Enriched graphitic N in nitrogen-doped graphene as a superior metal-free electrocatalyst for the oxygen reduction reaction

Lu, Xiangyu; Wang, Dan; Ge, Liping; Xiao, Liyang; Zhang, Haiyan; Liu, Lilai; Zhang, Jinqiu; Liu, Anmin; Yang, Peixia

doi:10.1039/c8nj04857f

Cited by 93 publications

(39 citation statements)

References 43 publications

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“…The 4e − reaction pathway is preferred to the 2e − one yielding to water molecules, and it9 is considered a plausible pathway for ORR on doped graphene in both acid and alkaline media [17]. However, there are still debates related to the nature of the active sites for ORR contained in the nitrogen-doped carbon materials; some studies indicate the graphitic N, while others consider the pyridinic N or pyrrolic N as the active centers in the ORR process [18]. Moreover, different opinions are pointed out related to the significance of nitrogen percentages from N-doped materials onto their ORR catalytic performances; there are voices claiming improvements of catalytic activity with increases in the amount of nitrogen, while others consider the active center contents as being the key for catalytic performance [18].…”

Section: Introductionmentioning

confidence: 99%

Eco-Friendly Nitrogen-Doped Graphene Preparation and Design for the Oxygen Reduction Reaction

et al. 2021

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Four N-doped graphene materials with a nitrogen content ranging from 8.34 to 13.1 wt.% are prepared by the ball milling method. This method represents an eco-friendly mechanochemical process that can be easily adapted for industrial-scale productivity and allows both the exfoliation of graphite and the synthesis of large quantities of functionalized graphene. These materials are characterized by transmission and scanning electron microscopy, thermogravimetry measurements, X-ray powder diffraction, X-ray photoelectron and Raman spectroscopy, and then, are tested towards the oxygen reduction reaction by cyclic voltammetry and rotating disk electrode methods. Their responses towards ORR are analysed in correlation with their properties and use for the best ORR catalyst identification. However, even though the mechanochemical procedure and the characterization techniques are clean and green methods (i.e., water is the only solvent used for these syntheses and investigations), they are time consuming and, generally, a low number of materials can be prepared, characterized and tested. In order to eliminate some of these limitations, the use of regression learner and reverse engineering methods are proposed for facilitating the optimization of the synthesis conditions and the materials’ design. Thus, the machine learning algorithms are applied to data containing the synthesis parameters, the results obtained from different characterization techniques and the materials response towards ORR to quickly provide predictions that allow the best synthesis conditions or the best electrocatalysts’ identification.

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Section: Introductionmentioning

confidence: 99%

Eco-Friendly Nitrogen-Doped Graphene Preparation and Design for the Oxygen Reduction Reaction

et al. 2021

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“…Both these effects are accountable for increasing the electron scattering rate and hence the intensity of the 2D peak decreases with the increase of dopant concentration . It must be noted that the introduction of defects in the NG‐PPy sample also leads to the formation of more catalytic sites, which is beneficial for ORR activity …”

Section: Resultsmentioning

confidence: 99%

Polymer‐Assisted Electrophoretic Synthesis of N‐Doped Graphene‐Polypyrrole Demonstrating Oxygen Reduction with Excellent Methanol Crossover Impact and Durability

Mohmad

Sarkar

Biswas

et al. 2020

Chemistry A European J

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The designa nd synthesis of metal-free catalysts with superior electrocatalytic activity,h ighd urability,l ow cost, and under mild conditions is extremely desirable but remains challenging. To address this problem,apolymer-assisted electrochemical exfoliation technique of graphitei n the presence of an aqueous acidic mediumi sr eported. This simple, cost-effective,a nd mass-scale production approach could open the possibility for the synthesis of high-quality nitrogen-doped graphene-polypyrrole (NG-PPy). The NG-PPy catalyst displays an improved half wave potential (E 1/2 = 0.77 V) in alkaline medium compared with G-PPy (E 1/2 = 0.66 V). Most importantly,t his catalystd emonstrates excellent stability with high methanol tolerance, and it outperforms the commercial Pt/C catalyst and other previouslyr e-portedm etal-free catalysts. The content of graphitic nitrogen atoms is the key factor for the enhancement of electrocatalytic activityt owards oxygen reduction reactions (ORR). Interestingly,t he NG-PPy catalystc an be used as ac athode materiali naz inc-airb attery,w hich demonstrates ah igher peak powerd ensity (59 mW cm À2)t han G-PPy (36.6 mW cm À2), highlighting the importance of the low-cost materials ynthesis approach towards the development of metal-free efficient ORR catalysts for fuel cell and metal-air battery applications.R emarkably, the polymer-assisted electrophoretic exfoliation of graphite with ah igh yield (% 88 wt %) of few-layer graphene flakesc ould pave the way towardst he mass production of high-quality graphene for a varietyo fapplications.

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“…The plot of capacitive current from CVs (at 1.1 V) versus scan rate yields a straight line with a slope equal to C dl (Figure S9d, Supporting Information) and ECSA is generally assumed to be proportional to the C dl . [85] The estimated C dl values of HCNB@G-600, HCNB@G-700, and HCNB@G-800 are 23, 16, and 12 mF cm −2 , respectively. Thus, the highest value of the C dl for the HCNB@G-700 implying higher ECSA that leads to the better exposure and enhanced utilization of the active sites along with facile charge transfer which agrees with the robust HER and OER activities.…”

Section: Wwwadvmatinterfacesdementioning

confidence: 90%

Hollow Carbon Nanoballs on Graphene as Metal‐Free Catalyst for Overall Electrochemical Water Splitting

Begum

Ahmed

Jung

2021

Adv Materials Inter

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A great deal of research effort has been dedicated for designing an efficient bifunctional metal‐free carbon catalyst for electrochemical water splitting, however, it remains challenging to introduce multiactive sites into a single catalyst. Herein, a series of bifunctional catalysts is designed that exploit intramolecular reorientation of nitrogen atom within the hollow nanoball from polyacrylonitrile on graphene through thermal treatment to achieve covalent doping. The as synthesized hollow carbon nanoballs on graphene (HCNB@G) catalysts have huge defective edges and microporous channels and contain a high density of electroactive graphitic‐N and pyridinic‐N as dual‐active sites. As a result, the optimized HCNB@G‐700 enhances electrocatalytic activities for both oxygen evolution and hydrogen evolution reactions (OER and HER) in 1.0 m KOH by generating 217 and 108 mV overpotential to gain a current density of 10 mA cm−2, respectively. This remarkable electrocatalytic activity mainly originates from the appropriate combination of suitable nitrogen active sites and edge defects with microchannels that not only facilitate the penetration of electrolyte but also improve the stability of the HCNB@G. In addition, the superior conductivity and high surface area of HCNB@G boost electrocatalytic activity by supporting efficient charge transport and enabling rapid mass diffusion with gas release, respectively.

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Enriched graphitic N in nitrogen-doped graphene as a superior metal-free electrocatalyst for the oxygen reduction reaction

Abstract: The active center of N-G catalysts for ORR is confirmed to be related to the graphitic N, and the total N content in N-G catalysts is not the key factors to determine the ORR activity.

Cited by 93 publications

References 43 publications

Eco-Friendly Nitrogen-Doped Graphene Preparation and Design for the Oxygen Reduction Reaction

Eco-Friendly Nitrogen-Doped Graphene Preparation and Design for the Oxygen Reduction Reaction

Polymer‐Assisted Electrophoretic Synthesis of N‐Doped Graphene‐Polypyrrole Demonstrating Oxygen Reduction with Excellent Methanol Crossover Impact and Durability

Hollow Carbon Nanoballs on Graphene as Metal‐Free Catalyst for Overall Electrochemical Water Splitting

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