Hydrogen Bond between Molybdate and Glucose for the Formation of

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Surfaces, Interfaces, and Applications

Hydrogen Bond between Molybdate and Glucose for the Formation of Carbon-Loaded MoS Nanocomposites with High Electrochemical Performance 2

Nan Wang, Yuqi Zhou, Sarmad Yousif, Tetsuro Majima, and Lihua Zhu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.9b12013 • Publication Date (Web): 28 Aug 2019 Downloaded from pubs.acs.org on August 28, 2019

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ACS Applied Materials & Interfaces

Hydrogen Bond between Molybdate and Glucose for the Formation of Carbon-Loaded MoS2 Nanocomposites with High Electrochemical Performance Nan Wang, Yuqi Zhou, Sarmad Yousif, Tetsuro Majima*, and Lihua Zhu* aKey

laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of

Education，School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan 430074, China Abstract The effects of glucose on the growth and surface properties of MoS2 with nanosheet structure were investigated in detail. In the presence of glucose, the hydrothermal reaction of sodium molybdate and thiourea yields carbon-loaded MoS2 nanocomposites (C/MoS2). Compared with bare MoS2 nanosheets with more than six layers obtained in the absence of glucose and carbon spheres with diameter of 500 nm prepared from the carbonization of glucose, C/MoS2 consist of one or three layered MoS2 and carbon spheres with diameter less than 1 nm to give large BET surface area (3 ~ 20 times larger than the individual materials). The surface characterizations reveal that both MoS2 and carbon spheres of C/MoS2 have negative charge on the surface, suggesting that the previously reported explanation, in which the adsorption of MoS2 and/or molybdate ions on carbon spheres inhibits the growth and aggregation of MoS2, is not correct. Based on FT-IR and 1H NMR spectra, it is demonstrated that glucose acts as 1

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the hydrogen bond donor toward polyoxomolybdate species such as Mo8O264−, Mo7O246−, and MoO42− in the range of pH = 2 ~ 12. The intermolecular hydrogen bond not only inhibits the growth of both (002) plane of MoS2 and carbon spheres, but also enables the formation of C−O−Mo bonds in the in situ generated C/MoS2. Compared with bare MoS2, C/MoS2 not only show a lower over-potential by 60 mV for the electrocatalytic evolution of hydrogen, but also has a larger mass specific capacitance by three times, due to the larger surface area and the interfacial interaction through C−O−Mo bonds. KEYWORDS: MoS2, glucose, hydrogen bond, Mo polyoxoanion, carbon spheres

2


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1. INTRODUCTION Molybdenum disulfide (MoS2) as a two-dimensional (2D) material has gained widespread interests in lithium batteries,1 hydrogen evolution,2 CO2 reduction,3 and gas sensing.4,5 However, the easy aggregation of MoS2 limits its performance.6,7 To solve this drawback, various semiconductors and carbon materials such as amorphous carbon, carbon spheres, carbon nanotubes (CNTs), and graphene have been used as a spacer for MoS2.8−13 The fabrication of carbon-loaded MoS2 nanocomposites (C/MoS2) includes three approaches: (i) preparation of exfoliated MoS2 and carbon spheres, followed by a combination process; (ii) in-situ growth of MoS2 from the precursors on carbon spheres; (iii) one-step synthesis of C/MoS2 from the chemical reaction of molecular building blocks. Comparably, the latter two approaches are of particular interest due to the morphological compatibility between two materials and time-saving.14,15 The hydrothermal reaction is widely used to prepare C/MoS2 from Mo(VI) precursors such as Na2MoO4 and (NH4)2MoO4, sulfurization reagents such as CSN2H4, CH3CSNH2, and Na2S, and carbon materials like graphene oxide and acid-treated CNTs. These carbon materials usually contain functional groups such as carboxyl and hydroxyl groups to induce negative charge on the surface, leading to repelling interaction with MoO42− and MoS42−.14,15 To achieve favorable electrostatic

interaction,

many

cationic

surfactants

and

polymers

such

as

cetyltrimethylammonium bromide, polyaniline and poly(ethyleneimine) are explored to change the surface charge of carbon materials from negative to positive.16−19 However, the

3



large linkers make the interfacial contact weaker to lose the properties of the interface in C/MoS2. The favorable interaction between MoS2 and carbon spheres is important to maximize the performance of C/MoS2. Alternatively, some researchers have employed small organic compounds to prepare C/MoS2 via the hydrothermal reaction. Sun et al. reported a hydrothermal reaction to prepare C/MoS2 in the presence of ascorbic acid.20 Chang et al. synthesized MoS2-graphene with L-cysteine as the linker.21 They also prepared amorphous C/MoS2 by using glucose as both the carbon source and linker.22 Ding et al. reported that glucose induces the growth of MoS2 on the surface of CNTs.23 Glucose has been also employed as the linker to help MoS2 nanosheets to grow on the surface of other one dimensional nanomaterials such as TiO2 nanotubes, TiO2 nanowires and CdS nanowires.24−26 The added glucose plays a crucial role in the generation of MoS2 nanosheets with smaller size and thinner thickness.22−26 A tentative explanation is considered to be that the adsorption of MoS2 or anionic precursors like MoO42− or MoS42− on in-situ produced carbon spheres suppress the growth of MoS2.22 However, this is not well accepted, because both MoS2 and carbon spheres have negative charge on the surface,15 eliminating the binding each other. The interaction between precursors and/or products is essential for fabricating C/MoS2 in spite of little attention. In the present paper, we study the role of glucose on the preparation of C/MoS2 through the hydrothermal reaction. The results reveal that the intermolecular hydrogen bond between glucose and anionic precursors of Mo is essential for inhibiting the growth of MoS2. 4


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2. EXPERIMENTAL 2.1. Chemicals and materials. Glucose, sodium molybdate dihydrate (Na2MoO4•2H2O), and thiourea (CSN2H4) were purchased from Sinopharm Chemical Reagent, China). All other chemical reagents were of analytical grade and used without further purification. 2.2. Preparation of C/MoS2. In a typical hydrothermal synthesis of C/MoS2, Na2MoO4•2H2O (0.30 g), and CSN2H4 (0.60 g) were dissolved into 60 mL water under stirring for 10 min, then a certain amount of glucose was added to the solution. After unltrasonication for 10 min, the resulting solution was transferred into an 80 mL Teflon-lined stainless steel autoclave and heated at 180 oC for 24 h. Then the autoclave was cooled down to room temperature. Precipitates were collected, and washed with water and ethanol alternately to neutral pH. At last, the precipitates were re-dispersed to water and stored. For convenience, C/MoS2 was named an nGlu/nMoC/MoS2 with nGlu/nMo of the molar ratio of glucose to Mo in solution. The preparation processes of bare MoS2 and carbon spheres were described above, except no addition of either glucose or Na2MoO4, and CSN2H4, respectively. 2.3. Characterizations of C/MoS2. The morphology of as-prepared C/MoS2 was observed on a FEI Tecnai G2 T20 transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) was obtained on a VG Multilad 2000 spectrometer (Thermo Electron Corporation). X-ray diffraction (XRD) analysis was performed using SmartLab X-ray diffractometer (Rigaku Corporation) with Cu K-source. Fourier transform infrared (FT-IR) spectra were measured on a Bruker VERTEX 70 IR spectrometer. Before these measurements, the as-prepared C/MoS2 were dried in a vacuum oven at 60 °C for 24 h. 5



Atomic force microscope (AFM) was SPM 9700 Shimadzu. Zeta potentials were measured on a Malvern ZEN 3690. Thermogravimetric analyses were performed on a NETZSCH TG 209 F3 thermal analyzer. C/MoS2 were analyzed at a heating rate of 10 °C min−1 to 950 °C under an atmosphere of air. Each C/MoS2 weight was 10 mg. Proton nuclear magnetic resonance (1H NMR) spectra of glucose or a mixture of glucose and Na2MoO4 in D2O solution were recorded on Bruker Ascend 400 MHz. Chemical shifts of 1H

are recorded in parts per million (ppm) and referenced to the NMR solvent residual peak

(D2O: δ 4.74) relative to tetramethylsilane. 2.4. Electrochemical measurements. A three-electrode cell was used for electrochemical measurements on a CHI660D electrochemical station (Shanghai CH instrument, China) by using platinum foil electrode and Ag/AgCl electrode as the counter and reference electrodes, respectively. Prior to measurements, MoS2 and C/MoS2 were annealed at 800 °C for 3 h in H2/Ar (5/95, v/v). Then, 2 mg of MoS2 or C/MoS2 and 10 L of 5 wt% Nafion solution were dispersed in 1 mL of water/ethanol (4:1, v/v) mixture, followed by ultrasonication for 30 min. Finally, 10 L dispersions were dropped down on the surface of glassy carbon electrode (GCE), and dried at 60 °C. Cyclic voltammetry (CV) was performed in 1 mol L−1 Na2SO4 as electrolyte in a potential window from −0.6 to 0.4 V. Linear sweep voltammetry (LSV) was carried out in 0.5 M H2SO4 with a scan rate of 5 mV s−1. 3. RESULTS AND DISCUSSION 3.1. Effect of glucose on properties of C/MoS2. Figure 1 illustrates TEM and highresolution TEM (HRTEM) images of MoS2 prepared in the absence and presence of glucose. 6


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In the absence of glucose, the products show platelet-like structure consisted of densely stacked sheet-like subunits and have several parallel dark lines with a spacing of approximately 0.62 nm (Figure 1a) assigned to the (002) plane of MoS2.27 Two pronounced Raman peaks appeared at 372.5 and 400.4 cm−1 with the energy difference of Δ∼27.8 cm−1 (Figure S1). According to the relationship between the Δ value and the number of MoS2 layers,28 the thickness of bare MoS2 was larger than six layers. In the presence of glucose at nGlu/nMo of 1.7, the as-prepared products exhibit a small portion of thin flakey structures on edges, in which the interlayer separation greatly increases to larger than 0.8 nm, corresponding to the expanded (002) plane of MoS2 (Figure 1b). The Raman peaks corresponding to MoS2 were not observed, while new peaks appeared at 1360 and 1580 cm−1 (Figure S1) assigned to the typical D and G bands of carbonaceous materials, respectively.29, 30 When nGlu/nMo increases to 2.5, C/MoS2 exhibit a large area of wrinkled and nearly transparent nanosheets with one ~ three layers MoS2 (Figure 1c). The AFM images are comparable with that of bare MoS2, while the thickness of C/MoS2 obtained in the presence of glucose at nGlu/nMo = 2.5 decreases from approximately 5 to 2 nm (Figure S2). An increase of D and G bands corresponds to the formation of more carbon spheres (Figure S1). The energydispersive X-ray spectroscopy (EDS) shows that C/MoS2 consist of Mo, S, C, and O elements which are uniformly distributed (Figures 1e−i), indicating the successful preparation of C/MoS2. As a control, the hydrothermal reaction of glucose gave the product with a spherical structure (diameter of 800 nm) (Figure 1d), similar to carbon spheres (diameter of 600 nm) derived from the hydrothermal reaction of glucose reported by Gong and co-workers.30 7



Therefore, glucose and MoS2 precursors play an important role on inhibiting the growth of MoS2 and carbon spheres, respectively. As expected, 2.5C/MoS2 have a larger BET specific surface area with three and twenty times larger than that for bare MoS2 and carbon spheres (Table S1), respectively.

8


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(a)

(b) 0.62 nm

0.61 nm 5 nm

0.87 nm 500 nm

5 nm

500 nm

(c)

0.84 nm

(d)

5 nm

500 nm

200 nm

(f)

(e)

(g)

200 nm

(h)

200 nm

(i)

200 nm 200 nm

200 nm

Figure 1. TEM or HRTEM images of bare MoS2 prepared in the absence of glucose (a), C/MoS2 prepared in the presence of glucose with nGlu/nMo of 1.7 (b) and 2.5 (c), and carbon spheres prepared from glucose (d). EDS image of 2.5C/MoS2 (e) and elemental mappings of Mo (f), S (g), O (h), and C (i). 9



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Figure 2a compares XRD patterns of MoS2 prepared in the absence and presence of glucose at nGlu/nMo = 2.5. In the absence of glucose, the as-prepared sample shows broad diffraction peaks at 13.8, 32.5, 35.8, 43.8, and 57.8 °, which are assigned to the (002), (100), (103), (105), and (110) planes of hexagonal MoS2 (JCPDS 37-1492), respectively.15,

20-22, 31

Annealing

treatment at 800 °C in H2/Ar (5/95, v/v) for 3 h causes an increase in the intensities of all diffraction peaks with slight shifts to higher angle, especially for the (002) peak, indicating more-stacked layers and improved crystallinity of MoS2 after annealing.22 In the presence of glucose, the as-prepared C/MoS2 shows similar diffraction peaks at 32.5 and 57.8 °, but the peak at approximately 14 ° disappears, indicating that the introduction of glucose inhibited the c-axis stacking of MoS2 nanosheets.22 Moreover, two new peaks appear at 8.4 and 17.0 °. The peak at 8.4 ° corresponds to the diffraction of the greatly expanded (002) plane of MoS2 with an interlayer space of 1.0 nm,22 and the other at 17.0 ° possibly results from amorphous carbon. As a control, carbon spheres obtained from the hydrothermal treatment of glucose shows one broad peak at 23 ° (Figure S3) to be assigned to the (002) peak of highly disordered and low crystalline carbon atoms.30 This peak shifts to lower diffraction angle by 6 ° in C/MoS2, indicating an increase in the interlayer spacing due to the insertion of MoS2 into the carbon layers.30 These phenomena are in agreement with HRTEM images. Additionally, the annealed C/MoS2 exhibits a slight increase in the intensity and a slight shift to higher diffraction angle, but no peak at 14 or 23 °C indicates that the stacking of both MoS2 and carbon layers does not take place during annealing.

10


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(a)

100

(002)

(b)

80 (105)

(110) (201) 1' 1

Weight /%

(100) (103)

Intensity

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


MoS2

60

1.7C/MoS2 40

2.5C/MoS2 Carbon spheres

20

2 2'

5

20

35

 

50

65

0

80

100

250

400

o

550

700

Temperature / C

Figure 2. (a) XRD patterns of bare MoS2 (1, 1’) and 2.5C/MoS2 (2, 2’) before (1, 2) and after (1’, 2’) annealing treatment at 800 °C in H2/Ar (5/95, v/v) for 3 h. (b) TG curves in air of bare MoS2, C/MoS2, and carbon spheres. Next, thermogravimetric (TG) measurements were conducted to determine the relative content of MoS2 in the bulk of MoS2 and C/MoS2. As shown in Figure 2b, TG curve of bare MoS2 in air shows weight losses of approximately 7% and 20% in the range of 50 ~ 200 °C and 200 ~ 480 °C, corresponding to the loss of adsorbed water and surface OH groups, and the oxidation of MoS2 to MoO3, respectively.20, 23 When nGlu/nMo increases from 0 to 2.5, the as-prepared C/MoS2 shows an increased weight loss in 200 ~ 480 °C from 20% to 60%, due to the decomposition of carbon spheres based on comparison with the TG curve of carbon spheres.20 When the final product after TG measurements is pure MoO3, the weight content of MoS2 is calculated to be 80%, 54%, and 37% in MoS2, 1.7C/MoS2, and 2.5C/MoS2, respectively. Moreover, the bulk compositions of carbon, sulfur, hydrogen, and oxygen are also determined using C/H/S/N and O elemental analyzers. The weight fraction of carbon and sulfur changes from 0.6% to 23.2% and from 30.5% to 20.4% in MoS2 and 2.5C/MoS2, 11



respectively (Table S1). Since carbon, sulfur, oxygen, hydrogen, and molybdenum exist in MoS2 and C/MoS2 in 100% content, the weight content of Mo is calculated to be 50.4% and 29.4% in MoS2 and 2.5C/MoS2, respectively. That is, the weight content of MoS2 is 80.9% and 49.7% in MoS2 and 2.5C/MoS2, which are comparable with 80% and 37% obtained by the TG measurement, respectively. The slight deviations are explained by the formation of other products containing Mo and/or S in minor yields. The surface chemical composition was determined by XPS analysis. Both bare MoS2 and C/MoS2 gave XPS signals of Mo, S, O, and C (Figure S4). For bare MoS2, two strong peaks at 229.3 and 232.4 eV were characteristics of Mo4+ 3d5/2 and 3d3/2 in Mo–S, respectively, while the weak doublets of Mo 3d at 230.3/233.3 and 233.9/236.8 eV corresponded to Mo4+ and Mo6+ in Mo–O (Figure 3a), respectively.15,

18, 32

An additional peak at 236.8 eV was

assigned to S 2s. The double peaks of S 2p at 163 and 162 eV were assigned to 2p3/2 and 2p1/2 of S2−, while the peaks at 169.0 and 170.2 eV was identified as 2p3/2 and 2p1/2 of S6+, respectively (Figure 3b).27,

31−34

Generally, MoS2 prepared from a hydrothermal reaction

contain a small amount of Mo6+ and S6+, because the defect and edge sites on MoS2 have high reactivity with oxygen for the oxidation reaction.27,

33, 34

The atomic ratio of S/Mo was

calculated to be 1.79 lower than that of MoS2 due to partly oxidation of the surface of MoS2 (Table S2). Accordingly, a considerably strong O 1s signal was fitted into lattice oxygen (O2−) in Mo−O (531.6 eV), surface OH group (532.3 eV), and adsorbed H2O (533.2 eV) (Figure 3c).35 The weak C 1s peak was deconvoluted into three peaks at 284.8, 286.6, and 289.0 eV

12


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(Figure 3d), corresponding to inevitable carbon contamination, C–N, and O–C=O groups, respectively. MoS2

(a)

(b) Mo 3d3/2 4+

MoS2

Mo4+ 3d5/2

MoS2

S2- 2p1/2 6+

Mo-O

Mo-S

S6+ 2p1/2

Counts

2.5C/MoS2

238

233 228 Binding energy /eV

S2- 2p3/2

2.5C/MoS2

172

223

(c)

168

164

160

Binding energy /eV

(d) Mo-OH H2O

6+

2.5C/MoS2

4+

Mo -O-C

Carbon spheres

C-N

adventitious C

C-OH, C-OMo

2.5C/MoS2 O-C=O

C-N

4+

C=C-C

Carbon spheres

C-O-C O-H

536

MoS2

2

Mo -O

Counts

MoS2

538

S 2p3/2

S 2s

Mo-O

Counts

Mo6+ 3d3/2

Mo-S

Mo6+ 3d5/2

Counts

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


C=O

534 532 Binding energy /eV

C-O-C

O-C=O

530

291

288

C-OH

C=C-C

285

282

Binding energy /eV

Figure 3. High-resolution XPS spectra of Mo 3d (a), S 2p (b), O 1s (c), and C 1s (d) of bare MoS2, 2.5C/MoS2, and carbon spheres.

In the presence of glucose, C/MoS2 have Mo 3d and S 2p signals at lower binding energies (Figures 3a and b), implying the higher electron densities at Mo and S. The peak intensities of Mo6+ 3d and S6+ 2p became weaker, because glucose as a reducing agent inhibits the oxidation of Mo4+ and S2−. As a result, the S/Mo atomic ratio in MoS2 gradually increased from 1.79 to 1.97 with increasing the initial nGlu/nMo from 0 to 5 (Table S2), which is 13



consistent with the results obtained by elemental analysis (Table S1). Compared with bare MoS2, C/MoS2 showed stronger C1s peak but weaker O1s peak (Figures 3c and d), because H2S derived from CSN2H4 reduces oxygen-containing groups on carbon spheres during the hydrothermal reaction. The O 1s of C/MoS2 was deconvoluted into four components at 531.2, 532.0, 532.9, and 533.7 eV, corresponding to Mo–O, O−C=O, C−O−C, and C−OH, respectively.15 Notably, the O 1s peak for Mo–O in C/MoS2 shifts to a lower binding energy by 0.4 eV relative to that for bare MoS2, indicating the formation of a covalent C−O−Mo4+ bond on C/MoS2.15 The C 1s peak consists of four components at 284.9, 285.6, 286.8, and 289.0 eV assigned to aromatic C=C–C, ethers, C–OH/C−OMo4+, and carboxyl, respectively,15 in which C=C–C is the major carbon-containing groups for C/MoS2, indicating π-conjugation on the surface of carbon spheres. It should be noted that all XPS signals of Mo 3d, S 2p, and O 1s for C/MoS2 shift to the lower binding energy than bare MoS2, and the C 1s of C=C–C does to the higher binding energy by 0.1 eV. Such phenomenon is also observed in the previous reported MoS2-based hybrids such as g-C3N4/MoS2 and TiO2/MoS2.10,35 This suggests a strong interaction at the interface of C/MoS2 due to the formation of C−O−Mo bond, which facilitates the interfacial charge transfer in C/MoS2 nanocomposites. Figure 4a shows FT-IR spectra of bare MoS2 and C/MoS2. Bare MoS2 exhibits the absorption peaks of O−H at 3400, 1620, and 1151 cm−1, N−H at 3120 and 1400 cm−1, and Mo=O/Mo−O at 866 ~ 965 cm−1. With increasing nGlu/nMo from 0.5 to 5, the intensities of the absorption peaks of O−H and N−H decrease, indicating that N−H and O−H adsorbed on the surface of MoS2 decrease. The υO−H band shifts to a smaller wavenumber by 40 cm−1, while 14


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the υMo=O/Mo–O band shifts from 892 to 903 cm−1. A new absorption peak at 1715 cm−1 assigned to C=O group appeared at larger wavenumber than 1700 cm−1 for carbon spheres prepared from glucose, confirming the formation of C−O−Mo bond in C/MoS2. The absorption peak at 1620 cm−1 in C/MoS2 is much stronger than that for carbon spheres and bare MoS2, suggesting that both glucose and H2S released from CSN2H4 favor the reduction of oxygen-containing groups of carbon spheres to C=C groups. The changes in surface functional groups affect surface charges of C/MoS2. When dispersing in aqueous solution at pH 5.5, C/MoS2 exhibit negatively charged surfaces, and the absolute value of zeta potential becomes smaller (i.e., from −33 to −27 V) with nGlu/nMo from 0.5 to 5 (Figure 4b). In addition, most C/MoS2 have less negative zeta potential than those of MoS2 (−32 V) and bare carbon spheres (−46 V). This is due to the decreased oxygen-containing groups on C/MoS2 as verified in XPS and FT-IR analyses (Figures 3d and 4a). When the solution pH varies from 2 to 12, bare MoS2, carbon spheres, and C/MoS2 have the negative charge on the surface, and the absolute values of zeta potential gradually increase (Figure 4c). At a given pH in a wide range from 5 to 12, the absolute values of zeta potential increase in the order of C/MoS2 (−32 ~ −30 V) < bare MoS2 (−40 ~ −32 V) 20 cm–1) (Figure 6b and Table 1). The O–H stretching band of the mixture is at smaller wavenumber than for Mo8O264−, but larger than for glucose, indicating the formation of hydrogen bond between Mo8O264− and glucose at pH = 2. (b)

(a)

glucose

pH 2 pH 5.5







mixture Transmittance

Transmittance

pH 12 Na2MoO4 pH 2

 

Na2MoO4



pH 5.5 pH 12

glucose

3800 3300





1600

1200

-1

800

400 3800 3300

1600

Wavenumber /cm

1200

-1



800

400

Wavenumber /cm

(c)

(d) glucose

glucose 



mixture

mixture

Transmittance



Transmittance

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


Na2MoO4  





Na2MoO4









3800

3000 1600

1200

800



400

3800 3300

1600

1200

800

400

-1

-1

Wavenumber /cm

Wavenumber /cm

Figure 6. FT-IR spectra of Na2MoO4, glucose (a), and their mixture at pH = 2 (b), 5.5 (c), and 12 (d). The solid marks and dotted lines show the peak changes and shifts.

Table 1. Characteristic IR absorption peaks of Na2MoO4, glucose, and their mixtures at different pH. Absorption peak a /cm−1

Samples

pH 2

O=Mo–O

Mo–O–Mo

O–H

Na2MoO4

949, 904, 810

707, 637, 592

3448, 1634, 1398

mixture

949, 904, 773

701, 637, 569

3410, 1634, 1406

19



glucose pH 5.5

3395, 1640, 1368

Na2MoO4

900, 859, 826

640, 592, 545

3300, 1680, 1380

mixture

880, 854, 826

640, 592, 561

3368, 1642, 1383

glucose pH 12

3395, 1640, 1375

Na2MoO4

900 (w), 859, 826

640, 592, 545

3300, 1680, 1382

mixture

900 (w), 853, 826

640, 592, 561

3368, 1640, 1383

glucose a The

Page 20 of 35

3395, 1640, 1365

letter “w” in parenthesis represents the weak absorption peak. The bold number denotes

the changed peak. At pH = 5.5, the vibrational peaks of Mo7O246− at 900 cm–1 and MoO42− at 859 cm–1 shift to smaller wavenumbers (i.e., 880 and 854 cm–1, respectively), and Mo–O–Mo absorption peak at 545 cm–1 shifts to a larger wavenumber (i.e., 561 cm–1) (Figure 6c and Table 1). In addition, no O–H vibrational peak of H2O (3300 and 1680 cm−1) adsorbed on Na2MoO4 is observed, while the vibrational peaks of O–H and C=O of glucose are observed due to the competitive adsorption of H2O and glucose on Na2MoO4. Compared with glucose, the O–H stretching mode in the mixture shifts from 3395 cm−1 to a smaller wavenumber at 3368 cm−1, while the deformation mode of O–H shifts from 1375 to 1383 cm−1, indicating the formation of hydrogen bond between glucose and Mo7O246−/MoO42− at pH = 5.5. Similarly, the formation of hydrogen bond between MoO42− and glucose at pH= 12 is supported by no O–H vibrational bands of MoO42− at 3300 and 1680 cm–1, and the peaks shifted to 853 cm–1 (Mo=O/MO–O), 561 cm–1 (Mo–O–Mo), and 1365 cm–1 (O–H in glucose) (Figure 6d and Table 1).

20


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To further clarify the hydrogen bond, 1H NMR spectra of glucose were measured before and after mixing with Na2MoO4 solution without any pH adjustments (i.e., pH = 5.5). As shown in Figure 7a, glucose in D2O shows NMR spectrum with many signals, because glucose in aqueous solution exists as a mixture of α and β anomers due to the mutarotation. αD-glucose has nonexchangeable protons of H1 at  5.13 (1H, d), H6b and H5 at  3.77 ~ 3.74 (2H, m), H6a and H3 at  3.65 ~ 3.60 (2H, m), H2 at  3.46 ~ 3.43 (1H, dd), and H4 at  3.34 ~ 3.30 (1H, t).40 On the other hand, β-D-glucose shows characteristic signals of H1 at  4.57 (1H, d), H6a at  3.83 ~ 3.79 (1H, d), H6b at  3.69 ~ 3.68 (1H, d), H3 and H5 at 3.40~ 3.36 (2H, m), H4 at  3.34 ~ 3.30 (1H, t), and H2 at  3.17 ~ 3.13 (1H, t). After mixing glucose with 100 L Na2MoO4 in D2O, the chemical shifts of all nonexchangeable protons of glucose shift to the lower magnetic field. With increasing Na2MoO4 concentration from 0.2 to 0.9 mmol L−1, the mean chemical shift changes of protons increase from 0.005 to 0.010 ppm. In a control test, the mixture of glucose and 100 L D2O shows a slight shift to the higher magnetic field (i.e., −0.003 ppm) due to the decrease of the hydrogen bond network of glucose, strongly indicating the formation of intermolecular hydrogen bond between glucose and Na2MoO4. Moreover, the chemical shift changes of protons of glucose depend on the positions of the substitution. The H1 and H2 protons in α-D-glucose exhibit a larger chemical shifts than others (Figure 7b), suggesting that both C1-OH and C2-OH act as hydrogen bond donors. For β-D-glucose, the H1 and H3/H5 protons show a larger chemical shifts than others (Figure 7c). With the acetalization reaction, D-glucose loses the

21



OH group attached to C5, indicating that both C1–OH and C3–OH in β-D-glucose interact with molybdate ions.

Figure 7. 1H NMR spectra of glucose in D2O (a) before (1) and after adding of 100 L D2O containing Na2MoO4 at 0 (2), 0.2 (3), 0.6 (4), and 0.9 mmol L−1 (5). The dotted lines show the peak shifts. Effect of Na2MoO4 concentration on the chemical shift changes of protons of αD-glucose (b) and β-D-glucose (c). Based on the above results, Scheme 1 illustrates the hydrogen bonds between glucose and Na2MoO4. At pH = 5.5, Na2MoO4 exists as two main forms, i.e., MoO42− and Mo7O246− in the equilibrium, while glucose has a predominant six-membered heterocyclic structure (i.e., glucopyranose) due to the acetalization reaction between C1−CHO and C5−OH. The lone pair

22


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electrons of O in MoO42−/Mo7O246− act as the proton acceptor to form the intermolecular hydrogen bond with OH groups of glucose. For α-D-glucose, the OH groups attached to C1 and C2 lie on the same side of the plane, inducing two hydrogen bonds with octahedral MoO6 or tetrahedral MoO4 as shown in Schemes 1a and b. For β-D-glucose, the C1−OH and C3−OH groups lie on the same side of the plane, while the C2−OH lies on the opposite side. Due to the larger distance between C1−OH and C3−OH, β-D-glucose preferably forms hydrogen-bonds with octahedral MoO6 (Scheme 1c). (a)

OH 6 5 OH

4

(b)

O 2

3

OH -D-glucose

OH

1

OH 6 5 OH

4

OH

(c)

O

OH O

O

O Mo O

-D-glucose

OH

O

OH O

O

OH

O Mo

O

O

O

O

O

4

6 5

O

O

OH 3

O

Mo

Mo

1

2

3

O

O

O

O

OH O

2

1

OH

OH -D-glucose

Scheme 1. Hydrogen bonds between glucose and Na2MoO4 in the forms of α-D-glucose and octahedral MoO6 (a), α-D-glucose and tetrahedral MoO4 (b), and β-D-glucose and octahedral MoO6 (c). 3.3. Role of glucose on inhibiting growth of MoS2. Using Na2MoO4 and CSN2H4, the hydrothermal reaction for preparation of MoS2 is expressed in eqs. 3 and 4. 

 175 C CSN 2 H 4  2H 2 O   2NH 3  CO 2  H 2S

4MoO 4

2

2

 9H 2S  4MoS2  SO 4  6H 2 O  6OH 

(3) (4)

At temperature higher than 175 °C, CSN2H4 easily decomposes to H2S to simultaneously replace O2– and reduce Mo6+ in MoO42−. In the absence of glucose, with decreasing pH from 12 to 2, Mo6+ species change from MoO42− to Mo7O246−, and finally to Mo8O264−. Compared 23



with MoO42−, the polyoxoanion species have more difficulty to be reduced and exchanged by S2−,36 resulting in the formation of thinner MoS2 at lower pH. After adding glucose, three Mo6+ species (MoO42−, Mo7O246−, and Mo8O264−) bind with glucose through the intermolecular hydrogen bond. As a result, the reduction of Mo6+ and the replacement of O in Mo(VI)xOyn– by S2− are suppressed, and thereby the generation of MoS2 and the growth along (002) plane are inhibited. Meanwhile, this intermolecular interaction inhibits the dehydration, polymerization and carbonization of glucose. Therefore, the as-prepared C/MoS2 consist of MoS2 with 1 ~ 3 layers and carbon spheres with diameter smaller than 5 nm. It should be pointed out that less attention has been paid for the intermolecular hydrogen bond at the interfaces between two materials, although it may exist in the interaction of the precursor of MoS2 with not only glucose but also other molecules. For instance, glucose serves as a binder to help thinner MoS2 nanosheets to be grown on the surface of TiO2 nanotubes, TiO2 nanowires, and CdS nanowires.24−26 H2C2O4 helps the vertical growth of layered MoS2 from Mo7O246− as the Mo precursor on the negatively charged graphene oxide.15 MoS2 nanosheets stand vertically on the surface of TiO2,35 in which Mo may bound to OH groups on TiO2. The formation of C−O−Mo or Ti−O−Mo bonds at the interface of MoS2-based composites is assumed by XPS analysis to make MoS2 nanosheets attach tightly with graphene or TiO2, enhancing the structural stability and interfacial electronic interaction at the interface.15,35 It is suggested that such strong interaction between MoS2 nanosheets and graphene or TiO2 is resulted from the intermolecular hydrogen bond between two precursors. Similarly, H2C2O4 and OH groups on TiO2 surface can be hydrogen-bond donors for Mo7O246− or MoO42− anions as the Mo precursor. The electrocatalytic activity of C/MoS2 in the hydrogen evolution was studied. Figure 8a illustrates linear sweep voltammogram (LSV) curves of bare MoS2 and 2.5C/MoS2. C/MoS2 24


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show a current density of 10 mA cm−2 at over-potential of 435 mV in 0.5 M H2SO4 to be lower than bare MoS2 by 60 mV. The Tafel plots show that C/MoS2 have a Tafel slope and intercept of 138 mV dec−1 and 246 mV to be smaller than 146 mV dec−1 and 308 mV for bare MoS2, respectively (Figure 8b). These results indicate that C/MoS2 possess higher electrocatalytic activity for hydrogen evolution than bare MoS2. In addition, carbon spheres without MoS2 nanosheets showed no electrocatalytic activity for hydrogen evolution in the same potential range as previously reported.41,42 This suggests that carbon materials in C/MoS2 composites were used only as supporting materials and MoS2 possess the active sites for the hydrogen evolution. To elucidate the high activity of C/MoS2, the number of active sites and turnover frequency (TOF) were studied by an electrochemical approach.42, 43 Figure 8c gives cyclic voltammogram (CV) curves of bare MoS2 and 2.5C/MoS2 in 1.0 M Na2SO4. In the tested potential range, 2.5C/MoS2 electrode shows higher mass-specific current densities (−2 ~ 4 A g-1) than bare MoS2 (−0.7 ~ 1 A g-1). The mass-specific capacitance and active sites are calculated to be 39.3 F g−1 and 2.03  10−4 mol g−1 for 2.5C/MoS2, both of which are three times larger than those for bare MoS2 (12.7 F g−1 and 0.66  10−4 mol g−1) (Figure S5a). This may relate to a larger BET specific surface area of 2.5C/MoS2 (58.5 m2 g−1) than bare MoS2 (18.8 m2 g−1) to have more exposed active sites. The TOF number of hydrogen evolution (s−1 g−1) for MoS2 is obtained from polarization curves normalized by the number of active sites and the amount of MoS2 loading. The ratio of TOF for 2.5C/MoS2 to that for bare MoS2 is calculated to be 1.4 ± 0.1 in the tested potential range (Figure S5b), indicating the improved intrinsic activity of active sites on C/MoS2. This is due to the direct interaction between MoS2 and carbon spheres through the C−O−Mo bond, which can improve electric conductivity and electrochemical activity of MoS2.

25



0

(a)

0.6

j /mA cm

-2

-20

C/MoS2

-40

-60 -0.6

4

-1

Potential /V vs. RHE

MoS2

Current density /A g

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

-0.4 -0.2 Potential /V vs. RHE

0.0

Page 26 of 35

(b)

0.4 MoS2 C/MoS2 0.2

0.0 0.0

0.5

1.0

1.5

-2

log(j /mA cm )

(c)

2

MoS2 C/MoS2

0

-2

-4 -0.6

-0.4 -0.2 0.0 0.2 Potential /V vs. Ag/AgCl

0.4

Figure 8. LSV curves (a), and Tafel plots (b) of MoS2 and 2.5C/MoS2 in 0.5 M H2SO4 at a scan rate of 5 mV s−1. CV curves of MoS2 and 2.5C/MoS2 in 1.0 M Na2SO4 at a scan rate of 50 mV s−1 (c). 4. Conclusion This work elucidates the role of glucose on the structure of MoS2 during the hydrothermal reaction of sodium molybdate and thiourea. In the presence of glucose, the abundant OH groups of glucose can act as the proton donor to interact with the lone pair electrons of O in polyoxomolybdate ions such as MoO42−, Mo7O246−, and Mo8O264−, forming two hydrogen bonds as evidenced by FT-IR and NMR spectra. The growth and aggregation of MoS2 are 26


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inhibited in a wide range of pH = 2 ~ 12. Moreover, MoS2 tightly bounds to in-situ generated carbon spheres through Mo−O−C bonds, leading to high electrocatalytic activity for evolution of hydrogen and larger capacitance. This result offers a new approach to manipulate the structure of MoS2-based composites for enhancing surface properties for electrochemical catalysis, energy storage, and so on. ASSOCIATED CONTENT Supporting Information Supporting figures (Figures S1−S5), and table (Tables S1 and S2), as mentioned in the supporting information. This material is available free of charge via the Internet at http://pubs.acs.org. AUTHOR INFORMATION Corresponding Author * Fax: +86 27 8754 3632; E-mail: [email protected] (T. Majima), [email protected] (L. Zhu). Notes The authors declare no competing financial interest. Acknowledgments The authors acknowledge the funding support from the National Natural Science Foundation (Grants Nos. 21976063 and 21477043), and “1000 Foreign Experts Program” (No. WQ2017420438), as well as characterizations of materials from the Analytical and Testing Center of Huazhong University of Science and Technology. 27



References (1) Ding, S.; Zhang, D.; Chen, J. S.; Lou, X. W. Facile Synthesis of Hierarchical MoS2 Microspheres Composed of Few-Layered Nanosheets and their Lithium Storage Properties, Nanoscale 2012, 4, 95–98. (2) Li, Y.; Wang, L.; Zhang, S.; Dong, X.; Song, Y.; Cai, T.; Liu, Y. Cracked Monolayer 1T MoS2 with Abundant Active Sites for Enhanced Electrocatalytic Hydrogen Evolution, Catal. Sci. Technol. 2017, 7, 718–724. (3) Asadi, M.; Kumar, B.; Behranginia, A.; Rosen, B. A.; Baskin, A.; Repnin, N.; Pisasale, D.; Phillips, P.; Zhu, W.; Haasch, R.; Klie, R. F.; Král, P.; Abiade, J.; Salehi-Khojin, A. Robust Carbon Dioxide Reduction on Molybdenum Disulphide Edges, Nat. Commun. 2014, 5, 1–8. (4) Cho, S.-Y.; Kim, S. J.; Lee, Y.; Kim, J.-S.; Jung, W.-B.; Yoo, H.-W.; Kim, J.; Jung, H.T. Highly Enhanced Gas Adsorption Properties in Vertically Aligned MoS2 Layers, ACS Nano 2015, 9, 9314–9321. (5) Choudhary, N.; Park, J.; Hwang, J. Y.; Choi, W. Growth of Large-Scale and ThicknessModulated MoS2 Nanosheets, ACS Appl. Mater. Interfaces 2014, 6, 21215−21222. (6) Zhang, P.; Fujitsuka, M.; Majima, T. Hot Electron Driven Hydrogen Evolution using Anisotropic Gold Nanostructures Assembled Monolayer MoS2, Nanoscale 2017, 9, 1520– 1526. (7) Huang, X.; Zeng, Z.; Zhang, H. Metal Dichalcogenide Nanosheets: Preparation, Properties and Applications, Chem. Soc. Rev. 2013, 42, 1934–1946. 28


Page 28 of 35

Page 29 of 35 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


(8) Zhou, W.; Yin, Z.; Du, Y.; Huang, X.; Zeng, Z.; Fan, Z.; Liu, H.; Wang, J.; Zhang, H. Synthesis of Few-Layer MoS2 Nanosheet-Coated TiO2 Nanobelt Heterostructures for Enhanced Photocatalytic Activities, Small 2013, 9,140–147. (9) Shi, X.; Fujitsuka, M.; Majima, T. Electron Transfer Dynamics of Quaternary Sulfur Semiconductor/MoS2 Layer-on-Layer for Efficient Visible-Light H2 Evolution, Appl. Catal. B Environ. 2018, 235, 9–16. (10) Shi, X.; Fujitsuka, M.; Kim, S.; Majima, T. Faster Electron Injection and More Active Sites for Efficient Photocatalytic H2 Evolution in g-C3N4/MoS2 Hybrid, Small 2018, 14, 1703277. (11) Wan, Z.; Shao, J.; Yun, J.; Zheng, H.; Gao, T.; Shen, M.; Qu, Q.; Zheng, H. Core-Shell Structure of Hierarchical Quasi-Hollow MoS2 Microspheres Encapsulated Porous Carbon as Stable Anode for Li-Ion Batteries, Small 2014, 10, 4975−4981. (12) Zhang, L.; Lou, X. W. D. Hierarchical MoS2 Shells Supported on Carbon Spheres for Highly Reversible Lithium Storage, Chem. -Eur. J. 2014, 20, 5219−5223. (13) Wang, J.; Liu, J.; Chao, D.; Yan, J.; Lin, J.; Shen, Z. X. Self-Assembly of Honeycomblike MoS2 Nanoarchitectures Anchored into Graphene Foam for Enhanced Lithium-Ion Storage, Adv. Mater. 2014, 26, 7162−7169. (14) Wang, C.; Wan, W.; Huang, Y.; Chen, J.; Zhou, H. H.; Zhang, X. X. Hierarchical MoS2 Nanosheet/Active Carbon Fiber Cloth as a Binder-Free and Free-Standing Anode for Lithium-Ion Batteries, Nanoscale 2014, 6, 5351−5358.

29



(15) Teng, Y.; Zhao, H.; Zhang, Z.; Li, Z.; Xia, Q.; Zhang, Y.; Zhao, L.; Du, X.; Du, Z.; Lv, P.; Świerczek, K. MoS2 Nanosheets Vertically Grown on Graphene Sheets for Lithium-Ion Battery Anodes, ACS Nano 2016, 10, 8526–8535. (16) Huang, G.; Chen, T.; Chen, W.; Wang, Z.; Chang, K.; Ma, L.; Huang, F.; Chen, D.; Lee, J. Y. Graphene-like MoS2/Graphene Composites: Cationic Surfactant-Assisted Hydrothermal Synthesis and Electrochemical Reversible Storage of Lithium, Small 2013, 9, 3693−3703. (17) Wang, Z.; Chen, T.; Chen, W.; Chang, K.; Ma, L.; Huang, G.; Chen, D.; Lee, J. Y. CTAB-assisted Synthesis of Single-layer MoS2-Graphene Composites as Anode Materials of Li-Ion Batteries, J. Mater. Chem. A 2013, 1, 2202−2210. (18) Tian, J.; Zhang, H.; Li, Z. Synthesis of Double-Layer Nitrogen-Doped Microporous Hollow Carbon@MoS2/MoO2 Nanospheres for Supercapacitors, ACS Appl. Mater. Interfaces 2018, 10, 29511−29520. (19) Liu, M.-C.; Xu, Y.; Hu, Y.-X.; Yang, Q.-Q.; Kong, L.-B.; Liu, W.-W.; Niu, W.-J.; Chueh, Y.-L. Electrostatically Charged MoS2/Graphene Oxide Hybrid Composites for Excellent Electrochemical Energy Storage Devices, ACS Appl. Mater. Interfaces 2018, 10, 35571−35579. (20) Sun, W.; Hu, Z.; Wang, C.; Tao, Z.; Chou, S.-L.; Kang, Y.-M.; Liu, H.-K. Effects of Carbon Content on the Electrochemical Performances of MoS2-C Nanocomposites for Li-Ion Batteries, ACS Appl. Mater. Interfaces 2016, 8, 22168−22174.

30


Page 30 of 35

Page 31 of 35 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


(21) Chang, K.; Chen, W. L-Cysteine-Assisted Synthesis of Layered MoS2/Graphene Composites with Excellent Electrochemical Performances for Lithium Ion Batteries, ACS Nano 2011, 5, 4720−4728. (22) Chang, K.; Chen, W.; Ma, L.; Li, H.; Li, H.; Huang, F.; Xu, Z.; Zhang, Q.; Lee, J.Y. Graphene-like MoS2/Amorphous Carbon Composites with High Capacity and Excellent Stability as Anode Materials for Lithium Ion Batteries, J. Mater. Chem. 2011, 21, 6251−6257. (23) Ding, S.; Chen, J. S.; Lou, X. W. Glucose-Assisted Growth of MoS2 Nanosheets on CNT Backbone for Improved Lithium Storage Properties, Chem. Eur. J. 2011, 17, 13142−13145. (24) Xu, X.; Fan, Z.; Ding, S.; Yu D.; Du, Y. Fabrication of MoS2 Nanosheet@TiO2 Nanotube Hybrid Nanostructures for Lithium Storage, Nanoscale, 2014, 6, 5245–5250. (25) Li, X.; Li, W.; Li, M.; Cui, P.; Chen, D.; Gengenbach, T.; Chu, L.; Liu, H.; Song, G. Glucose-Assisted Synthesis of the Hierarchical TiO2 Nanowire@MoS2 Nanosheet Nanocomposite and its Synergistic Lithium Storage Performance, J. Mater. Chem. A 2015, 3, 2762–2769. (26) Li, Y.; Wang, L.; Cai, T.; Zhang, S.; Liu, Y.; Song, Y.; Dong, X.; Hu, L.; GlucoseAssisted Synthesize 1D/2D nearly Vertical CdS/MoS2 Heterostructures for Efficient Photocatalytic Hydrogen Evolution, Chem. Eng. J. 2017, 321, 366–374. (27) Qiao, X.; Hu, F.; Hou, D.; Li, D. PEG Assisted Hydrothermal Synthesis of Hierarchical MoS2 Microspheres with Excellent Adsorption Behavior, Mater. Lett. 2016, 169, 241−245.

31



(28) Lee, C.; Yan, H.; Brus, L. E.; Heinz, T. F.; Hone, J.; Ryu, S. Anomalous Lattice Vibrations of Single and Few-Layer MoS2, ACS Nano 2010, 4, 2695–2700. (29) Lei, M.; Wang, N.; Zhu, L.; Xie, C.; Tang, H. A Peculiar Mechanism for the Photocatalytic Reduction of Decabromodiphenyl Ether over Reduced Graphene Oxide-TiO2 Photocatalyst, Chem. Eng. J. 2014, 241, 207–215. (30) Gong, Y.; Wang, H.; Wei, Z.; Xie, L.; Wang, Y. An Efficient Way to Introduce Hierarchical Structure into Biomass-Based Hydrothermal Carbonaceous Materials, ACS Sustainable Chem. Eng. 2014, 2, 2435−2441. (31) Lia, Y.; Yin, K.; Wang, L. Lu, X.; Zhang, Y.; Liu, Y.; Yan, D.; Song, Y.; Luo, S. Engineering MoS2 Nanomesh with Holes and Lattice Defects for Highly Active Hydrogen Evolution Reaction, Appl. Catal. B: Environ. 2018, 239, 537–544. (32) Zhang, Y.; Tao, H.; Li, T.; Du, S.; Li, J.; Zhang, Y.; Yang, X. Vertically OxygenIncorporated MoS2 Nanosheets Coated on Carbon Fibers for Sodium-Ion Batteries, ACS Appl. Mater. Interfaces 2018, 10, 35206−35215. (33) Kondekar, N. P.; Boebinger, M. G.; Woods, E. V.; McDowell, M. T. In Situ XPS Investigation of Transformations at Crystallographically Oriented MoS2 Interfaces, ACS Appl. Mater. Interfaces 2017, 9, 32394−32404. (34) Xu, S.; Lei, Z.; Wu, P. Facile Preparation of 3D MoS2/MoSe2 Nanosheet-Graphene Networks as Efficient Electrocatalysts for the Hydrogen Evolution Reaction, J. Mater. Chem. A 2015, 3, 16337–16347.

32


Page 32 of 35

Page 33 of 35 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


(35) Liu, C.; Wang, L.; Tang, Y.; Luo, S.; Liu, Y.; Zhang, S.; Zeng, Y.; Xu,Y. Vertical Single or Few-layer MoS2 Nanosheets Rooting into TiO2 Nanofibers for Highly Efficient Photocatalytic Hydrogen Evolution, Appl. Catal. B: Environ. 2015, 164, 1–9. (36) Hu, W.-H.; Han, G.-Q.; Dai, F.-N.; Liu, Y.-R.; Shang, X.; Dong, B.; Chai, Y.-M.; Liu, Y.-Q.; Liu, C.-G. Effect of pH on the Growth of MoS2 (002) Plane and Electrocatalytic Activity for HER, Int. J. Hydrogen Energy 2016, 41, 294–299. (37) Ma, L.; Zhao, B.; Wang, X.; Yang, J.; Zhang, X.; Zhou, Y.; Chen, J. MoS2 Nanosheets Vertically Grown on Carbonized Corn Stalks as Lithium-Ion Battery Anode, ACS Appl. Mater. Interfaces 2018, 10, 22067−22073. (38) Davantès, A.; Lefèvre, G. In Situ Real Time Infrared Spectroscopy of Sorption of (Poly)molybdate Ions into Layered Double Hydroxides, J. Phys. Chem. A 2013, 117, 12922−12929. (39) Lv, H.; Wang, N.; Zhu, L.; Zhou, Y.; Li, W.; Tang, H. Alumina-Mediated Mechanochemical Method for Simultaneously Degrading Perfluorooctanoic Acid and Synthesizing a Polyfluoroalkene, Green Chem. 2018, 20, 2526−2533. (40) Bagno, A.; Rastrelli, F.; Saielli, G. Prediction of the 1H and 13C NMR Spectra of r-DGlucose in Water by DFT Methods and MD Simulations, J. Org. Chem. 2007, 72, 7373−7381. (41) Chatti, M.; Gengenbach, T.; King, R.; Spiccia, L.; Simonov, A. N. Vertically Aligned Interlayer Expanded MoS2 Nanosheets on a Carbon Support for Hydrogen Evolution Electrocatalysis, Chem. Mater. 2017, 29, 3092−3099.

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(42) Hyeon, Y.; Jung, S.-H.; Jang, W.; Kim, M.; Kim, B.-S.; Lee, J.-H.; Nandanapalli, K. R.; Jung, N.; D. Whang. Unraveling the Factors Affecting the Electrochemical Performance of MoS2-Carbon Composite Catalysts for Hydrogen Evolution Reaction: Surface Defect and Electrical Resistance of Carbon Supports, ACS Appl. Mater. Interfaces 2019, 11, 5037−5045. (43) Yan, Y.; Xia, B.Y.; Ge, X.; Liu, Z.; Wang, J.-Y.; Wang, X. Ultrathin MoS2 Nanoplates with Rich Active Sites as Highly Efficient Catalyst for Hydrogen Evolution, ACS Appl. Mater. Interfaces 2013, 5, 12794−12798.

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TOC Graphic


Hydrogen Bond between Molybdate and Glucose for the Formation of

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