Electrochemical probing into the active sites of graphitic-layer encapsulated iron oxygen reduction reaction electrocatalysts

Zhong, Lijie; Jensen, Jens Oluf; Cleemann, Lars; Pan, Chao; Li, Qingfeng

doi:10.1016/j.scib.2017.11.017

Cited by 18 publications

(8 citation statements)

References 41 publications

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“…However, the diffractograms of Fe-N-ox-V (marked black) and Fe-N-aPRS KOH (marked blue) have low intensity but sharp peaks beside the carbon peaks in the range of 40–50°. Those cannot be properly identified due to small intensity but are presumed to be assigned to metallic Fe or Fe 3 C as reported in the literature [ 12 , 57 , 58 ]. Furthermore, the C (002) reflection becomes sharper for the Fe-N-aPRS KOH sample.…”

Section: Resultsmentioning

confidence: 99%

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

et al. 2020

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Fe-N-C materials are promising non-precious metal catalysts for the oxygen reduction reaction in fuel cells and batteries. However, during the synthesis of these materials less active Fe-containing nanoparticles are formed in many cases which lead to a decrease in electrochemical activity and stability. In this study, we reveal the significant properties of the carbon support required for the successful incorporation of Fe-N-related active sites. The impact of two carbon blacks and two activated biomass-based carbons on the Fe-N-C synthesis is investigated and crucial support properties are identified. Carbon supports having low portions of amorphous carbon, moderate surface areas (>800 m2/g) and mesopores result in the successful incorporation of Fe and N on an atomic level and improved oxygen reduction reaction (ORR) activity. A low surface area and especially amorphous parts of the carbon promote the formation of metallic iron species covered by a graphitic layer. In contrast, highly microporous systems with amorphous carbon provoke the formation of less active iron carbides and carbon nanotubes. Overall, a phosphoric acid activated biomass is revealed as novel and sustainable carbon support for the formation of Fe-Nx sites. Overall, this study provides valuable and significant information for the future development of novel and sustainable carbon supports for Fe-N-C catalysts.

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Section: Resultsmentioning

confidence: 99%

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

et al. 2020

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“…Previous work verified that CoN bond showed remarkable effect in ORR . In order to eliminate the contribution of CoN bonds which derived from the nitrogenous precursor (Figure S4d, Supporting Information), the CoP–DC was first dipped in 10 × 10 −3 m KSCN solution for 60 min to restrain the catalytic activity of CoN species and then tested in 0.1 m KOH for ORR . As shown in Figure S10 of the Supporting Information, LSV curves of CoP–DC and KSCN treated CoP–DC show ignorable difference, indicating the ORR performance was mainly contributed by the synergistic effect of CoP and DC rather than CoN bonds .…”

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confidence: 91%

Defective Carbon–CoP Nanoparticles Hybrids with Interfacial Charges Polarization for Efficient Bifunctional Oxygen Electrocatalysis

Lin

Yang

Zhang

et al. 2018

Advanced Energy Materials

233

147

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ideal performance toward ORR or OER, the high price, scarcity, and instability still hampers their large-scale generalization. At present, developing efficient and nonnoble-metal catalysts has attracted extensive interest. [11][12][13][14][15][16][17][18] For ORR, defective carbon-based materials, typically heteroatom-doped carbon, are extensively demonstrated as efficient electrocatalysts. [19][20][21][22] For OER, in addition to common transition metal oxides or (oxy)hydroxides, transition metal phosphides (TMPs) have achieved considerable research and development attention due to superior performance. [23][24][25][26][27] In this regard, the composites of the TMPs and defective carbon are considered as promising candidates for both ORR and OER. More recently, some works reported that the composites of the TMPs and defective carbon compared to the single component displayed enhanced catalytic performance, which was probably attributed to the increased electronic conductivity due to the introduction of conductive carbon. [28][29][30] However, the promoting factor was not well understood. For the composites, undoubtedly, the interfacial properties, especially the interfacial charge states, are important parameters that could influence the catalytic performance. [31,32] Therefore, in order to overcome high catalytic reaction barrier, designing the hybrids of the TMPs and defective carbon and probing the interfacial charge distribution behavior are highly desirable to realize bifunctional oxygen electrocatalysis.Herein, we constructed a new type of hybrids of the CoP and defective carbon (marked as CoP-DC). We revealed the interfacial charge transfer process of the hybrids by multiple synchrotron-based X-ray absorption structure, ultraviolet photoelectron spectra (UPS), X-ray photoelectron spectroscopy (XPS), and density functional theory (DFT) calculations. The interfacial charge redistribution was observed, which subsequently contributed to enhanced ORR activity on the defective carbon and enhanced OER activity on the CoP.The CoP-DC hybrids were synthesized through a simple phosphorization reaction toward the Co 2+ -contained polymer hydrogel. Typically, the polymer hydrogel was obtained by inserting Co 2+ into polymer hydrogel framework under alkaline condition according to previous reports, and then was phosphorized The development of efficient catalysts for both oxygen reduction and evolution reactions (oxygen reduction reaction (ORR) and oxygen evolution reaction (OER)) is central to regenerative fuel cells and rechargeable metalair batteries. It is highly desirable to achieve the efficient integration of dual active components into the catalysts and to understand the interaction between the dual components. Here, a facile approach is demonstrated to construct defective carbon-CoP nanoparticle hybrids as bifunctional oxygen electrocatalysts, and further probe the interfacial charge distribution behavior. By combining multiple synchrotron-based X-ray spectroscopic characterizations with density functional theo...

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“…Meanwhile, the poisoning trend of Ru Δc→h /C < Ru Δhcp /C < Ru hcp /C < Ru ccp /C suggests that the RuC X phase on Ru Δc→h /C and Ru Δhcp /C may play a role in the catalysis and that these nanoparticles are not considerably affected by anion poisoning. [ 52 ] In addition, the stronger SCN – poisoning for Ru Δhcp /C than for Ru Δc→h /C implicated the different positions of the RuC X phase on their surfaces. Together with the XPS, HRPES analyses, and DFT calculations noted above, this less poisoning effect observed for Ru Δc→h /C can be another clear evidence for the well formation of RuC X on the surface of Ru Δc→h /C.…”

Section: Resultsmentioning

confidence: 99%

Crystal Phase Transition Creates a Highly Active and Stable RuC_X Nanosurface for Hydrogen Evolution Reaction in Alkaline Media

Kim

Ruqia

et al. 2021

Advanced Materials

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Although metastable crystal structures have received much attention owing to their utilization in various fields, their phase‐transition to a thermodynamic structure has attracted comparably little interest. In the case of nanoscale crystals, such an exothermic phase‐transition releases high energy within a confined surface area and reconstructs surface atomic arrangement in a short time. Thus, this high‐energy nanosurface may create novel crystal structures when some elements are supplied. In this work, the creation of a ruthenium carbide (RuCX, X < 1) phase on the surface of the Ru nanocrystal is discovered during phase‐transition from cubic‐close‐packed to hexagonal‐close‐packed structure. When the electrocatalytic hydrogen evolution reaction (HER) is tested in alkaline media, the RuCX exhibits a much lower overpotential and good stability relative to the counterpart Ru‐based catalysts and the state‐of‐the‐art Pt/C catalyst. Density functional theory calculations predict that the local heterogeneity of the outermost RuCX surface promotes the bifunctional HER mechanism by providing catalytic sites for both H adsorption and facile water dissociation.

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Electrochemical probing into the active sites of graphitic-layer encapsulated iron oxygen reduction reaction electrocatalysts

Cited by 18 publications

References 41 publications

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

Defective Carbon–CoP Nanoparticles Hybrids with Interfacial Charges Polarization for Efficient Bifunctional Oxygen Electrocatalysis

Crystal Phase Transition Creates a Highly Active and Stable RuC_X Nanosurface for Hydrogen Evolution Reaction in Alkaline Media

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Electrochemical probing into the active sites of graphitic-layer encapsulated iron oxygen reduction reaction electrocatalysts

Cited by 18 publications

References 41 publications

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

Relevant Properties of Carbon Support Materials in Successful Fe-N-C Synthesis for the Oxygen Reduction Reaction: Study of Carbon Blacks and Biomass-Based Carbons

Defective Carbon–CoP Nanoparticles Hybrids with Interfacial Charges Polarization for Efficient Bifunctional Oxygen Electrocatalysis

Crystal Phase Transition Creates a Highly Active and Stable RuCX Nanosurface for Hydrogen Evolution Reaction in Alkaline Media

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Crystal Phase Transition Creates a Highly Active and Stable RuC_X Nanosurface for Hydrogen Evolution Reaction in Alkaline Media