Ultralong N-doped

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Surfaces, Interfaces, and Applications

Three-dimensional Hierarchical MoS2 Nanosheets/Ultralong N-doped Carbon Nanotubes as High-Performance Electromagnetic Wave Absorbing Material Lianlian Liu, Shen Zhang, Feng Yan, Chunyan Li, Chunling Zhu, Xitian Zhang, and Yujin Chen ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b00709 • Publication Date (Web): 04 Apr 2018 Downloaded from http://pubs.acs.org on April 4, 2018

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ACS Applied Materials & Interfaces

Three-dimensional Hierarchical MoS2 Nanosheets/Ultralong N-doped Carbon Nanotubes as High-Performance Electromagnetic Wave Absorbing Material Lianlian Liu,†,#‡ Shen Zhang † Feng Yan, † Chunyan Li,† Chunling Zhu,*,‡ Xitian Zhang,# Yujin Chen*,† † Key Laboratory of In-Fiber Integrated Optics, Ministry of Education, and College of Science, Harbin Engineering University, Harbin 150001, China ‡ College of Material Science and Chemical Engineering, Harbin Engineering University, Harbin 150001, China # Key Laboratory for Photonic and Electronic Bandgap Materials, Ministry of Education, and School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025, China.

KEYWORDS: Three-dimensional Hierarchical structure, MoS2 nanosheets, Ultralong N-doped carbon nanotube, Electromagnetic wave, Absorption property

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ABSTRACT: Here we report a simple method to grow thin MoS2 nanosheets (NSs) on the ultralong nitrogen-doped carbon nanotubes through anion exchange reaction. The MoS2 NSs are grown on of the ultralong nitrogen-doped carbon nanotube surfaces, leading to an interesting three-dimensional hierarchical structure. The fabricated hybrid nanotubes have a length of approximately 100 µm, where the MoS2 nanosheets have a thickness of less than 7.5 nm. The hybrid nanotubes show excellent electromagnetic wave attenuation performance with effective absorption bandwidth is 5.4 GHz at the thicknesses of 2.5 mm, superior to the pure MoS2 nanosheets and the MoS2 nanosheets grown on the short N-doped carbon nanotube surfaces. The experimental results indicate that the direct growth of MoS2 on the ultralong nitrogen-doped carbon nanotube surfaces is a key factor for the enhanced electromagnetic wave attenuation property. The results open an avenue for the development of ultralong transition metal dichalcogenides for electromagnetic wave absorbers.


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1. INTRODUCTION Layered transition-metal dichalcogenide (TMD) nanostructures have drawn wide attention because of their different physicochemical performance from the bulk counterparts. Among those TMDs, layered MoS2 nanosheets have been reported as electrocatalyts toward hydrogen evolution reaction, anode for Li/Na secondary batteries, and photoelectric devices because their performance can be adjusted through the number of layers, lateral size, and interlayer distance.1–7 Their physicochemical properties can be further improved by designing three-dimensional (3D), hollow, and hierarchical MoS2 structures. Those MoS2-based structures include 3D MoS2 nanosheets,8,9 3D MoS2@carbon nanotube (CNT)/reduced graphene oxide (rGO),10 3D MoS2 nanoleaves/carbon fiber,11 3D MoS2/graphene hierarchical structures,12–14 hierarchical MoS2 hollow nanospheres,15 3D multiwalled carbon@MoS2@carbon hollow nanocables,16 layered MoS2 hollow spheres,17 hollow fullerene-like MoS2 nanocages,18 hollow MoS2/carbon nanospheres,19,20 MoS2 hierarchical hollow cages,21 and hollow inorganic-fullerene-type MoS2 nanoparticles,22 etc. However, the fabrication of MoS2 nanosheets grown on 3D ultralong Ndoped CNTs has never been reported so far. Electromagnetic wave (EMW) absorbers have drawn wide attention due to serious EM interference issues induced by wide utilization of electronic devices operating at gigahertz band. Recently, the potential applications of the MoS2 nanosheets and their composites in the EMW absorption properties have been reported.23-27 For example, the minimal reflection loss (RL, min) of the exfoliated MoS2 nanosheets prepared in n-butyl lithium solvent was around –38.4 dB.23 The MoS2 nanosheets synthesized by a solvothermal method exhibited RL,

min

of –47.8 dB at 12.8


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GHz.24 However, the addition amount of those MoS2 nanosheets into the matrix was as high as 60 wt.%, which may not meet the requirements regarding lightweight absorbing material. Therefore, the EMW adsorption properties of layered MoS2 nanostructures have a room to be increased. Recently, some 3D heteostructures have been reported to exhibit enhanced EMW absorption property compared to one-dimensional counterparts.28–36 Xu et al prepared 3D hierarchical Fe3O4@CuSiO3 core/shell nanocomposite with superior EMW absorption property to Fe3O4 nanorods.28 Zhou et al designed urchinlike α-MnO2 nanostructures and found that the 3D nanostructures exhibited RL, min of –41.0 dB at a thickness of 1.9 mm as the weight percentage in the wax was 50 wt.%.29 Our previous results showed that 3D G/Fe3O4 nanorods and G/PANI nanorods exhibited excellent EMW absorption properties even as their weight percentage in the matrix was only 20 wt.%.30,31 Song et al modified reduced graphene oxide foam using ZnO naowires and found that the 3D composite had improved EMW absorption performance in comparison to those of both ZnO nanowires and rGO nanosheets.32 Besides, hollow or tubular nanostructures have shown superior EMW absorption property to the solid counterparts because they could provide additional free space for the attenuation of EMW energy.37–47 Among the above designed materials, 3D structures containing 1D ultralong nanostructures are more interesting because the conductive networks are easily formed among the 1D nanostructures. For example, Hou et al fabricated Fe/SiC hybrid fibers, exhibiting excellent EMW absorption property with a minimal RL of about −46.3 dB at 6.4 GHz.47 However, the fabrication and the EMW absorption property of 3D architecture based on ultralong N-doped CNTs have never been reported.


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Here we report a method for growing MoS2 nanosheets on ultralong N-doped CNTs (MoS2 NS/U-NCNTs) and investigate the EMW absorption property of the 3D hollow heterostructures. In the 3D heterostructures, the length is up to about one hundred micrometer. MoS2 nanosheets with the lateral length and the thickness of around 175 and 7.5 nm, respectively, are uniformly grown on the ultralong NCNTs. Compared to the MoS2 nanosheets grown short N-doped CNTs (MoS2 NS/S-NCNTs) and pure MoS2 NSs, the MoS2 NS/U-NCNTs exhibited significantly enhanced EMW absorption property. Furthermore, the EMW absorption property of MoS2 NS/U-NCNTs is favorably comparable to that of most 3D or hollow structures previously reported.

2. EXPERIMETNAL SECTION The preparation processes and the structural characterizations of U-MoO3@polypyrrole (Ppy), U-MoO3@NC,

U-NCNTsand

MoS2

NS/U-NCNTs,

and

electromagnetic

parameter

measurements were described in Supporting Information.


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Figure 1 The fabrication of the MoS2 NS/U-NCNTs.


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Figure 2 SEM images (a, b), TEM and HRTEM images (c, d) of as-fabricated U-MoO3 nanobelts. SEM images (e,f), TEM and HRTEM images (g,h) of the U-MoO3@Ppy core-shell nanobelts. SEM images (i,j) and TEM and HRTEM images (k,l) of the U-MoO3@NC nanobelts. The insets in c-d parts show SAED patterns of U-MoO3, U-MoO3@Ppy core-shelled and UMoO3@NC nanobelts, respectively.


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3. RESULTS AND DISCUSSION The fabrication of MoS2 NS/U-NCNTs is involved four steps (Figure 1). In the first step, ultralong MoO3 nanobelts were synthesized through a method reported by Yao et al.48 In the second step, Ppy layers were coated over the ultralong MoO3 nanobelts through a lowtemperature polymerization strategy, forming U-MoO3@Ppy core-shell nanobelts. Then, UMoO3@NC nanobelts were obtained after heating U-MoO3@Ppy at 400oC for 30 min under an Ar flow. Finally, the MoS2 NS/U-NCNTs were prepared through a solvothermal method at 200oC for 54 h. Figure 2a-c show that the as-fabricated MoO3 nanobelts have a length of > 130 micrometers and the width of about 400 nm, similar to the previous reports.43 High-resolution transmission electron microscopy (HRTEM) and the selected area electron diffraction (SAED) pattern reveal crystal character of the ultralong nanobelts (Figure 2d and the inset of Figure 2c). The well-resolved lattice spacings of 0.37 and 0.40 nanometer correspond to (002) and (200) planes of orthorhombic MoO3 (Figure 2d), respectively. X-ray diffraction analysis confirms the crystal nature of ultralong MoO3 nanobelts (JCPDs no. 35-0609) (Figure S1a, Supporting Information). SEM, SAED and XRD analyses demonstrate that the size and crystal nature of MoO3 nanobelts are not changed by the Ppy coatings in comparison to the bare MoO3 nanobelts (Figure 2e,f, the inset in Figure 2g and Figure S1b). High-magnification SEM and TEM observations indicate that the Ppy coatings have a thickness of around 30 nm (Figure 2f,g). Lattice fringes are not observed in shell region, revealing the amorphous nature of the Ppy coatings (Figure 2h). After the heating of U-MoO3@Ppy core-shell nanobelts, the Ppy changed to N-doped amorphous carbon. All the peaks in the Figure S1c come from orthorhombic MoO3, revealing the unchanged crystal structure of the MoO3 nanobelts after the heating process. Figure 2i indicates that the U-MoO3@NC nanobelts have a length above 130 µm, having little


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difference from those of the U-MoO3 and U-MoO3@Ppy core-shell nanobelts. Highmagnification SEM and TEM image indicates that the thickness of N-doped the carbon layer is approximately 25 nanometers (Figure 2j and 2k), which is thinner than that of the Ppy coatings due to the heating treatment. HRTEM image and SAED confirm the unchanged crystal structure of the MoO3 nanobelts after the heating process (Figure 2l and the inset in Figure 2k). The marked lattice spacings are 0.37 and 0.40 nm, which are assigned to (002) and (200) planes of orthorhombic MoO3 (Figure 2l), respectively, in line with the SAED pattern (the inset in Figure 2k).

Figure 3 Structural characterizations of MoS2 NS/U-NCNTs. (a) XRD, (b) SEM image, (c) TEM images of MoS2 NS/U-NCNTs. (d-f) TEM and HRTEM images of the MoS2 nanosheets on UNCNTs surfaces.


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After the solvothermal treatment, U-MoO3@NC core-shell nanobelts could be transformed to MoS2 NS/U-NCNTs through anion exchange reaction. Figure 3a shows XRD pattern of MoS2 NS/U-NCNTs. The labeled diffraction peaks by Miller indices come from 2H-MoS2 (JCPDS no. 37-1492), while the broad one at 2θ of around 22 degree comes from N-doped carbon in UMoO3@NC core-shell nanobelts. Figure S2 shows that MoS2 NS/U-NCNTs have a length of approximately 100 µm, suggesting their ultralong feature. High-magnification SEM image indicates that uniform MoS2 NSs with a lateral length of 175 nm are formed on U-NCNT surfaces with an angle, leading to an interesting 3D hierarchical structure (Figure 3b). The MoS2 nanosheets are curling, indicating their ultrathin characteristics. The diameter of MoS2 NS/UNCNTs ranges from 450 to 650 nanometer (Figure 3b,c). The TEM image clearly shows that the NCNTs exhibit hollow and tubular morphologies (Figure 3c). The high-magnification TEM image shows that the maximum thickness of the MoS2 nanosheets is about 7.5 nanometers, approximately 12 S–O–S layers at the edges of the MoS2 NSs (Figure 3d). Figure 3e displays that the interlayer distance is 0.63 nm, suggesting slightly expanded (002) plane of MoS2 nanosheets in comparison to that of bulk MoS2 (0.615 nm). Figure 3f shows a HRTEM image recorded from the basal planes of MoS2 NSs, in which the labeled lattice distances are 0.27 and 0.23 nm, being the distances of (100) and (103) adjacent planes of MoS2 nanosheets. The diffraction rings in the SAED origin from (110) and (103) planes of MoS2 nanosheets, confirming the crystal nature of MoS2 (the inset in Figure 3d). MoS2 NS/U-NCNTs have ultralong and tubular features, implies that they have a big surface area. Nitrogen adsorption-desorption isotherms analysis demonstrates that the MoS2 NS/UNCNTs exhibit type IV hysteresis, suggesting the mesopores exisit in the nanosheets (Figure S3a). Brunauer–Emmett–Teller (BET) surface area of the MoS2 NS/U-NCNTs is around 54.7 m2


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g–1. In terms of the Barrett–Joyner–Halenda method, the average pore size is around 12.7 nanometer, and the corresponding cumulative pore volume is about 0.24 cm3 g–1 for the MoS2 NS/U-NCNTs (the inset in Figure S3a). Figure S4 displays the Raman spectrum of the MoS2 NS/U-NCNTs. Two peaks centered at 1375 and 1560 cm–1 are observed, characteristic feature of carbonaceous materials. The peak at 1375 cm–1 (D band) comes from the defect in NCNTs, whereas the peak at 1560 cm–1 (G band) is due to lattice-ordered carbon. The ID/IG is about 1: 1, suggesting amorphous feature of carbon in the MoS2 NS/U-NCNTs. Thermogravimetric (TG) analysis indicates that the content of MoS2 NSs in the 3D MoS2 NS/U-NCNTs is about 75 wt% (Figure S5).

Figure 4 (a) Mo 3d, (b) S 2p, (c) N 1s, and (d) C 1s XPS spectra of the MoS2 NS/U-NCNTs. The surface structural information of the MoS2 NS/U-NCNTs was analyzed by X-ray photoelectron spectroscopy (XPS). In Figure 4a, the peaks at 229.5 and 232.7 eV correspond to Mo4+ and Mo4+ 3d3/2 species, respectively.19,49 Besides, the peak at about 226.7 eV can be


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assigned to the S 2s binding energy in MoS2. The peaks at 162.2 and 163.3 eV correspond to S2− 2p3/2 and S2− 2p1/2 species, respectively (Figure 4b).10,50 In Figure 4c , two peaks at 395.3 and 398.2 eV correspond to pyridinic N and pyrrolic N, respectively.51 In XPS spectrum of C 1s core level, the peaks at 285.9 eV is attributed to C-N groups (Figure 4d).47 The existence of C–N species suggests the successful doping of nitrogen into the carbon matrix. According to the integrated peak areas, the N content is estimated to be 22.07 at.%. In addition, the peak at 288.6 eV corresponds to to C-O species.

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The above structural characterizations demonstrate that

MoS2 NS/S-NCNTs are composed of crystal MoS2 nanosheets and amorphous N-doped CNTs.

Figure 5 RL–f curves for the pure MoS2 nanosheets (a), the MoS2 NS/S-NCNTs (b), and the MoS2 NS/U-NCNTs (c). (d) The attenuation constant α data of the pure MoS2 nanosheets, MoS2 NS/S-NCNTs, and the MoS2 NS/U-NCNTs. (e) The real parts of the pure MoS2 nanosheets,


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MoS2 NS/S-NCNTs, and the MoS2 NS/U-NCNTs. f) The imaginary parts of the pure MoS2 nanosheets, MoS2 NS/S-NCNTs, and the MoS2 NS/U-NCNTs. For comparison, the pure MoS2 nanosheets and MoS2 nanosheets grown on short NCNTs (MoS2 NS/S-NCNTs) were also prepared. The pure MoS2 nanosheets were synthesized through a previous method.48 The SEM images show that the MoS2 nanosheets have a lateral length of about 165 nm, similar to previous reports (Figure S6).53,54 The MoS2 NS/S-NCNTs were prepared through the same steps as those for the MoS2 NS/U-NCNTs except that the ultralong MoO3 nanobelts were replaced with the short MoO3 nanorods that synthesized by a previous method.55, 56 Low-magnifications SEM image (Figure S7a) shows that the length and diameter of MoS2 NS/S-NCNTs are about 3 micrometers and 300 nanometer, respectively. The lateral length and thickness of the MoS2 NSs are approximately 160 and 6 nanometer, respectively (Figure S7b-d). TG analysis demonstrates that the MoS2 content in the MoS2 NS/S-NCNTs is about 69 wt%, slightly different from that in the MoS2 NS/U-NCNTs (Figure S8). The electromagnetic parameters of the paraffin composite containing 30 wt% of the absorbers were measured to investigate their EMW attenuation properties. The RL data is estimated by the below equations,57 Zin=Z0(µr/εr)1/2tanh[j2πfd/c(µrεr)1/2]

RL (dB) = 20 log

Z in - Z0 Zin + Z0

(1)

(2)

in which, Z0 and Zin are denoted as impedances of free space and the absorbing material, respectively; εr =ε′−jε″ and µr =µ′−jµ″ are relative complex permittivity and permeability of the absorbing material, respectively; c is the velocity of electromagnetic wave in the free space, f is the frequency of electromagnetic wave and d is the thickness of absorbing material. Because our


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samples have not magnetic loss toward EMW, the measured µr is close to 1−j0 (Figure S9). Thus, we mainly studied the effect of dielectric loss on EMW absorption performance of our samples. In general, as RL value is below –10 dB, 90% of EMW energy can be attenuated, suggesting that the absorber can be applied practically by the structural design of the absorbers. The relative frequency range is named as effective absorption bandwidth (EAB). As for practical application of the absorber, the EAB is required to be as large as possible at a thickness as small as possible. In terms of Equations 1,2, the RL−f curves for our MoS2-based absorbers at different thickness can be plotted. The minimal RL (RL, min) values for pure MoS2 nanosheets at d in range of 1.5 – 5.0 mm are above −10 dB (Figure 5a), indicating their very weak EMW attenuation performance. However, the EMW absorption property was remarkably enhanced by growing the MoS2 nanosheets on the S-NCNTs in terms of the EAB and the minimal RL values. The minimal RL values of the MoS2 NS/S-NCNTs are blow−10 dB at d ranging from 2.0 to 5.0 mm, and the minimal RL value reaches −20.3 dB at f = 6.5 GHz (Figure 5b). The EAB values for the MoS2 NS/S-NCNTs are 4.0, 3.5, 3.2, 2.9, 2.7 and 2.5 GHz at the absorber thickness of 2.5, 3.0, 3.5, 4.0, 4.5, and 5 micrometer, respectively. Interestingly, the EMW attenuation performance was further improved through coupling the MoS2 nanosheets with the ultralong NCNTs. The RL, min values of the MoS2 NS/U-NCNTs are blew −20 dB at d in range of 2.5 - 5.0 mm, and the RL,min value is −38.3 dB at a frequency of 9.4 GHz (in Figure 5c). The EAB values for the MoS2 NS/U-NCNTs are 5.4, 4.7, 4.3, 3.8, 3.1 and 2.5 GHz at d = 2.5, 3.0, 3.5, 4.0, 4.5 and 5.0 mm, respectively. Notably, the MoS2 NS/U-NCNTs and the MoS2 NS/S-NCNTs have slight difference in the MoS2 content. For more fair comparison, we inecreased the addition amount of the MoS2 NS/S-NCNTs into the paraffin matrix to 32.6 wt%. In the case, the MoS2 NS/S-NCNTs exhibit slightly enhanced EMW absorption property, but still show weaker EMW absorption performance than


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that of MoS2 NS/U-NCNTs, as shown Figure S10 and Table S1. The data including RL,min and EAB demonstrate that the MoS2 NS/U-NCNTs exhibit the best EMW attenuation performance among the tested samples. Furthermore, our MoS2 NS/U-NCNTs have comparable or better EMW absorption property in comparison to the reported absorber in terms of EAB and the addition amount into the matrix (Table S1). Besides the reflection loss, the attenuation constant, α, can be used to evaluate the absorption property of an absorber toward EMW (Equation (3)). 58

α=

2 µ ′ε ′πf c

µ ′′ε ′′ µ ′′ε ′′ 2 ε ′′ 2 µ ′′ 2 −1+ ( ) + ( ) + ( ) +1 µ ′ε ′ µ ′ε ′ ε′ µ′

(3)

The MoS2 NS/U-NCNTs have the largest α data at f ranging from 2 to 18 GHz among the tested samples, further confirming their good EMW attenuation performance (Figure 5d). Based on the RL, min and α data, the MoS2 NS/U-NCNTs have potential application in the EMW absorbing area. To analyze reasons for the enhancement in EMW property, we compared the relative complex permittivity data of the MoS2-based absorber, as shown in Figure 5e,f. ε′ and ε″ values for the MoS2 nanosheets are in range of 3.4-4.6 and 0.6-1.9, 4.7-7.9 and 1.6-3.9 for the MoS2 NS/S-NCNTs, and 5.0-8.8 and 2.0-7.3 for the MoS2 NS/U-NCNTs, respectively. Based on the measurement results, both ε′ and ε″ values of the MoS2 nanosheets are increased through coupling them with the NCNTs. Furthermore, the tan δe of our samples decreases in the order MoS2 NS/U-NCNTs > the MoS2 NS/SNCNTs > the pure MoS2 nanosheets (Figure S11), consistent with their order of the EMW absorption properties. Due to the negligible magnetic loss (Figure S9), the improvement of the EMW attenuation properties can be explained by the increased dielectric loss of the MoS2 NS/S-NCNTs and the MoS2 NS/S-NCNTs.


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The dielectric loss of the EMW absorbers is related to dipole polarization relaxations. In general, the higher surface area the absorber has, the more dipoles will produce in the absorber surface, which facilitates the enhanced dipole polarization relaxations as the absorber irradiated by the EMW.23-25 Nitrogen adsorption-desorption isotherms measurements (Figure S3b,c) give the BET surface areas of the MoS2 NS/S-NCNTs and the pure MoS2 nanosheets of 20.4 and 14.1 m2 g–1, approximately 2.4 and 3.9 times smaller than that of the MoS2 NS/U-NCNTs (54.7 m2 g– 1

), respectively. Thus, the enhanced dipole polarization relaxations induced by dipoles are

responsible for the enhanced EMW absorption property of MoS2 NS/U-NCNTs. In addition, the improved EMW attenuation property of the MoS2 NS/U-NCNTs is relevant to their ultralong feature.29, 32 As for the pure MoS2 nanosheets, it is difficult to form the interconnected network structure in the paraffin matrix due to their small lateral size (more then hundred nanometers). In contrast, the length of the MoS2 NS/U-NCNTs is above 100 µm, and thus the interconnected network structure can be formed more readily. In the case of the MoS2 NS/S-NCNTs, their length is merely several micrometers, and thus it is possible to form the interconnected network structure; however, the number of such interconnected network structure should be less than that in the MoS2 NS/S-NCNTs-based absorber. Upon the absorbers irradiated by the EMW, the microcurrent will produce and pass through the interconnected network structure, which can consume the energy of the EMW. Therefore, the enhanced EMW attenuation properties can be attributed to the ultralong feature of the MoS2 NS/U-NCNTs. Moreover, the enhanced EMW absorption property of the MoS2 NS/U-NCNTs is directly relevant to the MoS2 NSs grown on the NCNTs. To evaluate importance of the growth of MoS2 NSs, we compare the EMW absorption properties between the MoS2 NS/U-NCNTs and the physical mixture of the MoS2 nanosheets and U-NCNTs. U-NCNTs were prepared through an alkaline etching process (see Experimental


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Section for detail). SEM images (Figure S12) show that U-NCNTs exhibit tubular characteristics and their length is approximately 70 µm. The MoS2 content in the physical mixture was the same as that in the MoS2 NS/U-NCNTs for a fair comparison. The electromagnetic parameters of the mixture were evaluated and the RL value of the physical mixture is obtained by Equations 1 and 2. As shown in Figure S13, the RL, min values of the physical mixture are larger than –5.0 dB, inferior to those of the MoS2 NS/U-NCNTs. In addition, the RL –f curves for the U-NCNTs alone were also calculated in terms of their EM parameters (Figure S14a). As shown in Figure S14b, RL, min values for the U-NCNTs reach to –10.0 dB at d in range of 2.0 - 5.0 mm, however, they are larger than –15.0 dB. The results demonstrate that the U-NCNTs can be used as EMW absorbers, but they exhibit inferior EMW absorption property to that of the MoS2 NS/U-NCNTs. Thus, the growth of MoS2 nanosheets on U-NCNTs, forming the 3D hierarchal structure, is crucial to their EMW absorption property. Based on the above analyses, the porous and ultralong feature, high surface area, and direct growth of MoS2 nanosheets on the NCNTs benefit the enhanced EMW absorption property of the MoS2 nanosheets, which may be also importance for the design of absorbers based on other layered TMDs.

4. Conclusions

In summary, through anion exchange reaction 3D hierarchical nanostructures composed of thin MoS2 nanosheets and ultralong nitrogen-doped carbon nanotubes were successfully fabricated. The length of as-fabricated hybrid nanotubes is ~ 100 µm, and the thickness of MoS2 NSs on the nitrogen-doped carbon nanotube surfaces is less than 7.5 nm. The hybrid nanotubes show great improved EME attenuation performance compared with the pure MoS2 nanosheets and the MoS2 nanosheets on the short nitrogen-doped carbon nanotube surfaces. The enhanced EMW


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attenuation performance can be explained by direct growth of MoS2 nanosheets on the outmost surface of the nitrogen-doped carbon nanotubes, the high surface area and the ultralong feature. Our findings highlight the importance of ultralong transition-metal dichalcogenides to highperformance electromagnetic wave absorbing materials.

ASSOCIATED CONTENT Supporting Information Available: Figure S1-Figure S12 and Table S1. XRD patterns of the U-MoO3 nanobelts, the U-MoO3@Ppy core-shell nanobelts, the U-MoO3@NC nanobelts, and MoS2 NS/S-NCNTs. SEM images of the MoS2 NS/U-NCNTs nanosheets, the MoS2 NS/SNCNTs, the pure MoS2 nanosheets, and U-NCNTs. Nitrogen adsorption/desorption isotherms of MoS2 NS/U-NCNT, MoS2 NS/S-NCNTs, and the pure MoS2 nanosheets. Raman spectra of the MoS2 NS/U-NCNTs nanosheets. TG curves of the MoS2 NS/U-NCNTs and MoS2 NS/S-NCNTs. Relative complex permeability of the MoS2 NS/U-NCNTs nanosheets. The dielectric loss tangent of the MoS2 NS/S-NCNTs, the MoS2 NS/S-NCNTs and the pure MoS2 nanosheets. RL–f curves for the physical mixture of the MoS2 nanosheets and U-NCNTs. RL–f curves for the UNCNTs and the MoS2 NS/S-NCNTs. This Supporting Information is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author *E-mail: [email protected]; [email protected] Notes The authors declare no competing financial interest.


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ACKNOWLEDGMENT The work is funded by the NNSF (Grant No. 51572051), the NSF of Heilongjiang Province (E2016023), the FRF for the Central Universities (HEUCF201708), and Key Laboratory for Photonic and Electric Bandgap Materials, Ministry of Education (PEBM201508). REFERENCES (1) Jaramillo, T.; Jørgensen, K.; Bonde, J.; Nielsen, J.; Horch, S.; Chorkendorff, I. Identification

of

Active

Edge

Sites

for

Electrochemical

H2 Evolution

from

MoS2 Nanocatalysts. Science 2007, 317, 100-102. (2) Xie, J.; Zhang, J.; Li, S.; Grote, F.; Zhang, X.; Zhang, H.; Wang, R.; Lei, Y.; Pan, B.; Xie, Y. Controllable Disorder Engineering in Oxygen-Incorporated MoS2 Ultrathin Nanosheets for Efficient Hydrogen Evolution. J. Am. Chem. Soc. 2015, 135, 17881-17888. (3) Jiang, H.; Ren, D.; Wang, H.; Hu, Y.; Guo, S.; Yuan, H.; Hu, P.; Zhang, L.; Li, C. 2D Monolayer MoS2-Carbon Interoverlapped Superstructure: Engineering Ideal Atomic Interface for Lithium Ion Storage. Adv. Mater. 2015, 27, 3687-3695. (4) Hu, Z.; Wang, L.; Zhang, K.; Wang, J.; Cheng, F.; Tao, Z.; Chen, J. MoS2 Nanoflowers with Expanded Interlayers as High-Performance Anodes for Sodium-Ion Batteries. Angew. Chem., Int. Ed. 2014, 53, 12794-12798. (5) Yu, H.; Yu, X.; Chen, Y.; Zhang, S.; Gao, P.; Li, C. A Strategy to Synergistically Increase the Number of Active Edge Sites and the Conductivity of MoS2 Nanosheets for Hydrogen Evolution. Nanoscale 2015, 7, 8731-8738. (6) Yu, H.; Ma, C.; Ge, B.; Chen, Y.; Xu, Z.; Zhu, C.; Li, C.; Ouyang, Q.; Gao, P.; Li, J.; Sun, C.; Qi, L.; Wang, Y.; Li, F. Three-Dimensional Hierarchical Architectures Constructed by


19


Page 20 of 28

Graphene/MoS2 Nanoflake Arrays and Their Rapid Charging/Discharging Properties as Lithium-Ion Battery Anodes. Chem. Eur. J. 2013, 19, 5818-5823. (7) Zhang, S.; Yu, X.; Yu, H.; Chen, Y.; Gao, P.; Li, C.; Zhu, C. Growth of Ultrathin MoS2 Nanosheets with Expanded Spacing of (002) Plane on Carbon Nanotubes for HighPerformance Sodium-Ion Battery Anodes. ACS Appl. Mater. Interfaces 2015, 6, 21880-21885. (8) Geng, X.; Wu, W.; Li, N.; Sun, W.; Armstrong, J.; Al-hilo, A.; Brozak, M.; Cui, J.; Chen, T. Three-Dimensional Structures of MoS2 Nanosheets with Ultrahigh Hydrogen Evolution Reaction in Water Reduction. Adv. Funct. Mater. 2014, 24, 6123-6129. (9) Wang, H.; Lu, Z.; Kong, D.; Sun, J.; Hymel, T.; Cui, Y. Electrochemical Tuning of MoS2 Nanoparticles on Three-Dimensional Substrate for Efficient Hydrogen Evolution. ACS Nano 2014, 8, 4940-4947. (10) Wang, S.; Zhu, J.; Shao, Y.; Li, W.; Wu, Y.; Zhang, L.; Hao, X. Three-Dimensional MoS2@CNT/RGO Network Composites for High-Performance Flexible Supercapacitors. Chem. Eur. J. 2017, 23, 3438 -3446. (11) Zhang, F.; Tang, Y.; Yang, Y.; Zhang, X.; Lee, C. In-situ Assembly of ThreeDimensional MoS2 Nanoleaves/Carbon Nanofiber Composites Derived from Bacterial Cellulose as Flexible and Binder-free Anodes for Enhanced Lithium-Ion Batteries. Electrochim. Acta 2016, 211, 404-410. (12) Ding, J.; Zhou, Y.; Li, Y.; Guo, S.; Huan, X. MoS2 Nanosheet Assembling Superstructure with a Three-Dimensional Ion Accessible Site: A New Class of Bifunctional Materials for Batteries and Electrocatalysis. Chem. Mater. 2016, 28, 2074-2080. (13) Zhou, W.; Zhou, K.; Hou, D.; Liu, X.; Li, G.; Sang, Y.; Liu, H.; Li, L.; Chen, S. ThreeDimensional Hierarchical Frameworks Based on MoS2 Nanosheets Self-Assembled on


20

Page 21 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Graphene Oxide for Efficient Electrocatalytic Hydrogen Evolution. ACS Appl. Mater. Interfaces 2014, 6, 21534-21540. (14) Cao, X.; Shi, Y.; Shi, W.; Rui, X.; Yan, Q.; Kong, J.; Zhang, H. Preparation of MoS2Coated Three-Dimensional Graphene Networks for High-Performance Anode Material in Lithium-Ion Batteries. Small 2013, 9, 3433-3438. (15) Wang, Y.; Yu, L.; Lou, X. Synthesis of Highly Uniform Molybdenum–Glycerate Spheres and Their Conversion into Hierarchical MoS2 Hollow Nanospheres for Lithium-Ion Batteries. Angew. Chem., Int. Ed. 2016, 55, 7423-7426 . (16) Wang, Y.; Qu, Q.; Li, G.; Gao, T.; Qian, F.; Shao, J.; Liu, W.; Shi, Q.; Zheng, H. 3D Interconnected and Multiwalled Carbon@MoS2@Carbon Hollow Nanocables as Outstanding Anodes for Na-Ion Batteries. Small 2016, 12, 6033-6041. (17) Tan, L.; Wang, S.; Xu, K.; Liu, T.; Liang, P.; Niu, M.; Fu, C.; Shao, H.; Yu, J.; Ma, T.; Ren, X.; Li, H.; Dou, J.; Ren, J.; Meng, X. Layered MoS2 Hollow Spheres for HighlyEfficient Photothermal Therapy of Rabbit Liver Orthotopic Transplantation Tumors. Small 2016, 12, 2046-2055. (18) Zuo, X.; Chang, K.; Zhao, J.; Xie, Z.; Tang, H.; Li. B.; Chang, Z.; Bubble-TemplateAssisted Synthesis of Hollow Fullerene-Like MoS2 Nanocages as a Lithium Ion Battery Anode Material. J. Mater. Chem. A 2016, 4, 51-58. (19) Guo, B.; Yu, K.; Song, H.; Li, H.; Tan, Y.; Fu, H.; Li, C.; Lei, X.; Zhu, Z. Preparation of Hollow Microsphere@Onion-Like Solid Nanosphere MoS2 Coated by a Carbon Shell as a Stable Anode for Optimized Lithium Storage. Nanoscale 2016, 8, 420-430.


21


Page 22 of 28

(20) Jin, J.; Kim, B.; Kim, M.; Park, N.; Kang, S.; Lee, S.; Kim, H.; Son, S. Template Synthesis of Hollow MoS2-Carbon Nanocomposites Using Microporous Organic Polymers and Their Lithium Storage Properties. Nanoscale 2015, 7, 11280-11284. (21) Ye, L.; Guo, W.; Yang, Y.; Du, Y.; Xie, Y. Directing the Architecture of Various MoS2 Hierarchical Hollow Cages through the Controllable Synthesis of Surfactant/Molybdate Composite Precursors. Chem. Mater. 2007, 19, 6331-6337. (22) Etzkorn, J.; Therese, H.; Rocker, F.; Zink, N.; Kolb, U.; Tremel, W. Metal-Organic Chemical Vapor Deposition Synthesis of Hollow Inorganic-Fullerene-Type MoS2 and MoSe2 Nanoparticles. Adv. Mater. 2005, 17, 2372-2375. (23) Ning, M.; Lu, M.; Li, J.; Chen, Z.; Dou, Y.; Wang, C.; Rehman, F.; Cao, M.; Jin, H. Two-Dimensional Nanosheets of MoS2: a Promising Material with High Dielectric Properties and Microwave Absorption Performance. Nanoscale 2015, 7, 15734-15740. (24) Liang, X.; Zhang, X.; Liu, W.; Tang, D.; Zhang, B.; Ji, G. A Simple Hydrothermal Process to Grow MoS2 Nanosheets with Excellent Dielectric Loss and Microwave Absorption Performance. J. Mater. Chem. C 2016, 4, 6816-6821. (25) Zhang, W.; Jiang, D.; Wang, X.; Hao, B.; Liu,Y.; Liu J. Growth of Polyaniline Nanoneedles on MoS2 Nanosheets, Tunable Electroresponse, and Electromagnetic Wave Attenuation Analysis. J. Phys. Chem. C 2017, 121, 4989-4998. (26) Mu, C.; Song,J.; Wang, B.; Zhang, Can.; Xiang, J.; Wen, F.; Liu Z. Two-Dimensional Materials and Onedimensional Carbon Nanotube Composites for Microwave Absorption. Nanotechnology 2018, 29, 025704.


22

Page 23 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(27) Sun,Y.; Zhong,W.; Wang, Y.; Xu, X.; Wang, T.; Wu, L.; Du, Y. MoS2-Based MixedDimensional van der Waals Heterostructures: A New Platform for Excellent and Controllable Microwave-Absorption Performance. ACS Appl. Mater. Interfaces 2017, 9, 34243-34255. (28) Xu, J.; Liu, J.; Che, R.; Liang, C.; Cao, M.; Li, Y.; Liu, Z. Polarization Enhancement of Microwave Absorption by Increasing Aspect Ratio of Ellipsoidal Nanorattles with Fe3O4 Cores and Hierarchical CuSiO3 Shells. Nanoscale 2016, 6, 5782-5790. (29) Zhou, M.; Zhang, X.; Wei, J.; Zhao, S.; Wang, L.; Feng, B. Morphology-Controlled Synthesis and Novel Microwave Absorption Properties of Hollow Urchinlike γ-MnO2 Nanostructures. J. Phys. Chem. C 2011, 115, 1398-1402. (30) Ren, Y.; Zhu, C.; Zhang, S.; Li, C.; Chen, Y.; Gao, P.; Yang, P.; Ouyang, Q. ThreeDimensional SiO2@Fe3O4 Core/Shell Nanorod Array/Graphene Architecture: Synthesis and Electromagnetic Absorption Property. Nanoscale 2013, 5, 12296-12303. (31) Yu, H.; Wang, T.; Wen, B.; Lu, M.; Xu, Z.; Zhu, C.; Chen, Y.; Xue, X.; Sun, C.; Cao, M.; Graphene/Polyaniline Nanorod Arrays: Synthesis and Excellent Electromagnetic Absorption Properties. J. Mater. Chem. 2012, 22, 21679-21685. (32) Song, C.; Yin, X.; Han, M.; Li, X.; Hou, Z.; Zhang, L.; Cheng, L. Three-Dimensional Reduced Graphene Oxide Foam Modified with ZnO Nanowires for Enhanced Microwave Absorption Properties. Carbon 2017, 116, 50-58. (33) Wang, Y.; Chen, D.; Yin, X.; Xu, P.; Wu, F.; He, M.; Hybrid of MoS2 and Reduced Graphene Oxide: A Lightweight and Broadband Electromagnetic Wave Absorber. ACS Appl. Mater. Interfaces 2015, 7, 26226-26234. (34) Zhang, X.; Li, S.; Wang, S.; Yin, Z.; Zhu, J.; Guo, A.; Wang, G.; Yin, P.; Guo, L. SelfSupported Construction of Three-Dimensional MoS2 Hierarchical Nanospheres with Tunable


23


Page 24 of 28

High-Performance Microwave Absorption in Broadband. J. Phys. Chem. C 2016, 120, 2201922027. (35) Zhang, H.; Zhu, C.; Chen, Y.; Gao, H. Growth of Fe3O4 Nanorod Arrays on Graphene Sheets for Application in Electromagnetic Absorption Fields. ChemPhysChem 2014, 15, 2261-2266. (36) Shu, R.; Zhang, G.; Zhang, J.; Wang, X.; Wang, M.; Gan, Y.; Shi, J.; He, J. Fabrication of Reduced Graphene Oxide/Multi-Walled Carbon Nanotubes/Zinc Ferrite Hybrid Composites as High-Performance Microwave Absorbers. J. Alloys Compd. 2018, 736, 1-11. (37) Xia, J.; Ge, Y.; Zhao, D.; Di, J.; Ji, M.; Yin, S.; Li, H.; Chen, R. Microwave-Assisted Synthesis of Few-Layered MoS2/BiOBr Hollow Microspheres with Superior Visible-LightResponse Photocatalytic Activity for Ciprofloxacin Removal. CrystEngComm 2015, 17, 3645-3651. (38) Huang, T.; He, M.; Zhou, Y.;Li, S.; Ding, B.; Pan, W.; Huang, S.; Tong, Y. Solvothermal Synthesis of Flower-Like CoS Hollow Microspheres with Excellent Microwave Absorption Properties. RSC Adv. 2016, 6, 100392-100400. (39) Lv, H.; Ji, G.; Liu, W.; Zhang, H.; Du, Y. Achieving Hierarchical Hollow Carbon@Fe@Fe3O4 Nanospheres with Superior Microwave Absorption Properties and Lightweight Features. J. Mater. Chem. C 2015, 3, 10232-10241. (40) Qiu, J.; Qiu, T. Fabrication and Microwave Absorption Properties of Magnetite Nanoparticle–Carbon Nanotube–Hollow Carbon Fiber Composites. Carbon 2015, 81, 20-28. (41) Wang, F.; Liu, J.; Kong, J.; Zhang, Z.; Wang, X.; Itohb, M.; Machida, K. Template Free Synthesis and Electromagnetic Wave Absorption Properties of Monodispersed Hollow Magnetite Nano-Spheres. J. Mater. Chem. 2011, 21, 4314-4320.


24

Page 25 of 28 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(42) Cao, M.; Lian, H.; Hu, C. Ligand-Assisted Fabrication of Hollow CdSe Nanospheres via Ostwald Ripening and Their Microwave Absorption Properties. Nanoscale 2010, 2, 26192623. (43) Zhao, B.; Zhao, W.; Shao, G.; Fan, B.; Zhang, R. Corrosive Synthesis and Enhanced Electromagnetic Absorption Properties Ofhollow Porous Ni/SnO2 Hybrids. Dalton. Trans. 2015, 44, 15984-15998. (44) Zhu, C.; Zhang, M.; Qiao, Y.; Xiao, G.; Zhang, F.; Chen, Y.; Fe3O4/TiO2 Core/Shell Nanotubes: Synthesis and Magnetic and Electromagnetic Wave Absorption Characteristics. J. Phys. Chem. C 2010, 114, 16229-16235. (45) Qu, B.; Zhu, C.; Li, C.; Zhang, X.; Chen, Y. Coupling Hollow Fe3O4-Fe Nanoparticles with Graphene Sheets for High-Performance Electromagnetic Wave Absorbing Material. ACS Appl. Mater. Interfaces 2016, 8, 3730-3735. (46) Xu, H.; Yin, X.; Zhu, M.; Han, M.; Hou, Z.; Li, X.; Zhang, L.; Cheng, L. Carbon Hollow Microspheres with a Designable Mesoporous Shell for High Performance Electromagnetic Wave Absorption. ACS Appl. Mater. Interfaces 2017, 9, 6332-6359. (47) Hou,Y.; Cheng, L.; Zhang, Y.; Yang, Y.; Deng, C.; Yang,Z.; Chen, Q.; Wang, P.; Zheng, L. Electrospinning of Fe/SiC Hybrid Fibers for Highly Efficient Microwave Absorption. ACS Appl. Mater. Interfaces 2017, 9, 7265-7271. (48) Yao, B.; Huang, L.; Zhang, J.; Gao, X.; Wu, J.; Cheng, Y.; Xiao, X.; Wang, B.; Li, Y.; Zhou, J. Flexible Transparent Molybdenum Trioxide Nanopaper for Energy Storage, Adv. Mater. 2016, 28, 6353-6358.


25


Page 26 of 28

(49) Chen, Z.; Cummins, D.; Reinecke, B.; Clark, E.; Sunkara, M.; Jaramillo, T. Core–Shell MoO3–MoS2 Nanowires for Hydrogen Evolution: A Functional Design for Electrocatalytic Materials. Nano Lett. 2011, 11, 4168-4175. (50) Laursen, A.; Kegnæs, S.; Dahl, S.; Chorkendorff, I. Molybdenum Sulfides-Efficient and Viable Materials for Electro- and Photoelectrocatalytic Hydrogen Evolution. Science 2012, 5, 5577-5591. (54) Zhao, Y.; Zhao, F.; Wang, X.; Xu, C.; Zhang, Z.; Shi, G.; Qu, L. Graphitic Carbon Nitride Nanoribbons: Graphene-Assisted Formation and Synergic Function for Highly Efficient Hydrogen Evolution. Angew. Chem., Int. Ed. 2014, 53, 13934-13939. (52) Silva, R.; Voiry, D.; Chhowalla, M.; Asefa, T. Efficient Metal-Free Electrocatalysts for Oxygen Reduction: Polyaniline-Derived N- and O-Doped Mesoporous Carbons. J. Am. Chem. Soc. 2013, 135, 7823-7826. (53) Xie, J.; Zhang, J.; Li, S.; Grote, F.; Zhang, X.; Zhang, H.; Wang, R.; Lei, Y.; Pan, B.; Xie, Y. Controllable Disorder Engineering in Oxygen-Incorporated MoS2 Ultrathin Nanosheets for Efficient Hydrogen Evolution. J. Am. Chem. Soc. 2013, 135, 17881-17888. (54) Qu, B.; Sun, Y.; Liu, L.; Li, C.; Yu, C.; Zhang, X,; Chen, Y. Ultrasmall Fe2O3 Nanoparticles/MoS2 Nanosheets Composite as High-Performance Anode Material for Lithium Ion Batteries. Sci. Rep. 2017, 7, 42772- 42782. (55) Wang, Q.; Lei, Z.; Chen, Y.; Ouyang, Q.; Gao, P.; Qi, L.; Zhu, C.; Zhang, J. Branched Polyaniline/Molybdenum Oxide Organic/Inorganic Heteronanostructures: Synthesis and Electromagnetic Absorption Properties. J. Mater. Chem. A 2013, 1, 11795-11801.


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(56) Fang, L.; Shu, Y.; Wang, A.; Zhang, T. Green Synthesis and Characterization of Anisotropic Uniform Single-Crystal α-MoO3 Nanostructures. J. Phys. Chem. C 2007, 111, 2401-2408. (57) Natio, Y.; Suetake, K. Application of Ferrite to Electromagnetic Wave Absorber and Its Characteristics. IEEE Trans. Microw. Theory Tech. 1971, 19, 65-72. (58) Liu, X.; Ou, Z.; Geng, D.; Han, Z.; Xie, Z.; Zhang, Z. Enhanced Natural Resonance and Attenuation Properties in Superparamagnetic Graphite-coated FeNi3 Nanocapsules. J. Phys. D Appl. Phys. 2009, 42, 155004-155008.


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Table of Contents Graphic and Synopsis


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Ultralong N-doped

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