Fast and cost-effective room temperature synthesis of high quality graphene oxide with excellent structural intactness

https://doi.org/10.1016/j.susmat.2020.e00198Get rights and content

Abstract

Graphene oxide (GO) is well known as a key material to the commercialization of graphene-based applications due to its excellent processability and abundant starting materials. However, producing high quality GO with excellent structural intactness still remains a challenge despite the significant research effort over the past decade. Herein, we demonstrate an effective approach to achieving well-oxidized GO within only 5 h of oxidation time at 5 °C or 25 °C from expanded graphite as a starting material. Our finding reveals that the well-oxidized GO synthesized at 25 °C can regain more graphitic sp2 networks and thus becomes as conductive as the GO prepared at 5 °C by means of thermal annealing or green chemical reduction. We also found that green chemical reduction using vitamin C (VC) is more efficient in restoring the electrical conductivity and reducing the defects in the GO produced at room temperature. The protocol reported in this paper offers a promising, sustainable way to fabricate high quality GO with minimal energy input, while being cost-effective.

Introduction

Since the discovery in 2004, graphene, a monolayer of carbon atoms arranged in hexagonal rings, has been sitting in the spotlight owing to its fascinating properties [1,2]. As the most important graphene derivatives, graphene oxide (GO) and its reduced form, reduced graphene (rGO), have been the subject of intense exploration and achieved great success in a diverse range of applications, ranging from energy-storage and -conversion devices [3,4] to ionic and molecular sieving membranes [5,6] to biomedical applications [[7], [8], [9], [10]]. The ultimate goal of developing these applications is to promote the broad commercialization of graphene-based products with high performance and cost-effectiveness [11]. In order to realize this goal, the scalable and cost-effective fabrication of GO materials is of significant importance [12]. Currently, the exfoliation of chemically oxidized graphite into single layers using the KMnO4-based Hummers method [13], namely the graphite oxide route, is the most extensively used method to produce GO in bulk [12]. Typically, it involves the edge-to-core diffusion of oxidizing agents in the narrow graphite interlayer galleries, which determines the reaction rate of forming GO [14]. To facilitate the conversion of graphite into GO, one common strategy is to pre-intercalate graphite with foreign species which enables to expand the interlayer spacings [[15], [16], [17], [18]]. The spacing expansion is more dramatic when gasifying the thermo-decomposable intercalants, namely forming the expanded graphite [19,20]. In addition, applying external heating (≥ 35 °C) can thermodynamically favor the diffusion process [21,22]. Owing to the inexpensive sources, good dispersibility, rich oxygen functional groups and high product yield, graphite oxide route has been successfully scaled up from lab-scale researches to industrial mass production [12,23].

Despite its preliminary commercialization, the graphite oxide route with harsh oxidation conditions, such as the use of strong acids, oxidants and heating, usually introduces uncontrollable functionalities and enormous permanent defects into final products. This will result in poor electronic properties of rGO, including electrical conductivity and charge-carrier mobility, which are undesirable for electroconductive applications [24]. To preserve the sp2 honeycomb structure in graphene basal plane, using low reaction temperature (<0 °C) in the graphite oxide route can effectively minimize the loss of carbon atoms in the GO. The resulting highly intact rGO exhibited excellent electronic properties that are comparable to the pristine graphene [[25], [26], [27]]. However, the low temperature modified methods are of higher cost due to the necessity for low temperature control, poor GO yield (<50%) and significantly more time-consuming process (>1 day per batch).

To obtain high quality GO without compromising cost-effectiveness, our group recently reported a simple but effective method to synthesize GO with rich thermally labile oxygen functional groups from pre-intercalated graphite at room temperature (25 °C) [28]. In comparison to the conventional graphite oxide routes (reaction temperature ≥ 35 °C), the advantages of our approach are that the resultant GO is not only less defective but also restores more electrical conductivity after simple thermal annealing at only 150 °C in ambient air. This makes the room temperature GO (RT-GO) more conducive and cost-effective to electroconductive applications relative to the traditional GO. For example, RT-GO can be blended well into composite slurry and converted to conductive binders in lithium ion batteries after mild annealing at 150 °C [28]. The benefits of the facile deoxygenation and high structural integrity of RT-GO have also been demonstrated by Li and co-workers [29]. Furthermore, it is worth noting that the RT-GO prepared by Li’s group, which was oxidized for 3 h, exhibited comparable defect density and electrical conductivity to the GO oxidized at 5 °C for 12 h (low T-GO) after chemical reduction.

The diffusion of oxidants in natural graphite or pre-intercalated graphite proceeds in a noticeably slower manner at room temperature and below, thus requiring much longer reaction time [14,28,30]. To address this issue, the use of expanded graphite with larger inter-galleries spacing as the starting material is likely to facilitate the propagation of oxidation under mild conditions [19,20,[31], [32], [33], [34]]. Herein, we demonstrated that the conversion of expanded graphite into monolayered GO can be accomplished within only 5 h at both 5 °C (low temperature) and 25 °C (room temperature). Further, this enabled the direct comparisons between RT-GO and low T-GO under the same reaction conditions except for temperature. We further found that in spite of its higher oxidation degree and lower electrical conductivity, RT-GO could regain considerably more electrical conductivity as compared to the low T-GO after a simple thermal treatment at 150 °C or mild chemical reduction by vitamin C (VC). In addition, VC was found to be more efficient for the restoration of conductivity than the mild thermal annealing process. Extensive characterizations revealed that more conjugated sp2 carbon networks and less defective structure recovered from VC reduction led to the greater increase in the conductivity of the RT-GO with respect to that of the low-T GO. On account of the mild but efficient oxidation process coupled with eco-friendly reduction methods, it is expected that the RT-GO derived from expanded graphite will offer significant advantages towards the bulk-scale, sustainable production of graphene materials at low cost for electroconductive applications.

Section snippets

Materials

Expanded graphite powder (≥ 99% carbon, 6 μm) was purchased from Qingdao FRT Graphite Co. Ltd. KMnO4 (99.0%), concentrated H2SO4 (98%), aqueous H2O2 solution (30% w/w), N,N-dimethylformamide (DMF), ethanol (undenatured, 100%) and hydrochloric acid (32 wt%) were all purchased from Chem-Supply. Vitamin C (l-ascorbic acid, C6H8O6) was purchased from Ajax Chemicals. Deionized (DI) water was used in all experimental procedures, including the synthesis reaction and purification.

Synthesis of RT-GO and low-T GO

GO samples were

Chemical properties of as-prepared RT-GO and low T-GO

In this work, we prepared GO samples using two different oxidation temperatures, namely 5 °C and 25 °C, from expanded graphite (see experimental detail). XRD was used to investigate the conversion of expanded graphite to graphite oxide, as shown in Fig. 1a. As compared to the original expanded graphite, all GO samples lost the strong graphitic peak at 26.4°, which can be associated with the interlayer spacing between unoxidized graphene sheets (3.46 Å). Instead, the main characteristic peak at

Conclusions

In this paper, we have further studied the chemical method to produce monolayered GO with excellent solution processability from expanded graphite at room temperature. The use of expanded graphite significantly facilitated the conversion to GO within only 5 h at both 5 °C and 25 °C. This allows a more rational comparison between low T-GO (at 5 °C) and RT-GO (at 25 °C) using the same synthesis conditions. We found that GO produced at 25 °C was able to recover considerably more electrical

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

The authors acknowledge the support from the Australian Research Council (DP190100120, LP160101521 and FT160100207).

References (70)

  • G.A. Zickler et al.

    A reconsideration of the relationship between the crystallite size La of carbons determined by X-ray diffraction and Raman spectroscopy

    Carbon

    (2006)
  • A. Sadezky et al.

    Raman microspectroscopy of soot and related carbonaceous materials: spectral analysis and structural information

    Carbon

    (2005)
  • J.D. Herdman et al.

    A comparison of Raman signatures and laser-induced incandescence with direct numerical simulation of soot growth in non-premixed ethylene/air flames

    Carbon

    (2011)
  • K.S. Novoselov et al.

    Electric field effect in atomically thin carbon films

    Science

    (2004)
  • A.K. Geim et al.

    The rise of graphene

    Nat. Mater.

    (2007)
  • F. Bonaccorso et al.

    Graphene, related two-dimensional crystals, and hybrid systems for energy conversion and storage

    Science

    (2015)
  • R. Raccichini et al.

    The role of graphene for electrochemical energy storage

    Nat. Mater.

    (2014)
  • Y. Yang et al.

    Large-area graphene-nanomesh/carbon-nanotube hybrid membranes for ionic and molecular nanofiltration

    Science

    (2019)
  • L. Chen et al.

    Ion sieving in graphene oxide membranes via cationic control of interlayer spacing

    Nature

    (2017)
  • K. Kostarelos et al.

    Graphene devices for life

    Nat. Nanotechnol.

    (2014)
  • C. Chung et al.

    Biomedical applications of graphene and graphene oxide

    Acc. Chem. Res.

    (2013)
  • D. Voiry et al.

    Low-dimensional catalysts for hydrogen evolution and CO2 reduction

    Nat. Rev. Chem.

    (2018)
  • A. Zurutuza et al.

    Challenges and opportunities in graphene commercialization

    Nat. Nanotechnol.

    (2014)
  • W.S. Hummers et al.

    Preparation of graphitic oxide

    J. Am. Chem. Soc.

    (1958)
  • A.M. Dimiev et al.

    Mechanism of Graphene oxide formation

    ACS Nano

    (2014)
  • N.I. Kovtyukhova et al.

    Layer-by-layer assembly of ultrathin composite films from micron-sized graphite oxide sheets and polycations

    Chem. Mater.

    (1999)
  • L. Dong et al.

    Synthesis and reduction of large sized graphene oxide sheets

    Chem. Soc. Rev.

    (2017)
  • Y. Xu et al.

    Flexible Graphene films via the filtration of water-soluble noncovalent functionalized graphene sheets

    J. Am. Chem. Soc.

    (2008)
  • D. Li et al.

    Processable aqueous dispersions of graphene nanosheets

    Nat. Nanotechnol.

    (2008)
  • S.H. Aboutalebi et al.

    Spontaneous formation of liquid crystals in ultralarge graphene oxide dispersions

    Adv. Funct. Mater.

    (2011)
  • L. Dong et al.

    Reactivity-controlled preparation of ultralarge graphene oxide by chemical expansion of graphite

    Chem. Mater.

    (2017)
  • D.C. Marcano et al.

    Improved synthesis of graphene oxide

    ACS Nano

    (2010)
  • W. Ren et al.

    The global growth of graphene

    Nat. Nanotechnol.

    (2014)
  • X.-Y. Wang et al.

    Precision synthesis versus bulk-scale fabrication of graphenes

    Nat. Rev. Chem.

    (2017)
  • S. Eigler et al.

    Wet chemical synthesis of graphene

    Adv. Mater.

    (2013)
  • Cited by (6)

    • Progress of research on the sustainable preparation of graphene and its derivatives

      2023, Graphene Extraction from Waste: A Sustainable Synthesis Approach for Graphene and Its Derivatives
    • Effect of free radicals and electric field on preparation of coal pitch-derived graphene using flash Joule heating

      2022, Chemical Engineering Journal
      Citation Excerpt :

      Moreover, the various excellent properties of graphene can only be displayed when the quality of graphene is high. With the increase of the number of layers and the accumulation of internal defects, the superior properties of graphene will be reduced[9,10]. Most bulk graphene is produced by the top-down method of exfoliating graphite, which usually requires a large amount of solvents for high-energy mixing, shearing, ultrasonic or electrochemical treatment[11,12].

    • Mechanistic insights into ion-beam induced reduction of graphene oxide: An experimental and theoretical study

      2022, Radiation Physics and Chemistry
      Citation Excerpt :

      C 1s spectra of pristine and irradiated samples were deconvoluted into five components at: 284.8, 286.9, 288.1, 288.9 and 290.3 eV. At ∼ 284.8 eV, peaks from sp2 CC (Jovanovic et al., 2017; Hareesh et al., 2017; Malinsk ý et al., 2017; Rathnayake et al., 2017; L ó pez-D í az et al., 2017a; Guex et al., 2017; Sysoev et al., 2018), sp3 C–C (Jovanovic et al., 2017; Malinsk ý et al., 2017; Wei et al., 2020; Rathnayake et al., 2017; Guex et al., 2017; Sysoev et al., 2018; Yuan et al., 2020) or from convolute of these bonds CC/C–C (Khandelwal et al., 2019; Jovanovi ć et al., 2020; Sengupta et al., 2020; Sieradzka et al., 2020; Qin et al., 2020) are usually observed. The peak at ∼286.9 eV is usually assigned to C–O from phenol, hydroxyl, ether and epoxy groups (Jovanovic et al., 2017; Hareesh et al., 2017; Khandelwal et al., 2019; Malinsk ý et al., 2017; Wei et al., 2020; Rathnayake et al., 2017; L ó pez-D í az et al., 2017a; Guex et al., 2017; Sysoev et al., 2018; Yuan et al., 2020; Jovanovi ć et al., 2020; Sengupta et al., 2020; Qin et al., 2020; Stobinski et al., 2014; Dash et al., 2016).

    • Enhanced electrochemical production and facile modification of graphite oxide for cost-effective sodium ion battery anodes

      2021, Carbon
      Citation Excerpt :

      EG is manufactured by intercalating flake graphite with thermally volatile agents, the decomposition of which upon thermal shock can provoke an immediate expansion in the volume of graphite [21,22]. The overall interlayer spacing of EG, however, barely changes with respect to pristine graphite [23–25], and this will pose a challenge to their efficacy as a major active material in SIB anodes. In terms of GrO, the excess functional groups between graphene layers will not only impede the intercalation of sodium ions, but also reduce the charge transfer due to the low electrical conductivity [4].

    View full text