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Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents
Journal Pre-proofs Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents Yang Li, Jingjing Liu, Lihua Zhang, Qian Ren, Bin Shen PII: DOI: Reference:
S0167-577X(20)30102-6 https://doi.org/10.1016/j.matlet.2020.127397 MLBLUE 127397
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
22 November 2019 4 January 2020 20 January 2020
Please cite this article as: Y. Li, J. Liu, L. Zhang, Q. Ren, B. Shen, Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents, Materials Letters (2020), doi: https://doi.org/10.1016/ j.matlet.2020.127397
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier B.V.
Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents Yang Lia,*, Jingjing Liua, Lihua Zhangb, Qian Renb, Bin Shenb,* a
College of Chemistry and Pharmaceutical Engineering, Huanghuai University,
Zhumadian, Henan Province, 463000, China b
Ningbo Key Lab of Polymer Materials, Ningbo Institute of Materials Technology
and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang Province, 315201, China
Abstract: Porous graphene film (PGF) with unique surface consisting mostly of thermal-exfoliated worm-like graphene sheets were fabricated through flame expansion-exfoliation of graphene oxide film with non-exfoliated graphite oxide powders precipitated at its bottom. The resultant PGF showed not only faster adsorption rate during oil/solvent collection in comparison with traditional PGFs, but also similar high adsorption capacity and reliable recyclability. For instance, the adsorption capacities of the new PGF for organic solvents were in the range of ~11-33 times of its own weight, and they displayed good stability during ten exchange-evaporation recycling process. Moreover, this approach can be easily scalable and applied to prepare other PGF composites. Keywords: carbon materials; porous materials; flame expansion-exfoliation; faster adsorption; high adsorption capacity; reliable recyclability
*Corresponding authors. E-mail addresses: [email protected] (Y. L.), [email protected] (B. S.). 1
1. Introduction The frequent oil spill accidents together with toxic chemical leaks have resulted in serious water pollution, greatly hindering the sustainable development of society and economy. To date, more attention has been paid to the development of highly porous adsorbents [1], and graphene-based porous materials have recently been regarded as “star” adsorbers for the removal of oils and organic solvents [2], owing to its extreme high theoretical specific surface area (SSA) of ~2600 m2/g, good chemical stability, and intrinsically hydrophobic and oleophilic surface. Porous graphene films (PGFs) have been verified to be very effective for kinds of oil/solvent adsorption due to their high adsorption capacity and reliable recyclability, and they can be regenerated after each use by drying in a vacuum oven, annealing in a furnace, hand-pressing with a paper, or direct combustion [3, 4]. Though possessing porous network structure inside, the PGF always have dense outside surfaces owing to the presence of un-exfoliated graphene layers [5]. Consequently, they could have high adsorption capacity, but with relatively slower adsorption rate in comparison with other porous graphene materials like graphene foams, which have interconnected open network structure inside and macroporous surfaces outside [6], and thereby exhibiting both high adsorption capacity and fast adsorption rate. Hence, the fabrication of PGFs with large adsorption capacity and ultrafast adsorption rate, is of practical significance. This article demonstrates facile fabrication of a novel PGF with unique surface consisting mostly of worm-like graphene sheets through flame expansion-exfoliation of graphene oxide (GO) film with non-exfoliated graphite oxide powders precipitated at its bottom. The new PGF showed not only high adsorption capacity and reliable recyclability, but also faster adsorption rate to organic solvents in contrast with the PGF counterparts by traditional methods. This approach can be easily scalable and applied to design other PGFs.
2. Experimental GO suspension was obtained by ultrasonic exfoliation of graphite oxide 2
(prepared by Hummers’ method) in water for 1 hour (without centrifugation). Then, GO film was fabricated by direct evaporation of the GO suspension under mild heating (60 °C). Finally, the new PGF was fabricated by flame expansion of GO film for several seconds on the alcohol flame. For comparison, the traditional PGF fabricated by the leavening strategy and low-temperature exfoliation method were also prepared according to the previous works [7, 8]. More details are shown in the Supplementary Information.
3. Results and Discussion As displayed in Figure S1A, the evaporation-induced self-assembly method was utilized to prepare layered GO films. It should be noted that, the GO suspension used for film formation was not treated by strong centrifugation. Thus, the non-exfoliated graphite oxide powders after ultrasonication could gradually precipitate at the bottom of GO film during the evaporation of water. SEM observations confirmed that the top surface of such GO film was relatively smooth with many thin ripples on it (Figure S1C), while its bottom face was randomly inlaid with lots of granules (Figure S1B), which should be the non-exfoliated powders of graphite oxide in the suspension. For ultrafast expansion-exfoliation, the prepared GO film was treated by alcohol flame as shown in Figure 1A, in which the appearance of GO film changed from dark brown on both sides to silver black on the top surface and deep black on the bottom. As the alcohol flame can generate high temperature of ~600-800 oC, and could rapidly decompose the oxygen-containing groups in the GO film, resulting in ultrafast expansion-exfoliation. The whole process was finished only in few seconds, and further increasing the processing time would burn off the PGF gradually [9], because of the low decomposition temperature of graphene in air (less than ~600 °C) [10]. Figure 1B-1C indicated that, the layer-by-layer structure in GO film has been exfoliated with the formation of a cross-linked macroporous texture and the occurrence of ca. 18-fold volume expansion with increased thickness from ~15 μm to ~270 μm. According to previous reports [8, 11], the stacked layers of GO film could be thermally exfoliated under rapid heating to form porous structures inside, and at 3
the same time, the non-exfoliated graphite oxide powders at the bottom could be explosively expanded to form multilayered graphene aggregates. So the top surface of PGF (Figure 1D) was dense and accompanied with some cracks due to the explosive expansion induced by flame heating, while its bottom face was loose and porous, consisting mostly of thermal-exfoliated worm-like graphene sheets protruding from the surface (Figure 1E and 3F). These results are quite different from the dense and relatively smooth surface of the PGFs fabricated by the leavening and thermal-exfoliation strategies (Figure S2), so are their cross-section morphology with micro/macroporous networks, confirming the successful fabrication of new PGF by rapid flame heating method.
Figure 1. (A) The expansion-exfoliation process of GO film and the photographs of the as-prepared PGF. (B-C) SEM images of the cross-section of GO film and PGF. (D-E) SEM images of the top and bottom surface of PGF. The deoxygenation and structural integrity of the PGF were investigated. In the XPS spectra (Figure 2A), the C/O atom ratio was about ~9.5 and ~8.7 for the new PGF’s top and bottom surface respectively, which was much higher than that of GO 4
film (~2.4), suggesting the elimination of oxygen groups after flame heating. Moreover, their C1s scan spectrums were divided into three carbon components as displayed in Figure 2B, including C=C/C-C (~284.5 eV), C-O (~286.5 eV), and C=O (~288.0 eV) [6]. It is obvious in Figure 2C that, the percentage of C=C/C-C was increased noticeably when compared with GO film, and that of C-O and C=O was decreased for the PGF’s top and bottom surface due to the successful deoxygenation. In the Raman spectra (Figure 2D), the value of ID/IG decreased from ~1.16 for GO film to ~1.01 and ~1.04 for the PGF’s top and bottom surface, indicating the increase in the average size of sp2 carbon domains owing to the partial repairing of defects.
Figure 2. (A-B) XPS full spectrums and high-resolution C 1s spectrums of GO film and PGF. (C) Carbon components calculated from the C1s spectral deconvolution. (D) Raman spectrums of GO film and new PGF. The adsorption properties of the new PGF were evaluated in Figure 3. As seen in Figure 3A-3B, the new PGF quickly adsorbed the heptane completely when contacting the heptane (stained with Sudan red), showing a strong selectively sorption capability for organic solvent. To highlight the advantage of the loose and porous surface, the adsorption rate of the new PGF was first qualitatively investigated in comparison with the two traditional PGF as mentioned above based on the bottom 5
surface. In Figure 3C, the two traditional PGF could not completely adsorb the heptane drop even after 3 seconds, however, the new PGF with same sample size could finish the adsorption only within 1 second, implying the faster adsorption rate of our PGF for the oil/solvent collection. The selective adsorption behaviour of the PGF can be ascribed to its hydrophobicity and superwettablity [6], while the ultrahigh adsorption rate is the synergistic effect of its coarse surface and interior porous structure, which can provide the organic with numerous tiny channels to quickly diffuse under capillary force [3], and endow itself with large specific surface area for good adsorpiton capacity.
Figure 3. (A) A piece of new PGF rapidly adsorbed the heptane and (B) selectively adsorbed the heptane on the surface of water. The heptane was labeled with Sudan red dye for clear visualization. (C) Comparison of the adsorption rates of the PGFs fabricated by low-temperature thermal-exfoliation (top), leavening strategy (middle), and our flame heating method (bottom). (D) The adsorption capacity of our PGF for 6
several organic solvents. (E) The recyclability of the new PGF over ten heptane adsorption cycles by exchange-evaporation process. The inset is a demonstration of recycling the new PGF by the direct-combustion method. (F) SEM images of the bottom surface of the new PGF before and after ten recycles. The quantitative adsorption capacities of the new PGF toward organic solvents were further investigated in terms of its weight gain. In Figure 3D, the sample exhibited ~1100%-3300% weight gain for the molded pollutants, depending on the viscosity, density, as well as the surface tension of the liquids. The adsorption capacity of the new PGF is comparable to that of the PGF (1750% for toluene) fabricated by the leavening strategy [7], and that of the PGFs (~1500%-1700% for n-heptane) fabricated by low-temperature exfoliation [8]. The new PGF can also be recycled by an exchange-evaporation process: (a) immersing the PGF adsorbed with organic liquids into hexane to exchange the adsorbed liquid with hexane; (b) evaporating the low-boiling hexane to regenerate the PGF. As shown in Figure 3E-3F, the new PGF still exhibited high adsorption capacity of heptane similar to the initial value even after ten exchange-evaporation process, and no obvious structure damage of its bottom surface was observed, indicating a reliable recyclability. Moreover, the recycling could also be achieved by directly burning the adsorbed organics in the PGF as illustrated in the inset of Figure 3E, and its service life could be largely extended by incorporating montmorillonite nanoplatelets into the PGF as shown in Figure S3 and discussed in the Supplementary Information, demonstrating the simply and scalable feature of our approach.
4. Conclusions The
PGF
with
unique
surface
was
fabricated
through
flame
expansion-exfoliation of GO film with non-exfoliated graphite oxide powders precipitated at its bottom. The resultant PGF exhibited a cross-linked macroporous network with bottom surface consisting of thermal-exfoliated worm-like graphene sheets, which endows itself with not only high adsorption capacity to organic solvents and reliable recyclability, but also faster adsorption rate than traditional PGFs. 7
Acknowledgements This work was funded by the Key Scientific and Technological Project of Henan Province (182102210412), National Project Cultivation Foundation of Huanghuai University (XKPY-2019008), S&T Innovation 2025 Major Special Programme of Ningbo (2018B10054), and Natural Science Foundation of Ningbo (2018A610004).
References [1] S. Gupta, N.-H. Tai, J. Mater. Chem. A 4 (2016) 1550-1565. [2] G. Ning, X. Ma, M. Wang, Y. Li, Nanoscale 9 (2017) 12647-12651. [3] X. Du, H.-Y. Liu, Y.-W. Mai, ACS Nano 10 (2016) 453-462. [4] T. Liu, M. Huang, X. Li, C. Wang, C.-X. Gui, Z.-Z. Yu, Carbon 100 (2016) 456-464. [5] B. Shen, W.T. Zhai, W.G. Zheng, Adv. Funct. Mater. 24 (2014) 4542-4548. [6] Y. Li, H.B. Zhang, L.H. Zhang, B. Shen, W.T. Zhai, Z.Z. Yu, W.G. Zheng, ACS Appl. Mater. Interfaces 9 (2017) 13323-13330. [7] Z. Niu, J. Chen, H.H. Hng, J. Ma, X. Chen, Adv. Mater. 24 (2012) 4144-4150. [8] S.J. Yang, J.H. Kang, H. Jung, T. Kim, C.R. Park, J. Mater. Chem. A 1 (2013) 9427-9432. [9] L. Dong, C. Hu, L. Song, X. Huang, N. Chen, L. Qu, Adv. Funct. Mater. 26 (2016) 1470-1476. [10] X. Mei, J. Ouyang, Carbon 49 (2011) 5389-5397. [11] B. Shen, D.D. Lu, W.T. Zhai, W.G. Zheng, J. Mater. Chem. C 1 (2013) 50-53.
Highlights Graphene oxide (GO) film with asymmetric structure was self-assembled. The GO film was flame-expanded and exfoliated into porous graphene film (PGF). 8
The PGF shows ultrahigh adsorption rate for organics.
Author Statement
Yang Li: Conceptualization, Writing-Original Draft, Funding Acquisition. Jingjing Liu: Methodology, Investigation. Lihua Zhang: Data Curation, Investigation. Qian Ren: Investigation. Bin Shen: Supervison, Writing-Reviewing and Editing, Funding Acquisition.
Conflict of Interest
We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled “Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents”.
Declaration of interests
☒ 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.
9
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Graphical Abstract
10
S0167-577X(20)30102-6 https://doi.org/10.1016/j.matlet.2020.127397 MLBLUE 127397
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
22 November 2019 4 January 2020 20 January 2020
Please cite this article as: Y. Li, J. Liu, L. Zhang, Q. Ren, B. Shen, Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents, Materials Letters (2020), doi: https://doi.org/10.1016/ j.matlet.2020.127397
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
© 2020 Published by Elsevier B.V.
Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents Yang Lia,*, Jingjing Liua, Lihua Zhangb, Qian Renb, Bin Shenb,* a
College of Chemistry and Pharmaceutical Engineering, Huanghuai University,
Zhumadian, Henan Province, 463000, China b
Ningbo Key Lab of Polymer Materials, Ningbo Institute of Materials Technology
and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang Province, 315201, China
Abstract: Porous graphene film (PGF) with unique surface consisting mostly of thermal-exfoliated worm-like graphene sheets were fabricated through flame expansion-exfoliation of graphene oxide film with non-exfoliated graphite oxide powders precipitated at its bottom. The resultant PGF showed not only faster adsorption rate during oil/solvent collection in comparison with traditional PGFs, but also similar high adsorption capacity and reliable recyclability. For instance, the adsorption capacities of the new PGF for organic solvents were in the range of ~11-33 times of its own weight, and they displayed good stability during ten exchange-evaporation recycling process. Moreover, this approach can be easily scalable and applied to prepare other PGF composites. Keywords: carbon materials; porous materials; flame expansion-exfoliation; faster adsorption; high adsorption capacity; reliable recyclability
*Corresponding authors. E-mail addresses: [email protected] (Y. L.), [email protected] (B. S.). 1
1. Introduction The frequent oil spill accidents together with toxic chemical leaks have resulted in serious water pollution, greatly hindering the sustainable development of society and economy. To date, more attention has been paid to the development of highly porous adsorbents [1], and graphene-based porous materials have recently been regarded as “star” adsorbers for the removal of oils and organic solvents [2], owing to its extreme high theoretical specific surface area (SSA) of ~2600 m2/g, good chemical stability, and intrinsically hydrophobic and oleophilic surface. Porous graphene films (PGFs) have been verified to be very effective for kinds of oil/solvent adsorption due to their high adsorption capacity and reliable recyclability, and they can be regenerated after each use by drying in a vacuum oven, annealing in a furnace, hand-pressing with a paper, or direct combustion [3, 4]. Though possessing porous network structure inside, the PGF always have dense outside surfaces owing to the presence of un-exfoliated graphene layers [5]. Consequently, they could have high adsorption capacity, but with relatively slower adsorption rate in comparison with other porous graphene materials like graphene foams, which have interconnected open network structure inside and macroporous surfaces outside [6], and thereby exhibiting both high adsorption capacity and fast adsorption rate. Hence, the fabrication of PGFs with large adsorption capacity and ultrafast adsorption rate, is of practical significance. This article demonstrates facile fabrication of a novel PGF with unique surface consisting mostly of worm-like graphene sheets through flame expansion-exfoliation of graphene oxide (GO) film with non-exfoliated graphite oxide powders precipitated at its bottom. The new PGF showed not only high adsorption capacity and reliable recyclability, but also faster adsorption rate to organic solvents in contrast with the PGF counterparts by traditional methods. This approach can be easily scalable and applied to design other PGFs.
2. Experimental GO suspension was obtained by ultrasonic exfoliation of graphite oxide 2
(prepared by Hummers’ method) in water for 1 hour (without centrifugation). Then, GO film was fabricated by direct evaporation of the GO suspension under mild heating (60 °C). Finally, the new PGF was fabricated by flame expansion of GO film for several seconds on the alcohol flame. For comparison, the traditional PGF fabricated by the leavening strategy and low-temperature exfoliation method were also prepared according to the previous works [7, 8]. More details are shown in the Supplementary Information.
3. Results and Discussion As displayed in Figure S1A, the evaporation-induced self-assembly method was utilized to prepare layered GO films. It should be noted that, the GO suspension used for film formation was not treated by strong centrifugation. Thus, the non-exfoliated graphite oxide powders after ultrasonication could gradually precipitate at the bottom of GO film during the evaporation of water. SEM observations confirmed that the top surface of such GO film was relatively smooth with many thin ripples on it (Figure S1C), while its bottom face was randomly inlaid with lots of granules (Figure S1B), which should be the non-exfoliated powders of graphite oxide in the suspension. For ultrafast expansion-exfoliation, the prepared GO film was treated by alcohol flame as shown in Figure 1A, in which the appearance of GO film changed from dark brown on both sides to silver black on the top surface and deep black on the bottom. As the alcohol flame can generate high temperature of ~600-800 oC, and could rapidly decompose the oxygen-containing groups in the GO film, resulting in ultrafast expansion-exfoliation. The whole process was finished only in few seconds, and further increasing the processing time would burn off the PGF gradually [9], because of the low decomposition temperature of graphene in air (less than ~600 °C) [10]. Figure 1B-1C indicated that, the layer-by-layer structure in GO film has been exfoliated with the formation of a cross-linked macroporous texture and the occurrence of ca. 18-fold volume expansion with increased thickness from ~15 μm to ~270 μm. According to previous reports [8, 11], the stacked layers of GO film could be thermally exfoliated under rapid heating to form porous structures inside, and at 3
the same time, the non-exfoliated graphite oxide powders at the bottom could be explosively expanded to form multilayered graphene aggregates. So the top surface of PGF (Figure 1D) was dense and accompanied with some cracks due to the explosive expansion induced by flame heating, while its bottom face was loose and porous, consisting mostly of thermal-exfoliated worm-like graphene sheets protruding from the surface (Figure 1E and 3F). These results are quite different from the dense and relatively smooth surface of the PGFs fabricated by the leavening and thermal-exfoliation strategies (Figure S2), so are their cross-section morphology with micro/macroporous networks, confirming the successful fabrication of new PGF by rapid flame heating method.
Figure 1. (A) The expansion-exfoliation process of GO film and the photographs of the as-prepared PGF. (B-C) SEM images of the cross-section of GO film and PGF. (D-E) SEM images of the top and bottom surface of PGF. The deoxygenation and structural integrity of the PGF were investigated. In the XPS spectra (Figure 2A), the C/O atom ratio was about ~9.5 and ~8.7 for the new PGF’s top and bottom surface respectively, which was much higher than that of GO 4
film (~2.4), suggesting the elimination of oxygen groups after flame heating. Moreover, their C1s scan spectrums were divided into three carbon components as displayed in Figure 2B, including C=C/C-C (~284.5 eV), C-O (~286.5 eV), and C=O (~288.0 eV) [6]. It is obvious in Figure 2C that, the percentage of C=C/C-C was increased noticeably when compared with GO film, and that of C-O and C=O was decreased for the PGF’s top and bottom surface due to the successful deoxygenation. In the Raman spectra (Figure 2D), the value of ID/IG decreased from ~1.16 for GO film to ~1.01 and ~1.04 for the PGF’s top and bottom surface, indicating the increase in the average size of sp2 carbon domains owing to the partial repairing of defects.
Figure 2. (A-B) XPS full spectrums and high-resolution C 1s spectrums of GO film and PGF. (C) Carbon components calculated from the C1s spectral deconvolution. (D) Raman spectrums of GO film and new PGF. The adsorption properties of the new PGF were evaluated in Figure 3. As seen in Figure 3A-3B, the new PGF quickly adsorbed the heptane completely when contacting the heptane (stained with Sudan red), showing a strong selectively sorption capability for organic solvent. To highlight the advantage of the loose and porous surface, the adsorption rate of the new PGF was first qualitatively investigated in comparison with the two traditional PGF as mentioned above based on the bottom 5
surface. In Figure 3C, the two traditional PGF could not completely adsorb the heptane drop even after 3 seconds, however, the new PGF with same sample size could finish the adsorption only within 1 second, implying the faster adsorption rate of our PGF for the oil/solvent collection. The selective adsorption behaviour of the PGF can be ascribed to its hydrophobicity and superwettablity [6], while the ultrahigh adsorption rate is the synergistic effect of its coarse surface and interior porous structure, which can provide the organic with numerous tiny channels to quickly diffuse under capillary force [3], and endow itself with large specific surface area for good adsorpiton capacity.
Figure 3. (A) A piece of new PGF rapidly adsorbed the heptane and (B) selectively adsorbed the heptane on the surface of water. The heptane was labeled with Sudan red dye for clear visualization. (C) Comparison of the adsorption rates of the PGFs fabricated by low-temperature thermal-exfoliation (top), leavening strategy (middle), and our flame heating method (bottom). (D) The adsorption capacity of our PGF for 6
several organic solvents. (E) The recyclability of the new PGF over ten heptane adsorption cycles by exchange-evaporation process. The inset is a demonstration of recycling the new PGF by the direct-combustion method. (F) SEM images of the bottom surface of the new PGF before and after ten recycles. The quantitative adsorption capacities of the new PGF toward organic solvents were further investigated in terms of its weight gain. In Figure 3D, the sample exhibited ~1100%-3300% weight gain for the molded pollutants, depending on the viscosity, density, as well as the surface tension of the liquids. The adsorption capacity of the new PGF is comparable to that of the PGF (1750% for toluene) fabricated by the leavening strategy [7], and that of the PGFs (~1500%-1700% for n-heptane) fabricated by low-temperature exfoliation [8]. The new PGF can also be recycled by an exchange-evaporation process: (a) immersing the PGF adsorbed with organic liquids into hexane to exchange the adsorbed liquid with hexane; (b) evaporating the low-boiling hexane to regenerate the PGF. As shown in Figure 3E-3F, the new PGF still exhibited high adsorption capacity of heptane similar to the initial value even after ten exchange-evaporation process, and no obvious structure damage of its bottom surface was observed, indicating a reliable recyclability. Moreover, the recycling could also be achieved by directly burning the adsorbed organics in the PGF as illustrated in the inset of Figure 3E, and its service life could be largely extended by incorporating montmorillonite nanoplatelets into the PGF as shown in Figure S3 and discussed in the Supplementary Information, demonstrating the simply and scalable feature of our approach.
4. Conclusions The
PGF
with
unique
surface
was
fabricated
through
flame
expansion-exfoliation of GO film with non-exfoliated graphite oxide powders precipitated at its bottom. The resultant PGF exhibited a cross-linked macroporous network with bottom surface consisting of thermal-exfoliated worm-like graphene sheets, which endows itself with not only high adsorption capacity to organic solvents and reliable recyclability, but also faster adsorption rate than traditional PGFs. 7
Acknowledgements This work was funded by the Key Scientific and Technological Project of Henan Province (182102210412), National Project Cultivation Foundation of Huanghuai University (XKPY-2019008), S&T Innovation 2025 Major Special Programme of Ningbo (2018B10054), and Natural Science Foundation of Ningbo (2018A610004).
References [1] S. Gupta, N.-H. Tai, J. Mater. Chem. A 4 (2016) 1550-1565. [2] G. Ning, X. Ma, M. Wang, Y. Li, Nanoscale 9 (2017) 12647-12651. [3] X. Du, H.-Y. Liu, Y.-W. Mai, ACS Nano 10 (2016) 453-462. [4] T. Liu, M. Huang, X. Li, C. Wang, C.-X. Gui, Z.-Z. Yu, Carbon 100 (2016) 456-464. [5] B. Shen, W.T. Zhai, W.G. Zheng, Adv. Funct. Mater. 24 (2014) 4542-4548. [6] Y. Li, H.B. Zhang, L.H. Zhang, B. Shen, W.T. Zhai, Z.Z. Yu, W.G. Zheng, ACS Appl. Mater. Interfaces 9 (2017) 13323-13330. [7] Z. Niu, J. Chen, H.H. Hng, J. Ma, X. Chen, Adv. Mater. 24 (2012) 4144-4150. [8] S.J. Yang, J.H. Kang, H. Jung, T. Kim, C.R. Park, J. Mater. Chem. A 1 (2013) 9427-9432. [9] L. Dong, C. Hu, L. Song, X. Huang, N. Chen, L. Qu, Adv. Funct. Mater. 26 (2016) 1470-1476. [10] X. Mei, J. Ouyang, Carbon 49 (2011) 5389-5397. [11] B. Shen, D.D. Lu, W.T. Zhai, W.G. Zheng, J. Mater. Chem. C 1 (2013) 50-53.
Highlights Graphene oxide (GO) film with asymmetric structure was self-assembled. The GO film was flame-expanded and exfoliated into porous graphene film (PGF). 8
The PGF shows ultrahigh adsorption rate for organics.
Author Statement
Yang Li: Conceptualization, Writing-Original Draft, Funding Acquisition. Jingjing Liu: Methodology, Investigation. Lihua Zhang: Data Curation, Investigation. Qian Ren: Investigation. Bin Shen: Supervison, Writing-Reviewing and Editing, Funding Acquisition.
Conflict of Interest
We declare that we have no financial and personal relationships with other people or organizations that can inappropriately influence our work, there is no professional or other personal interest of any nature or kind in any product, service and/or company that could be construed as influencing the position presented in, or the review of, the manuscript entitled “Porous graphene films with worm-like graphene surface as ultrafast adsorbents for oils and organic solvents”.
Declaration of interests
☒ 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.
9
☐The authors declare the following financial interests/personal relationships which may be considered as potential competing interests:
Graphical Abstract
10