Interplay between morphology and electrochemical performance of “core–shell” electrocatalysts for oxygen reduction reaction based on a PtNix carbon nitride “shell” and a pyrolyzed polyketone nanoball “core”

Negro, Enrico; Polizzi, Stefano; Vezzù, Keti; Toniolo, Luigi; Cavinato, G.; Noto, Vito Di

doi:10.1016/j.ijhydene.2013.08.053

Cited by 62 publications

(51 citation statements)

References 33 publications

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“…ECs. Pd-trimetallic "core-shell" ECs show an ORR performance which increases as: (a) T f is raised; and (b) the N concentration in the "shell" decreases 5,35,36 (see Fig. 4).…”

Section: Fig 1 (A) Schematic Representation Of Hio-pn and Z-iope Prmentioning

confidence: 99%

Origins, Developments, and Perspectives of Carbon Nitride-Based Electrocatalysts for Application in Low-Temperature FCs

et al. 2015

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F uel cells (FCs) operating at low temperatures (T < 200 °C)show several very attractive features, including: (a) relatively simple assembly; (b) good compatibility with the environment; and (c) very high efficiency with respect to internal combustion engines. However, the full potential of low-temperature FCs can only be achieved by addressing a number of crucial issues involved in their operation. One of the most important bottlenecks is represented by the slow kinetics of the oxygen reduction reaction (ORR).1 Typical examples of low-temperature fuel cells include proton exchange membrane fuel cells (PEMFCs) and anion-exchange membrane fuel cells (AEMFCs).1 To achieve energy conversion efficiencies and power densities compatible with applications, all these devices require suitable ORR electrocatalysts (ECs) to minimize cathode polarization losses.Ideally, ORR ECs should possess the following features: a) Active sites capable of the highest turnover frequency at the lowest overpotentials; b) A large active surface area, maximizing the number of active sites; c) A morphology that facilitates the efficient transport of reactants and products to and from the active sites; d) High electron conductivity, to minimize ohmic losses; e) A high dielectric environment to aid the ion exchange processes between the active sites and the ion-conducting membrane; f) High stability under operating conditions, to achieve high durability.To comply with these requirements, state-of-the-art ORR ECs consist of Pt-nanocrystals supported on conductive carbon nanoparticles (NPs) that possess a spherical morphology and a large surface area 2 (indicated as "Pt/C ref. ECs"). These systems are characterized by a high dispersion of the ORR active sites, which are easily accessible by the reactants. Their performance is comparable to that of pristine "Pt-black" ECs, but with a reduced loading of precious metal. However, the large-scale rollout of FC technology employing Pt/C ref. ECs is hindered by their insufficient durability and very high costs."Carbon nitride-based electrocatalysts" (CN-based ECs) have shown great promise to address the issues outlined above. CN-based ECs are composed of a carbon-based matrix embedding nitrogen atoms. The matrix coordinates metal-based species, including: (a) NPs of metals (e.g., Pt, Pd), metal alloys (e.g., PtNi x , PdCo y Ni z ), oxides (e.g., Fe 3 O 4 ) or carbides (e.g., FeC x ); or (b) coordination complexes of single metal atoms (e.g., Fe, Co).3 There are two main driving forces behind the development of CN-based ECs. CN-based ECs including Pt-group elements (PGMs) show very high ORR activity and a remarkable tolerance towards the oxidizing conditions typical at the cathodes of low-temperature FCs. 4 The carbon nitride (CN) matrix embeds the various inorganic NPs in "nitrogen coordination nests". 5These strong interactions inhibit the main mechanisms involved in the long-term degradation of typical Pt/C ref. ECs, especially particle agglomeration and particle detachment from the support.

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“…ECs. Pd-trimetallic "core-shell" ECs show an ORR performance which increases as: (a) T f is raised; and (b) the N concentration in the "shell" decreases 5,35,36 (see Fig. 4).…”

Section: Fig 1 (A) Schematic Representation Of Hio-pn and Z-iope Prmentioning

confidence: 99%

Origins, Developments, and Perspectives of Carbon Nitride-Based Electrocatalysts for Application in Low-Temperature FCs

et al. 2015

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“…In detail, N atoms are expected to bind the PdCoNi alloy NPs in "N coordination nests". [20,[24][25][26] These latter processes inhibit the diffusion of metal atoms in the matrix and consequently restrain the growth processes of alloy NPs. The overall distribution of the alloy NPs phases identified in the PdCoNi-CN x T f /G electrocatalysts is coherent with the results of the chemical analysis reported in Table 1.…”

Section: Structural Studiesmentioning

confidence: 99%

“…These alloy NPs are bonded in "nitrogen coordination nests" of the CN "shell" matrix. [20,[24][25][26] The structure of the electrocatalysts is studied by powder XRD; the morphology is elucidated by HR-TEM. Indeed, it is well-known that the size, distribution, and structural features of NPs play an important role in the catalytic processes.…”

Section: Introductionmentioning

confidence: 99%

Interplay between Nitrogen Concentration, Structure, Morphology, and Electrochemical Performance of PdCoNi “Core–Shell” Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

et al. 2014

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This report describes the electrochemical behavior of a family of “core‐shell” electrocatalysts consisting of a carbon nitride (CN) “shell” matrix and a “core” of conducting carbon nanoparticles (NPs). The CN “shell” matrix embeds PdCoNi alloy NPs and covers homogeneously the carbon “core”. The chemical composition of the materials is determined by inductively‐coupled plasma atomic emission spectroscopy (ICP‐AES) and microanalysis; the structure is studied by powder X‐ray diffraction (powder XRD); the morphology is investigated by high‐resolution transmission electron microscopy (HR‐TEM). The surface activity and structure are probed by CO stripping. The oxygen reduction reaction (ORR) kinetics, reaction mechanism, and tolerance towards contamination from chloride anions are evaluated by cyclic voltammetry with the thin‐film rotating ring‐disk electrode (CV‐TF‐RRDE) method. The effect of N concentration in the matrix (which forms “coordination nests” for the Pd‐based alloy NPs bearing the active sites) on the ORR performance of the electrocatalysts is described. Results show that N atoms: 1) influence the evolution of the structure of the materials during the preparation processes, and 2) interact with alloy NPs, affecting the bifunctional and electronic ORR mechanisms of active sites and the adsorption/desorption processes of oxygen molecules and contaminants. Finally, the best PdCoNi electrocatalyst shows a higher surface activity in the ORR at 0.9 V vs. RHE with respect to the Pt‐based reference (388 μA cmPd‐2 vs. 153 μA cmPt‐2).

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“…The SSA of Co-bpdc/MWCNTs-100 is almost three orders of magnitude lower than the Pt/C Refs. [42,43].…”

Section: Resultsmentioning

confidence: 99%

A Novel Metal–Organic Framework Route to Embed Co Nanoparticles into Multi-Walled Carbon Nanotubes for Effective Oxygen Reduction in Alkaline Media

Zhu

Chen

et al. 2017

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Metal-organic framework (MOF) materials can be used as precursors to prepare non-precious metal catalysts (NPMCs) for oxygen reduction reaction (ORR). Herein, we prepared a novel MOF material (denoted as Co-bpdc) and then combined it with multi-walled carbon nanotubes (MWCNTs) to form Co-bpdc/MWCNTs composites. After calcination, the cobalt ions from Co-bpdc were converted into Co nanoparticles, which were distributed in the graphite carbon layers and MWCNTs to form Co-bpdc/MWCNTs. The prepared catalysts were characterized by TEM (Transmission electron microscopy), XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy), BET (Brunauer-Emmett-Teller), and Raman spectroscopy. The electrocatalytic activity was measured by using rotating disk electrode (RDE) voltammetry. The catalysts showed higher ORR catalytic activity than the commercial Pt/C catalyst in alkaline solution. Co-bpdc/MWCNTs-100 showed the highest ORR catalytic activity, with an initial reduction potential and half-wave potential reaching 0.99 V and 0.92 V, respectively. The prepared catalysts also showed superior stability and followed the 4-electron pathway ORR process in alkaline solution.

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Interplay between morphology and electrochemical performance of “core–shell” electrocatalysts for oxygen reduction reaction based on a PtNix carbon nitride “shell” and a pyrolyzed polyketone nanoball “core”

Cited by 62 publications

References 33 publications

Origins, Developments, and Perspectives of Carbon Nitride-Based Electrocatalysts for Application in Low-Temperature FCs

Origins, Developments, and Perspectives of Carbon Nitride-Based Electrocatalysts for Application in Low-Temperature FCs

Interplay between Nitrogen Concentration, Structure, Morphology, and Electrochemical Performance of PdCoNi “Core–Shell” Carbon Nitride Electrocatalysts for the Oxygen Reduction Reaction

A Novel Metal–Organic Framework Route to Embed Co Nanoparticles into Multi-Walled Carbon Nanotubes for Effective Oxygen Reduction in Alkaline Media

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