Understanding the chemisorption-based activation mechanism of the oxygen reduction reaction on nitrogen-doped graphitic materials

Ferre-Vilaplana, Adolfo; Herrero, Enrique

doi:10.1016/j.electacta.2016.04.039

Cited by 32 publications

(38 citation statements)

References 49 publications

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“…In addition, it has been shown that in basic medium, these materials show an intrinsic activity close to that of Pt. [149] Nitrogen doping can also be combined with the use of metals in the form of isolated atoms. Thus, it has been shown that Co 1 ÀN x /C or Fe 1 ÀN x /C catalysts exhibit an electrochemical activity greater than that of the supports alone doped with nitrogen.…”

Section: Oxygen Reduction Reactionmentioning

confidence: 99%

Single Atom Catalysts on Carbon‐Based Materials

2018

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Metal particle size is an important parameter to consider when looking at supported catalyst performances. As for other properties, surface reactivity of metallic nanoparticles is thus highly size‐dependent. The smallest size that can be reached for this type of object is of course the isolated atom deposited on a support. The preparation of single‐atom catalysts (SAC) is not trivial, since to avoid clustering, the mean adsorption energy of the metal on the support should be higher than its cohesive energy. The choice of a support that allows a strongly interacting environment with the metal is therefore a key step in the preparation of such catalysts. The spectrum of carbon (nano)materials is very broad, and their structure as well as their surface chemistry, although sometime complex, can be tuned and exploited for the stabilization of SAC. This Review summarizes in a comprehensive manner experimental and computational studies aiming at: i) preparing SAC on carbon materials, ii) understanding the metal‐support interactions in SAC, and iii) studying how this relates to catalytic performances. The use of SAC follows well the needs dictated by society (energy and environment issues), and many studies have already been published in various fields, such as thermal catalysis, photocatalysis and electrocatalysis.

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Section: Oxygen Reduction Reactionmentioning

confidence: 99%

Single Atom Catalysts on Carbon‐Based Materials

2018

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“…16.57 Å. Moreover, since previous results indicate that the hydrogenation of pyridinic nitrogen in graphitic materials could play a role in the molecular oxygen activation, 21 different hydrogenation states were explored searching for the relevant one.…”

Section: Methodsmentioning

confidence: 99%

“…Both observations can be explained by the lower stability of the adsorbed superoxide state on the investigated material in comparison with those present in other graphitic materials. [20][21] An activating step less favorable implicates a smaller activity an adsorbed superoxide state presenting lower stability implicates that the adsorbate can be more easily desorbed upon protonation to the solution to yield HOO -in alkaline media.…”

Section: Oxygen Reduction Reactionmentioning

confidence: 99%

“…When these materials are doped with nitrogen, their ORR activity improves, but increasing their selectivity towards the formation of water. [5][6][7][8][9][10][11][12][13][14][15][16][17] Computational results suggest that the ORR activity of these materials depends on the specific location of the nitrogen-dopants, [18][19] In a pair of previous works, [20][21] the role played by different forms of nitrogen-dopants in the activation of the molecular oxygen on graphitic materials has been elucidated. The need of destabilized carbons and available charge, and the role played by the hydrogenation of pyridinic nitrogendopants and the solvation effect was established.…”

Section: Introductionmentioning

confidence: 99%

“…Our previous results suggest that such a kind of active sites could be enabled by pyridinic nitrogen-dopants at the zigzag edges of graphitic materials. 21 The assembling of porous materials from molecular building blocks allows the control not only of the composition but also of the microstructure and is essential for a heterogeneous catalyst. Aza-fused π-conjugated microporous polymers (Aza-CMP), which are assembled from molecular building blocks, present a high number of pyridinic nitrogen-dopants at edges with a zig-zag characteristic.…”

Section: Introductionmentioning

confidence: 99%

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An Aza-Fused π-Conjugated Microporous Framework Catalyzes the Production of Hydrogen Peroxide

et al. 2016

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ABSTRACT:The electrochemical production of hydrogen peroxide can be implemented in small-scale plants under "on demand" approach. For that, selective catalysts for the oxygen reduction reaction (ORR) towards the desired species are required. Here, we report about the synthesis, characterization, ORR electrochemical behavior and reaction mechanism of an aza-fused π-conjugated microporous polymer, which presents high selectivity towards hydrogen peroxide. It was synthesized by polycondensation of 1,2,4,5-benzenetetramine tetrahydrochloride and triquinoyl octahydrate. A cobaltmodified version of the material was also prepared by a simple post-synthesis treatment with a Co(II) salt. The characterization of the material is consistent with the formation of a conductive robust porous covalent laminar poly-aza structure. The ORR properties of these catalysts were investigated using rotating disk and rotating disk-ring arrangements. The results indicate that hydrogen peroxide is almost exclusively produced at very low overpotential values on these materials. Density functional theory calculations provide key elements to understand the reaction mechanism. It is found that, at the relevant potential for the reaction, half of the nitrogen atoms of the material would be hydrogenated. This hydrogenation process would destabilize some carbon atoms in the lattice and provides segregated charge. On the destabilized carbon atoms, molecular oxygen would be chemisorbed with the aid of charge transferred from the hydrogenated nitrogen atoms and solvation effects. Due to the low destabilization of the carbon sites, the resulting molecular oxygen chemisorbed state, which has the characteristics of a superoxide species, would be only slightly stable and would promote the formation of hydrogen peroxide.

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Active Sites and Mechanism of Oxygen Reduction Reaction Electrocatalysis on Nitrogen‐Doped Carbon Materials

2018

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The oxygen reduction reaction (ORR) is a core reaction for electrochemical energy technologies such as fuel cells and metal–air batteries. ORR catalysts have been limited to platinum, which meets the requirements of high activity and durability. Over the last few decades, a variety of materials have been tested as non‐Pt catalysts, from metal–organic complex molecules to metal‐free catalysts. In particular, nitrogen‐doped graphitic carbon materials, including N‐doped graphene and N‐doped carbon nanotubes, have been extensively studied. However, due to the lack of understanding of the reaction mechanism and conflicting knowledge of the catalytic active sites, carbon‐based catalysts are still under the development stage of achieving a performance similar to Pt‐based catalysts. In addition to the catalytic viewpoint, designing mass transport pathways is required for O2. Recently, the importance of pyridinic N for the creation of active sites for ORR and the requirement of hydrophobicity near the active sites have been reported. Based on the increased knowledge in controlling ORR performances, bottom‐up preparation of N‐doped carbon catalysts, using N‐containing conjugative molecules as the assemblies of the catalysts, is promising. Here, the recent understanding of the active sites and the mechanism of ORRs on N‐doped carbon catalysts are reviewed.

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Understanding the chemisorption-based activation mechanism of the oxygen reduction reaction on nitrogen-doped graphitic materials

Cited by 32 publications

References 49 publications

Single Atom Catalysts on Carbon‐Based Materials

Single Atom Catalysts on Carbon‐Based Materials

An Aza-Fused π-Conjugated Microporous Framework Catalyzes the Production of Hydrogen Peroxide

Active Sites and Mechanism of Oxygen Reduction Reaction Electrocatalysis on Nitrogen‐Doped Carbon Materials

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