Polyethyleneimine-Mediated Fabrication of Two-Dimensional Cobalt

Jun 27, 2019 - (6−10) However, these electrochemical reactions are usually hindered by the slow electron/ion-transport process inside the electrodes...
0 downloads 0 Views 4MB Size
Download PDF
Research Article www.acsami.org

Cite This: ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Polyethyleneimine-Mediated Fabrication of Two-Dimensional Cobalt Sulfide/Graphene Hybrid Nanosheets for High-Performance Supercapacitors Man Wang,†,∥ Juan Yang,*,†,∥ Siyu Liu,† Chao Hu,† Shaofeng Li,‡ and Jieshan Qiu*,‡,§ †

School of Chemical Engineering and Technology, Xi’an Jiaotong University, Xi’an 710049, China State Key Lab of Fine Chemicals, School of Chemical Engineering, Liaoning Key Lab for Energy Materials and Chemical Engineering, Dalian University of Technology, Dalian 116024, China § College of Chemical Engineering, Beijing University of Chemical Technology, Beijing 100029, China

Downloaded via GUILFORD COLG on July 19, 2019 at 02:38:58 (UTC). See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.

‡

S Supporting Information *

ABSTRACT: Two-dimensional (2D) hybrid nanosheets made of electrochemically active materials and graphene, featuring fast reaction kinetics and excellent structural stability, are appealing as electrodes for supercapacitors. Herein, we report a general polyethyleneimine (PEI)-mediated fabrication of the 2D cobalt sulfide/graphene hybrid nanosheets via a facile hydrothermal strategy. Detailed analysis reveals that the uniform cobalt sulfide (CoS) nanoparticles are well-anchored on the 2D graphene surface. Thereinto, the nitrogen species originating from the PEI molecules as bridging sites are helpful in enhancing the coupling effect between the graphene and CoS species, which endows the hybrid nanosheets with high electroactivity and excellent structural stability. The as-obtained hybrid nanosheets with typical pseudocapacitive features demonstrate a high specific capacitance (320 F g−1@1 A g−1) and a superior electrochemical stability with the initial capacitance of 86.5% after 20 000 cycles as electrodes for supercapacitors. The assembled asymmetric supercapacitors by combining activated carbon electrodes further show a high charge storage of 28.8 Wh kg−1 with an output power of 130 W kg−1. More importantly, the similar strategy can be easily extended to fabricate other 2D hybrid nanosheets with extraordinary electrochemical performance with the maximum charge storage of 815 F g−1 and energy density of 44. 6 Wh kg−1. The present work, which achieves the general fabrication of 2D hybrid nanosheets with tuned compositions, may provide a new opportunity for the development of supercapacitors. KEYWORDS: graphene, cobalt sulfide, polyethyleneimine, 2D hybrid nanosheets, supercapacitors well-developed carbon-based hybrids.12−17 Among them, the two-dimensional (2D) carbon-based hybrid electrodes designed by decorating active materials on two-dimensional (2D) conductive scaffolds including graphene or graphene-like carbon nanosheets were employed as a universal strategy to improve the electrochemical reaction kinetics.18−22 It is believed that such a hybrid configuration not only affords a large surface area and opens frameworks to guarantee exposure of abundant electroactive sites and accessibility of electrolyte ions but also delivers high conductivity and short distance to ensure rapid electron/ion transport.23−25 For example, Leite et al. fabricated the layered MoS2/graphene hybrid nanosheets via a simple microwave-assisted heating method, in which the high specific capacitance of 265 F g−1 was achieved as electrodes for supercapacitors.26 Lin et al. developed the novel NiO@graphene hybrid nanosheets by plasma-enhanced

1. INTRODUCTION Supercapacitors, as an important branch of energy-storage devices, have attracted great attention due to excellent chargestorage capability, long operating lifespan, and low electrode resistance.1−5 In particular, the supercapacitors accompanied by surface-electrochemical reactions are more attractive in many high-energy-density modules, evidenced by this kind of supercapacitor that is capable of boosting the high charge storage while maintaining a high power density.6−10 However, these electrochemical reactions are usually hindered by the slow electron/ion-transport process inside the electrodes and thus result in the storage and/or release efficiency of the supercapacitors that is below expectation. Improving the reaction kinetics of the electrode materials is undoubtedly considered as one of the critical strategies to further enhance the electrochemical performance of the supercapacitors.11 Because of this, extensive efforts have been concentrated on searching various electrode materials with excellent electrochemical activity and fast reaction kinetics for supercapacitors, such as transition-metal-based oxides/hydroxides, sulfides, and © XXXX American Chemical Society

Received: March 9, 2019 Accepted: June 27, 2019 Published: June 27, 2019 A

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

Figure 1. Schematic illustration of the fabrication process for the G-P-CoS hybrid nanosheets.

stability. In addition, the current strategy was also applied to fabricate other 2D hybrid nanosheets with extraordinary electrochemical performance (e.g., G-P-NiCoS, G-P-FeOOH, and G-P-NiOOH).

chemical vapor deposition strategy. The as-obtained hybrid electrodes possess a high capacity of 1073 C g−1 at a low current density.27 Although considerable progress has been made, the 2D hybrid nanosheets available now still have limits in terms of the electroactivity and structural stability due to the incompatibility between the active species and the carbonaceous substrate. The development of 2D hybrid electrodes with a high electrochemical activity and strong coupling effects among the components is highly desired for high-performance supercapacitors. Recently, the polymer molecules bridging electroactive species and carbon materials into 2D hybrid nanosheets hold significant potential in tuning their structures and coupling effects conveniently.28 Fan et al. fabricated Co3O4/poly(3,4ethylenedioxythiophene) (PEDOT)@MnO2 core/shell structure on the three-dimensional porous graphite thin foams, where PEDOT acts as a bridge to mediate the incompatibility between the different metal species and thus shows improved electrochemical performance for supercapacitors.29 Our previous work also demonstrated the fabrication of 2D hybrid nanosheets (e.g., NiCo2O4/graphene) using polyaniline as the structure-coupling agent, resulting in nanosheet electrodes with large specific capacitance and superior cycling stability for supercapacitors.7 However, these currently reported 2D hybrid nanosheets still suffer from the limitations of chemical compositions and uncontrollable size of the electroactive species; thus, the general fabrication of 2D hybrid nanosheets composed of various electroactive species with well-controlled particle size on graphene via a facile yet simple strategy remains a challenge. Transition-metal sulfides and their nanohybrids, for example, cobalt sulfide and cobalt sulfide/graphene with rich redox sites and high electrical conductivity, are considered as advanced electrode materials for supercapacitors. 30−32 Herein, a polyethyleneimine (PEI)-mediated strategy for the first time was designed to fabricate 2D cobalt sulfide/graphene hybrid nanosheets (denoted by G-P-CoS). It has been found that the nitrogen-containing groups from PEI molecules function as bridging sites to tune the coupling effect between the graphene and CoS species. The as-obtained 2D G-P-CoS hybrid nanosheets possess a high specific capacitance of 320 F g−1 at 1 A g−1 and a superior electrochemical stability of 86.5% after 20 000 cycles as electrodes for supercapacitors, highlighting the high electroactivity and excellent structural

2. EXPERIMENTAL METHODS 2.1. Fabrication of PEI-Functionalized Graphene Oxide (GO) Nanosheets (G-P). In a typical procedure, a modified Hummers’ method was employed to prepare the GO nanosheets.33 The GO powder (50 mg) was first dispersed into 100 mL of deionized water, and then the GO dispersion was mixed with PEI polymer (150 mg), followed by vigorous stirring at 80 °C for 12 h. The G-P samples can be easily obtained after washing with deionized water for several times. 2.2. Fabrication of 2D Cobalt Sulfide/Graphene (G-P-CoS) Hybrid Nanosheets. For a typical run, a G-P mixture solution (30 mL, 4 mg mL−1) was first prepared by directly dispersing the G-P samples into deionized water, and then CoCl2·6H2O (1 mmol) was added into the above dispersion under vigorous stirring for 6 h at room temperature. Subsequently, the trithiocyanuric acid trisodium salt (C3N3S3Na3, 1.2 mmol) was added into 10 mL of deionized water and then poured into the above solution under stirring. The mixture solution was then transferred into a Teflon-lined stainless steel autoclave (50 mL) and kept at 180 °C for 12 h. Finally, the sample was collected by centrifugation and washed several times by deionized water. It should be noted that the methods involved in the preparation of the G-P-CoS hybrid nanosheets are totally different from those reported in previous literature.34,35 2.3. Fabrication of Other 2D G-P-X Hybrid Nanosheets (X Stands for NiCoS, FeOOH, NiOOH). The 2D G-P-X hybrid nanosheets can be easily realized by reacting G-P with other metal salts. For example, CoCl2·6H2O (0.5 mmol) and NiCl2·6H2O (0.5 mmol) were added into the G-P dispersion, the following steps were similar to that of G-P-CoS samples, and the as-obtained product was named as G-P-NiCoS. For the G-P-FeOOH and G-P-NiOOH samples, urea (50 mmol), FeCl3·6H2O (1 mmol), and NiCl2·6H2O (1 mmol) were first added into the G-P dispersion. The aqueous solution was kept at 180 °C for 12 h, and then the samples were collected under the aforementioned conditions. 2.4. Material Characterization. The morphologies of the asobtained samples were examined by MAIA3 LMH field-emission scanning electron microscopy (FE-SEM) and JEOL JEM-F200 transmission electron microscopy (TEM). X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) were characterized using Shimadzu XRD6100 and Nicolet iS50. Surface elements distribution was measured by Thermo Fisher ESCALAB Xi+ X-ray photoelectron spectroscopy (XPS). The N2 adsorption/desorption isotherm was recorded by Micromeritics ASAP 2460. ThermograviB

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

Figure 2. (a) XRD patterns of the as-synthesized CoS, G-CoS, and G-P-CoS samples. (b) Raman spectra of the G-P and G-P-CoS samples.

Figure 3. (a) High-resolution N 1s XPS spectra of the G-P and G-P-CoS samples. High-resolution (b) S 2p, (c) Co 2P, and (d) C 1s XPS spectra of the CoS, G-CoS, and G-P-CoS samples. metric analysis was conducted on a STA449F5 instrument from 30 to 900 °C in the air. 2.5. Electrochemical Characterization. A three-electrode cell with 6 M KOH aqueous electrolyte on a VMP3 electrochemical workstation (Bio-logic) was used to test the electrochemical properties of the as-prepared samples. The working electrodes were fabricated by cutting the slices consisting of active material (80 wt %), carbon black (15 wt %), and polytetrafluoroethylene (5 wt %), followed by a drying procedure at 80 °C for 12 h. Next, pieces of slices were loaded onto the nickel foam, where the mass of the samples was about 3 mg cm−2. The platinum foil was the counter electrode with Hg/HgO as the reference for cyclic voltammetry (CV) and galvanostatic charge and discharge tests. Besides, in the twoelectrode system, the asymmetric supercapacitor using the as-obtained 2D hybrid nanosheet electrodes, cellulose acetate membrane, and activated carbon (AC) electrodes was assembled. The charge balance or mass ratio of the electrodes was calculated according to the CV results. For the G-P-CoS//AC asymmetric supercapacitor, the mass ratio of the G-P-CoS hybrids and AC was evaluated to be about 2:1. The electrochemical test of the asymmetric supercapacitor was operated in a two-electrode cell with aqueous electrolyte (6 M KOH).

Figure 1. First, the PEI molecules were coated on the GO surface (G-P) via the chemical grafting reaction between the amino groups from the PEI molecules and the carboxyl/epoxy groups on GO.36 The ζ-potential test was carried out to evaluate the surface potential of the G-P sample. As displayed in Figure S1, the surface of the G-P sample showed the negatively charged feature. Subsequently, the metal salts (e.g., CoCl2·6H2O) were mixed with the G-P nanosheets dispersion followed by hydrothermal treatment. During this process, the Co2+ ions could be easily adsorbed onto the surface of the G-P nanosheets through complexation and electrostatic interaction, in which the PEI nanostructures function as a confined space to induce the growth of cobalt sulfide nanoparticles on the GO substrate, yielding the 2D hybrid nanosheets with unique nanoparticle size and excellent structural stability. The FT-IR spectra were first recorded to analyze the surface chemical properties of the GO and G-P samples, and the corresponding results are displayed in Figure S2. In comparison to the GO sample, an obvious peak of the G-P sample at 1734 cm−1 corresponding to an amide bond can be clearly observed.37 This indicates that PEI molecules are successfully grafted on the GO surface, which can further mediate the growth and distribution of the electroactive

3. RESULTS AND DISCUSSION As discussed in Experimental Methods section, the fabrication process of the G-P-CoS hybrid nanosheets is illustrated in C

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

Figure 4. FE-SEM images of (a) CoS, (b, c) G-CoS, and (d−f) G-P-CoS samples. (g−i) TEM and HR-TEM images of the G-P-CoS samples. (j) Scanning transmission electron microscope image of the G-P-CoS hybrids and elemental distribution of C, N, Co, and S.

displayed in Table S1. The high-resolution XPS spectra of N 1s are presented in Figure 3a, in which the two peaks at 399.7 and 402.2 eV can be attributed to the −CONH− and −NH2 groups of the PEI, respectively.39 Obviously, the peak intensity associated with the −NH2 group of the G-P-CoS sample shows a significant decrease in comparison to the G-P sample; moreover, the characteristic peak of the nitrogen species for the G-P-CoS sample has a small positive shift. These results indicate that the CoS active species were successfully linked to the G-P surface via the coordination interaction. Figure 3b shows the high-resolution S 2p spectra of the as-obtained samples, in which the two major peaks corresponding to the metal−sulfur bonds can be clearly observed in all of the samples.40,41 The typical Co 2p spectra of the samples are shown in Figure 3c.41,42 Compared with the CoS and G-CoS samples, there is an obvious shift toward a low binding energy for the G-P-CoS hybrid nanosheets, which further confirms the strong coupling effect between the graphene and CoS species in the presence of PEI. This is in agreement with the results of the Raman spectra mentioned above. The C 1s XPS spectra are shown in Figure 3d, in which the main peak can be segmented into three main peaks, corresponding to C−C, C−O/C−N, and CO in the carbon matrix.39 These results imply that some functional groups are still present on the hybrid nanosheets, which are beneficial for enhancing the structural stability of the electrode materials.43 The morphologies of the as-made samples were further observed by FE-SEM and TEM characterizations, as seen in Figure 4. The typical FE-SEM image shows that the pristine CoS nanoparticles with a size of about 100 nm tend to form an aggregated structure (Figure 4a). For the G-CoS nanohybrids,

species. The SEM image (Figure S3a) shows that the G-P sample has a well-defined and flexible 2D sheet structure, which is in line with the TEM result of the G-P (Figure S3b), indicating the homogeneous distribution of the PEI on the GO surface through chemical grafting reaction. The XRD patterns of the as-obtained G-P-CoS hybrid nanosheets and the compared samples are shown in Figure 2a, in which all of those diffraction peaks can be indexed to the (204), (220), (306), and (330) planes of the spinel CoS1.097 phase (JCPDS Card no. 19−366). It is noted that there is no observable diffraction peak of the G-P, probably due to its low intensity in comparison to that of the CoS phase. Raman spectra of the GP-CoS and G-P samples are displayed in Figure 2b, in which two sharp peaks at around 1350 and 1580 cm−1 can be obviously observed. This is attributed to the disordered structures (D band) and the graphitic structure (G band), respectively. The intensity ratios (ID/IG) of the G-P-CoS and G-P samples are both higher than that of GO sample, indicating that more structural defects were present on the graphene surface. In addition, according to the Raman spectra of the G-P-CoS and CoS samples from 450 to 800 cm−1, there is a slight shift of the characteristic peaks for the G-P-CoS sample in comparison to that for the CoS sample (Figure S4), which is mainly due to the strong interaction between the graphene and CoS species in the presence of PEI.38 In addition, the XPS spectrum was applied to further detect the surface electronic states and compositions of the asobtained samples. The peaks in the survey spectrum of the GP-CoS hybrid nanosheets can be assigned to S, Co, C, and N elements, respectively (Figure S5), and the corresponding contents of these elements in the G-P-CoS hybrids are D

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

Figure 5. (a) CV curves of the various electrodes prepared by CoS, G-CoS, and G-P-CoS samples at 20 mV s−1. (b) CV curves of the G-P-CoS hybrid electrodes (scan rate: 2−50 mV s−1). (c) Charge/discharge curves of the CoS, G-CoS, and G-P-CoS electrodes at 10 A g−1. (d) The corresponding specific capacitances of the CoS, G-CoS, and G-P-CoS electrodes. (e) Cycling stability of the G-P-CoS electrodes at 4 A g−1.

nanosheets have been successfully fabricated, whose crystallographic structures are confirmed by the XRD patterns as shown in Figures S10−S12.44−46 The morphologies of the asobtained samples are further revealed by FE-SEM and TEM images, in which the typical 2D hybrid nanosheet structure decorated with uniform nanoparticles can be observed (Figures S13 and S14). The as-obtained samples were prepared as the working electrode to test the electrochemical performance in a threeelectrode cell. As displayed in Figure 5a, two pairs of redox peaks can be seen in the CV curves of the CoS, G-CoS, and GP-CoS hybrid electrodes at 20 mV s−1, which can be attributed to the reversible Faradic reaction related to Co2+/Co3+/Co4+, indicating the typical pseudocapacitive feature. It should be mentioned that the G-P nanosheet substrates make negligible contribution to the total capacitance of the hybrid electrode, as confirmed by the CV curves (Figure S15). The strongest peak intensity of the CV curve for the G-P-CoS hybrid electrodes compared to those of other electrodes also demonstrates the highest electrochemical activity among them. Moreover, all of the CV curves of the G-P-CoS hybrid electrodes exhibit similar shapes with no obvious distortion at various scan rates from 2 to 50 mV s−1 (Figure 5b), indicative of fast redox reaction kinetics of this kind of hybrid electrode. Figure 5c presents the charge−discharge curves of the CoS, G-CoS, and G-P-CoS samples at 10 A g−1, where the nearly symmetrical charge and discharge behaviors demonstrate their high Coulombic efficiency. The highest specific capacitance of the G-P-CoS hybrid electrodes can be also confirmed by the longest discharge time among all of the samples, which is in agreement

some inhomogeneous CoS nanoparticles are anchored on the graphene surface, and there is no 2D morphology observable in the hybrids (Figure 4b,c). In the presence of PEI, however, typical 2D nanosheets with a well-defined hierarchically porous structure can be found in the G-P-CoS nanohybrids (Figure 4d−f). Furthermore, a large amount of CoS nanoparticles with the size of 5−10 nm are uniformly bridged on the 2D graphene, as confirmed by the TEM images of the G-P-CoS nanohybrids in Figure 4g,h, which is obviously smaller than that of the G-CoS hybrids (ca. 50 nm, Figure S6). The corresponding specific surface area and pore volume of the GP-CoS hybrids are 132 m2 g−1 and 0.32 cm3 g−1, respectively, as shown in Figure S7. Furthermore, the thermogravimetric analysis result indicates that the loading of the CoS species on the G-P surface is about 71.2 wt % (Figures S8 and S9). These results further show that the nitrogen species from PEI play a critical role in mediating the growth and distribution of the CoS nanoparticles on graphene. The lattice fringes of the representative nanoparticles are detected in the high-resolution transmission electron microscopy (HR-TEM) image (Figure 4i). The measured interplanar lattice spacing is about 0.26 nm, which corresponds to the (220) plane of the spinel CoS1.097 phase. The elemental mapping analysis of the G-P-CoS hybrids is presented in Figure 4j, which shows that the nitrogen, cobalt, and sulfide components are uniformly distributed on the graphene surface. In addition, this kind of PEI-mediated strategy can be further extended to fabricate other 2D hybrid nanosheets with well-controlled particle size on the graphene by reacting the G-P sample with the corresponding metal salts. The G-P-NiCoS, G-P-FeOOH, and G-P-NiOOH hybrid E

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces

4. CONCLUSIONS In summary, a facile and general PEI-mediated strategy has been designed for fabrication of the series of 2D hybrid nanosheets with a well-controlled homogeneous distribution of nanoparticles. The nitrogen species from the PEI molecules function as bridging sites to enhance the coupling effect between the graphene and electroactive species, which endows the 2D hybrid nanosheets with high electroactivity and excellent structural stability. The as-obtained hybrid nanosheets demonstrate high specific capacitance and excellent electrochemical stability for the long-term cycling test, indicative of their potential as a promising electrode for supercapacitors with a high charge storage.

with the CV results. The corresponding specific capacitances of the as-prepared series of electrodes are displayed in Figure 5d. It can be seen that the G-P-CoS hybrid electrodes show a remarkably high specific capacitance of 320 F g−1 at 1 A g−1, which is obviously higher than those of the CoS (167 F g−1 at 1 A g−1) and G-CoS hybrids (213 F g−1 at 1 A g−1). For the GP-CoS hybrid electrodes, the high capacitance retention rate of around 62.5% (208 F g−1) can also be obtained even at 20 A g−1. Moreover, the G-P-CoS hybrid electrodes further exhibit an excellent cycling stability that the initial capacitance of 86.5% can be maintained after 20 000 cycles at 4 A g−1, as shown in Figure 5e. It is noted that the slight attenuation during the first few cycles can be attributed to the partial irreversible conversion of the redox associated with the partial dissolution of the active material.47,48 It should be noted that these electrochemical performances are comparable, and even superior to those of the Co-based electrodes reported previously (Table S2). In addition, the electrochemical performances of the other 2D hybrid nanosheet electrodes (e.g., G-P-NiCoS, G-P-FeOOH, and G-P-NiOOH) were also evaluated under the same conditions. The CV and charge/ discharge tests of the as-obtained hybrid electrodes are shown in Figures S16 and S17, respectively, and the corresponding specific capacitance is summarized in Table S3. As expected, all of the hybrid electrodes show excellent electrochemical performance. For example, the G-P-NiCoS hybrid electrodes can deliver 815 F g−1 at 1 A g−1, showing a high specific capacitance feature. To further evaluate the practical application of the as-made G-P-CoS and other hybrid nanosheets (e.g., G-P-NiCoS, G-PFeOOH, and G-P-NiOOH), the asymmetric supercapacitors are assembled where the 2D hybrid nanosheets and AC are used as positive and negative electrodes, respectively. Figures S18−S21 show the CV and galvanostatic charge−discharge curves of the as-made asymmetric supercapacitors, in which stable operation windows of 1.6 V can be achieved (scan rate ranging from 2 to 70 mV s−1). Accordingly, the assembled GP-CoS//AC asymmetric supercapacitor delivers a high energy density of 28.8 Wh kg−1, with a 130 W kg−1 of power density, and other asymmetric supercapacitors can also exhibit attractive electrochemical performances (e.g., a high charge storage of 44.6 Wh kg−1 at 700 W kg−1 for the G-P-NiCoS// AC asymmetric supercapacitor), this is obviously higher than those of the other asymmetric supercapacitors reported previously and the AC//AC symmetric supercapacitors (Figure S23). Furthermore, the cycling stability of the G-PCoS//AC asymmetric supercapacitor was tested, in which the superior cycling stability with a capacitance retention of 83% after 20 000 cycles at 2 A g−1 can be achieved (Figure S24). The excellent performance of the 2D hybrid electrodes for supercapacitors can be attributed to the systematically synergistic effects of various components including PEI, graphene, and electroactive species, although the electrical conductivity of the G-P nanosheet may be slightly reduced (Figure S25). First, the unique and small-size features of the CoS nanoparticles anchored on the G-P surface provide numerous electroactive sites, and this will contribute to improving the total charge storage. Second, the 2D morphology of the hybrid electrodes with an interconnected structure creates short path lengths for fast electron/ion transport. Moreover, the strong interaction between electroactive species and G-P substrate endows the 2D hybrid electrodes with excellent structural stability.

■

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acsami.9b03934.

■

Surface-charge investigation of the G-P sample with various pH values by ζ-potential measurements; FT-IR spectra of the GO and G-P samples; SEM and TEM images of the G-P sample; Raman spectra of the CoS and G-P-CoS nanohybrids; XPS survey spectrum of the G-P-CoS hybrids; TEM images of the G-CoS sample; nitrogen adsorption−desorption isotherm and pore size distribution of the G-P-CoS hybrids (PDF)

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected] (J.Y.). *E-mail: [email protected] (J.Q.). ORCID

Juan Yang: 0000-0002-2922-357X Chao Hu: 0000-0003-4538-6018 Jieshan Qiu: 0000-0002-6291-3791 Author Contributions ∥

M.W. and J.Y. contributed equally to this work.

Author Contributions

All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

■

ACKNOWLEDGMENTS This research was supported by the National Natural Science Foundation of China (No. 51802251), the Fundamental Research Funds for the Central Universities (No. xjj2018036), the National Key Research & Development Program (No. 2018YFB0604604), and the China Postdoctoral Science Foundation (No. 2018M631168, 2019T120915). We thank Jiao Li at the instrument Analysis Center of Xi’an Jiao Tong University for her assistance with the TEM test.

■

REFERENCES

(1) Miller, J. R.; Simon, P. Electrochemical Capacitors for Energy Management. Science 2008, 321, 651−652. (2) Zhang, C.; Lv, W.; Tao, Y.; Yang, Q. H. Towards Superior Volumetric Performance: Design and Preparation of Novel Carbon Materials for Energy Storage. Energy Environ. Sci. 2015, 8, 1390− 1403. F

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces (3) Lu, X.; Yu, M.; Wang, G.; Tong, Y.; Li, Y. Flexible Solid-State Supercapacitors: Design, Fabrication and Applications. Energy Environ. Sci. 2014, 7, 2160−2181. (4) González, A.; Goikolea, E.; Barrena, J. A.; Mysyk, R. Review on Supercapacitors: Technologies and Materials. Renewable Sustainable Energy Rev. 2016, 58, 1189−1206. (5) Choudhary, N.; Li, C.; Moore, J.; Nagaiah, N.; Zhai, L.; Jung, Y.; Thomas, J. Asymmetric Supercapacitor Electrodes and Devices. Adv. Mater. 2017, 29, No. 1605336. (6) Yang, J.; Yu, C.; Fan, X.; Zhao, C.; Qiu, J. Ultrafast SelfAssembly of Graphene Oxide-Induced Monolithic NiCo-Carbonate Hydroxide Nanowire Architectures with a Superior Volumetric Capacitance for Supercapacitors. Adv. Funct. Mater. 2015, 25, 2109−2116. (7) Yang, J.; Yu, C.; Liang, S.; Li, S.; Huang, H.; Han, X.; Zhao, C.; Song, X.; Hao, C.; Ajayan, P. M.; Qiu, J. Bridging of Ultrathin NiCo2O4 Nanosheets and Graphene with Polyaniline: A Theoretical and Experimental Study. Chem. Mater. 2016, 28, 5855−5863. (8) Barbieri, O.; Hahn, M.; Herzog, A.; Kötz, R. Capacitance Limits of High Surface Area Activated Carbons for Double Layer Capacitors. Carbon 2005, 43, 1303−1310. (9) Augustyn, V.; Simon, P.; Dunn, B. Pseudocapacitive Oxide Materials for High-Rate Electrochemical Energy Storage. Energy Environ. Sci. 2014, 7, 1597−1614. (10) Liao, J.; Zou, P.; Su, S.; Nairan, A.; Wang, Y.; Wu, D.; Wong, C. P.; Kang, F.; Yang, C. Hierarchical Nickel Nanowire@NiCo2S4 Nanowhisker Composite Arrays with a Test-Tube-Brush-Like Structure for High-Performance Supercapacitors. J. Mater. Chem. A 2018, 6, 15284−15293. (11) Xiong, Q.; Zheng, C.; Chi, H.; Zhang, J.; Zhenguo, J. Reconstruction of TiO2/MnO2-C Nanotube/Nanoflake Core/Shell Arrays as High-Performance Supercapacitor Electrodes. Nanotechnology 2017, 28, No. 055405. (12) Xie, M.; Xu, Z.; Duan, S.; Tian, Z.; Zhang, Y.; Xiang, K.; Lin, M.; Guo, X.; Ding, W. Facile Growth of Homogeneous Ni(OH)2 Coating on Carbon Nanosheets for High-Performance Asymmetric Supercapacitor Applications. Nano Res. 2018, 11, 216−224. (13) Wang, R.; Yan, X.; Lang, J.; Zheng, Z.; Zhang, P. A Hybrid Supercapacitor Based on Flower-Like Co(OH)2 and Urchin-Like VN Electrode Materials. J. Mater. Chem. A 2014, 2, 12724−12732. (14) Li, X.; Ding, S.; Xiao, X.; Shao, J.; Wei, J.; Pang, H.; Yu, Y. N,S Co-Doped 3D Mesoporous Carbon-Co3Si2O5(OH)4 Architectures for High-Performance Flexible Pseudo-Solid-State Supercapacitors. J. Mater. Chem. A 2017, 5, 12774−12781. (15) Hu, H.; Guan, B. Y.; Lou, X. W. D Construction of Complex CoS Hollow Structures with Enhanced Electrochemical Properties for Hybrid Supercapacitors. Chem 2016, 1, 102−113. (16) Xu, X.; Liu, Y.; Dong, P.; Ajayan, P. M.; Shen, J.; Ye, M. Mesostructured CuCo2S4/CuCo2O4 Nanoflowers as Advanced Electrodes for Asymmetric Supercapacitors. J. Power Sources 2018, 400, 96−103. (17) Wang, Y.; Zhu, T.; Zhang, Y.; Kong, X.; Liang, S.; Cao, G.; Pan, A. Rational Design of Multi-Shelled CoO/Co9S8 Hollow Microspheres for High-Performance Hybrid Supercapacitors. J. Mater. Chem. A 2017, 5, 18448−18456. (18) Dong, Y.; Wu, Z.-S.; Ren, W.; Cheng, H.-M.; Bao, X. Graphene: A Promising 2D Material for Electrochemical Energy Storage. Sci. Bull. 2017, 62, 724−740. (19) Zhang, X.; Luo, J.; Tang, P.; Ye, X.; Peng, X.; Tang, H.; Sun, S. G.; Fransaer, J. A Universal Strategy for Metal Oxide Anchored and Binder-Free Carbon Matrix Electrode: A Supercapacitor Case with Superior Rate Performance and High Mass Loading. Nano Energy 2017, 31, 311−321. (20) Cao, F.; Zhao, M.; Yu, Y.; Chen, B.; Huang, Y.; Yang, J.; Cao, X.; Lu, Q.; Zhang, X.; Zhang, Z.; Tan, C.; Zhang, H. Synthesis of Two-Dimensional CoS1.097/Nitrogen-Doped Carbon Nanocomposites Using Metal−Organic Framework Nanosheets as Precursors for Supercapacitor Application. J. Am. Chem. Soc. 2016, 138, 6924−6927.

(21) Xiao, X.; Yu, H.; Jin, H.; Wu, M.; Fang, Y.; Sun, J.; Hu, Z.; Li, T.; Wu, J.; Huang, L.; Gogotsi, Y.; Zhou, J. Salt-Templated Synthesis of 2D Metallic MoN and Other Nitrides. ACS Nano 2017, 11, 2180− 2186. (22) Guan, C.; Ximeng, L.; Weina, R.; Xin, L.; Chuanwei, C.; John, W. Rational Design of Metal-Organic Framework Derived Hollow NiCo2O4 Arrays for Flexible Supercapacitor and Electrocatalysis. Adv. Energy Mater. 2017, 7, No. 1602391. (23) Yan, J.; Ren, C. E.; Maleski, K.; Hatter, C. B.; Anasori, B.; Urbankowski, P.; Sarycheva, A.; Gogotsi, Y. Flexible MXene/ Graphene Films for Ultrafast Supercapacitors with Outstanding Volumetric Capacitance. Adv. Funct. Mater. 2017, 27, No. 1701264. (24) Khan, A. H.; Ghosh, S.; Pradhan, B.; Dalui, A.; Shrestha, L. K.; Acharya, S.; Ariga, K. Two-Dimensional (2D) Nanomaterials towards Electrochemical Nanoarchitectonics in Energy-Related Applications. Bull. Chem. Soc. Jpn. 2017, 90, 627−648. (25) Zhou, J.; Qin, J.; Zhang, X.; Shi, C.; Liu, E.; Li, J.; Zhao, N.; He, C. 2D Space-Confined Synthesis of Few-Layer MoS2 Anchored on Carbon Nanosheet for Lithium-Ion Battery Anode. ACS Nano 2015, 9, 3837−3848. (26) da Silveira Firmiano, E. G.; Rabelo, A. C.; Dalmaschio, C. J.; Pinheiro, A. N.; Pereira, E. C.; Schreiner, W. H.; Leite, E. R. Supercapacitor Electrodes Obtained by Directly Bonding 2D MoS2 on Reduced Graphene Oxide. Adv. Energy Mater. 2014, 4, No. 1301380. (27) Lin, J.; Jia, H.; Liang, H.; Chen, S.; Cai, Y.; Qi, J.; Qu, C.; Cao, J.; Fei, W.; Feng, J. In Situ Synthesis of Vertical Standing Nanosized NiO Encapsulated in Graphene as Electrodes for High-Performance Supercapacitors. Adv. Sci. 2018, 5, No. 1700687. (28) Wei, L.; Karahan, H. E.; Zhai, S.; Liu, H.; Chen, X.; Zhou, Z.; Lei, Y.; Liu, Z.; Chen, Y. Amorphous Bimetallic Oxide−Graphene Hybrids as Bifunctional Oxygen Electrocatalysts for Rechargeable Zn−Air Batteries. Adv. Mater. 2017, 29, No. 1701410. (29) Xia, X.; Chao, D.; Fan, Z.; Guan, C.; Cao, X.; Zhang, H.; Fan, H. J. A New Type of Porous Graphite Foams and Their Integrated Composites with Oxide/Polymer Core/Shell Nanowires for Supercapacitors: Structural Design, Fabrication, and Full Supercapacitor Demonstrations. Nano Lett. 2014, 14, 1651−1658. (30) Lin, T. W.; Dai, C. S.; Tasi, T. T.; Chou, S. W.; Lin, J. Y.; Shen, H. H. High-Performance Asymmetric Supercapacitor Based on Co9S8/3D Graphene Composite and Graphene Hydrogel. Chem. Eng. J. 2015, 279, 241−249. (31) Patil, S. J.; Kim, J. H.; Lee, D. W. Graphene-Nanosheet Wrapped Cobalt Sulphide as a Binder Free Hybrid Electrode for Asymmetric Solid-State Supercapacitor. J. Power Sources 2017, 342, 652−665. (32) Tan, Y.; Liang, M.; Lou, P.; Cui, Z.; Guo, X.; Sun, W.; Yu, X. In Situ Fabrication of CoS and NiS Nanomaterials Anchored on Reduced Graphene Oxide for Reversible Lithium Storage. ACS Appl. Mater. Interfaces 2016, 8, 14488−14493. (33) Hummers, W. S.; Offeman, R. E. Preparation of Graphitic Oxide. J. Am. Chem. Soc. 1958, 80, 1339. (34) Yuan, B.; Xu, C.; Liu, L.; Shi, Y.; Li, S.; Zhang, R.; Zhang, D. Polyethylenimine-Bridged Graphene Ixide−Gold Film On Glassy Carbon Electrode and Its Electrocatalytic Activity Toward Nitrite and Hydrogen Peroxide. Sens. Actuators, B 2014, 198, 55−61. (35) Xu, C.; Zhang, L.; Liu, L.; Shi, Y.; Wang, H.; Wang, X.; Wang, F.; Yuan, B.; Zhang, D. A Novel Enzyme-Free Hydrogen Peroxide Sensor Based on Polyethylenimine-Grafted Graphene Oxide-Pd Particles Modified Electrode. J. Electroanal. Chem. 2014, 731, 67−71. (36) Sui, Z. Y.; Cui, Y.; Zhu, J. H.; Han, B. H. Preparation of ThreeDimensional Graphene Oxide−Polyethylenimine Porous Materials as Dye and Gas Adsorbents. ACS Appl. Mater. Interfaces 2013, 5, 9172− 9179. (37) Li, X.; Cheng, Y.; Zhang, H.; Wang, S.; Jiang, Z.; Guo, R.; Wu, H. Efficient CO2 Capture by Functionalized Graphene Oxide Nanosheets as Fillers To Fabricate Multi-Permselective Mixed Matrix Membranes. ACS Appl. Mater. Interfaces 2015, 7, 5528−5537. G

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX

Research Article

ACS Applied Materials & Interfaces (38) Chen, C.-Y.; Shih, Z.-Y.; Yang, Z.; Chang, H.-T. Carbon Nanotubes/Cobalt Sulfide Composites as Potential High-Rate and High-Efficiency Supercapacitors. J. Power Sources 2012, 215, 43−47. (39) Yu, D.; Dai, L. Self-Assembled Graphene/Carbon Nanotube Hybrid Films for Supercapacitors. J. Phys. Chem. Lett. 2010, 1, 467− 470. (40) Liu, G.; Wang, B.; Liu, T.; Wang, L.; Luo, H.; Gao, T.; Wang, F.; Liu, A.; Wang, D. 3D Self-Supported Hierarchical Core/Shell Structured MnCo2O4@CoS Arrays For High-Energy Supercapacitors. J. Mater. Chem. A 2018, 6, 1822−1831. (41) Zeng, W.; Zhang, G.; Wu, X.; Zhang, K.; Zhang, H.; Hou, S.; Li, C.; Wang, T.; Duan, H. Construction of Hierarchical CoS Nanowire@NiCo2S4 Nanosheet Arrays via One-Step Ion Exchange for High-Performance Supercapacitors. J. Mater. Chem. A 2015, 3, 24033−24040. (42) Gao, H.; Zhou, T.; Zheng, Y.; Zhang, Q.; Liu, Y.; Chen, J.; Liu, H.; Guo, Z. CoS Quantum Dot Nanoclusters for High-Energy Potassium-Ion Batteries. Adv. Funct. Mater. 2017, 27, No. 1702634. (43) Zhao, R.; Kong, W.; Sun, M.; Yang, Y.; Liu, W.; Lv, M.; Song, S.; Wang, L.; Song, H.; Hao, R. Highly Stable Graphene-Based Nanocomposite (GO−PEI−Ag) with Broad-Spectrum, Long-Term Antimicrobial Activity and Antibiofilm Effects. ACS Appl. Mater. Interfaces 2018, 10, 17617−17629. (44) Xiong, X.; Waller, G.; Ding, D.; Chen, D.; Rainwater, B.; Zhao, B.; Wang, Z.; Liu, M. Controlled Synthesis of NiCo2S4 Nanostructured Arrays on Carbon Fiber Paper for High-Performance Pseudocapacitors. Nano Energy 2015, 16, 71−80. (45) Wang, B.; Wu, H.; Yu, L.; Xu, R.; Lim, T.-T.; Lou, X. W. Template-Free Formation of Uniform Urchin-Like α-FeOOH Hollow Spheres with Superior Capability for Water Treatment. Adv. Mater. 2012, 24, 1111−1116. (46) Pan, J.; Sun, Y.; Wan, P.; Wang, Z.; Liu, X. Synthesis, Characterization and Electrochemical Performance of Battery Grade NiOOH. Electrochem. Commun. 2005, 7, 857−862. (47) Xiao, T.; Li, J.; Zhuang, X.; Zhang, W.; Wang, S.; Chen, X.; Xiang, P.; Jiang, L.; Tan, X. Wide Potential Window and High Specific Capacitance Triggered via Rough NiCo2S4 Nanorod Arrays with Open Top for Symmetric Supercapacitors. Electrochim. Acta 2018, 269, 397−404. (48) Gao, X.-P.; Yao, S.-M.; Yan, T.-Y.; Zhou, Z. Alkaline Rechargeable Ni/Co Batteries: Cobalt Hydroxides as Negative Electrode Materials. Energy Environ. Sci. 2009, 2, 502−505.

H

DOI: 10.1021/acsami.9b03934 ACS Appl. Mater. Interfaces XXXX, XXX, XXX−XXX