In situ MoS2 Decoration of Laser-Induced Graphene as Flexible

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In situ MoS2-decoration of laser induced graphene as flexible supercapacitor electrodes Francesca Clerici, Marco Fontana, Stefano Bianco, Mara Serrapede, Francesco Perrucci, Sergio Ferrero, Elena Tresso, and Andrea Lamberti ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b00808 • Publication Date (Web): 01 Apr 2016 Downloaded from http://pubs.acs.org on April 2, 2016

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ACS Applied Materials & Interfaces

In situ MoS2-decoration of laser induced graphene as flexible supercapacitor electrodes F. Clerici, M. Fontana, S. Bianco, M. Serrapede, F. Perrucci, S. Ferrero, E. Tresso and A. Lamberti* Department of Applied Science and Technology, Politecnico di Torino, C.so Duca degli Abruzzi 24, 10129 Turin, Italy * corresponding author, E-mail: [email protected]

Abstract Herein we are reporting a rapid one-pot synthesis of MoS2-decorated Laser Induced Graphene (MoS2-LIG) by direct writing of polyimide foils. By covering the polymer surface with a layer of MoS2 dispersion before processing, it is possible to obtain an in-situ decoration of porous graphene network during laser writing. The resulting material is a 3-dimensional arrangement of agglomerated and wrinkled graphene flakes decorated by MoS 2 nanosheets with good electrical properties and high surface area, suitable to be employed as electrodes for supercapacitors, enabling both electric double layer and pseudo-capacitance behavior. A deep investigation of the material properties has been performed to understand the chemicalphysical

characteristics

of

the

hybrid

MoS2-graphene-like

material.

Symmetric

supercapacitors have been assembled in planar configuration exploiting polymeric electrolyte: the resulting performances of the here proposed material allow to predict the enormous potentialities of these flexible energy storage devices for industrial-scale production.

Keywords: laser writing, graphene, polyimide, MoS2, flexible supercapacitor

1. Introduction In the field of electrochemical energy storage, graphene and graphene-like materials have been intensively studied,1 and in the last three years the research focus has been broaden on new layered 2D-materials such as MoS2 and other transition metal dichalcogenides.2-4 Both 1 ACS Paragon Plus Environment


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graphene and MoS2 have been exploited for fabrication of nanostructured electrodes, since they represent ideal candidates for electrochemical supercapacitors because of the superior electrical properties and the high available surface area. Supercapacitors (SCs) are unique devices that bridge the gap between conventional capacitors and rechargeable batteries, thanks to fast charge/discharge capacity, extremely long cycling life, wide range of operating temperatures, lightweight, environmentally friendly and safety. In particular, flexible SCs on polymeric substrates are very appealing for portable, miniaturized, wearable, large-scale electronics applications. Depending on the employed active material, two different charge storage mechanisms can be obtained in a SC. Carbon-based nanomaterials, and in particular graphene, provide the formation of an electrical double-layer distributed on the electrode surface and supply the so-called electrochemical double-layer supercapacitance (EDLC). Metal-oxides5 and metal-sulfide, in particular layered MoS2, contribute to the pseudocapacitance, which originates from faradaic charge transfer mechanisms such as redox reactions occurring between the electrolyte and the electrode active material. Porous structures with highly accessible surface area and optimal electric conductivity are required for efficient EDLC-electrodes. Many synthesis techniques and engineering designs for obtaining graphene 3D architectures have been proposed, from few layers stacks of graphene sheets obtained by exfoliation procedures to graphene aerogels/hydrogels,6 with processes that often require high temperatures or long chemical synthesis routes. The research efforts are, up to date, towards a simple and scalable method for obtaining graphene-based electrodes on flexible and/or wire-shaped substrates (in view of wearable electronics) and with easy patterning procedures (in view of micro-supercapacitors). In this perspective, laser direct writing (LDW) of materials has been significantly developed in recent years as a very powerful tool with highly promising features. The possibility to modify a variety of materials at the nanoscale and using fast production times provides laser direct writing with unique capabilities to produce novel nanostructures and devices. There is a vast range of LDW 2 ACS Paragon Plus Environment

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processes, and in particular we can categorize them into three main classes: i. laser direct write subtraction (LDW-), where material is removed by ablation; ii. laser direct-write modification (LDWM), where material is modified to produce a desired effect; iii. laser direct-write addition (LDW+), where material is added by the laser. The laser irradiation on inexpensive graphene oxide (GO) films has demonstrated to enable the reduction to conducting rGO nanostructures and, at the same time, the patterning of different geometries with micrometric resolution.7 Interesting results have been obtained by laser patterning of free-standing hydrated GO films, reaching specific capacitance values of 2.9 mF/cm2 with sandwiched devices and aqueous Na2SO4 electrolyte.8 More than 100 interdigitated graphene micro-SCs have shown to be obtainable on a single DVD disc using a consumer-grade LightScribe burner on a GO film.9 Recently, Tour and co-workers have demonstrated the production of laser induced graphene (LIG), a porous graphene film with 3D network, by performing pulsed laser irradiation on a commercial polymer, insulating polyimide, and obtaining specific capacitance values of 9 mF/cm2 with solid state electrolyte and planar configuration. 10,11 Looking towards an increase of the specific capacitance, other new nanomaterials have been proposed. In particular MoS2, with a layered structure similar to graphene and electronic properties that can vary from semiconducting to metallic depending on its crystalline phase, has attracted widespread attention for application in SC electrodes. Different electrochemical processes have been suggested to explain the contribution of MoS2 to the SC specific capacitance: Faradaic electron transfer given by the change of oxidation states, ions intercalation between neighboring layers, ions adsorption at the surface with electric double layer formation.6 Taking advantage from the high electrical conductivity and the efficient ion intercalation, exfoliated layers of metallic 1T-MoS2 have been employed in planar SCs with extraordinary capacitances and stability performance.12 With less sophisticated preparation techniques, some examples of hybrid graphene/MoS2 (in the more common semiconducting 3 ACS Paragon Plus Environment


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2H-phase) electrodes for SC have also been recently proposed. Solution exfoliated sheets of both MoS2 and graphene were synthesized and filtered on PVDF to obtain membranes composed by horizontally stacked flakes and symmetrical coin cell SC.13 Using the LIGtechnique, the group of Tour has also reported hydrid MOx-LIG nanostructure and borondoped LIG, by mixing metal-complex precursors into polyimide blends.14,15 The obtained SCs exhibit good performance, with specific capacitance values up to 16 mF/cm2 for the Bodoped LIG electrodes, nevertheless the need of a home-made formulation of the polymer increases the cost and the complexity of the fabrication process. Moreover, the employment of metal-complex for preparing these hybrid materials is not environmentally benign. In this paper, we proposed an alternative solution to the fabrication of hybrid LIG electrode coupling commercial materials, highly simplifying the manufacturing procedure. We deposit by spin-coating a commercial dispersion of MoS2 flakes onto standard polyimide foil. The CO2 laser writing process (LDWM) induces the graphenization of the polymer allowing at the same time MoS2 decoration of the obtained porous graphene network (MoS2-LIG). Highly flexible supercapacitors were fabricated exploiting polymeric electrolyte and the electrochemical characterizations demonstrated an excellent stability, also in bended condition. 2. Results and discussion Figure 1 shows a 3D scheme of the MoS2-LIG fabrication process. The direct laser writing setup described in the experimental section was used to graphenize polyimide substrates. In particular, the set of laser parameters were optimized in order to produce LIG with a porous morphology on large area (from 0.01 up to 50 cm2). The overlapping of the laser spot has been taken into account to produce an homogeneous structure, so a grid hatch was selected and the parameters employed are reported in Table S1.

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Figure 1. 3D scheme of the laser writing process onto MoS2-covered polyimide foil and FESEM images at different magnification showing the morphology of the MoS2-decorated LIG.

In order to increase the specific capacitance, MoS2 dispersion was used to wet the surface of the pristine polyimide foil and left dry before laser writing. Optical measurements (see Figure S2) were conducted in order to verify the success of the coating process. When the modified surface was irradiated by the laser the in-situ decoration of MoS2 nanosheets on the wall of the porous LIG was achieved. The 3D structure of graphenized polyimide and its morphology at the nanoscale were characterized by FESEM. Since the as-prepared samples are electrically conductive (see Figure S7 in the supporting information), no metallic coating was required for electron microscopy. Low-magnification images, such as the one presented in Figure 1, show the porous 3D architecture of the laser written region. A foam-like structure is obtained after laser writing, with micrometric holes generated by the emission of gases during the irradiation process.10,15 High magnification images (bottom right of Figure 1) suggest that the entire structure is composed of agglomerated and wrinkled graphene flakes, which result in a boost of the surface area (see Figure S5 in the supporting information). In fact, the combination of a holey foam-like structure which promotes the impregnation with an electrolyte and nanostructured surface morphology is very promising for supercapacitor applications. 10 5 ACS Paragon Plus Environment


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During FESEM measurements, it was not possible to identify the commercial MoS2 flakes inside the graphene-based structure, since their lateral size (typically 20-100 nanometers) is comparable with the size of carbonized polyimide flakes (see Figure S3 in the supporting information). As will be discussed later, the presence of MoS2 was confirmed by Raman, XPS and TEM analyses. The Raman spectrum of the LIG decorated with MoS2 nanoflakes is reported in Figure 2a. Three main peaks, related with the carbon structure, are clearly visible: the D peak at ~1350 cm-1, related with the reduction in size of in-plane sp2 domains induced by the creation of defects, vacancies or bent sp2 bonds, the G peak at ~1580 cm-1 originated from a first-order inelastic scattering process involving the degenerate iTO and iLO phonons at the G point (E2g mode), and the 2D peak at ~2700 cm-1, related with the second order zone-boundary phonons.

Figure 2. (a) Raman characterization of the LIG-MoS2, showing the main feature of the graphenized structure and (inset) the typical 2H-MoS2 vibration features. High-resolution XPS spectra of C1s (b), S2p (c) and Mo3d/S2s (d) regions of MoS2-decorated LIG sample.


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The intensity ratio between the D and G peaks (ID/IG) is related with the degree of crystallization in the porous structure, and in our case a value of 0.78 indicates the formation of a highly crystallized film. More interestingly, the 2D peak is symmetric and can be fitted with a single Lorentzian profile centered at ~2700 cm-1 with a full width at half maximum of ~80 cm-1, which is a typical feature of highly ordered 2D graphite consisting of randomly stacked graphene layers along the c axis.10 In the inset of Figure 2a a zoom of the spectrum at low wavenumbers evidences the MoS2-related peaks. The two main Raman modes, compatible with the presence of few-layers 2H-MoS2, are the A1g at ~383 cm-1 (due to opposing vibrations of the two S atoms with respect to the Mo atom) and the E2g mode at ~408 cm-1 (related with the in-plane vibration in opposite directions of the Mo and S atoms).16 The intensity of the peaks is very low because of the very low amount of material added for the decoration of the carbon structure. In order to reach a deeper understanding of the chemical composition of the active material, high-resolution XPS spectra were acquired. Due to the high surface sensitivity of XPS (sampling death < 10 nm), this technique is well-suited for the investigation of materials constituted of very thin flakes. At first, survey spectra were acquired in order to identify the different elements present in the sample, yielding immediate confirmation of the presence of MoS2 (Figure S6). In fact, the detected chemical elements were C, O, Mo, S. The absence of N and the atomic concentration ratio C/O = 25.9 were a preliminary confirmation of the successful graphenization of polyimide. Subsequently, high resolution acquisitions of the most significant regions of the photoelectron energy spectrum were performed and they are depicted in Figure 2b-d. Further proof of the conversion of polyimide into few-layer graphene is provided by the analysis of the C 1s region: besides small contribution from peaks associated to bonds between carbon and oxygen, the most important features are the C-C peak 7 ACS Paragon Plus Environment


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at 284.5 eV and the shake-up satellite peak at about 291 eV, which both are distinctive of a graphitic structure.17 The S 2p and Mo 3d/ S 2s regions confirm the presence of MoS 2 flakes: the S 2p doublet at (162.2, 163.3) eV, the Mo3d doublet at (229.3, 232.5) eV and the S 2s peak at (226.7) eV are all typical features of MoS2.13 The broad peak centered around 169 eV in the S 2p region and the Mo 3d doublet at (232.6, 235.8) eV can be ascribed to the presence of molybdenum oxysulfides 18 due to partial oxidation of MoS2.19

Figure 3. (a) Low magnification TEM image of LIG decorated with two MoS2 flakes (highlighted in red). (b) HRTEM image of the edge of a wrinkled LIG flake, showing few-layer features; the inset zooms on the edge. (c) HRTEM image of the largest MoS2 flake shown in (a), with related FFT in the inset.

Further information on the LIG/MoS2 structure was gained by means of transmission electron microscopy. Figure 3a provides a low-magnification view of a LIG region, showing typical wrinkled structure of the graphenized polyimide, in accordance with previously reported results.10 Moreover, MoS2 flakes decorating the LIG can be identified as a consequence of diffraction contrast due to their high crystalline quality. In fact, Fast Fourier Transforms of


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high-resolution images (such as figure 3c and inset), lead to characteristic hexagonally symmetrical spots which can be ascribed to the {100} (d ≈ 2.73Å) and {210} (d ≈ 1.58Å) families of crystallographic planes of the 2H-MoS2 crystal structure. Figure 3b provides a high-resolution image of the edge of a rippled LIG flake, exhibiting few-layer features, with approximately 3.4 Å interlayer distance, characteristic of (002) planes in graphitic materials. In conclusion, the morphological, chemical and structural characterizations prove the successful conversion of polyimide into few-layer graphene with simultaneous decoration with highly-crystalline MoS2 flakes.

Figure 4. Three-electrodes CVs (a) and Nyquist plots (b) of MoS2-LIG sample; two symmetric electrodes CVs in device configuration (c) (in the inset the assembled flexible device is shown); comparison of capacitance vs. scan rate of LIG and MoS2-LIG (d) (in the inset CVs at 10 mV/s are compared), capacitance retention of MoS 2LIG device (e) (in the inset the charge-discharge of LIG and MoS2-LIG samples at 0.25 mA/cm2 are compared) and Ragone plot (f).

Cyclic voltammetry, i-interruption and AC impedance were performed in a three electrode configuration in order to characterize the laser-induced graphene material decorated with MoS2 nanosheets before assembling the device. Figure 4a shows CV curves of MoS2/LIG 9 ACS Paragon Plus Environment


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measured at various scan rates from 10 mV s-1 to 1 mV s-1. The pictured box-like rectangular curves without any remarkable Faradaic redox peak are consistent with the electrochemical double-layer energy storage mechanism of the graphene-like and the pseudo-capacitance of the MoS2.12 The uncompensated resistance at the working electrode was measured by both iinterruption and EIS with an average Ru of 480 Ω and 505 Ω, respectively. From EIS measurements (see Figure 4b), the normalized equilibrium series resistance (ESR) at 1 kHz was evaluated to be equal to 102 Ω. Bode plots (Figure S8 in the Supporting Information) suggest the transition frequency between the transmission line (45 degree) and capacitive behavior (90 degree) to be around 1 Hz. Because of the large uncompensated resistance, the potential window in the two electrode symmetric device was increased to 1 V. The cyclic voltammetry measurements in device configuration with two symmetric LIGMoS2 electrodes with a solid PVP-based electrolyte are reported in Figure 4c (while for comparison purposes the measurements for the device with bare LIG electrodes in the same experimental conditions are collected in Figure S9 of the Supporting Information). A slightly more resistive profile is obtained in the assembled device because of the lower conduction properties of the ionic mediator with respect to the liquid electrolyte. The capacitance values estimated by voltammetric scans for the supercapacitor made with LIG-MoS2 are provided for different scan rates and compared to those calculated from bare LIG symmetrical devices under the same conditions (Figure 4d). The inset of the latter figure shows the comparison of the voltammograms in the two devices at 10 mV s-1, giving evidence to the great contribution from the pseudo-capacitance associated with MoS2 decoration of the graphene-based electrode. Galvanostatic charge-discharge cycles are presented as inset of Figure 4e, which are

consistent

with

capacitive

behavior

clearly

seen

in

the

linearity

of

the

chronopotentiograms. We also measured the long cycle life of as-prepared flexible supercapacitors with and without mechanical deformation. From this galvanostatic


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experiment, it is possible to state that the devices own a very good cyclability with almost invariant capacitance retention over 2000 cycles (Figure 4e). Because of the remarkable lightness of the active material (LIG or LIG/MoS2) under investigation and of the difficulty to completely remove the material from the polymeric substrate (proving excellent adhesion of the active material), all the capacitances are normalized with respect to the geometrical area. For a given scan rate, the specific energy (E; Wh/cm2) of the device was determined by using 1 E  CV 2 2

where C is the specific capacitance modified to be in units of Ah/cm2, and V is the potential window employed (V). Specific power (P; W/ cm2) was determined using the expression: P  Et 1

where E is the specific energy (Wh/ cm2), and t is the duration of the discharge half cycle in the voltammogram (h). The calculation of specific energy and power is shown in Figure 4f (Ragone diagram) where the comparison of this flexible device with other stretchable devices are presented.20-25



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Figure 5. CVs recorded at 1V/s (a) and plot of the capacitance retention (b) varying the bending radius.

In order to evaluate the strength of MoS2-LIG supercapacitors for the use as flexible energy storage, the device was placed under mechanical deformation at various bending radius and its performance was investigated. Figure 5a shows the CV curves in different bending condition (digital photographs of the different bending states are reported as inset in Figure 5b) for the assembled flexible devices. As shown in Figure 5b, the specific capacitance seems to be independent upon the bending radius with only a slight reduction in the highly bent state. The above results clearly reveal that MoS2-LIG exhibits significantly improved electrochemical energy storage performance if compared with previously reported LIG-based supercapacitors. Moreover the proposed fabrication approach shows better potentialities for practical applications thanks to optimized process parameters: higher power (6 W compared to 4.8 W)10,11,14 and faster scar rate (500 mm/s compared to 90mm/s) 10,11,14 inevitably leads to higher throughput and lower production cost. 12 ACS Paragon Plus Environment

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Figure 6. Charge profile of MoS2-LIG supercapacitor using one and two DSCs as energy conversion device (a) and photographs of the motor used as demonstrator (b). The sketch of the used circuit is reported as inset of panel a).

The integration of energy harvesting and storage systems is awakening even more interest. Indeed, the supercapacitors must not only drive loads but be capable of storing efficiently the energy produced by various energy sources which, if renewable, appears to be inherently intermittent. Energy storage technologies have the potentialities to offset the intermittency problem of renewable energy sources by storing the generated intermittent energy and then making it accessible upon demand. Among current renewable energy sources, solar energy is the cleanest and most abundant source but obviously subjected to fluctuations depending on geographical location, day cycle and weather conditions. In order to demonstrate the effective integration of supercapacitors with distributed renewable energy source, photovoltaic cells were coupled to the here presented MoS2-LIG -based storage devices. Dye-sensitized solar cells (DSCs) were selected among third generation photovoltaics since they are a promising 13 ACS Paragon Plus Environment


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alternative to silicon based solar cells, with relatively high light-to-energy conversion efficiency and low production costs.26 The major benefits lie in the materials and the technologies needed for DSCs production, such as low temperature and atmospheric pressure based manufacturing processes, making them compatible with roll-to-roll mass production. More details on DSCs fabrication and characterization can be found in the Electronic Supporting Information (ESI) and in previous work.27 A switchable stand-alone self-powered system consisting of DSCs (one or two in series), a supercapacitor, and a fan motor (“demonstration electric motor”, Solaronix) is schematically illustrated in the inset of Figure 6a. When a small LED lamp (3W power) is switched on, the DSCs convert light energy and stored it into the supercapacitor. After 140 s charging under the illumination, the voltage of supercapacitor reaches about 1.3 V (Figure 6a). When the illumination source was turned off the charged supercapacitor could power the fan motor (Figure 6b) for a time period depending on the DSCs configuration used (several seconds for one DSC, tens of second for the two DSC in series) demonstrating the effective integration of DSC and supercapacitors as self-powered system to harvest solar energy and drive small electrical devices.

3. Conclusion In summary, this study demonstrated the design of flexible thin film supercapacitor devices with high performance and simple manufacturing process. The direct laser writing of MoS 2coated polyimide foils provides an amazingly simple strategy for addressing the key challenges that usually limit the large-scale application of graphene-based materials and other 2D materials (or, as in this case, the combination of the two categories). The micro and nanostructuration of the LIG allow the high-rate transportation of electrolyte ions and electrons throughout the electrode network while the in-situ decoration with MoS2 flakes permits the comprehensive utilization of pseudo and double-layer capacitance, resulting in excellent 14 ACS Paragon Plus Environment

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electrochemical performances. Moreover the obtained material represents flexible and binderfree electrodes for highly flexible supercapacitors in which the current collector and the active element are joined in the same polymeric substrate without further processing. By taking advantage of all these unique properties we have demonstrated that MoS2-LIG can be considered a promising electrode for flexible supercapacitors with high capacity, excellent rate capability, and long-term stability.

4. Experimental Section 4.1 Laser writing. The electrodes were fabricated using a micromachining system produced by Microla Optoelectronics srl equipped with a CO2 pulsed laser working at 10.6 m wavelength, with tunable process parameters (power, frequency and scan speed). In particular the operating laser ranges are reported in Table S2, while the laser system composed by beam expander (2X), and galvanometric scanner with a focusing objective of 100 mm is sketched in Figure S1 in the supporting information. In order to obtain a film on the polymeric substrate 2 ml of molybdenum disulfide (MoS2) flakes dispersion (Graphene Supermarket, concentration 18 mg/L in ethanol/water solution) was mixed with 1 ml of nonionic surfactant (Triton™ X-100, Sigma-Aldrich) and spin-coated (3000 rpm for 60 sec) on commercial polyimide foil. MoS2-coated polyimide sample was tape-fixed in the working area, to avoid thermal deformation during laser process. Direct laser writing parameters are summarized in Table S2. 4.2 Device assembly. The as-prepared electrodes were coated with a Polyvinylpyrrolidone (PVP, Sigma Aldrich) gel electrolyte (1 M of NaCl in water) and heated at 70 °C for 5 minutes to allow partial solidification of the polymeric electrolyte. After cooling, electrodes were assembled in



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symmetric planar configuration and heated again at 70 °C for other 5 minutes. As a comparison, devices with bare LIG layer were assembled following the same procedure. 4.3 Characterizations. The morphology of the MoS2-decorated LIG samples was investigated by means of Field Emission Scanning Electron Microscopy (FESEM) with a Zeiss Supra 40 microscope. Raman spectroscopy was performed by means of a Renishaw inVia Reflex micro-Raman spectrophotometer, equipped with a cooled CCD camera. Samples were excited with an ArKr laser source with a wavelength of 514.5 nm. X-ray photoelectron spectroscopy (XPS) was carried out using a PHI 5000 Versaprobe scanning X-ray photoelectron spectrometer (monochromatic Al K-alpha X-ray source with 1486.6 eV energy) in order to investigate the chemical composition. Survey and highresolution (HR) spectra were acquired on 500 × 500 µm2 regions. Different pass energy values were employed: 187.85 eV for survey spectra and 23.5 eV for HR acquisitions. Charge neutralization was achieved using combined electron and ion gun neutralizers. Spectra were analyzed using Multipak 9.6 and CasaXPS softwares. All core-level peak energies were referenced to C1s peak at 284.5 eV (C-C/C-H bonds) and the background contribution in HR scans was subtracted by means of a Shirley function (Shirley DA. High-Resolution X-Ray Photoemission Spectrum of the Valence Bands of Gold. Physical Review B 1972; 5: 47094714). TEM characterization was performed with a FEI Tecnai G2 F20 S-TWIN microscope operated at 200kV acceleration voltage. Concerning sample preparation, a portion of the LIG/MoS2 sample was detached by brief sonication into ethanol and subsequently transferred to a holey-carbon TEM grid. Optical absorbance and transmittance spectra were measured by a PerkinElmer LAMBDA 35 spectrophotometer in the light wavelengths range 200-1000 nm. Current-voltage curves were recorded through a Keithley 2440 source measure unit. 16 ACS Paragon Plus Environment

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Three electrodes cell measurements were carried out with a Metrohm Autolab PGSTAT128 potentiostat/galvanostat in 1 M NaCl solution deaerated with nitrogen, a SMSE homemade reference electrode (680 mV vs. SHE) and a platinum bar as counter electrode. Cyclic voltammetry was performed between -1.4 V and -0.5 V at multiple scan rates and electrochemical impedance spectroscopy at OCP in the frequency range from 10 kHz to 5 mHz with 5 mV amplitude. Experiments in device configuration (e.g. two symmetrical electrodes) were carried out with a quasi-solid electrolyte (PVP charged with 1 M NaCl in water), using the Metrohm both for CV and galvanostatic charge-discharge.

Supporting Information Supporting Information is available from the ACS Online Library or from the author. Additional experimental details, optical UV-Vis spectra, additional FESEM images, additional XPS measurements, additional electrical and electrochemical measurements, DSC fabrication and characterization details.

Acknowledgements Authors would like to acknowledge Microla Optoelectronics srl (www.micro-la.com) for the support in laser ablation processes and Center for Space Human Robotics (IIT@PoliTO) for the TEM facility.

References (1) Stoller, M. D.; Park, S.; Zhu, Y.; An, J. Graphene-Based Ultracapacitors, Nano Lett. 2008, 8, 3498-3502. (2) Gao, M. R.; Xu, Y. F.; Jiang, J.; Yu, S. H. Nanostructured Metal Chalcogenides: Synthesis, Modification, and Applications in Energy Conversion and Storage Devices, Chem. Soc. Rev. 2013, 42, 2986-3017. 17 ACS Paragon Plus Environment


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In situ MoS2 Decoration of Laser-Induced Graphene as Flexible

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