Effect of water molecules co-intercalation and hydrolysis on the electrochemical deconsolidation of matrix graphite in aqueous nitric acid

Jiao, Zengtong; Zhang, Chi; Zhang, Wei; He, Liang; Lu, Zhenming; Qi, Meili; Li, Caixia; Cheng, Suwei; Xu, Gang; Chen, Xiaotong; Liu, Bing; Tang, Yaping

doi:10.1016/j.carbon.2022.02.025

Cited by 5 publications

(5 citation statements)

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“…The I D /I G ratio also increases with HNO 3 vol%, Figure 8c. However, a singular minimum is found in all cases at 50% vol, consistent with two different situations: anion intercalation, oxidation of graphite and exfoliation at vol% HNO 3 below 50% and intercalation, oxidation and expansion of graphite oxide for vol% above 50% [62]. Higher I D /I G values were obtained for REGO prepared in 0.1 M (NH 4 ) 2 SO 4 + 5 mM HNO 3 compared to those prepared in 0.1 M (NH 4 ) 2 SO 4 + 1 M HNO 3 .…”

Section: Exfoliation Of Graphite Foil In Mixed Electrolytessupporting

confidence: 76%

“…The XPS spectra show that the oxygen and nitrogen contents increase when HNO 3 (50 vol%) is combined with 0.1 M (NH 4 ) 2 SO 4 or 0.1 M H 2 SO 4. As expected, the increase in the oxygen content is more pronounced with 1 M vs. 5 mM HNO 3 because of the strong oxidation power of this acid which favors the oxidation of graphite [62], Figures 3a and 5a. The C 1s and N 1s spectra of REGO were deconvoluted the same way as those obtained for REGO prepared in 0.1 M (NH 4 ) 2 SO 4 (Figures 2b and 2d, respectively).…”

Section: Exfoliation Of Graphite Foil In Mixed Electrolytessupporting

confidence: 76%

“…The I D /I G ratio also increases with HNO 3 vol%, Figure8c. However, a singular minimum is found in all cases at 50% vol, consistent with two different situations: anion intercalation, oxidation of graphite and exfoliation at vol% HNO 3 below 50% and intercalation, oxidation and expansion of graphite oxide for vol% above 50%[62]. Higher I D /I G values were obtained for REGO prepared in 0.1 M (NH 4 ) 2 SO 4 + 5 mM HNO 3…”

supporting

confidence: 74%

“…Previous works on the electrochemical exfoliation of graphite rods [ 98 ] or on the electrochemical oxidation of natural graphite flakes [ 99 ] in H 2 SO 4 :HNO 3 mixtures do not mention the presence of nitrogen species on the products. However, a study on the electrochemical deconsolidation of matrix graphite using HNO 3 as electrolyte showed an increase of the nitrogen content (from 0.53 to 1.08%) with the 1 M HNO 3 (from 4 to 68%) [ 62 ]. According to the authors, the trend suggests the formation of HNO 3 -graphite intercalation compound.…”

Section: Discussionmentioning

confidence: 99%

“…On the one hand, (NH 4 ) 2 SO 4 and H 2 SO 4 were selected for their high exfoliation efficiency due to the facile intercalation of HSO 4 − /SO 4 2− anions between the graphitic layers [ 44 , 61 ]. On the other hand, both (NH 4 ) 2 SO 4 and HNO 3 [ 62 ] were used as nitrogen sources for substitutional doping of the graphene material after thermal treatment at 900 °C.…”

Section: Introductionmentioning

confidence: 99%

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Nitrogen-Doped Graphene Materials with High Electrical Conductivity Produced by Electrochemical Exfoliation of Graphite Foil

Kammoun,

Ossonon,

Tavares

2024

Nanomaterials

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Nitrogen-doped graphene-based materials are of utmost importance in sensing and energy conversion devices due to their unique physicochemical properties. However, the presence of defects such as pyrrolic nitrogen and oxygenated functional groups reduces their electrical conductivity. Herein, a two-step approach based on the electrochemical exfoliation of graphite foils in aqueous mixed electrolytes followed by thermal reduction at 900 °C is used to prepare high-quality few layers of N-doped graphene-based materials. The exfoliations were conducted in 0.1 M (NH4)2SO4 or H2SO4 and HNO3 (5 mM or 0.1 M) electrolytes mixtures and the HNO3 vol% varied. Chemical analysis demonstrated that the as-prepared graphene oxides contain nitro and amine groups. Thermal reduction is needed for substitutional N-doping. Nitrogen and oxygen surface concentrations vary between 0.23–0.96% and 3–8%, respectively. Exfoliation in (NH4)2SO4 and/or 5 mM HNO3 favors the formation of pyridinic-N (10–40% of the total N), whereas 1 M HNO3 favors the formation of graphitic-N (≈60%). The electrical conductivity ranges between 166–2705 Scm−1. Raman spectroscopy revealed a low density of defects (ID/IG ratio between 0.1 and 0.7) and that most samples are composed of mono-to-bilayer graphene-based materials (IG/I2D integrated intensities ratio). Structural and compositional stability of selected samples after storage in air for three months is demonstrated. These results confirm the high quality of the synthesized undoped and N-doped graphene-type materials.

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Section: Exfoliation Of Graphite Foil In Mixed Electrolytessupporting

confidence: 76%

Section: Exfoliation Of Graphite Foil In Mixed Electrolytessupporting

confidence: 76%

“…The I D /I G ratio also increases with HNO 3 vol%, Figure8c. However, a singular minimum is found in all cases at 50% vol, consistent with two different situations: anion intercalation, oxidation of graphite and exfoliation at vol% HNO 3 below 50% and intercalation, oxidation and expansion of graphite oxide for vol% above 50%[62]. Higher I D /I G values were obtained for REGO prepared in 0.1 M (NH 4 ) 2 SO 4 + 5 mM HNO 3…”

supporting

confidence: 74%