Crystalline/Amorphous Heterophase with Self-Assembled Hollow Structure for Highly Efficient Electrochemical Hydrogen Production

Open AccessCCS ChemistryRESEARCH ARTICLE3 Oct 2022Crystalline/Amorphous Heterophase with Self-Assembled Hollow Structure for Highly Efficient Electrochemical Hydrogen Production Zhengqing Liu, Kunkun Nie, Yanling Yuan, Binjie Li, Pei Liu, Shaokun Chong, Yaping Du and Wei Huang Zhengqing Liu *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, Xi'an 710129 , Kunkun Nie Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, Xi'an 710129 , Yanling Yuan Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, Xi'an 710129 , Binjie Li Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, Xi'an 710129 , Pei Liu School of Chemistry and Chemical Engineering, Northwestern Polytechnical University, Xi'an 710072 , Shaokun Chong Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, Xi'an 710129 , Yaping Du *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Tianjin Key Lab for Rare Earth Materials and Applications, Center for Rare Earth and Inorganic Functional Materials, School of Materials Science and Engineering & National Institute for Advanced Materials, Nankai University, Tianjin 300350 and Wei Huang *Corresponding authors: E-mail Address: [email protected] E-mail Address: [email protected] E-mail Address: [email protected] Frontiers Science Center for Flexible Electronics, Xi'an Institute of Flexible Electronics (IFE), Xi'an Institute of Biomedical Materials and Engineering, Northwestern Polytechnical University, Xi'an 710129 https://doi.org/10.31635/ccschem.021.202101598 SectionsSupplemental MaterialAboutAbstractPDF ToolsAdd to favoritesDownload CitationsTrack Citations ShareFacebookTwitterLinked InEmail Heterophase nanomaterials composed of multiple phases have attracted increasing attention due to their enhanced performance in electrocatalytic field. Nevertheless, constructing two-dimensional (2D) crystalline/amorphous heterophase nanostructures with the same chemical composition remains a great challenge. Herein, we report the preparation of a 2D crystalline/amorphous heterophase of MoS2 nanosheets with the same elemental components via a facile solvothermal method. The obtained MoS2 heterophase nanosheets can self-assemble into hollow structures with high morphological yield, referred to as c/a-hollow MoS2. Furthermore, the as-prepared c/a-hollow MoS2 can serve as templates to grow uniform Pt nanoparticles with a low mass loading of 5%, forming c/a-hollow MoS2-Pt nanocomposites. Impressively, when used as electrocatalysts, c/a-hollow MoS2 and c/a-hollow MoS2-Pt nanocomposites exhibit excellent electrochemical performance toward hydrogen production with low onset potentials of −112 and −26 mV and Tafel slopes as small as 45 and 34 mV/dec, respectively, which are among the best reported hydrogen evolution reaction electrocatalysts. Download figure Download PowerPoint Introduction Heterophase nanomaterials consisting of more than one phase have received considerable attention due to the synergistic effects of different phases and promising catalytic applications.1–4 Recent studies have shown that phase engineering can design and synthesize nanomaterials with unconventional crystal phases,5,6 which makes possible the formation of heterophase nanostructures by fine-tuning the crystal phases of materials. Compared with controlling the composition, morphologies, facets, and dimensionalities of the nanomaterials, constructing heterophase nanostructures provide new opportunities for tunable phase-dependent properties.7–9 In addition to the unconventional crystalline phase, amorphous nanomaterials have recently been proven to have unique physicochemical properties and enhanced performance in energy storage and conversion applications.3,5,10 Therefore, the construction of heterophase nanostructures with amorphous components could boost their catalytic performance, such as CuS (crystalline)/Pd-Cu-S (amorphous),11 Co (crystalline)/Co3O4 (amorphous),12 and Pd-P (crystalline)/Pd-P (amorphous).2 Nevertheless, most of the reported crystalline/amorphous heterophase nanostructures are made of different chemical compositions. Furthermore, complex experimental procedures and additional post-processing procedures are required to generate some heterophase nanostructures, such as complicated cation exchange and ion irradiation treatment of the presynthesized crystalline nanomaterials.13,14 Therefore, the construction of crystalline/amorphous heterophase nanostructures via facile experimental methods is still a great challenge. Two-dimensional (2D) transition-metal dichalcogenides (TMDs) nanomaterials represented by MoS2 have attracted widespread attention owing to their extraordinary physicochemical properties.15 Especially in recent years, studies have shown that TMDs nanomaterials with different phases (e.g., 1T, 1T′, and 1T″) will significantly affect their properties and applications due to their unique atomic arrangement.16,17 In addition, 2D TMDs heterophase nanostructures were also constructed through phase engineering, which showed great application potential due to the synergistic effect between different phases and the existence of phase boundaries.16,18,19 However, most previously reported studies of TMDs heterophase nanostructures have focused on the preparation of crystalline/crystalline heterostructures, where only a few successful crystalline/amorphous studies have been reported. For instance, the crystallinity of MoS2 nanosheets can be adjusted by oxygen doping and endow them with high conductivity and abundant catalytic active sites, which in turn exhibits excellent electrocatalytic performance toward the hydrogen evolution reaction (HER).20 Herein, we report a facile solvothermal method to synthesize uniform MoS2 hollow structures by self-assembly of the 2D crystalline/amorphous heterophase MoS2 nanosheets, referred to as c/a-hollow MoS2. c/a-Hollow MoS2 consists of amorphous and crystalline nanosheets with the same chemical compositions. As a proof-of-concept application, the as-synthesized c/a-hollow MoS2 is used as an electrocatalyst for HER. Benefitting from the unique 2D crystalline/amorphous heterophase and hollow structures, the c/a-hollow MoS2 exhibits enhanced catalytic performance in comparison with its crystalline counterparts (obtained by annealing c/a-hollow MoS2 in an argon atmosphere at 500 °C for 1 h), such as a low onset potential of −112 mV, small Tafel slope of 45 mV/dec, and remarkable stability of 10,000 cycles, which is comparable with or better than most non-noble metal-based HER electrocatalysts. It is worth noting that the synergistic effect of the crystalline/amorphous phase and the self-assembled hollow structure can introduce lattice strain and distortion, thereby effectively altering its electronic structure and improving its HER performance. Additionally, the liquid-phase growth of Pt nanoparticles (NPs) onto the as-obtained c/a-hollow MoS2 to form c/a-hollow MoS2-Pt nanocomposites was also demonstrated. Importantly, the c/a-hollow MoS2 supports only 5% Pt NPs to achieve the electrocatalytic performance of commercial Pt/C with a mass loading of 10%, which greatly reduces the cost of noble metal Pt. This work offers a universal and effective way to study the relationship between heterophase properties and electrocatalysis. Experimental Methods Preparation of Mo-DDTC 0.05 mol of molybdenum(V) chloride and 0.25 mol of sodium diethyldithiocarbamate (NaDDTC) were first dissolved in 100 mL of distilled water, respectively. Then, the two above-mentioned solutions were thoroughly mixed with stirring in a 500-mL beaker. The resulting purple precipitate was filtered, washed with distilled water, and dried in a vacuum oven at 60 °C. Synthesis of c/a-hollow MoS2 A given amount of Mo-DDTC (55 mg) was dissolved in 18 mL of hexylamine in a 20-mL Teflon-lined autoclave. The autoclave was sealed and heated at 160–200 °C for 72 h, and then cooled to room temperature. The as-formed product was collected by centrifugation and washed several times with absolute ethanol and then dried in a vacuum at 60 °C overnight. Growth of Pt NPs on c/a-hollow MoS2 Typically, 1 mL of c/a-hollow MoS2 solution (0.8 mg/mL) is added into 19 mL of aqueous solution containing 0.1 mM potassium tetrachloroplatinate and 0.15 mM trisodium citrate in a glass vial. After that, the mixed solution was irradiated with a 150 W halogen lamp (Fiber-Lite MI-150) for 2 h at 80% of its full intensity. The ice bath was used to cool the glass vial and prevent light-induced overheating. After the photochemical reduction reaction was finished, the solution was centrifuged at 6500 rpm for 15 min and washed with deionized water three times. Finally, the as-formed products were re-dispersed in deionized water before further characterization. Electrocatalytic measurements for HER The synthesized catalysts, including c/a MoS2 nanosheets, c-hollow MoS2, c/a-hollow MoS2, c/a-hollow MoS2-Pt nanocomposites, and 10% Pt on charcoal (Pt/C), were tested for HER. The catalyst dispersion was prepared by mixing the aqueous catalyst solution (1.25 mg/mL), 99.9% ethanol, and 5% Nafion solution (in ethanol) at a volume ratio of 4:1:0.1. After sonication for 30 min, the catalyst dispersion (10 μL, containing 10 μg catalysts) was loaded onto a 3-mm glassy carbon electrode and dried overnight in ambient conditions. Linear sweep voltammetry (LSV) was carried out in 0.5 M H2SO4 (deaerated by N2) with a scan rate of 2 mV/s using a graphite electrode as the counter electrode and 3 M Ag/AgCl electrode as the reference electrode. Cyclic voltammograms (CVs) were conducted using the same standard three-electrode setup with various scan rates (20, 50, 100 mV/s, etc.) at room temperature. Nyquist plots of electrocatalysts were measured at an overpotential of 350 mV from 100 kHz to 0.1 Hz with amplitudes of 5 mV. Results and Discussion The X-ray diffraction (XRD) pattern of the MoS2 product is shown in Figure 1a. Compared with the d = 0.62 nm spacing of the conventional 2H phase MoS2 (a = b = 0.315 nm, c = 1.230 nm, JCPDS: 73-1508), the obtained MoS2 possesses a larger interlayer spacing of 0.98 nm calculated by the (002) peak in the low-angle region. Larger layer spacing is beneficial to regulating the electronic structure and enhancing the conductivity of the catalytic sites at the edges of MoS2, thereby improving the catalytic performance.21,22 Moreover, the calculated XRD pattern using an interlayer spacing of 0.98 nm along the c axis is consistent with the pattern of the as-obtained MoS2 product (Figure 1a). Scanning electron microscopy (SEM, Figure 1b and Supporting Information Figure S1a) revealed that the obtained MoS2 possesses high morphological purity with an average size of ∼1.10 ± 0.04 μm in length and ∼0.60 ± 0.03 μm in width. Furthermore, as clearly demonstrated from the inset of Figure 1b, the MoS2 presents a well-defined hollow structure. The corresponding transmission electron microscopy (TEM) image (Figure 1c) verified the hollow morphology of the MoS2 product and the thickness of the shell was ∼55 nm. Close examination of the high-angle annular dark-field scanning TEM (HAADF–STEM) image of a MoS2 hollow structure (inset of Figure 1c) indicated that the MoS2 hollow structure is composed of ultrathin MoS2 nanosheets. Energy dispersive spectroscopy (EDS) data ( Supporting Information Figure S1b) acquired from SEM confirmed the ratio of Mo and S elements was ∼1:2, which is consistent with the composition of MoS2. Figure 1 | (a) XRD pattern of MoS2 product, and calculated XRD pattern from the c axis of the MoS2 cell with enlarged interlayer spacing. (b) SEM and (c) TEM images of the as-prepared hollow MoS2. Insets of (b) and (c) represent SEM and STEM images of a single hollow MoS2, respectively. (e and f) HRTEM images taken from the corresponding area of (d) MoS2. Insets of (e and f) represent the corresponding FFT patterns, respectively. (g and h) Atomic distortion maps for basal planes of MoS2 in different directions obtained by GPA analysis of the HRTEM images from (e) and (f), respectively. (i) EDS elemental mapping and corresponding line scan profiles for Mo and S elements along the red line. Download figure Download PowerPoint The high-resolution TEM (HRTEM) images of MoS2 hollow structures are shown in Figures 1d–1f. The vertically stacked MoS2 nanosheets (Figure 1d) display an interlayer spacing of 0.98 nm, which is consistent with the XRD results. Figures 1e and 1f are HRTEM images of different areas in Figure 1d, respectively. The image taken in region 1 (Figure 1e) demonstrates that the obtained hollow MoS2 is partially crystallized and its lattice fringe is 0.27 nm, belonging to the (100) plane of hexagonal phase MoS2. The corresponding fast Fourier transform (FFT) pattern (inset in Figure 1e) displays the six independent diffraction arcs, which indicates that there are a large number of defects.23 The defect structure was supposed to be able to expose more active edge sites, which could improve the catalytic performance.24,25 In contrast, Figure 1f taken at area 2 shows the completely amorphous phase of MoS2, as further demonstrated by the corresponding FFT pattern (inset of Figure 1f), which shows a distinct amorphous ring. The HRTEM images and corresponding FFT patterns proved the coexistence of the crystalline and amorphous phases in the obtained hollow MoS2. For comparison, the crystalline hollow MoS2 ( Supporting Information Figure S2) was also prepared by annealing c/a-hollow MoS2 in an argon atmosphere at 500 °C for 1 h, as demonstrated by XRD, HRTEM, and selected area electron diffraction, and referred to as c-hollow MoS2. In addition, the distortion maps for the basal plane of crystalline and amorphous MoS2 were obtained by geometric phase analysis (GPA) analysis of their atomic-scale HRTEM images (Figures 1e and 1f). As shown in Figures 1g and 1h, crystalline MoS2 is subjected to ∼1% lattice distortion, while that of amorphous MoS2 is about ∼3%, which was three times that of crystalline MoS2, consistent with the HRTEM images analysis. The larger lattice distortion is beneficial to tuning the band structure of MoS2 and reducing its hydrogen adsorption free energy (∆GH*).26 The EDS elemental mapping and line scan EDS analysis (Figure 1i) reveal that the Mo and S elements are uniformly distributed in the as-formed c/a-hollow MoS2. The chemical states of Mo and S in c/a-hollow MoS2 were examined by X-ray photoelectron spectroscopy (XPS). The XPS core-level spectra (Figure 2a) of Mo 3d peaks are located at 232.1 and 228.8 eV, belonging to the Mo 3d3/2 and Mo 3d5/2 orbitals of 2H-MoS2, respectively, revealing characteristics of Mo4+ in MoS2.27,28 The binding energies of 161.7 and 162.8 eV (Figure 2b) in S 2p spectra are attributed to the S2− of MoS2.28 Figures 2c and 2d show the nitrogen adsorption–desorption isotherms and pore size distribution curves of c/a-hollow MoS2, respectively. As displayed in Figure 2c, the as-obtained c/a-hollow MoS2 is ascribed to a type IV nitrogen isotherm with characteristics of a mesoporous feature. The Brunauer–Emmett–Teller specific surface area of the MoS2 product was calculated as ∼82 m2 g−1. Barrett–Joyner–Halenda analysis demonstrated that the hollow MoS2 was mesoporous with mean diameters of ∼4.6 and 31.8 nm (Figure 2d). Such a high surface area and mesoporous structure of c/a-hollow MoS2 could be desirable for catalytic applications. Figure 2 | XPS spectra of (a) Mo 3d and (b) S 2p. (c) N2 adsorption/desorption isotherms and (d) pore size distribution of the c/a-hollow MoS2. (e) Room temperature UV–vis absorption spectrum and (f) fluorescence spectrum of c/a-hollow MoS2. Inset of (f) represents a digital photograph of c/a-hollow MoS2 dispersed in ethanol. Download figure Download PowerPoint The UV–vis absorption spectra in Figure 2e exhibited continuous absorption across the UV–vis wavelength range and three distinguishable absorption peaks were centered on 276, 405, and 640 nm, showing semiconductor optical properties of the as-produced c/a-hollow MoS2. The fluorescence spectrum of c/a-hollow MoS2 was measured with 280 nm excitation and exhibited blue emission wavelengths at 402, 425, and 450 nm (Figure 2f). The 450 nm peak was caused by transitions mediated by defect states,29 indicating structural defects in c/a-hollow MoS2, such as point defects, distortions, and phase boundaries. These structural defects could affect the population of excitons, induce disordered localization, and regulate the electrical behavior of the c/a-hollow MoS2.30 Moreover, in our synthesis, the hexylamine served as both solvent and surface ligand ( Supporting Information Figure S3), containing six carbon atoms and being soluble in low-polar (e.g., ethanol) solvents, thus the MoS2 could be easily and well dispersed in polar solvents without further surface modification for catalytic applications (inset of Supporting Information Figure S3). In the current synthesis, the reaction time and temperature play an important role in the formation of a high-quality c/a-hollow MoS2. For instance, 55 mg molybdenum diethyl dithiocarbamate (Mo-DDTC) was dissolved in 18 mL hexylamine and reacted at 180 °C for different reaction times, where the hollow structure of MoS2 formed gradually with increasing reaction time, as shown in Figures 3a–3c. Interestingly, our results showed that the overlapped part of the two adjacent MoS2 hollows gradually fused when the reaction time exceeded 96 h. Eventually, the two adjacent MoS2 became a complete one (Figure 3d). Under the same reaction conditions, except for increasing reaction temperature from 160 (Figure 3e) to 180 °C (Figure 1c) and 200 °C (Figure 3f), three different MoS2 hollow morphologies were produced. As indicated by the TEM images in Figure 3g, the as-obtained MoS2 hollow structures gradually became round in shape as the reaction temperature elevated. Figure 3 | TEM images of MoS2 products formed from the reaction of 55 mg Mo-DDTC in 18 mL hexylamine at 180 °C for different reaction times: (a) 6 h, (b) 12 h, (c) 24 h, and (d) 96 h. TEM images of the products obtained from the reaction of 55 mg Mo-DDTC in 18 mL hexylamine at (e) 160 °C, (f) 200 °C for 72 h. (g) Morphology evolution of c/a-hollow MoS2 nanostructures under different reaction temperatures. Download figure Download PowerPoint The electrocatalytic HER performance of the as-prepared c/a-hollow MoS2 was studied at room temperature using a standard three-electrode setup. The polarization curves and Tafel plots were obtained by testing LSV from 0.1 to −0.5 V [vs reversible hydrogen electrode (RHE)]. For comparison, the LSV curves and Tafel slopes of c/a-MoS2 nanosheets (Figure 3a) and c-hollow MoS2 (obtained by annealing c/a-hollow MoS2 in an argon atmosphere at 500 °C for 1 h) were also tested under the same conditions. Compared with the c-hollow MoS2 and c/a-MoS2 nanosheets, the c/a-hollow MoS2 exhibited superior HER electrocatalytic activity. As displayed in Figures 4a and 4b, the current density of c/a-hollow MoS2 reached −10 mA/cm2 at 172 mV, which is much lower than that of c-hollow MoS2 (235 mV) and c/a-MoS2 nanosheets (204 mV), demonstrating the advantages of crystalline/amorphous heterophase and hollow structures. Moreover, c/a-hollow MoS2 shows a much lower onset potential of −112 mV than c-hollow MoS2 (−150 mV) and c/a-MoS2 nanosheets (−130 mV). The Tafel plots in Figure 4c show that the Tafel slope of c/a-hollow MoS2 is 45 mV/dec, which is much smaller than the c-hollow MoS2 (68 mV/dec) and c/a-MoS2 nanosheets (59 mV/dec), indicating faster kinetics of the electrochemical hydrogen production on c/a-hollow MoS2.31 In addition to current density and Tafel slope, catalytic stability is also a crucial factor. To study the stability of c/a-hollow MoS2, cyclic voltammetry of 10,000 cycles was conducted from −0.45 to −0.2 V (vs RHE) at a scan rate of 100 mV/s. It is noteworthy that the activity loss of c/a-hollow MoS2 after 10,000 cycles is negligible (Figure 4d), indicating the c/a-hollow MoS2 possessed excellent stability in an acidic environment. Based on the aforementioned results, the c/a-hollow MoS2 exhibited outstanding HER performance, which is comparable with or better than most of the previously reported electrocatalysts (Figure and Supporting Information Figure | (a) curves of c/a-hollow MoS2, c-hollow MoS2, and c/a-MoS2 nanosheets. (b) at 10 and onset potential of c/a-hollow MoS2, c-hollow MoS2, and c/a-MoS2 nanosheets. (c) Tafel plots of c/a-hollow MoS2, c-hollow MoS2, and c/a-MoS2 nanosheets. (d) curves of c/a-hollow MoS2 before and after 10,000 voltammetry cycles (vs (e) of c/a-hollow MoS2 at 10 mA/cm2 with some recently reported HER electrocatalysts. Download figure Download PowerPoint possible to the superior HER catalytic performance of the c/a-hollow MoS2. The was the atomic and the synergistic effects of the crystalline/amorphous heterophase The was that hollow structures could effectively prevent structural thus more active edge Moreover, the layer of the hollow MoS2 structure lattice strain and distortion, which could the electronic structure and boost the HER The one was that the high specific surface area of hollow structures with the area with the thus the and electrochemical To better the crystalline/amorphous heterophase nanostructures for such electrocatalytic performance of c/a-hollow MoS2, we the electrochemical surface area of c/a-hollow MoS2 and c-hollow MoS2 by testing the Supporting Information Figures and show the of c/a-hollow MoS2 and c-hollow MoS2 taken with different scan rates (20, 50, 100 mV/s, etc.) in the range of V (vs respectively. the current density = at V (vs RHE) are scan The slope in Figure is to the electrochemical which can be used to the of c/a-hollow MoS2 and c-hollow the of c/a-hollow MoS2 was about of than that of c-hollow MoS2, that c/a-hollow MoS2 possesses a much larger active surface area and more active sites for hydrogen Figure 5 | (a) density = at V (vs RHE) different scan The electrochemical of c/a-hollow MoS2 and c-hollow MoS2. (b) of Nyquist plots of c/a-hollow MoS2 and c-hollow MoS2 at an overpotential of 350 mV from 100 kHz to 0.1 Hz with amplitudes of 5 mV. The and are experimental and respectively. Inset of (b) represents an electrical for the and maps for basal planes of crystalline and amorphous MoS2 in different directions obtained by GPA analysis of the HRTEM image of Figures 1e and respectively. Download figure Download PowerPoint Furthermore, electrochemical spectroscopy analysis was also conducted on c/a-hollow MoS2 and c-hollow MoS2. The Nyquist plots of c/a-hollow MoS2 in acidic solution exhibited (Figure The first one at high is to the surface of the while the one at low the the possesses a with the electrocatalytic the Nyquist plots of c/a-hollow MoS2 and c-hollow MoS2 at a given overpotential of 350 mV were and to the electrical (inset of Figure Under the same the for c/a-hollow MoS2 was about one of lower than that for c-hollow MoS2, indicating the faster electron kinetics of c/a-hollow MoS2, which was consistent with their HER activity. Moreover, strain maps for basal planes of amorphous and crystalline MoS2 in c/a-hollow MoS2 were obtained by GPA analysis of its atomic-scale HRTEM image (Figures 1e and 1f). As shown in Figures and atoms of amorphous MoS2 were subjected to strain than the crystalline MoS2 from the and It is that strain can the at some S active thus catalytic The most effective catalyst for HER is which exhibit onset metal nanocomposites also have been used as electrocatalysts for which that unique 2D TMDs with Pt NPs is an way to achieve high catalytic However, most of the previously are focused on the crystalline MoS2, and the effect of amorphous MoS2 to Pt been Based on the advantages of c/a-hollow MoS2, a small amount of Pt NPs by atomic emission spectroscopy was loaded on the surface of c/a-hollow MoS2. As shown in Figure uniform Pt NPs with a of nm are well distributed on the surface of MoS2. The HRTEM image (Figure shows the loaded Pt NPs with lattice and the lattice spacing of nm to the planes of Pt. Importantly, after Pt the onset potential and Tafel slope of catalyst to −26 mV and 34 (Figures and comparison, can be that the c/a-hollow MoS2 loaded with 5% Pt NPs can achieve the catalytic performance of commercial Pt/C with 10% which greatly reduces the cost of metal Pt and the for applications. Figure 6 | (a) TEM and (b) HRTEM images of c/a-hollow MoS2-Pt nanocomposites. (c) curves and (d) corresponding Tafel curves of c/a-hollow MoS2-Pt nanocomposites and Download figure Download PowerPoint In we have synthesized MoS2 hollow structures by self-assembly of c/a-MoS2 nanosheets via a facile solvothermal method. The crystalline/amorphous heterophase in MoS2 nanosheets the of more active sites for Furthermore, the morphology of c/a-hollow MoS2 could be by the reaction Then, the as-prepared c/a-hollow MoS2 was used as the for of Pt NPs to form c/a-hollow MoS2-Pt nanocomposites. As a proof-of-concept application, the c/a-hollow MoS2 and c/a-hollow MoS2-Pt nanocomposites were used as electrocatalysts for which exhibited excellent activity with a small onset potential of −112 and −26 mV, large current and a Tafel slope as small as 45 and 34 mV/dec, respectively. The of c/a-hollow MoS2 and c/a-hollow MoS2-Pt nanocomposites and them as HER a new the production of more crystalline/amorphous heterophase Supporting Information Supporting Information is and and of is of to This work was by the National Science of Functional for the