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Porous graphene synthesized by partial combustion for high-performance supercapacitors
Materials Letters 252 (2019) 345–348
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Porous graphene synthesized by partial combustion for high-performance supercapacitors Li Wang, Hongxin Tan, Jia Chen, Haijuan Zhang, Zhan Li ⇑, Hongdeng Qiu ⇑ CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
a r t i c l e
i n f o
Article history: Received 8 April 2019 Received in revised form 4 June 2019 Accepted 6 June 2019 Available online 7 June 2019 Keywords: Carbon materials Electrical properties Porous graphene Controlled pore size Partial combustion
a b s t r a c t Graphene with a porous structure can provide low-resistant pathways and short ion diffusion channels for energy storage, and thus is expected to be an excellent electrode material. Here, a simple partial combustion route was used to synthesize porous graphene with controllable pore size as a high-performance electrode material for supercapacitors. The results indicated that the obtained porous graphene exhibits the highest specific capacitance in this study is 284 F/g at the current density of 0.2 A/g in 6 M KOH. Moreover, porous graphene showed good cycle durability over 83% at the current density of 1.0 A/g after 5000 cycles, and with columbic efficiency over 95%. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Recently, many method for improving the performance of supercapacitor has been reported [1]. The introduction of pores on the surface of nanomaterials is an effective means for improving the performance of supercapacitor [2–4]. In Particular, the graphene has received extensive attention due to its unique physicochemical properties [5–7]. Porous graphene (PG) as a derivative of graphene has been developed as an electrode material for nextgeneration supercapacitors due to its unique porous structure combined with the inherent characteristics of graphene [8]. Nevertheless, some drawbacks, such as the complex process, high cost in the preparation still preclude practical use of these materials. Hence, it is highly desirable to design PG materials through a cost efficient route from low-cost and renewable resources. Although the method of preparing PG through partial combustion had been reported in the previous article [9], but the previous article mainly evaluated the photocatalytic properties of the PG/ZnO nanocomposite, and the structural properties of PG prepared under different conditions were not be compared. Herein, we first study the PG prepared by partial combustion as an electrode material to evaluate its electrical properties. PG with controllable pore size was produced rapidly by partial combustion within few minutes. Considering that the pore as an ion transmission channel has a great influence on the electrical ⇑ Corresponding authors. E-mail addresses: [email protected] (Z. Li), [email protected] (H. Qiu). https://doi.org/10.1016/j.matlet.2019.06.015 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
performance, consequently, the purpose of this study is: (1) precisely regulate the pore size and group functionality of PG; (2) study the structural stability and electrical performance of PG with different pore size. 2. Experimental The PG materials with controllable pore size were prepared by partial combustion. The defective pores of PG were realized by incompletely covering a layer of zinc salt on the surface of GO. The thermal effect would cause the redox reaction on the surface of graphene [10], with combustion temperature increasing, resulting in an increase in pore size on the surface of graphene. Three-electrode configurations with a computer-controlled CHI660E were used to evaluate capacitive performance of PG. KOH (6 M) aqueous is used as electrolyte solution. The electrodes were prepared by PG (4 mg, 80 wt%), acetylene black (10 wt%) and polytetrafluoroethylene (10 wt%), and then coat materials onto a nickel foam substrate which served as a current collector. The details of the material preparation method and capacity calculation were described in the Supporting Information (S.1 Experimental). 3. Results and discussion XRD patterns (Fig. 1A) showed the peak shape of PG-450 °C tended to be more sharp than PG-500 °C. The diffraction peak of
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Fig. 1. Characterizations of PGs. (A) XRD; (B) Raman spectra; (C) FT-IR spectra; (D) C1s spectra in XPS; (E) TEM.
Fig. 2. Galvanostatic charge–discharge curves of PG-450 °C (A) and PG-500 °C (B) electrodes; CV curves of PG-450 °C (C) and PG-500 °C (D) electrodes.
PG-500 °C is broadened due to the narrowing of the graphite sheet spacing, the decrease of crystal structure integrity, and the increase of disorder in graphene. The intensity ratios of D band to G band of PG-450 °C and PG500 °C in Raman spectra (Fig. 1B) were 0.95 and 0.85, respectively.
The sp2 carbon network structure increases with the removal of oxygen-containing functional groups on the graphite sheet, in which the sp2 region increases while the value of ID/IG decreases [11]. The FT-IR spectra (Fig. 1C) confirmed the carbon-thermal reaction cleaved the C–O, C–C and C@O bonds, with increasing of
L. Wang et al. / Materials Letters 252 (2019) 345–348
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Fig. 3. (A) Nyquist plots of PG-450 °C and PG-500 °C, the inset shows an expanded view for the high frequency range. (B) Cycle stability of PG-450 °C electrodes at a current density of 1 A/g.
reaction temperature, the intensity of the C–O, C–C, C@O bond diminished. The resultant C/O atom ratios of PG-450 °C and PG-500 °C in XPS (Fig. 1D) were about 8.1 and 10.4, respectively, which is higher than that of GO (2.7) [12].With the increase of combustion temperature, the content of C element in PG increasing and the content of O element decreasing, which indicating that the oxygen-containing functional group decomposes more thoroughly at higher temperature. TEM images (Fig. 1E) showed PGs with porous and multilayer graphene structure. Due to the pores cannot be formed below 400 °C, two temperature levels (450 °C, 500 °C) were set. Two kinds of pores were existed in PG, 2D pores on the sheets and 3D pores between the sheets. The formation of 2D pores is attributed to the absence of carbon atoms on the surface of the graphene, while the 3D pores originates from stacking and bending between graphene sheets [10]. The 2D pore size distribution of PG is presented in Fig. S1, pore sizes of PG-450 °C and PG-500 °C are mostly at 3 nm and 30 nm, respectively. The BET surface area of PG450 °C and PG-500 °C are 648 and 1815 m2/g, respectively. The nitrogen adsorption–desorption isotherms and 3D pore size distribution are showed in Fig. S2, 3D pore sizes of PGs are all mostly at 3.5 nm. Fig. 2A and B show the galvanostatic charge–discharge curves of PG-450 °C and PG-500 °C, respectively. It is found that specific capacitance decreases with increase of current density, which is related to the increase of diffusion limitation. At current densities of 0.2, 0.5, 1, 2, 5 A/g, the capacitances of 284, 241, 239, 187 and 140 F/g for PG-450 °C are attained, and capacitances of 278, 235, 223, 150 and 36 F/g for PG-500 °C. Fig. 2C and D exhibit the CV curves of PG-450 °C and PG-500 °C. The integrated Cv from CV curves of PG-450 °C at scanning rate of 1, 5, 10, 50 and 100 mV/s are 271, 196, 162, 65 and 39F/g, respectively. While for PG-500 °C, the capacitances of 243, 145, 109, 39 and 24F/g are attained. Zheng et al in 2014 had reported that, low scan rates condition could reveal the true energy storage capacity of materials [13]. The results indicate that PG-450 °C has better capacitive performance, at 0.2 A/g, the corresponding coulombic efficiency up to 100%, and energy efficiency up to 89%. In contrast, the PG-450 °C here has several unique features to ensure higher capacitance in aqueous electrolytes: (1) the 3D pores of the PG-450 °C and PG-500 °C are all mostly at 3.5 nm, while for the 2D pores which mainly affect the electrical properties of material, have larger differences. The PG-450 °C mainly contains
small mesopores (2–4 nm) are suitable to electrolyte [14]. (2) The PG-450 °C has higher crystallinity than PG-500 °C. (3) The PG-450 °C has more oxygen functional groups than PG-500 °C. The diffusion resistance for electrolyte migration into the micropores is higher than mesopores and macropores, so the electrolyte is difficult to enter micropores in a short time, resulting the materials cannot fully contact the electrolyte [15]. Through increasing oxygen content of the materials could improve the wettability of the internal structure of micropores, thus resulting in a corresponding increase in specific capacitance [16]. (4) The PG-450 °C has good conductivity (1 MPa: 8.19 106 S/m; 2 MPa: 8.85 106 S/m; 3 MPa: 9.52 106 S/m). The Nyquist plots for electrodes are shown in Fig. 3A. Compared with PG-500 °C, PG-450 °C demonstrates the relative shorter Warburg region portion, indicating the shorter electrolyte diffusion pathways, further demonstrate that the PG-450 °C sample has better electrical performance [13]. Coulombic efficiency remains 95– 100% within 5000 cycles (Fig. 3B), and no violent capacitance decay was observed after 5000 constant current charge/discharge cycles at a current density of 1 A/g (Fig. 3B), after 5000 times of continuous cycling, the devices still keep 83% capacitance. The comparison results with other graphene-based materials electrode (Table S1) confirming that the synthesized PG-450 °C sample is very promising as an electrode material for high performance supercapacitors. 4. Conclusions In summary, PG materials with controllable pore sizes, prepared rapidly by partial combustion, exhibit the good conductivity. The results demonstrate that the synergy effect among the proper porous structure, good crystallinity and electrical conductivity in electrode materials. The highly electrical conductivity and easily scaled-up production at low cost make PG potentially applicable in high performance supercapacitors. Declaration of Competing Interest None. Acknowledgement This research was supported by National Science Foundation of China (Nos. 21675164 and 21822407).
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Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.06.015. References [1] L. Shen, L. Du, S. Tan, Z. Zang, C. Zhao, W. Mai, Flexible electrochromic supercapacitor hybrid electrodes based on tungsten oxide films and silver nanowires, Chem. Commun. 52 (37) (2016) 6296–6299. [2] X. Yu, S. Yun, J.S. Yeon, P. Bhattacharya, L. Wang, S.W. Lee, X. Hu, H.S. Park, Emergent pseudocapacitance of 2D nanomaterials, Adv. Energy Mater. 8 (13) (2018) 1702930. [3] Q. Mahmood, M.G. Kim, S. Yun, S.-M. Bak, X.-Q. Yang, H.S. Shin, W.S. Kim, P.V. Braun, H.S. Park, Unveiling surface redox charge storage of interacting twodimensional heteronanosheets in hierarchical architectures, Nano Lett. 15 (4) (2015) 2269–2277. [4] X. Yu, S.K. Park, S.-H. Yeon, H.S. Park, Three-dimensional, sulfur-incorporated graphene aerogels for the enhanced performances of pseudocapacitive electrodes, J. Power Sour. 278 (2015) 484–489. [5] J. Wei, Z. Zang, Y. Zhang, M. Wang, J. Du, X. Tang, Enhanced performance of light-controlled conductive switching in hybrid cuprous oxide/reduced graphene oxide (Cu2O/rGO) nanocomposites, Opt. Lett. 42 (5) (2017) 911–914. [6] X. Liu, T. Xu, Y. Li, Z. Zang, X. Peng, H. Wei, W. Zha, F. Wang, Enhanced X-ray photon response in solution-synthesized CsPbBr 3 nanoparticles wrapped by reduced graphene oxide, Sol. Energy Mater. Sol. Cells 187 (2018) 249–254.
[7] Z. Zang, X. Zeng, M. Wang, W. Hu, C. Liu, X. Tang, Tunable photoluminescence of water-soluble AgInZnS–graphene oxide (GO) nanocomposites and their application in-vivo bioimaging, Sens. Actuat. B: Chem. 252 (2017) 1179–1186. [8] L. Jiang, Z. Fan, Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures, Nanoscale 6 (2014) 1922–1945. [9] L. Wang, Z. Li, J. Chen, Y. Huang, H. Zhang, H. Qiu, Enhanced photocatalytic degradation of methyl orange by porous graphene/ZnO nanocomposite, Environ. Pollut. 249 (2019) 801–811. [10] Z. Li, X. Zhang, H. Tan, W. Qi, L. Wang, M.C. Ali, H. Zhang, J. Chen, P. Hu, C. Fan, H. Qiu, Combustion fabrication of nanoporous graphene for ionic separation membranes, Adv. Funct. Mater. 28 (43) (2018) 1805026. [11] G. Li, C. Zhang, T. Zhang, M. Xia, Y. Luo, Effect of reduction time on the structure and properties of porous graphene, Mater. Res. Express. 4 (2017), 075603. [12] S. Stankovich, D.A. Dikin, R.D. Piner, K.A. Kohlhaas, A. Kleinhammes, Y. Jia, Y. Wu, S.T. Nguyen, R.S. Ruoff, Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide, Carbon 45 (2007) 1558–1565. [13] C. Zheng, X. Zhou, H. Cao, G. Wang, Z. Liu, Edge-enriched porous graphene nanoribbons for high energy density supercapacitors, J. Mater. Chem. A. 2 (20) (2014) 7484–7490. [14] A. Fuertes, G. Lota, T. Centeno, E. Frackowiak, Templated mesoporous carbons for supercapacitor application, Electrochim. Acta. 50 (14) (2005) 2799–2805. [15] H. Itoi, S. Hayashi, H. Matsufusa, Y. Ohzawa, Electrochemical synthesis of polyaniline in the micropores of activated carbon for high-performance electrochemical capacitors, Chem. Commun. 53 (22) (2017) 3201–3204. [16] C.-T. Hsieh, H. Teng, Influence of oxygen treatment on electric double-layer capacitance of activated carbon fabrics, Carbon 40 (2002) 667–674.
Contents lists available at ScienceDirect
Materials Letters journal homepage: www.elsevier.com/locate/mlblue
Porous graphene synthesized by partial combustion for high-performance supercapacitors Li Wang, Hongxin Tan, Jia Chen, Haijuan Zhang, Zhan Li ⇑, Hongdeng Qiu ⇑ CAS Key Laboratory of Chemistry of Northwestern Plant Resources and Key Laboratory for Natural Medicine of Gansu Province, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China
a r t i c l e
i n f o
Article history: Received 8 April 2019 Received in revised form 4 June 2019 Accepted 6 June 2019 Available online 7 June 2019 Keywords: Carbon materials Electrical properties Porous graphene Controlled pore size Partial combustion
a b s t r a c t Graphene with a porous structure can provide low-resistant pathways and short ion diffusion channels for energy storage, and thus is expected to be an excellent electrode material. Here, a simple partial combustion route was used to synthesize porous graphene with controllable pore size as a high-performance electrode material for supercapacitors. The results indicated that the obtained porous graphene exhibits the highest specific capacitance in this study is 284 F/g at the current density of 0.2 A/g in 6 M KOH. Moreover, porous graphene showed good cycle durability over 83% at the current density of 1.0 A/g after 5000 cycles, and with columbic efficiency over 95%. Ó 2019 Elsevier B.V. All rights reserved.
1. Introduction Recently, many method for improving the performance of supercapacitor has been reported [1]. The introduction of pores on the surface of nanomaterials is an effective means for improving the performance of supercapacitor [2–4]. In Particular, the graphene has received extensive attention due to its unique physicochemical properties [5–7]. Porous graphene (PG) as a derivative of graphene has been developed as an electrode material for nextgeneration supercapacitors due to its unique porous structure combined with the inherent characteristics of graphene [8]. Nevertheless, some drawbacks, such as the complex process, high cost in the preparation still preclude practical use of these materials. Hence, it is highly desirable to design PG materials through a cost efficient route from low-cost and renewable resources. Although the method of preparing PG through partial combustion had been reported in the previous article [9], but the previous article mainly evaluated the photocatalytic properties of the PG/ZnO nanocomposite, and the structural properties of PG prepared under different conditions were not be compared. Herein, we first study the PG prepared by partial combustion as an electrode material to evaluate its electrical properties. PG with controllable pore size was produced rapidly by partial combustion within few minutes. Considering that the pore as an ion transmission channel has a great influence on the electrical ⇑ Corresponding authors. E-mail addresses: [email protected] (Z. Li), [email protected] (H. Qiu). https://doi.org/10.1016/j.matlet.2019.06.015 0167-577X/Ó 2019 Elsevier B.V. All rights reserved.
performance, consequently, the purpose of this study is: (1) precisely regulate the pore size and group functionality of PG; (2) study the structural stability and electrical performance of PG with different pore size. 2. Experimental The PG materials with controllable pore size were prepared by partial combustion. The defective pores of PG were realized by incompletely covering a layer of zinc salt on the surface of GO. The thermal effect would cause the redox reaction on the surface of graphene [10], with combustion temperature increasing, resulting in an increase in pore size on the surface of graphene. Three-electrode configurations with a computer-controlled CHI660E were used to evaluate capacitive performance of PG. KOH (6 M) aqueous is used as electrolyte solution. The electrodes were prepared by PG (4 mg, 80 wt%), acetylene black (10 wt%) and polytetrafluoroethylene (10 wt%), and then coat materials onto a nickel foam substrate which served as a current collector. The details of the material preparation method and capacity calculation were described in the Supporting Information (S.1 Experimental). 3. Results and discussion XRD patterns (Fig. 1A) showed the peak shape of PG-450 °C tended to be more sharp than PG-500 °C. The diffraction peak of
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Fig. 1. Characterizations of PGs. (A) XRD; (B) Raman spectra; (C) FT-IR spectra; (D) C1s spectra in XPS; (E) TEM.
Fig. 2. Galvanostatic charge–discharge curves of PG-450 °C (A) and PG-500 °C (B) electrodes; CV curves of PG-450 °C (C) and PG-500 °C (D) electrodes.
PG-500 °C is broadened due to the narrowing of the graphite sheet spacing, the decrease of crystal structure integrity, and the increase of disorder in graphene. The intensity ratios of D band to G band of PG-450 °C and PG500 °C in Raman spectra (Fig. 1B) were 0.95 and 0.85, respectively.
The sp2 carbon network structure increases with the removal of oxygen-containing functional groups on the graphite sheet, in which the sp2 region increases while the value of ID/IG decreases [11]. The FT-IR spectra (Fig. 1C) confirmed the carbon-thermal reaction cleaved the C–O, C–C and C@O bonds, with increasing of
L. Wang et al. / Materials Letters 252 (2019) 345–348
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Fig. 3. (A) Nyquist plots of PG-450 °C and PG-500 °C, the inset shows an expanded view for the high frequency range. (B) Cycle stability of PG-450 °C electrodes at a current density of 1 A/g.
reaction temperature, the intensity of the C–O, C–C, C@O bond diminished. The resultant C/O atom ratios of PG-450 °C and PG-500 °C in XPS (Fig. 1D) were about 8.1 and 10.4, respectively, which is higher than that of GO (2.7) [12].With the increase of combustion temperature, the content of C element in PG increasing and the content of O element decreasing, which indicating that the oxygen-containing functional group decomposes more thoroughly at higher temperature. TEM images (Fig. 1E) showed PGs with porous and multilayer graphene structure. Due to the pores cannot be formed below 400 °C, two temperature levels (450 °C, 500 °C) were set. Two kinds of pores were existed in PG, 2D pores on the sheets and 3D pores between the sheets. The formation of 2D pores is attributed to the absence of carbon atoms on the surface of the graphene, while the 3D pores originates from stacking and bending between graphene sheets [10]. The 2D pore size distribution of PG is presented in Fig. S1, pore sizes of PG-450 °C and PG-500 °C are mostly at 3 nm and 30 nm, respectively. The BET surface area of PG450 °C and PG-500 °C are 648 and 1815 m2/g, respectively. The nitrogen adsorption–desorption isotherms and 3D pore size distribution are showed in Fig. S2, 3D pore sizes of PGs are all mostly at 3.5 nm. Fig. 2A and B show the galvanostatic charge–discharge curves of PG-450 °C and PG-500 °C, respectively. It is found that specific capacitance decreases with increase of current density, which is related to the increase of diffusion limitation. At current densities of 0.2, 0.5, 1, 2, 5 A/g, the capacitances of 284, 241, 239, 187 and 140 F/g for PG-450 °C are attained, and capacitances of 278, 235, 223, 150 and 36 F/g for PG-500 °C. Fig. 2C and D exhibit the CV curves of PG-450 °C and PG-500 °C. The integrated Cv from CV curves of PG-450 °C at scanning rate of 1, 5, 10, 50 and 100 mV/s are 271, 196, 162, 65 and 39F/g, respectively. While for PG-500 °C, the capacitances of 243, 145, 109, 39 and 24F/g are attained. Zheng et al in 2014 had reported that, low scan rates condition could reveal the true energy storage capacity of materials [13]. The results indicate that PG-450 °C has better capacitive performance, at 0.2 A/g, the corresponding coulombic efficiency up to 100%, and energy efficiency up to 89%. In contrast, the PG-450 °C here has several unique features to ensure higher capacitance in aqueous electrolytes: (1) the 3D pores of the PG-450 °C and PG-500 °C are all mostly at 3.5 nm, while for the 2D pores which mainly affect the electrical properties of material, have larger differences. The PG-450 °C mainly contains
small mesopores (2–4 nm) are suitable to electrolyte [14]. (2) The PG-450 °C has higher crystallinity than PG-500 °C. (3) The PG-450 °C has more oxygen functional groups than PG-500 °C. The diffusion resistance for electrolyte migration into the micropores is higher than mesopores and macropores, so the electrolyte is difficult to enter micropores in a short time, resulting the materials cannot fully contact the electrolyte [15]. Through increasing oxygen content of the materials could improve the wettability of the internal structure of micropores, thus resulting in a corresponding increase in specific capacitance [16]. (4) The PG-450 °C has good conductivity (1 MPa: 8.19 106 S/m; 2 MPa: 8.85 106 S/m; 3 MPa: 9.52 106 S/m). The Nyquist plots for electrodes are shown in Fig. 3A. Compared with PG-500 °C, PG-450 °C demonstrates the relative shorter Warburg region portion, indicating the shorter electrolyte diffusion pathways, further demonstrate that the PG-450 °C sample has better electrical performance [13]. Coulombic efficiency remains 95– 100% within 5000 cycles (Fig. 3B), and no violent capacitance decay was observed after 5000 constant current charge/discharge cycles at a current density of 1 A/g (Fig. 3B), after 5000 times of continuous cycling, the devices still keep 83% capacitance. The comparison results with other graphene-based materials electrode (Table S1) confirming that the synthesized PG-450 °C sample is very promising as an electrode material for high performance supercapacitors. 4. Conclusions In summary, PG materials with controllable pore sizes, prepared rapidly by partial combustion, exhibit the good conductivity. The results demonstrate that the synergy effect among the proper porous structure, good crystallinity and electrical conductivity in electrode materials. The highly electrical conductivity and easily scaled-up production at low cost make PG potentially applicable in high performance supercapacitors. Declaration of Competing Interest None. Acknowledgement This research was supported by National Science Foundation of China (Nos. 21675164 and 21822407).
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L. Wang et al. / Materials Letters 252 (2019) 345–348
Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.matlet.2019.06.015. References [1] L. Shen, L. Du, S. Tan, Z. Zang, C. Zhao, W. Mai, Flexible electrochromic supercapacitor hybrid electrodes based on tungsten oxide films and silver nanowires, Chem. Commun. 52 (37) (2016) 6296–6299. [2] X. Yu, S. Yun, J.S. Yeon, P. Bhattacharya, L. Wang, S.W. Lee, X. Hu, H.S. Park, Emergent pseudocapacitance of 2D nanomaterials, Adv. Energy Mater. 8 (13) (2018) 1702930. [3] Q. Mahmood, M.G. Kim, S. Yun, S.-M. Bak, X.-Q. Yang, H.S. Shin, W.S. Kim, P.V. Braun, H.S. Park, Unveiling surface redox charge storage of interacting twodimensional heteronanosheets in hierarchical architectures, Nano Lett. 15 (4) (2015) 2269–2277. [4] X. Yu, S.K. Park, S.-H. Yeon, H.S. Park, Three-dimensional, sulfur-incorporated graphene aerogels for the enhanced performances of pseudocapacitive electrodes, J. Power Sour. 278 (2015) 484–489. [5] J. Wei, Z. Zang, Y. Zhang, M. Wang, J. Du, X. Tang, Enhanced performance of light-controlled conductive switching in hybrid cuprous oxide/reduced graphene oxide (Cu2O/rGO) nanocomposites, Opt. Lett. 42 (5) (2017) 911–914. [6] X. Liu, T. Xu, Y. Li, Z. Zang, X. Peng, H. Wei, W. Zha, F. Wang, Enhanced X-ray photon response in solution-synthesized CsPbBr 3 nanoparticles wrapped by reduced graphene oxide, Sol. Energy Mater. Sol. Cells 187 (2018) 249–254.
[7] Z. Zang, X. Zeng, M. Wang, W. Hu, C. Liu, X. Tang, Tunable photoluminescence of water-soluble AgInZnS–graphene oxide (GO) nanocomposites and their application in-vivo bioimaging, Sens. Actuat. B: Chem. 252 (2017) 1179–1186. [8] L. Jiang, Z. Fan, Design of advanced porous graphene materials: from graphene nanomesh to 3D architectures, Nanoscale 6 (2014) 1922–1945. [9] L. Wang, Z. Li, J. Chen, Y. Huang, H. Zhang, H. Qiu, Enhanced photocatalytic degradation of methyl orange by porous graphene/ZnO nanocomposite, Environ. Pollut. 249 (2019) 801–811. [10] Z. Li, X. Zhang, H. Tan, W. Qi, L. Wang, M.C. Ali, H. Zhang, J. Chen, P. Hu, C. Fan, H. Qiu, Combustion fabrication of nanoporous graphene for ionic separation membranes, Adv. Funct. Mater. 28 (43) (2018) 1805026. [11] G. Li, C. Zhang, T. Zhang, M. Xia, Y. Luo, Effect of reduction time on the structure and properties of porous graphene, Mater. Res. Express. 4 (2017), 075603. [12] S. Stankovich, D.A. Dikin, R.D. Piner, K.A. Kohlhaas, A. Kleinhammes, Y. Jia, Y. Wu, S.T. Nguyen, R.S. Ruoff, Synthesis of graphene-based nanosheets via chemical reduction of exfoliated graphite oxide, Carbon 45 (2007) 1558–1565. [13] C. Zheng, X. Zhou, H. Cao, G. Wang, Z. Liu, Edge-enriched porous graphene nanoribbons for high energy density supercapacitors, J. Mater. Chem. A. 2 (20) (2014) 7484–7490. [14] A. Fuertes, G. Lota, T. Centeno, E. Frackowiak, Templated mesoporous carbons for supercapacitor application, Electrochim. Acta. 50 (14) (2005) 2799–2805. [15] H. Itoi, S. Hayashi, H. Matsufusa, Y. Ohzawa, Electrochemical synthesis of polyaniline in the micropores of activated carbon for high-performance electrochemical capacitors, Chem. Commun. 53 (22) (2017) 3201–3204. [16] C.-T. Hsieh, H. Teng, Influence of oxygen treatment on electric double-layer capacitance of activated carbon fabrics, Carbon 40 (2002) 667–674.