxygen reduction reaction (ORR) with demonstrated activity and stability approaching those of commercial Pt/C catalysts 20,21 . In addition, as suggested by numerous theoretical studies, M-N-Cs are promising candidates for catalysing a wide range of electrochemical processes, such as hydrogen reduction/oxidation 22 , CO 2 /CO reduction 23 and N 2 reduction 24 . A significant advantage of SACs is that the well-defined single atomic site could allow precise understanding of the catalytic reaction pathway, and rational design of targeted catalysts with tailored activity (in a manner similar to homogeneous catalyst design). However, this perceived advantage has been investigated theoretically

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Section: Resultsmentioning

confidence: 74%

Section: Nature Catalysismentioning

confidence: 99%

Section: Nature Catalysismentioning

confidence: 99%

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General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities

et al. 2018

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“…In Figure 3a, the C, N, O, and Co peaks can be seen clearly for all CoNHCS samples. All CoNHCS samples show dominant narrow C 1s, weak O 1s, N 1s, and Co 2p peaks at 284, 531, 400, and 786 eV, respectively [34][35][36]. For comparison, we also synthesized the CoHCS-900 by using the same treatment without NH3 dissociation and NHCS-900 without adding Co.…”

Section: Resultsmentioning

confidence: 99%

Nitrogen-Doped Hollow Carbon Spheres with Embedded Co Nanoparticles as Active Non-Noble-Metal Electrocatalysts for the Oxygen Reduction Reaction

Xing

Zhou

et al. 2018

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Transition metal (Fe, Co, Ni) complexes on carbon nanomaterials are promising candidates as electrocatalysts towards the oxygen reduction reaction (ORR). In this paper, nitrogen-doped hollow carbon spheres with embedded Co nanoparticles were successfully prepared via a controllable synthesis strategy. The morphology characterization shows that the hollow carbon spheres possess an average diameter of~150 nm with a narrow size distribution and a shell thickness of~14.5 nm. The content of N doping ranges from 2.1 to 6.6 at.% depending on the calcination temperature from 900 to 1050 • C. Compared with commercial Pt/C, the Co-containing nitrogen-doped hollow carbon spheres prepared at 900 • C (CoNHCS-900) as an ORR electrocatalyst shows a half-wave potential shift of only ∆E 1/2 = 55 mV, but a superior stability of about 90.2% maintenance after 20,000 s in the O 2 -saturated 0.1 M KOH at a rotating speed of 1600 rpm. This could be ascribed to the synergistic effects of N-containing moieties, Co-N x species, and Co nanoparticles, which significantly increase the density of active sites and promote the charge transfer during the ORR process.

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“…Less than 10% of graphitic N was found. The majority of pyridinic N resulting from the coordination with metal (Fe or Co) [38], verified the formation of metal nitride. The O 1s peaks at 530.0 and 531.7 eV (Figure 8f) were ascribed to the lattice oxygen coordinated with metal and surface hydroxyl oxygen, respectively [39].…”

Section: Surface Elements Analysismentioning

confidence: 96%

Cobalt-iron Oxide, Alloy and Nitride: Synthesis, Characterization and Application in Catalytic Peroxymonosulfate Activation for Orange II Degradation

et al. 2017

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Abstract:In meeting the need for environmental remediation in wastewater treatment and the development of popular sulfate-radical-based advanced oxidation processes (SR-AOPs), a series of Co/Fe-based catalysts with confirmed phase structure were prepared through extended soft chemical solution processes followed by atmosphere-dependent calcination. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and 57 Fe Mössbauer spectroscopy were employed to characterize the composition, morphology, crystal structure and chemical state of the prepared catalysts. It was shown that calcination in air, nitrogen and ammonia atmospheres generated Co-Fe catalysts with cobalt ferrite (CoFe 2 O 4 ), Co-Fe alloy and Co-Fe nitride as dominant phases, respectively. The prepared Co/Fe-based catalysts were demonstrated to be highly efficient in activating peroxymonosulfate (PMS) for organic Orange II degradation. The activation efficiency of the different catalysts was found to increase in the order CoFe 2 O 4 < Co-Fe nitride < Co-Fe alloy. Sulfate radical was found to be the primary active intermediate species contributing to the dye degradation for all the participating catalysts. Furthermore, a possible reaction mechanism was proposed for each of the studied catalysts. This study achieves progress in efficient cobalt-iron catalysts using in the field of SR-AOPs, with potential applications in environment remediation.

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Single-atom dispersed Co–N–C catalyst: structure identification and performance for hydrogenative coupling of nitroarenes

Abstract: The single-atom Co–N–C catalyst with the structure of CoN4C8-1-2O2 shows excellent performance for the chemoselective hydrogenation of nitroarenes to produce azo compounds under mild reaction conditions.

Cited by 601 publications

References 48 publications

General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities

General synthesis and definitive structural identification of MN4C4 single-atom catalysts with tunable electrocatalytic activities

Nitrogen-Doped Hollow Carbon Spheres with Embedded Co Nanoparticles as Active Non-Noble-Metal Electrocatalysts for the Oxygen Reduction Reaction

Cobalt-iron Oxide, Alloy and Nitride: Synthesis, Characterization and Application in Catalytic Peroxymonosulfate Activation for Orange II Degradation

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