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Cited by 1,011Electrocatalysts for Energy ConversionCO2 Reduction Techniques and CatalystsHydrogen Storage and Materials

Anchoring zero valence single atoms of nickel and iron on graphdiyne for hydrogen evolution

Open access
Xue, Yurui, Huang, Bolong, Yi, Yuanping, Guo, Yuan, Zuo, Zicheng, Li, Yongjun, Jia, Zhiyu, Liu, Huibiao +1 more·2018·Nature Communications
DOI 10.1038/s41467-018-03896-4PMC PMC5899097
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Abstract

Electrocatalysis by atomic catalysts is a major focus of chemical and energy conversion effort. Although transition-metal-based bulk electrocatalysts for electrochemical application on energy conversion processes have been reported frequently, anchoring the stable transition-metal atoms (e.g. nickel and iron) still remains a practical challenge. Here we report a strategy for fabrication of ACs comprising only isolated nickel/iron atoms anchored on graphdiyne. Our findings identify the very narrow size distributions of both nickel (1.23 Å) and iron (1.02 Å), typical sizes of single-atom nickel and iron. The precision of this method motivates us to develop a general approach in the field of single-atom transition-metal catalysis. Such atomic catalysts have high catalytic activity and stability for hydrogen evolution reactions.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper reports a two-step electrochemical strategy to anchor isolated zero-valence Ni and Fe atoms on graphdiyne, producing single-atom catalysts with narrow atomic size distributions and high hydrogen-evolution activity/stability. Fe/GD and Ni/GD show low overpotentials, small Tafel slopes, high mass activities and TOFs, with Fe/GD generally outperforming Ni/GD.

Key findings

  • Isolated Ni and Fe atoms were anchored on graphdiyne; HAADF-STEM size distributions were 1.23 ± 0.40 Å for Ni and 1.02 ± 0.33 Å for Fe, with ICP-MS loadings of 0.278 wt% Ni and 0.680 wt% Fe.
  • EXAFS showed only Ni–C (~1.6 Å) and Fe–C (~1.5 Å) contributions, with no Ni–Ni or Fe–Fe peaks, and XANES indicated Ni(0)/Fe(0) centers that remained metallic after H₂ reduction and after HER measurements.
  • For HER in 0.5 M H₂SO₄, Fe/GD had an onset overpotential of 9 mV and an overpotential of 66 mV at 10 mA cm⁻²; Ni/GD had 88 mV at 10 mA cm⁻². Tafel slopes were 37.8 mV dec⁻¹ for Fe/GD and 45.8 mV dec⁻¹ for Ni/GD, versus 33.9 mV dec⁻¹ for Pt/C.
  • At 0.2 V overpotential, mass activities were 80.0 A mgmetal⁻¹ for Fe/GD and 16.6 A mgmetal⁻¹ for Ni/GD, reported as 34.6 and 7.19 times greater than Pt/C (2.31 A mgmetal⁻¹); TOFs at 100 mV were 4.15 s⁻¹ for Fe/GD and 1.59 s⁻¹ for Ni/GD. Stability tests showed unchanged polarization after 5000 cycles and negligible losses after 116 h (Ni/GD) and 60 h (Fe/GD) constant electrolysis, with Faradaic efficiencies around 98%.

Methods

  • Graphdiyne foam (GDF) was grown on carbon cloth via an acetylenic cross-coupling reaction using hexaethynylbenzene, then Ni or Fe was anchored by electrochemical reduction/deposition: Ni from 5 mM NiSO₄ in 500 mM H₂SO₄ at 10 mA cm⁻² for 150 s; Fe from 10 mM FeCl₃ in 500 mM H₂SO₄ at 10 mA cm⁻² for 250 s.
  • Characterization included XPS, Raman, ICP-MS, SEM/TEM, XRD, aberration-corrected HAADF-STEM, XANES/EXAFS, and electrochemical measurements in H₂-saturated 0.5 M H₂SO₄ using a three-electrode system, plus EIS, cycling, and constant-electrolysis stability tests.
  • HER analysis included onset overpotential, overpotential at 10 mA cm⁻², Tafel slopes, mass activity, TOF, EIS resistance fitting, ECSA/Cdl, and DFT+U calculations of adsorption sites, binding energies, orbital interactions, and hydrogen chemisorption free energies.

Limitations

  • The paper does not state explicit limitations.
  • Evident from the text: HER performance was evaluated only in H₂-saturated 0.5 M H₂SO₄, so activity in alkaline or neutral media is not shown.
  • Evident from the text: TOF values assume all single metal atoms are active and accessible to the electrolyte, described as an upper-limit estimate; stability tests lasted 116 h for Ni/GD and 60 h for Fe/GD, and the theoretical suggestion that lower Ni or higher Fe coverage might optimize HER was not experimentally tested.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1038/s41467-018-03896-4

Cites

60 of 60 references verified0 citation errors · 0 not checkable

Statistics

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Claims the paper makes

0 of 13 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The sp/sp2 hybridization ratio of Ni/GD and Fe/GD remained equal to 2.

    “The sp/sp2 hybridization ratio remained equal to 2, suggesting that the anchoring of Ni/Fe atoms occurred without breaking any covalent bonds.”
    Quote in the paperSubstantial claim
  • Findingown data

    The C 1s XPS peaks of both Ni/GD and Fe/GD featured a satellite at 290.0 eV arising from the π-π* transition.

    “Compared with GDF (Supplementary Fig. 2, Supplementary Note 1), the C 1s XPS peaks of both Ni/GD and Fe/GD (Supplementary Fig. 3) all featured a satellite at 290.0 eV arising from the π–π* transition, which could be due to the restoration of the conjugated structure, indicative of interactions between Ni/Fe atoms and GD.”
    Quote in the paperNot a substantial claim
  • Findingnone given

    The Ni/GD and Fe/GD atomic catalysts have high catalytic activity and stability for hydrogen evolution reactions.

    “Such atomic catalysts have high catalytic activity and stability for hydrogen evolution reactions.”
    Quote in the paperNot a substantial claim
  • Findingown data

    The authors fabricated atomic catalysts comprising only isolated nickel and iron atoms anchored on graphdiyne (Ni/GD and Fe/GD).

    “Here we report a strategy for fabrication of ACs comprising only isolated nickel/iron atoms anchored on graphdiyne.”
    • Also stated in: § Introduction · plain
      “Here we show that the GD can be direct use as the AC support without any pretreatment and provide an excellent opportunity to fabricate stable ACs (Ni/GD and Fe/GD) by a fast, scalable, controllable, and efficient electrochemical synthesis method that can be scaled readily.”
    Quote in the paperSubstantial claim
  • Findingown data

    The Raman diffraction peaks of the diyne groups of Ni/GD and Fe/GD shifted slightly relative to GDF.

    “From Raman spectra (Supplementary Fig. 4), the diffraction peaks of the diyne groups of Ni/GD and Fe/GD shifted slightly, consistent with the formation of chemical bonds after TM atom anchoring.”
    Quote in the paperNot a substantial claim
  • May combine two claims. 37
  • Classified as probably not a substantial claim. 7

  • May combine two claims.

    Findingown data

    For Ni/GD, EXAFS shows only one notable peak at ~1.6 Å from the Ni-C contribution and no peak in the region 2-3 Å from the Ni-Ni contribution.

    “For Ni/GD, there was only one notable peak at ~1.6 Å from the Ni ~ C contribution and no peak in the region 2–3 Å from the Ni–Ni contribution (Fig. 3c), strongly confirming that Ni exists predominantly as isolated atoms.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    HAADF-STEM images show uniform dispersion of isolated Fe atoms in Fe/GD, with only isolated Fe atoms present.

    “For Fe/GD (Fig. 2g–l, Supplementary Fig. 7), HAADF images recorded at different regions clearly reveal that only isolated Fe atoms (white dots) are present and uniformly dispersed in Fe/GD.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The S1 site is more stable than the S2 site for Ni by 1.15 eV, while their 3d orbital energies are nearly the same at ~9.6 eV.

    “The S1 site shows more stable with 1.15 eV less than the S2 site for Ni, while their 3d orbital energies are nearly the same as ~9.6 eV.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For Fe/GD, EXAFS shows only one notable peak at ~1.5 Å from the Fe-C contribution and no Fe-Fe contribution at ~2.2 Å.

    “For Fe/GD, there was only one notable peak at ~1.5 Å from the Fe ~ C contribution for Fe/GD (Fig. 3f) and no Fe–Fe contribution (at ~2.2 Å) was observed, confirming the only presence of singly dispersed Fe atoms in catalyst (Supplementary Table 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Fe/GD shows an overpotential of 66 mV at 10 mA cm-2, smaller than Ni/GD (88 mV), GDF (578 mV), and CC (642 mV).

    “Fe/GD shows an overpotential of 66 mV at 10 mA cm–2, which is smaller than that of Ni/GD (88 mV), GDF (578 mV), and CC (642 mV) (Fig. 5a–c).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The derivative XANES indicates that Fe/GD and Ni/GD consist of an Fe(0) or Ni(0) center, respectively.

    “The derivative XANES indicates Fe/GD (or Ni/GD) consists of an Fe(0) [or Ni(0)] center (Supplementary Note 2).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The HER overpotential values of Fe/GD and Ni/GD are superior to other earth-abundant HER electrocatalysts such as Ni2P, MoS2, and exfoliated WS2, and compare favorably with noble-metal-based electrocatalysts such as Pt nanowires/single-layered Ni(OH)2.

    “The values are superior to other earth-abundant HER electrocatalysts [such as Ni2P (~110 mA cm–2)43, MoS2 (170 mA cm–2)44, and exfoliated WS2 (210 mA cm–2)45], and even compare favorably with noble-metal-based electrocatalysts such as Pt nanowires/single-layered Ni(OH)246.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [43] Popczun, E. J. et al. Nanostructured nickel phosphide as an electrocatalyst for the hydrogen evolution reaction. J. Am. Chem. Soc. 135, 9267–9270 (2013). source

      Not checked in the free run.

    • cites [44] Voiry, D. et al. The role of electronic coupling between substrate and 2D MoS2 nanosheets in electrocatalytic production of hydrogen. Nat. Mater. 15, 48–53 (2016). source

      Not checked in the free run.

    • cites [45] Voiry, D. et al. Enhanced catalytic activity in strained chemically exfoliated WS2 nanosheets for hydrogen evolution. Nat. Mater. 12, 850–855 (2013). source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation

    The Ni/GD and Fe/GD atomic catalysts were prepared by a two-step strategy: growth of three-dimensional graphdiyne foam on carbon cloth via acetylenic cross-coupling using hexaethynylbenzene, followed by electrochemical reduction to anchor Ni/Fe atoms.

    “The Ni/GD and Fe/GD ACs were prepared through a two-step strategy (Fig. 1), including the first preparation of three-dimensional (3D) GD foam (GDF) on carbon cloth (CC) surfaces via an acetylenic cross-coupling reaction using hexaethynylbenzene (HEB) as precursor26, followed by the anchoring of Ni/Fe atoms by a facile electrochemical reduction method.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [26] Kuang, C. et al. Highly efficient electron transport obtained by doping PCBM with graphdiyne in planar-heterojunction perovskite solar cells. Nano Lett. 15, 2756–2762 (2015). source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    HAADF-STEM images show uniform dispersion of isolated Ni atoms on the surface of graphdiyne, with only single Ni atoms present.

    “For Ni/GD, Fig. 2a–f clearly shows the uniform dispersion of isolated Ni atoms (white dots) on the surface of GD. Examination of various regions strongly confirms the only presence of single Ni atoms (Fig. 2a–f, Supplementary Figs. 5 and 6).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    For intercalation of transition metal between graphdiyne layers, Ni/Fe are inclined to absorb along route A, with the most favorable adsorption site at A1 (−1.98 and −1.66 eV for Fe and Ni, respectively).

    “The Ni/Fe are inclined to absorb along route A and the most favorable adsorption site is at A1 (−1.98 and −1.66 eV for Fe and Ni, respectively).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The ratio of D and G band intensities is 0.87 for Ni/GD and 0.85 for Fe/GD, both larger than that of GDF (0.77).

    “The ratio of the D and G band intensities for both Ni/GD (0.87) and Fe/GD (0.85) are larger than that of GDF (0.77), suggesting more defects had formed, forming more active sites and finally improving the catalytic efficiency.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The Ni loading on Ni/GD is 0.278 wt% and the Fe loading on Fe/GD is 0.680 wt% by ICP-MS.

    “Inductively coupled plasma mass spectrometry (ICP-MS) analysis indicated a Ni loading of 0.278 wt% on Ni/GD and Fe loading of 0.680 wt% on Fe/GD.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    For Ni/Fe adatoms absorbing on a single graphdiyne layer, site S1 is more energetically favorable than site S2, with binding energies of −3.72/−1.22 eV for Ni/Fe at S1 and −1.39/−0.37 eV at S2.

    “First, for the Ni/Fe adatoms absorbing on a single GD layer, the binding energies (Supplementary Table 2) show that the site S1 for Ni/Fe (−3.72/−1.22 eV, respectively) were more energetic favorable than the site S2 (−1.39/−0.37 eV).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Normalized to loading, both Fe/GD and Ni/GD possess significantly better mass activity toward HER than commercial Pt/C; at overpotential 0.2 V, mass activities are 80.0 A mgmetal-1 for Fe/GD and 16.6 A mgmetal-1 for Ni/GD, 34.6 and 7.19 times greater than Pt/C (2.31 A mgmetal-1).

    “Remarkably, normalized to respective loading, both Fe/GD and Ni/GD possess significantly better mass activity toward HER than commercial Pt/C (Fig. 5d), for example, at overpotential of 0.2 V, the mass activities of Fe/GD (80.0 A mgmetal–1) and Ni/GD (16.6 A mgmetal–1) are 34.6 and 7.19 times greater than that of Pt/C (2.31 A mgmetal–1), respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The Ni-3d orbital on graphdiyne exhibits a closed-shell effect with larger orbital potential, implying stronger orbital overlaps between Ni and neighboring C sites.

    “Differently, the Ni-3d orbital on the GD also exhibits a closed-shell effect but larger orbital potential implying stronger orbital overlaps between Ni and neighboring C sites (Fig. 4e).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Fe/GD exhibits the best HER activity with the smallest onset overpotential of 9 mV, very close to Pt/C (1.0 mV).

    “Fe/GD exhibits the best HER activity with the smallest onset overpotential of 9 mV, which is very close to Pt/C (1.0 mV, Supplementary Fig. 16).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Fe/GD and Ni/GD exhibit smaller solution resistance (Rs) and charge-transfer resistance (Rct) than GDF and CC.

    “Compared with GDF and CC (Fig. 5g and Supplementary Table 6), the smaller solution resistance (Rs) and charge-transfer resistance (Rct) of Fe/GD and Ni/GD indicate the improved charge-transfer behavior over the catalyst interface8.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The upper limit number of active sites for Ni/GD and Fe/GD was estimated to be 2.56 × 1016 and 2.38 × 1016 sites per cm2, respectively, which is more than that of Pt(111) (1.5 × 1015 sites per cm2).

    “Assuming that all single metal atoms in the catalyst are active and accessible to the electrolyte, the upper limit number of the active sites for Ni/GD and Fe/GD were estimated to be 2.56 × 1016 and 2.38 × 1016 sites per cm2, respectively, which are more than that of Pt(111) (1.5 × 1015 sites per cm2)36.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [36] Jaramillo, T. F. et al. Identification of active edge sites for electrochemical H2 evolution from MoS2 nanocatalysts. Science 317, 100–102 (2007). source

      Not checked in the free run.

    • The authors state this as an assumption: All single metal atoms in the catalyst are active and accessible to the electrolyte.

  • May combine two claims.

    Findingown data

    The geometrical exchange current density j0,geometrical for Ni/GD (0.25 mA cm-2) and Fe/GD (0.29 mA cm-2) are much larger than reported ACs such as Ni-doped graphene (5.3 × 10-2 mA cm-2) and most bulk HER catalysts such as CoP (0.14 mA cm-2).

    “The j0,geometrical for Ni/GD (0.25 mA cm–2) and Fe/GD (0.29 mA cm–2) are much larger than reported ACs [e.g., Ni-doped graphene (5.3 × 10–2 mA cm–2)8] and most of the bulk HER catalysts such as CoP (0.14 mA cm–2)48 (Supplementary Table 4), revealing the exceptional intrinsic HER activities of Fe/GD and Ni/GD ACs.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [8] Qiu, H. J. et al. Nanoporous graphene with single-atom nickel dopants: an efficient and stable catalyst for electrochemical hydrogen production. Angew. Chem. Int. Ed. 54, 14031–14035 (2015). source

      Not checked in the free run.

    • cites [48] Popczun, E. J., Read, C. G., Roske, C. W., Lewis, N. S. & Schaak, R. E. Highly active electrocatalysis of the hydrogen evolution reaction by cobalt phosphide nanoparticles. Angew. Chem. Int. Ed. 53, 5427–5430 (2014). source

      Not checked in the free run.

  • May combine two claims.

    Findingown data

    The Ni content is 0.278 wt% and the Fe content is 0.68%, calculated from ICP-MS data.

    “Their contents (Ni: 0.278 wt%; Fe: 0.68%)were calculated from the ICP-MS data.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    XPS and HAADF-STEM characterizations show no changes in composition and both Ni and Fe atoms presented as isolated atoms without aggregations for Ni/GD and Fe/GD during long-term cycling operation.

    “As evidenced by XPS and HAADF-STEM characterizations (Supplementary Figs. 26 and 27), no changes in the composition occurred and both Ni and Fe atoms were presented as isolated atoms without any aggregations for Ni/GD and Fe/GD during the long-term cycling operation.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The ECSA for Fe/GD, Ni/GD, GDF, and CC are 18, 8.3, 5.4, and 2.3 cm2, respectively.

    “The ECSA for Fe/GD, Ni/GD, GDF, and CC are 18, 8.3, 5.4, and 2.3 cm2, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The polarization curves of Ni/GD and Fe/GD are unchanged in current density after 5000 cycling tests, and they are superior on stability to commercial Pt/C.

    “The polarization curves of Ni/GD (Fig. 5h) and Fe/GD (Fig. 5i) are still unchanged in current density after 5000 cycling tests, which are much more superior on stability to commercial Pt/C (Supplementary Fig. 25).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Fe/GD and Ni/GD have hydrogen adsorption resistance of 1.19 Ω and 3.63 Ω, respectively.

    “Besides, the lower hydrogen adsorption resistance for Fe/GD (1.19 Ω) and Ni/GD (3.63 Ω) reveals the more favorable absorption of the hydrogen intermediates, which is substantially beneficial for the overall electrocatalytic performance.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    The TOF of Ni/GD and Fe/GD at 100 mV was calculated to be 1.59 and 4.15 s−1, respectively, which is much higher than other reported state-of-the-art electrocatalysts, such as CoP (0.046 s-1) and Ni2P (0.015 s-1).

    “The TOF of Ni/GD and Fe/GD at 100 mV were calculated to be 1.59 and 4.15 s−1 (Fig. 5f), respectively, which are much higher than other reported state-of-the-art electrocatalysts, such as CoP (0.046 s–1)47 and Ni2P (0.015 s–1)43 (Supplementary Table 5).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [47] Cheng, N. et al. Platinum single-atom and cluster catalysis of the hydrogen evolution reaction. Nat. Commun. 7, 13638 (2016). source

      Not checked in the free run.

    • cites [43] Popczun, E. J. et al. Nanostructured nickel phosphide as an electrocatalyst for the hydrogen evolution reaction. J. Am. Chem. Soc. 135, 9267–9270 (2013). source

      Not checked in the free run.

    • The authors state this as an assumption: All single metal atoms in the catalyst are active and accessible to the electrolyte.

  • May combine two claims.

    Findingown data

    Fe/GD and Ni/GD showed Tafel slopes of 37.8 and 45.8 mV dec-1, respectively, only little larger than Pt/C (33.9 mV dec-1).

    “As shown in Fig. 5e, Fe/GD and Ni/GD showed very small Tafel slopes of 37.8 and 45.8 mV dec–1, respectively, which are only little larger than that of Pt/C (33.9 mV dec–1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    At η = −100 mV, Fe/GD and Ni/GD show specific current densities (js) of 0.21 and 0.12 mA cm-2, respectively.

    “At η = −100 mV, Fe/GD and Ni/GD show js of 0.21 and 0.12 mA cm–2, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    More defects had formed in Ni/GD and Fe/GD than in GDF, forming more active sites and improving catalytic efficiency.

    “The ratio of the D and G band intensities for both Ni/GD (0.87) and Fe/GD (0.85) are larger than that of GDF (0.77), suggesting more defects had formed, forming more active sites and finally improving the catalytic efficiency.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Based on characterization data, both Ni/GD and Fe/GD consist of only isolated Ni and Fe atoms, respectively.

    “Based on the characterization data mentioned above, it is evident that both Ni/GD and Fe/GD consist of only isolated Ni and Fe atoms, respectively.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    Different electronically active C sites in Ni/Fe-on-GD show that the HER performance of Ni/Fe-on-GD is superior to pristine GD because it promotes both initial adsorption (rate-determining step) and final desorption.

    “Different electronically active C sites in Ni/Fe-on-GD system show that the HER performance of Ni/Fe-on-GD is superior to the pristine GD as it promotes both the initial adsorption (rate-determining step) and final desorption.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S2 (checkable). May combine two claims.

    Premisecitation

    Transition metals such as nickel and iron would discard noble-metal usage and possess high utilization potential for industry.

    “Transition metal [TM, such as nickel (Ni) and iron (Fe)] would discard the noble-metal usage and possess high utilization potential for industry28.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [28] Covacci, A., Telford, J. L., Giudice, G. D., Parsonnet, J. & Rappuoli, R. Helicobacter pylori virulence and genetic geography. Science 284, 1328–1333 (1999). source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The experimental results demonstrate the reproducibility and universality of the strategy for synthesizing atomic catalysts.

    “These experiment results again demonstrate the reproducibility and universality of our strategy for synthesizing ACs.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The sp hybridization of the -C≡C- linkages in graphdiyne enables arbitrary angle rotation of π/π* perpendicular to the axis, making it possible to point toward metal atoms and chelate a single metal atom.

    “In addition to sp2 hybridization, the sp hybridization of –C≡C– enables the arbitrary angle rotation of π/π* perpendicular to the axis, making it possible to point toward metal atoms and, thereby, chelate a single metal atom27.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [27] He, J. et al. Magnetic properties of single transition-metal atom absorbed graphdiyne and graphyne sheet from DFT+U calculations. J. Phys. Chem. C 116, 26313–26321 (2012). source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data

    The performances of GD-supported ACs are superior to all reported ACs and the most state-of-the-art bulk non-precious catalysts.

    “Their performances are superior to that all reported ACs and the most state-of-the-art bulk non-precious catalysts.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductown data

    The effects of scanning rate on HER performance were excluded before evaluating HER catalytic activity.

    “After excluding the effects of scanning rate on HER performance (Supplementary Fig. 14), we evaluated the HER catalytic activity of the Fe/GD and Ni/GD ACs in H2-saturated 0.5 M H2SO4 using a standard three-electrode system (the reference electrodes were calibrated daily with respect to reversible hydrogen electrode (RHE), Supplementary Fig. 15).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    The electrolyte was degassed by H2 before starting the experiment.

    “The electrolyte has been degassed by H2 before starting the experiment.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    The saturated calomel electrode (SCE) was calibrated daily with respect to RHE.

    “In our experiments, SCE was calibrated daily with respect to RHE (Supplementary Fig. 15).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The attainable spatial resolution defined by the probe-forming objective lens is better than 80 pm.

    “The attainable spatial resolution defined by the probe-forming objective lens is better than 80 pm.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    The GD-supported ACs exhibit extremely high catalytic activity and long-term stability for HER under acidic conditions.

    “These GD-supported ACs exhibit extremely high catalytic activity and long-term stability for HER under acidic conditions.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The binding energies were calculated with the basis set superposition error corrected.

    “The binding energies were calculated with the basis set superposition error corrected further.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Fe/GD and Ni/GD ACs have exceptional intrinsic HER activities.

    “The j0,geometrical for Ni/GD (0.25 mA cm–2) and Fe/GD (0.29 mA cm–2) are much larger than reported ACs [e.g., Ni-doped graphene (5.3 × 10–2 mA cm–2)8] and most of the bulk HER catalysts such as CoP (0.14 mA cm–2)48 (Supplementary Table 4), revealing the exceptional intrinsic HER activities of Fe/GD and Ni/GD ACs.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationown data

    The lower hydrogen adsorption resistance of Fe/GD and Ni/GD reveals more favorable absorption of hydrogen intermediates, which is beneficial for overall electrocatalytic performance.

    “Besides, the lower hydrogen adsorption resistance for Fe/GD (1.19 Ω) and Ni/GD (3.63 Ω) reveals the more favorable absorption of the hydrogen intermediates, which is substantially beneficial for the overall electrocatalytic performance.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    The reference electrodes were calibrated daily with respect to the reversible hydrogen electrode (RHE).

    “After excluding the effects of scanning rate on HER performance (Supplementary Fig. 14), we evaluated the HER catalytic activity of the Fe/GD and Ni/GD ACs in H2-saturated 0.5 M H2SO4 using a standard three-electrode system (the reference electrodes were calibrated daily with respect to reversible hydrogen electrode (RHE), Supplementary Fig. 15).”
    Quote in the paperSubstantial claim
43 of 43

  • The paper relies on this without support.

    Single atoms have a natural aggregation tendency, making successful anchoring on supports a significant challenge.

    “The prerequisite for practical application of ACs is successful anchoring single atoms on supports—a significant challenge due to the natural aggregation tendency of single atoms.”

  • The authors state this as an assumption.

    All single metal atoms in the catalyst are active and accessible to the electrolyte.

    “Assuming that all single metal atoms in the catalyst are active and accessible to the electrolyte”
    “The upper limit number of the actives was calculated based on the hypothesis that all single metal atoms (Ni and Fe) on GD form the active centers, and are accessible to the electrolyte.”
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  • Carbon-based materials, Fe-based materials, and single-atom catalysts are commonly used in the generation of reactive species other than SO4·- and ·OH.

    “Carbon-based materials, Fe-based materials, single-atom catalysts, etc., are commonly used in the generation of other reactive species than SO4 ·-and · OH[93-95].”

    From Advanced Oxidation Processes for Degradation of Water Pollutants—Ambivalent Impact of Carbonate Species: A Review (2023) · cites this paper as [94]

    The Abstract and Results (‘HER catalytic activity of ACs’; page not provided) describe iron and nickel single atoms on graphdiyne as catalysts for hydrogen evolution. Searches for reactive species other than sulfate and hydroxyl radicals, including superoxide and singlet oxygen, found no passage addressing their generation or how commonly these materials are used for it. (LLM, conf=0.75)

    Experimental — accuracy not yet measured

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. Koningsberger, D. C. & Prins, R. (eds) X-ray Absorption: Principles, Applications, Techniques of EXAFS, SEXAFS, and XANES, Vol. 92 (John Wiley & Sons: New York, 1988).
  2. Clark, S. J. et al. First principles methods using CASTEP. Z. Krist. 220, 567–570 (2005).

Cited by

Sorted by citations

Authors
Xue, Y., Huang, B., Yi, Y., Guo, Y., Zuo, Z., Li, Y., Jia, Z., Liu, H., & Li, Y.
Affiliations
  • Chinese Academy of Sciences (CN)
  • Hong Kong Polytechnic University (HK)
Corresponding author
  • Li, Yongjun
  • Li, Yuliang
ORCID
Venue
Nature Communications
Publisher
Springer Science and Business Media LLC
Published
2018-04-13
Volume
9
Issue
1
Pages
1460-1460
ISSN
2041-1723 (ISSN-L)
DOI
10.1038/s41467-018-03896-4
PMC
PMC5899097
OpenAlex
W2797324582
Semantic Scholar
c1e3bf6c0127a65f8c9f8f6cbc08d15ef3f69233
Cited by
1,011
References
60
Citations by year
2026: 52 · 2025: 74 · 2024: 122 · 2023: 135 · 2022: 159 · 2021: 179 · 2020: 154 · 2019: 106 · 2018: 30
FWCI
27.04
Type
journal article
Language
en
Open access
Licence
Locations
  • Nature Communications (publishedVersion, cc-by)
  • Europe PMC (PubMed Central) (publishedVersion, other-oa)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • PolyU Institutional Research Archive (Hong Kong Polytechnic University) (submittedVersion, cc-by)
Funders
  • Tianjin University of Technology
  • National Natural Science Foundation of China (21790051, QYZDY-SSW-SLH015, 21790050, 2016YFA0200104)
  • Chinese Academy of Sciences (QYZDY‐SSW‐SLH015, 21790051, 2016YFA0200104, 21790050)
  • Tianjin University
  • Beijing Synchrotron Radiation Facility
Topics
  • Physical Sciences › Energy › Renewable Energy, Sustainability and the Environment › Electrocatalysts for Energy Conversion
  • Physical Sciences › Energy › Renewable Energy, Sustainability and the Environment › CO2 Reduction Techniques and Catalysts
  • Physical Sciences › Materials Science › Materials Chemistry › Hydrogen Storage and Materials
Keywords
single-atom catalysts, graphdiyne, nickel single atoms, iron single atoms, hydrogen evolution reaction, electrocatalysis, transition metal atoms

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-06.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-06.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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