Designing 3D Multihierarchical Heteronanostructures for High

Subscriber access provided by - Access paid by the | UCSB Libraries

Article

Designing 3D multi-hierarchical hetero-nanostructures for high performance on-chip hybrid supercapacitors: PEDOT-coated diamond/silicon nanowire electrodes in aprotic ionic liquid David Aradilla, Fang Gao, Georgia Lewes Malandrakis, Wolfgang Müller-Sebert, Pascal Gentile, Maxime Boniface, Dmitry Aldakov, Boyan Iliev, Thomas J. S. Schubert, Christoph E. Nebel, and Gérard Marie Bidan ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.6b04816 • Publication Date (Web): 27 Jun 2016 Downloaded from http://pubs.acs.org on July 1, 2016

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

ACS Applied Materials & Interfaces is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 28

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

ACS Applied Materials & Interfaces

Designing 3D multi-hierarchical heteronanostructures for high performance on-chip hybrid supercapacitors: PEDOT-coated diamond/silicon nanowire electrodes in aprotic ionic liquid David Aradilla,*a,b,c Fang Gao,*d Georgia Lewes-Malandrakis,d Wolfgang Müller-Sebert,d Pascal Gentile,e,f Maxime Boniface,e,f Dmitry Aldakov,a,b,c Boyan Iliev,g Thomas J. S. Schubert,g Christoph E. Nebeld and Gérard Bidana,b,c a

Univ. Grenoble Alpes, INAC-SPRAM, F-38000 Grenoble, France b

c

d

CNRS, SPRAM, F-38000 Grenoble, France

CEA, INAC-SPRAM, F-38000 Grenoble, France

Fraunhofer-Institute for Applied Solid State Physics (IAF), Tullastraβe 72, DE79108 Freiburg, Germany e

Univ. Grenoble Alpes, INAC-SP2M, F-38000 Grenoble, France f

g

CEA, INAC-SP2M, F-38000 Grenoble, France

IOLITEC Ionic Liquids Technologies GmbH, Salzstrasse 184, 74076 Heilbronn, Germany *Corresponding author: [email protected] and [email protected]

ACS Paragon Plus Environment


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

Abstract A versatile and robust hierarchically multi-functionalized nanostructured material made of poly(3,4-ethylenedioxythiophene) (PEDOT)-coated diamond@silicon nanowires has been demonstrated to be an excellent capacitive electrode for supercapacitor devices. Thus, the electrochemical deposition of nanometric PEDOT films on diamond-coated SiNW electrodes using PYR13 TFSI ionic liquid displayed a specific capacitance value of 140 Fg-1 at a scan rate of 1 mVs-1. The as-grown functionalized electrodes were evaluated in a symmetric planar micro-supercapacitor using butyltrimethylammonium bis(trifluoromethylsulfonyl)imide (N1114 TFSI) aprotic ionic liquid as electrolyte. The device exhibited an extraordinary energy and power density values of 26 mJ cm-2 and 1.3 mW cm-2 within a large voltage cell of 2.5 V respectively. In addition, the system was able to retain 80% of its initial capacitance after 15 000 galvanostatic charge-discharge cycles at a high current density of 1 mA cm2

maintaining a coulombic efficiency around 100 %. Therefore, this multi-functionalized

hybrid device represents one of the best electrochemical performances concerning coated SiNW electrodes for high energy advanced on chip supercapacitor. Keywords: supercapacitors, diamond, conducting polymers, silicon nanowires, ionic liquids.


Page 2 of 28

Page 3 of 28

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


Introduction The advent of innovative miniaturized portable devices in a wide range of technological applications from aeronautics to biomedicine, as for example wireless micro-sensors or biomedical implants, has aroused an enormous interest in the field of energy storage devices. Technical specifications of such micro-devices require high performance small dimension sources concerning both volumetric power and energy densities as well as a long lifetime and excellent compatibility with the microelectronics industry.1 From this point of view, the research of energy storage micro-systems, as for example supercapacitors based on innovative nanostructured materials, results from vital importance in order to accomplish these commitments.2,3 During the last decade, intensive efforts have been devoted to the development of supercapacitors using nanostructured carbonaceous material electrodes. Thereby, micro-supercapacitor (MSC) devices based on onion-like carbon,4 carbide-derived carbon,5,6 carbon nanotubes,7,8 porous carbon,9-11 graphene,12-14 carbon nanoparticles15 or diamond foams16 have exhibited excellent capacitive properties in this field. Nevertheless, in spite of these promising results, the need of finding reliable solutions concerning their on-chip integration, minituarization and high electrochemical performance limits nowadays their use in commercial applications. Consequently, the investigation of high performance innovative nanostructured materials remains still a big challenge for our society. Within this context, over the past years silicon nanowires (SiNWs)17-20 and derivatives (e.g. silicon carbide nanowires, SiCNWs),21-23 as innovative and attractive 1D nanomaterials, have attracted a great deal of attention in the field of MSC devices. More specifically, MSCs based on SiNW electrodes have demonstrated interesting properties in terms of wide operating cell voltage (4V), high maximal power density (225 mW cm-2), extraordinary cycling stability (millions of galvanostatic cycles) and ultra-fast discharge rate (ms) using ionic liquid electrolytes (PYR13 TFSI or EMIM TFSI),17,18 demonstrating an enormous potential for the employment as high performance micro-power sources. Recently, we have reported several strategies to improve the capacitive properties of SiNW electrodes by means of (i) supernanostructuration (e.g. nanoforest of hyperbranched SiNWs, known commonly as silicon nanotrees, SiNTrs)24 and (ii) functionalization of SiNWs using the deposition of electroactive thin film coatings.25-27 Precisely, the functionalization of SiNWs by using pseudo-capacitive or electrochemical double layer materials, as for example conducting



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

polymers (PEDOT and PPy),25,26 transition metal oxides (MnO2 and NiO),27,28 or carbonaceous materials (porous carbon, graphitic carbon, crystalline diamond),29-32 have emerged as promising alternatives to enhance the electrochemical performances of supercapacitors in terms of energy and power densities maintaining an outstanding cycling stability. In this regard, the exploration of diamond, as a robust electroactive nanostructured carbonaceous material, has also attracted a great interest in the field of supercapacitor devices due to its interesting properties at energy storage and electrochemical level.33,34 Accordingly, we have recently reported the synergistic effect of diamond deposited on SiNW to be employed as supercapacitor electrode.31,32 Thus, MSCs based on diamond-coated SiNW electrodes exhibited a high areal capacitance (AC) and power density values of 1.5 mF cm-2 and 25 mW cm-2 within a wide cell voltage of 4V respectively.32 These values were clearly enhanced compared to our previous MSCs based on CVD-grown SiNWs (AC: 0.023 – 0.050 mF cm-2),17-20 or SiNTrs (AC: 0.058 mF cm-2),24 reflecting the enormous potential of diamond coating for SiNWs-based MSC devices. To the best of our knowledge, scarce works have been reported dealing with the functionalization of diamond using pseudo-capacitive materials for supercapacitor applications, which provided an improvement of capacitive properties owing to their faradaic reactions involved during the charge-discharge process.35-37 In this study, we have elaborated a novel 3-D hierarchical hetero-nanostructure composed of an electroactive conducting polymer (PEDOT), boron-doped crystalline diamond and SiNWs (hereafter denoted as PEDOT-D@SiNWs) to be employed as electrodes in a symmetric micro-supercapacitor device. The hybrid electrode was characterized by scanning electron microscopy (SEM), high resolution scanningtransmission electron microscopy (HRSTEM) equipped with EDX analysis and X-ray photoelectron spectroscopy (XPS) techniques. Subsequently, the electrochemical performance of the hybrid device exhibited excellent values of power and energy densities, as well as a remarkable cycling stability. On the basis of the obtained results, this strategy opens up a new dimension on the exploration of innovative multihierarchical nanostructured materials for supercapacitor applications.


Page 4 of 28

Page 5 of 28

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


Experimental section Materials and reagents. Highly p-doped Si (111) substrates (doping level: 5·1018 doping atoms cm-3) and resistivity less than 0.005 Ω cm were used as the substrate for SiNW growth. 3,4-ethylenedioxythiophene, ferrocene and silver trifluoromethanesulfonate were purchased from Sigma-Aldrich. Both N-methyl-Npropylpyrrolidinium bis(trifluoromethylsulfonyl)imide and butyltrimethylammonium bis(trifluoromethylsulfonyl)imide were purchased from IOLITEC (Ionic Liquids Technologies GmbH, Germany)

and used without further purification. The water

content of ionic liquids was determined by Karl-Fischer titration (88 and 42 ppm respectively). Growth of SiNWs and deposition of diamond. Highly doped SiNW electrodes and deposition of diamond on SiNWs were carried out by CVD and microwave enhanced CVD according to our works reported previously.38,31,32 Electropolymerization of EDOT on diamond-coated SiNWs. PEDOT was electropolymerized by means of a 3-electrode cell configuration using the same electrochemical conditions reported in our recent works.25,26 The mass of PEDOT deposited on the electrode was found to be 0.31 mg by substracting the difference before and after electrodeposition using a METLER balance with a 0.01 mg precision. Morphological characterization. The morphology of the resulting hybrid diamond-coated SiNW electrodes was examined by using a ZEISS Ultra 55 scanning electron microscope operating at an accelerating voltage of 10 kV and 4kV respectively. Energy dispersive X-ray spectroscopy (EDX) and high resolution scanning-TEM (HRSTEM) measurements were done in a probe-corrected Titan Themis TEM equipped with 4 superX EDX detectors at 200kV. HRSTEM measurements were then performed with a high-angle annular dark field detector (HAADF), 60 pA of beam current and a convergence semi-angle of 18.1 mrad. This was increased to 300 pA for EDX measurements in order to improve the signal on noise ratio (SNR) for hypermaps acquisition. Samples were prepared by drop-casting an extremely dilute dispersion of nanowires scratched from their substrate in ethanol onto lacey carbon-coated copper mesh grids. XPS analysis was carried out with a Versa Probe II spectrometer (ULVACPHI) equipped with a monochromated Al Kα source (hν = 1486.6 eV). The core level peaks were recorded with constant pass energy of 23.3 eV and 100 µm beam. The XPS



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

Page 6 of 28

spectra were fitted with CasaXPS software using Shirley background and a combination of Gaussian (70%) and Lorentzian (30%) distributions. Electrochemical

characterization

and

performance

of

the

micro-

supercapacitor device. The electrochemical characterization of a single hybrid electrode (PEDOT-coated D@SiNWs) was evaluated by cyclic voltammetry (CV) curves in a 3-electrode configuration using a non-aqueous Ag/Ag+ reference electrode and Pt foil as a counter electrode. The CV curves were calibrated using the ferrocene/ferrocenium (Fc/Fc+) redox couple. The half-wave potential of the Fc/Fc+ was evaluated using the following relation: E1/2, Fc,Fc+ = (Eap + Ecp)/2, where Eap and Ecp are the anodic and cathodic peak potentials at a scan rate of 20 mVs-1 using Pt as working and counter electrode in PYR13 TFSI solution. The half-wave potential value was found to be -381 mV related to Ag/Ag+ reference electrode.39 The specific capacitance (Cs) was calculated using the following equation: Cs=Q/(∆Vm), where Q is the average voltammetric charge, which is determined by integrating either the oxidative and reduction scans of the corresponding CV curve, ∆V is the potential range and m is the polymer mass on the electrode. Symmetric micro-supercapacitors were designed from hybrid electrodes made of PEDOT-coated D@SiNWs (1 cm2) using a 2-electrode cell configuration.25,26 The electrochemical techniques employed in this study were carried out by using a multichannel VMP3 potentiostat/galvanostat with Ec-Lab software (Biologic, France). All measurements were carried out using N1114 TFSI as electrolyte in an argon-filled glove box with oxygen and water levels less than 1 ppm at room temperature. The AC values of the device were calculated from the charge-discharge curves using the following equation AC = i/A(dV/dt), where the i is the discharge current, A is the area of the electrode and dV/dt corresponds to the slope of discharging curve. The energy density (E) and power density (P) values were calculated by using E=0.5AC(∆V)2 and P=E/t, where t is the total time of discharge. Coulombic efficiency (η) was evaluated as the ratio between the discharging and charging time (η = td /tc).


Page 7 of 28

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


Results and discussion Figure 1 illustrates a schematic representation for the elaboration of PEDOTD@SiNW electrodes employing different electrochemical and chemical vapor deposition techniques, such as potentiostatic and microwave enhanced chemical vapor deposition (MWCVD) methods. These procedures allow us to design and tune multihierarchical hetero-nanostructures with conformal polymer and carbonaceous nanometric coatings. The morphology of different nanostructured materials was examined by SEM and HR-STEM techniques. Thereby, Figure 2 shows the surface of SiNWs, diamond-coated SiNWs and PEDOT-coated on diamond/SiNWs examined by SEM. Figure 2a displays the SEM image corresponding to SiNWs grown by CVD on highly doped Si substrates, which were already studied and characterized in our previous work.40 Thus, the length of SiNWs was approximately 50 µm with a diameter range between 20 and 200 nm. Additionally, a high density of SiNWs (3·109 NWs per cm2) was calculated. The diamond coating by MWCVD was deposited uniformly and homogeneously along all the SiNWs with granular type morphology, which varies from tens of nanometers to approximately 150 nm (Fig. 2b). This morphological analysis was found identical to our recently reported studies.31,32 Finally, the structure of PEDOT onto diamond-coated SiNWs can be observed by low and high magnification SEM images. Accordingly, Figure 2c reflects the morphology of PEDOT deposited electrochemically at a constant voltage of 0.4V under a polymerization charge of 750 mC cm-2. As can be seen, diamond-coated SiNWs were covered by adherent, uniform and homogeneous thin PEDOT films having globular morphology. The thickness of the polymer on a PEDOT-D@SiNW is ~100 nm as seen on a cross-sectional view (Figure 2d). This thickness value is close to that of the diamond coating on SiNW surface according to the inset in Figure 2d, which was corroborated in our previous work.32 STEM EDX mapping and XPS techniques are useful tools to determine composition of materials and chemical bondings. Particularly, these techniques were employed to verify and identify the nature of the respective nanostructured materials in this work. Figure 3 shows a HRSTEM image and STEM-EDX elemental analysis of S, C and Si, which are attributed as distinguishable elements for PEDOT (S), diamond (C) and SiNWs (Si) respectively. As it can be seen, PEDOT and diamond conformal coatings were deposited on SiNWs with a hierarchical structure (Figure 3a and 3b), which is in excellent agreement with the SEM micrographs reported in Figure 2.



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

Further, a XPS analysis was carried out only for the polymer coating since the diamond coating was characterized by Raman spectroscopy previously.31 High resolution XPS spectra of C1s and S2p corresponding to polymer are analyzed in Figure 3c and Figure 3d. The C1s XPS spectrum of PEDOT indicates the presence of four types of carbon bonds, which correspond to carbons C-C (284.3 eV), C-S (286.1 eV), C-O-C (287.8 eV) and -CF3 bonds (292.2 eV). The first three peaks correspond to the thiophene ring whereas the last peak is ascribed to the TFSI- doping anion incorporated as counterion in the polymer backbone during the electro-polymerization process.41,42 For the S2p spectra (Figure 3d), three components were attributed to both the thiophene ring and the anion spin split sulphur couplings. Thus, the corresponding contributions were found at S2p3/2 (~ 163.7 eV), S2p1/2 (~164.4 eV), 164.8 and 165.5 eV respectively, whereas the peak at 168.2 eV corresponds to the TFSI anion.42,43 On the basis of these results, the electrochemical deposition of PEDOT on diamond-coated SiNWs was successfully confirmed. The capacitive response of PEDOT-D@SiNWs was evaluated in a standard 3electrode cell configuration using the CV technique. Figure 4a shows the CV curves at different scan rates from 1 to 20 mVs-1 within the potential window -1.80 to 0.20 V vs Fc/Fc+. The plots show the presence of faradaic peaks indicating a pseudo-capacitive behaviour associated with the polymer coating. More specifically, the observed redox couple corresponds to the oxidation-reduction reactions of PEDOT, which are ascribed mainly to the de-intercalation and intercalation of anions into the polymeric structure. At the same time, it is worth noting that the incorporation of cations on polymeric structures plays also an important role during the post-polymerization CV curves. Thus, adsorption EMIM+ or phosphonium cations on PPy+ TFSI- was evidenced by means of XPS and NRM analysis.44,45 In this direction, SiNTrs, SiNWs and diamond-coated SiNWs electrodes exhibited almost rectangular and symmetric CV curve shapes, implying a response of the pure electrochemical double layer capacitor (EDLC) associated with non-faradaic reactions.18,32 The electrochemical response of both PPycoated SiNTr (pseudo-capacitive) and SiNTr (EDLC) systems corroborated this tendency in our recent work.26 As a consequence, the contribution of capacitance provided by the electrode was attributed mainly to the PEDOT coating on the diamondcoated SiNW surface. The specific capacitance of the electrode as a function of scan rate is displayed in Figure 4b. The plot depicts the decrease of specific capacitance as the scan rate increases, thus, the value of this property decreased from 140 Fg-1 at 1


Page 8 of 28

Page 9 of 28

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


mVs-1 to 24 Fg-1 at 200 mVs-1, which can be justified by the slow diffusion of electrolyte ions at high scan rates. This suggests that, the faradaic reactions of ion insertion-disinsertion are involved in time dependent process. The CV technique was used to evaluate the electrochemical performance of the symmetric MSC device using various scan rates from 5 mVs-1 to 800 mVs-1. We compare the CV curves at low scan rates varying from 5 mVs-1 to 50 mVs-1 (Fig. 4c) and higher scan rates from 200 mVs-1 to 800 mVs-1 (Fig. 4d). At low scan rates, the device exhibits CV curves slightly distorted because of pseudo-capacitive behaviour induced by the PEDOT coating. Interestingly, the presence of two redox peak pairs can be observed, which are associated to the two hybrid electrodes placed in the symmetric configuration cell. Figure 4d presents CV curve shapes with a different capacitive behaviour specifically at scan rates above 0.4 Vs-1. In this specific case, titled CV curves evidence a resistive-like behaviour associated with the low diffusion of the electrolyte ions to the electrode surface, which was evidenced for PEDOT-coated SiNW MSCs.25 Nevertheless, it should be noted that the system exhibits a good electrochemical performance even at large scan rates according to the pseudo-capacitive behaviour of the material. The electrochemical performance characteristics of the device were also examined by galvanostatic charge-discharge cycles at different current densities ranging from 0.1 to 2 mA cm-2 as demonstrated in Figure 5a. The charge-discharge cycles behave as almost symmetric and triangular profiles (not ideal straight lines) with a small distortion, which confirms the pseudo-capacitive behaviour of the device. Moreover, the plots reflect good charge-discharge reversibility as well as a low ohmic drop. Figure 5b presents the areal capacitance calculated from discharging galvanostatic cycles depicted in Figure 5a. The device exhibits an areal capacitance of 9.5 mF cm-2 at a current density of 0.1 mA cm-2, which decreased down to 8.5 mF cm-2 at a current density of 1 mA cm-2. These values were found similar to our recently reported pioneer works concerning functionalized SiNWs- MSC based on pseudocapacitive materials, such as PEDOT/SiNWs (8 mF cm-2),25 PPy/SiNWs (10 mF cm-2),26 PPy/SiNTrs (14 mF cm-2),26 or MnO2/SiNWs (6 mF cm-2)27 evaluated at the same current density of 1 mA cm-2. It is worth noting that the obtained SC value in this study was also compared to EDL MSC based on nanostructured carbonaceous materials. Within this context, on-chip microsupercapacitors based on onion-like carbon, carbide derived carbon films, multi-walled carbon nanotubes (MWNTs) or graphene exhibited a SC value ranged from 1 up to 3 mF cm-2, respectively.4,6,8,13 Electrochemical impedance spectroscopy (EIS) is a



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

powerful technique to analyze the electrode-electrolyte interface and capacitive properties of supercapacitors. Figure 5c shows the Nyquist plot of the device over a frequency range from 400 kHz to 10 mHz at open circuit potential. As can be seen, a semi-arc and a straight line shapes were obtained from the EIS data. The intersection of the Nyquist plot at the x-axis indicates the equivalent series resistance (ESR). The ESR value is associated to the combination of the ionic resistance of the electrolyte, the intrinsic resistance of the active materials and the contact resistance at the active material/ current collector interface. A ESR value of approximately 47 Ω cm2 was estimated. At high frequencies, the semi-circle corresponds to the charge transfer resistance (Rct) associated to faradaic reactions induced by the polymer coating (Inset 5c1). The straight line in the low frequency region corresponds to the ion diffusioncontrolled region, where a capacitive behavior is represented. The tendency displayed in Figure 5c was corroborated in our previous work concerning vertically oriented graphene nanosheet-based MSC.13 The near straight line at low frequencies indicates a typical capacitive behavior.25,26 The inset of figure 5c (5c2) displays the evolution of C'' versus frequency for the micro-supercapacitor to calculate the relaxation time constant of the device (τo).46 This parameter is defined as the minimum time needed to discharge all the energy from the device with an efficiency of more than 50%. From the inset displayed in Figure 5c, the relaxation time constant was calculated to be 4s using the following relation (τo = 1/f). This value demonstrates great potential to deliver high energy at relative short times regarding the pseudo-capacitive behaviour of this system.2 The energy (E) and power (P) densities are important capacitive characteristics to define the electrochemical performance of a MSC. More specifically, E and P densities of our device were plotted in a Ragone plot. As expected according to Figure 5c, as the current density increases the energy slightly decreases whereas the power density increases rapidly. Thus, the E and P densities of our device ranging from 29 to 25 mJ cm-2 and from 0.1 to 3 mW cm-2 at current densities varying of 0.1 - 2 mA cm-2 respectively. Figure 5d presents also the state-of-the-art compared to our recent works dealing with MSCs based on ECP-coated SiNW electrodes. More specifically, the energy density was clearly enhanced compared to PEDOT-coated SiNW (E: 9 mJ cm-2) PPy-coated SiNW (E: 11 mJ cm-2) and PPy-coated SiNTr (E: 15 mJ cm-2) MSCs.25,26 In this way, the capacitive properties of this hybrid device were also compared to other works reported in the literature using functionalized SiNWs and SiNWs-based MSCs (Table 1). Therefore, this study proves that the deposition of PEDOT thin films on diamond-


Page 10 of 28

Page 11 of 28

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


coated SiNW electrodes implies an optimal strategy in order to achieve high energy and power density SiNW-based MSCs. Furthermore, a wide and stable operating cell voltage at 2.5 V was reached in this work, demonstrating the potential of diamond due to its chemical inertness, high overvoltage and very wide electrochemical windows as well as the excellent performance of N1114 TFSI as electrolyte in MSCs. Another important key factor affecting the capacitive properties of a microsupercapacitor concerns its lifetime. In this study, the cycling stability was determined by applying successive galvanostatic charge-discharge cycles at a current density of 1 mA cm-2 using an electrochemical window of 2.5 V. Figure 6a displays the specific capacitance variation as a function of number of cycles. As it can be seen, the device was able to retain 80% of its initial SC value after 15 000 complete galvanostatic cycles with an excellent coulombic efficiency (~100%), evidencing its high degree of reversibility (Figure 6b). The excellent electrochemical stability reported in this work was compared to other MSCs concerning ECP, oxides and carbon –coated SiNWs (Table 1). The results show that MSCs based on PEDOT-D@SiNW electrodes exhibit one of the best electrochemical stabilities at a wide cell voltage of 2.5V. The stability was also found higher than other MSC based on PPy/C-MEMS (loss of 56% after 1000 cycles),51 PPy shell@3-D Ni metal core (loss of 20% after 5000 cycles),52 or PEDOT:PSS/MnO2/PEDOT (loss of 10% after 5500 cycles) electrodes.53 The morphology of the electrodes after examined by SEM (Figure 6b) revealed that, the hetero-nanostructure of the multi-functionalized electrode remained unchanged even after cycling test presenting an excellent structural stability, comparable to those observed in Figure 2d.

Conclusions In this work, the design of an innovative 3D hierarchical heterostructure electrode composed by electrochemically deposited PEDOT on diamond-coated SiNWs has been successfully demonstrated. The elaboration of such novel hybrid electrode allowed us to address its functionality towards the field of electrochemical energy storage devices. More specifically, the excellent performance of a symmetric microsupercapacitor based on PEDOT-coated D@SiNWs was evaluated by means of EIS, CV, galvanostatic charge-discharge cycles at a voltage window of 2.5 V. The device was able to deliver a high areal capacitance (8.5 mF cm-2), energy (26 mJ cm-2) and power (1.3 mW cm-2) density values with an outstanding cycling stability (15 000



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

cycles) taking into account the pseudo-capacitive behaviour of the electrode. This performance was compared to our previous results dealing with ECP-coated SiNWbased MSC, which demonstrates the important progress carried out in this study to enhance one of the most important drawbacks of a supercapacitor, the energy density. Consequently, we can conclude that the strategy described in this work reflects the enormous potential of PEDOT-D@SiNW electrodes, as an advanced 3D hierarchically multi-functionalized nanostructured material, to be integrated in the next years as a micro power-energy source in consumer micro-electronic devices.

Acknowledgments The authors acknowledge D. Gaboriau for the preparation of Si substrates. This project has received funding from the European Union's Seventh Program for Research, Technological Development and Demonstration under Grant agreement no. 309143 (NEST Project, 2012 - 2016). This work has been performed with the use of the Hybriden facility at CEA-Grenoble (France).


Page 12 of 28

Page 13 of 28

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


References (1) Meng, C.; Maeng, J.; John, S. W. M.; Irazoqui, P. P. Ultrasmall Integrated 3D Micro-supercapacitors Solve Energy Storage for Miniature Devices. Adv. Energy Mater. 2014, 4, 1301269. (2) Beidaghi, M.; Gogotsi, Y. Capacitive Energy Storage in Micro-scale Devices: Recent Advances in Design and Fabrication of Micro-supercapacitors. Energy Environ. Sci. 2014, 7, 867 - 884. (3) Tyagi. A.; Tripathi, K. M.; Gupta, R. K. Recent Progress in Micro-scale Energy Storage Devices and Future Aspects. J. Mater. Chem. A 2015, 3, 22507 - 22541. (4) Pech, D.; Lin, R.; McDonough, J. K.; Brunet, M.; Taberna, P.-L.; Gogotsi, Y.; Simon P. On-chip Micro-supercapacitors for Operation in a Wide Temperature Range. Electrochem. Commmun. 2013, 36, 53 - 56. (5) Chmiola, J.; Largeot, C.; Taberna, P.-L.; Simon, P.; Gogotsi, Y. Monolithic Carbidederived Carbon Films for Micro-supercapacitors. Science 2010, 328, 480 - 483. (6) Huang, P.; Heon, M.; Pech, D.; Brunet, M.; Taberna, P.-L.; Gogotsi, Y.; Lofland, S.; Hettinger, J. D.; Simon, P. Micro-supercapacitors from Carbide Derived Carbon (CDC) Films on Silicon Chips. J. Power Sources 2013, 225, 240 - 244. (7) Hsia, B.; Marschewski, J.; Wang, S.; In, J. B.; Carraro, C.; Poulikakos, D.; Grigoropoulos, C. P.; Maboudian, R. Highly Flexible, All Solid-state Microsupercapacitors from Vertically Aligned Carbon Nanotubes. Nanotechnol. 2014, 25, 055401. (8) Dinh, T. M.; Armstrong, K.; Guay, D.; Pech, D. High-resolution On-chip Supercapacitors with Ultra-high Scan Rate Ability. J. Mater. Chem. A 2014, 2, 7170 7174. (9) Wang, S.; Hsia, B.; Carraro, C.; Maboudian, R. High-performance All Solid-state Micro-supercapacitor Based on Patterned Photoresist-derived Porous Carbon Electrodes and An Ionogel Electrolyte. J. Mater. Chem. A 2014, 2, 7997 - 8002. (10) Kim, M. S.; Hsia, B.; Carraro, C.; Maboudian, R. Flexible Micro-supercapacitors with High Energy Density from Simple Transfer of Photoresist-derived Porous Carbon Electrodes. Carbon 2014, 74, 163 - 169. (11) Hsia, B.; Kim, M. S.; Vincent, M.; Carraro, C.; Maboudian, R. Photoresist-derived Porous Carbon for On-chip Micro-supercapacitors. Carbon 2013, 57, 395 - 400.



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

(12) El-Kady, M. F.; Kaner, R. B. Scalable Fabrication of High-power Graphene Microsupercapacitors for Flexible and On-chip Energy Storage. Nat. Commun. 2013, 4:1475. (13) Aradilla, D.; Delaunay, M.; Sadki, S.; Gérard, J.-M.; Bidan, G. Vertically Aligned Graphene Nanosheets on Silicon Using an Ionic Liquid Electrolyte: Towards High Performance On-chip Micro-supercapacitors. J. Mater. Chem. A 2015, 3, 19254 19262. (14) Wu, Z.-S.; Parvez, K.; Feng, X.; Müllen, K. Graphene-based In-plane Microsupercapacitors with High Power and Energy Densities. Nat. Commun. 2013, 4:2487. (15) Jin, H.; Zhou, L.; Mak, C. L.; Huang, H.; Tang, W. M.; Chan, H. L. W. Improved Performance of Asymmetric Fiber-based Micro-supercapacitors Using Carbon Nanoparticles for Flexible Energy Storage. J. Mater. Chem. A 2015, 3, 15633 - 15641. (16) Gao, F.; Wolfer, M. T.; Nebel, C. E. Highly Porous Diamond Foam As a Thin-film Micro-supercapacitor Material. Carbon 2014, 80, 833 - 840. (17) Thissandier, F.; Dupré, L.; Gentile, P.; Brousse, T.; Bidan, G.; Buttard, D.; Sadki, S. Ultra-dense and Highly Doped SiNWs for Micro-supercapacitors Electrodes. Electrochim. Acta 2014, 117, 159 - 163. (18) Aradilla, D.; Gentile, P.; Bidan, G.; Ruiz, V.; Gomez-Romero, P.; Schubert, T. J.; Sahin, H.; Frackowiak, E.; Sadki, S. High Performance of Symmetric Microsupercapacitors Based on Silicon Nanowires Using N-methyl-N-propylpyrrolidinium bis(trifluoromethylsulfonyl)imide as Electrolyte. Nano Energy 2014, 9, 273 - 281. (19) Thissandier, F.; Pauc, N.; Brousse, T.; Gentile, P.; Sadki, S. Micro-ultracapacitors with Highly Doped Silicon Nanowires Electrodes. Nanoscale Res. Lett. 2013, 8:38 (20) Thissandier, F.; Le Comte, A.; Crosnier, O.; Gentile, P.; Bidan, G.; Hadji, E.; Brousse, T.; Sadki, S. Highly Doped Silicon Nanowires Based Electrodes for Microelectrochemical Capacitor Applications. Electrochem. Commun. 2012, 25, 109 - 111. (21) Alper, J. P.; Kim, M. S.; Vincent, M.; Hsia, B.; Radmilovic, V.; Carraro, C.; Maboudian, R. Silicon Carbide Nanowires as Highly Robust Electrodes for Microsupercapacitors. J. Power Sources 2013, 230, 298 - 302. (22) Gu, L.; Wang, Y.; Lu, R.; Wang, W.; Peng, X.; Sha, J. Silicon Carbide nanowires@Ni(OH)2 Core-shell Structures on Carbon Fabric for Supercapacitor Electrodes with Excellent Rate Capability. J. Power Sources 2015, 273, 479 - 485. (23) Gu, L.; Wang, Y.; Fang, Y.; Lu, R.; Sha, J. Performance Characteristics of Supercapacitor Electrodes Made of Silicon Carbide Nanowires Grown on Carbon Fabric. J. Power Sources 2013, 243, 648 - 653.


Page 14 of 28

Page 15 of 28

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


(24) Thissandier, F.; Gentile, P.; Brousse, T.; Bidan, G.; Sadki, S. Are Tomorrow’s Micro-supercapacitors Hidden in a Forest of Silicon Nanotrees? J. Power Sources 2014, 269, 740 - 746. (25) Aradilla, D.; Bidan, G.; Gentile, P.; Weathers, P.; Thissandier, F.; Ruiz, V.; Gomez-Romero, P.; Schubert, T. J. S.; Sahin, H.; Sadki, S. Novel Hybrid Microsupercapacitor Based on Conducting Polymer Coated Silicon Nanowires for Electrochemical Energy Storage. RSC Adv. 2014, 4, 26462 - 26467. (26) Aradilla, D.; Gaboriau, D.; Bidan, G.; Gentile, P.; Boniface, M.; Dubal, D.; Gomez-Romero, P.; Wimberg, J.; Schubert, T. J.; Sadki, S. An Innovative 3-D Nanoforest Heterostructure Made of Polypyrrole Coated Silicon Nanotrees for New High Performance Hybrid Micro-supercapacitors. J. Mater. Chem. A 2015, 3, 13978 13985. (27) Dubal, D. P.; Aradilla, D.; Bidan, G.; Gentile, P.; Schubert, T. J. S.; Wimberg, J.; Sadki, S.; Gomez-Romero, P. 3D Hierarchical Assembly of Ultrathin MnO2 Nanoflakes on Silicon Nanowires for High Performance Micro-supercapacitors in Li-doped Ionic Liquid. Sci. Rep. 2015, 5, 9771. (28) Lu, F.; Qiu, M.; Qi, X.; Yang, L.; Yin, J.; Hao, G.; Feng, X.; Li, J.; Zhong, J. Electrochemical Properties of High-power Supercapacitors Using Ordered NiO Coated Si Nanowire Array Electrodes. Appl. Phys. A 2011, 104, 545 - 550. (29) Devarapalli, R. R.; Szunerits, S.; Coffinier, Y.; Shelke, M. V.; Boukherroub, R. Glucose-derived Porous Carbon-coated Silicon Nanowires as Efficient Electrodes for Aqueous Micro-supercapacitors. ACS Appl. Mater. Interfaces 2016, 8, 4298 - 4302. (30) Alper, J. P.; Wang, S.; Rossi, F.; Salviati, G.; Yiu, N.; Carraro, C.; Maboudian, R. Selective Ultrathin Carbon Sheath on Porous Silicon Nanowires: Materials for Extremely High Energy Density Planar Micro-supercapacitors. Nano Lett. 2014, 14, 1843 - 1847. (31) Gao, F.; Lewes-Malandrakis, G.; Wolfer, M. T.; Müller-Sebert, W.; Gentile, P.; Aradilla, D.; Schubert, T.; Nebel, C. E. Diamond-coated Silicon Wires for Supercapacitor Applications in Ionic Liquids. Diamond Relat. Mater. 2015, 51, 1 - 6. (32) Aradilla, D.; Gao, F.; Lewes-Malandrakis, G.; Müller-Sebert, W.; Gaboriau, D.; Gentile, P.; Iliev, B.; Schubert, T.; Sadki, S.; Bidan, G.; Nebel, C. E. A Step Forward into

Hierarchically

Nanostructured

Materials

for

High

Performance

Micro-

supercapacitors: Diamond-coated SiNW Electrodes in Protic Ionic Liquid Electrolyte. Electrochem. Commun. 2016, 63, 34 - 38.



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

(33) Gao, F.; Nebel, C. E. Diamond-based Supercapacitors: Realization and Properties. ACS Appl. Mater. Interfaces 2016, DOI: 10.1021/acsami.5b07027. (34) Yang, N.; Foord, J. S.; Jiang, X. Diamond Electrochemistry at the Nanoscale: A Review. Carbon 2016, 99, 90 - 110. (35) Shi, C.; Li, H.; Li, C.; Li, M.; Qu, C.; Yang, B. Preparation of TiO2/Boron-doped diamond/Ta Multilayer Films and Use as Electrode Materials for Supercapacitors. Appl. Surf. Sci. 2015, 357, 1380 - 1387. (36) Gao, F.; Nebel, C. E. Diamond Nanowire Forest Decorated with Nickel Hydroxide as a Pseudocapacitive Material for Fast Charging-discharging. Phys. Status Solidi A 2015, 212, 2533 - 2538. (37) Yu, S.; Yang, N.; Zhuang, H.; Meyer, J.; Mandal, S.; Williams, O. A.; Lilge, I.; Schonherr, H.; Jian, X. Electrochemical Supercapacitors from Diamond. J. Phys. Chem. C 2015, 119, 18918 - 18926. (38) Gentile, P.; Solanki, A.; Pauc, N.; Oehler, F.; Salem, B.; Rosaz, G.; Baron, T.; Hertog, M. Den, Calvo, V. Effect of HCl on The Doping and Shape Control of Silicon Nanowires. Nanotechnol. 2012, 23, 215702. (39) Snook, G. A.; Best, A. S.; Pandolfo, A. G.; Hollenkamp, A. F. Evaluation of a Ag/Ag+ Reference Electrode for Use in Room Temperature Ionic Liquids. Electrochem. Commun. 2006, 8, 1405 - 1411. (40) Thissandier, F.; Gentile, P.; Pauc, N.; Brousse, T.; Bidan, G.; Sadki, S. Tuning Silicon Nanowires Doping Level and Morphology for Highly Efficient Microsupercapacitors. Nano Energy 2014, 5, 20 - 27. (41) Ahmad, S.; Deepa, M.; Singh, S. Electrochemical Synthesis and Surface Characterization of Poly(3,4-ethylenedioxythiophene) Films Grown in an Ionic Liquid. Langmuir 2007, 23, 11430 - 11433. (42) Fu, W.-C.; Hsieh, Y.-T.; Wu, T.-Y.; Sun, I.-W. Electrochemical Preparation of Porous Poly(3,4-ethylenedioxythiophene) Electrodes from Room Temperature Ionic Liquid for Supercapacitors. J. Electrochem. Soc. 2016, 163, G61 – G68. (43) Abdelhamid, M. E.; Snook, G. A.; O’Mullane, A. P. Electropolymerisation of Catalytically Active PEDOT from an Ionic Liquid on a Flexible Carbon Cloth Using a Sandwich Cell Configuration. ChemPlusChem 2015, 80, 74 - 82. (44) Viaua, L.; Hihna, J. Y.; Lakarda, S.; Moutarlier, V.; Flaud, V.; Lakarda, B. Full Characterization of Polypyrrole Thin Films Electrosynthesized in Room Temperature Ionic Liquids, Water or Acetonitrile. Electrochim. Acta 2014, 137, 298 - 310.


Page 16 of 28

Page 17 of 28

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


(45) Pringle, J. M.; MacFarlane, D. R.; Forsyth, M. Solid State NMR Analysis of Polypyrrole Grown in a Phosphonium Ionic Liquid. Synth. Met. 2005, 155, 684 - 689. (46) Taberna, P. L.; Simon, P.; Fauvarque, J. F. Electrochemical Characteristics and Impedance Spectroscopy Studies of Carbon-carbon Supercapacitors. J. Electrochem. Soc. 2003, 150, A292 - A300. (47) Alper, J. P.; Vincent, M.; Carraro, C.; Maboudian, R. Silicon Carbide Coated Silicon Nanowires as Robust Electrode Material for Aqueous Micro-supercapacitor. Appl. Phys. Lett. 2012, 100, 163901. (48) Grigoras, K.; Keskinen, J.; Grönberg, L.; Ahopelto, J.; Prunnila, M. Coated Porous Si for High Performance On-chip Supercapacitors. J. Phys: Conf. Ser. 2014, 557, 012058. (49) Chatterjee, S.; Carter, R.; Oakes, L.; Erwin, W. R.; Bardhan, R.; Pint, C. L. Electrochemical and Corrosion Stability of Nanostructured Silicon by Graphene Coatings: Toward High Power Porous Silicon Supercapacitors. J. Phys. Chem. C 2014, 118, 10893 - 10902. (50) Thissandier, F.; Gentile, P.; Pauc, N.; Hadji, E.; Le Comte, A.; Crosnier, O.; Bidan, G.; Sadki, S. Highly N-doped Silicon Nanowires as a Possible Alternative to Carbon for On-chip Electrochemical Capacitors. Electrochemistry 2013, 81, 777 - 782. (51) Beidaghi, M.; Wang, C. Micro-supercapacitors Based on Three Dimensional Interdigital Polypyrrole/C-MEMS Electrodes. Electrochim. Acta 2011, 56, 9508 - 9514. (52) Chen, G.-F.; Su, Y.-Z.; Kuang, P.-Y.; Liu, Z.-Q.; Chen, D.-Y.; Wu, X.; Li, N.; Qiao, S.-Z. Polypyrrole Shell@3D-Ni Metal Core Structured Electrodes for High Performance Supercapacitors. Chem. Eur. J. 2015, 21, 4614 - 4621. (53) Chen, Y.; Xu, J.; Yang, Y.; Zhao, Y.; Yang, W.; Mao, X.; He, X.; Li, S. The Preparation and Electrochemical Properties of PEDOT:PSS/MnO2/PEDOT Ternary Film and Its Application in Flexible Micro-supercapacitors. Electrochim. Acta 2016, 193, 199 - 205.



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

Page 18 of 28

Table Caption Table 1. Summary of main electrochemical performances dealing with SiNWs and functionalized SiNWs based planar microsupercapacitors reported in the literature. AC, E, P values were obtained according to the electrochemical method, unless specified otherwise. System

Method Si growth

AC (mF cm-2)

Ea (mJ cm-2)

PEDOT/D@SiNWs

CVD

8.5

26

PEDOT/SiNWs

CVD

8

PPy/SiNWs

CVD

PPy/SiNTrs

Pb (mW cm-2)

Cycling Stability

Electrochemical Method

Electrolyte

Ref.

1.3

15 000 (80%)

GCD (2.5 V 1 mA cm-2)

N1114 TFSI

This study

9

0.8

3500 (80%)

GCD (1.5 V 1mA cm-2)

PYR13 TFSI

25

10

11

0.8

------

GCD (1.5 V 1 mA cm-2)

PYR13 TFSI

26

CVD

14

15

0.8

10000 (70%)

GCD (1.5 V 1 mA cm-2)

PYR13 TFSI

26

MnO2/SiNWs

CVD

13 GCD (2.2V) 0.4 mA cm-2

32 GCD (2.2V) 0.4 mA cm-2

0.4 GCD (2.2V) 0.4 mA cm-2

5 000 (91%)

GCD (2.2 V 1mA cm-2)

PYR13 TFSI/ LiClO4

27

Diamond/SiNWs

CVD

1.5

11

25

1·106 (65%)

GCD (4 V 10 mA cm-2)

Et3NH TFSI

32

C/SiNWs

Etching

75

100

1

5000 (80%)

GCD (2.7 V 3 mA cm-2)

EMIM TFSI

30


Page 19 of 28

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48

a b


C/SiNWs

Etching

25.6 GCD (0.7V) 0.1 mA cm-2

SiC/SiNWs

Etching

1.7 CV (0.8V) 50 mVs-1

TiN/SiNWs

Etching

Graphene/SiNWs

Etching

SiNTrs

6.3 GCD (0.7V) 0.1 mA cm-2

0.04 GCD (0.7 V) 0.1 mA cm-2

25000 (75%)

GCD (0.7 V 1 mA cm-2)

1M Na2SO4

29

0.850 CV (0.8V) 50 mVs-1

------

1000 (95%)

CV (0.8 V 50 mVs-1)

1M KCl

47

2.6

5.2

1.2

------

GCD (2 V 1mA)

0.5 M TEABF4/PC

48

------

3.6

1

------

GCD (2.7 V 1.5 A/g)

EMIMBF4

49

CVD

0.058

0.26

------

1·106 (84%)

GCD (3 V 1 mA cm-2)

EMIM TFSI PC (1 M)

24

SiNWs

CVD

0.023

0.19

2

8·106 (75%)

GCD (4 V 1 mA cm-2)

PYR13 TFSI

18

SiNWs

CVD

0.007 0.051

0.003 0.037

------

2000 (98%)

GCD (1 V 10 µA cm-2)

1M NEt4BF4/PC

50

Energy was calculated using the following equation (E: 0.5*SC*V2) Power density was calculated using the following equation: (P: E/t)



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

Page 20 of 28

Figure Captions Figure 1. Schematic illustration for the elaboration of a 3D multi-hierarchically heterostructure

electrode

composed

of

diverse

nanostructured

polymer,

carbonaceous and semiconductor materials (PEDOT, Diamond and SiNWs respectively). Figure 2. SEM images of a) SiNWs grown by CVD on highly doped Si substrates. b) Diamond - coated SiNWs. Inset shows a high magnification SEM image of the nanostructure. Scale bar: 200 nm. c) PEDOT-coated D@SiNWs and d) Cross sectional view of PEDOT-coated D@SiNWs. Scale bar of inset: 100 nm. All the images were recorded at a tilt angle of 45°. Figure 3. a) HAADF-STEM image and b) EDX elemental mapping corresponding to a PEDOT-coated D@SiNW electrode showing the presence of S, C and Si. Scale bar: 100 nm. c) C1s and d) S2p core level XPS spectra of electrochemically deposited PEDOT on diamond-coated SiNWs. Figure 4. a) CV curves of a PEDOT-coated D@SiNW electrode within a potential from -1.80 V to 0.20 V (vs Fc/Fc+) at different scan rates from 1 to 20 mVs-1. b) Specific capacitance of the electrode calculated at various scan rates. c) CV curves of a MSC based on PEDOT-coated D@SiNW electrodes using a cell voltage of 2.5 V recorded at different scan rates from 5 to 50 mVs-1 and d) from 200 to 800 mVs1

.

Figure 5. a) Galvanostatic charge-discharge cycles of the hybrid MSC at various current densities from 0.1 to 2 mA cm-2 within a cell voltage of 2.5 V. b) Areal capacitance calculated as a function of current density from galvanostatic cycles recorded in a). c) Nyquist plot of the device measured at a frequency range from 400 kHz to 10 mHz. Insets shows a magnified high frequency region (c1) and the evolution of the imaginary capacitance versus frequency (c2) using the conditions described in c). The relaxation time (τ0) of the device is indicated in the plot by an arrow. d) Ragone plot of areal energy and average power densities for a MSC based on PEDOT-coated D@SiNW electrodes. The performance was compared with the published results concerning MSCs based on electroactive conducting polymers-coated SiNWs.


Page 21 of 28

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


Figure 6. a) Cycling stability of a PEDOT-coated D@SiNWs-based MSC performed using 15 000 complete galvanostatic charge-discharge cycles at a current density of 1 mA cm-2 between 0 and 2.5 V b) Coulombic efficiency as a function of number of galvanostatic cycles. Inset shows a SEM image of PEDOTcoated D@SiNWs after cycling under the conditions described in a) at 45° tilt angle. Scale bar: 200 nm.



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

Figure 1


Page 22 of 28

Page 23 of 28

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


Figure 2



c)

d)

2400

C1s

800

Experimental

S2p

Experimental PEDOT S2p3/2

C-C 1800

Intensity / a.u

Intensity / a.u

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

Page 24 of 28

CF3 C-O-C

1200

C-S

600

0

600

PEDOT S2p3/2 PEDOT S2p1/2 PEDOT S2p1/2

400

TFSI- S2p TFSI- S2p

200

0

280

284

288

292

296

155

Binding Energy / eV

159

163

167

171

Binding Energy / eV

Figure 3


175

a)

b)

1.00

j (mA cm-2)

0.50

0.00

1 mVs-1 2 mVs-1 5 mVs-1 10 mVs-1 20 mVs-1

-0.50

-1.00 -2.25

-1.75

-1.25

-0.75

Voltage (V vs

c)

-0.25

0.25

160

120

80

40

0 0

0.75

0.05

0.1

0.15

Scan rate (V

Fc/Fc+)

d)

1.00

0.2

0.25

s-1)

10.00

6.00

0.00

5 mVs-1 -0.50

-1.00 0.00

mVs-1

10 25 mVs-1 50 mVs-1 0.50

1.00

1.50

2.00

2.50

j (mA cm-2)

0.50

j (mA cm-2)

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


Specific Capacitance (F/g)

Page 25 of 28

2.00

-2.00

200 mVs-1 400 mVs-1 600 mVs-1

-6.00

800 mVs-1 -10.00 0.00

Voltage (V)

0.50

1.00

1.50

Voltage (V)

Figure 4


2.00

2.50

a)

b) 2.50

0.10 mA cm-2 Série1 0.25 mA cm-2 Série2 0.50 mA cm-2 Série3 0.75 mA cm-2 Série4

1.50

1.00 mA cm-2 Série5 2.00 mA cm-2 Série6

1.00 0.50 0.00 0

100

200

300

400

Page 26 of 28

10

9

8

7

6 0

500

0.5

-Z'' (Ω cm2)

1600

10

1200

8 6 4 2 0 46

c2) C'' (mF cm2)

800

400

48

50

52

54

56

Z' (Ω cm2)

τO

3.50 3.00 2.50 2.00 1.50 1.00 0.50 0.00 -2

0

2

4

6

Log f

0 0

400

800

Z' (Ω

1200

SiNWs/PEDOT (25) SiNWs/PPy (26)

d) c1)

Power density (mW cm-2)

Time (s)

c)

1

1.5

2

2.5

Current Density (mA cm-2)

2

1

SiNTrs/PPy (26)

Voltage (V)

2.00

-Z'' (Ω cm2)

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

Areal Capacitance (mF cm-2)


PEDOT-D@SiNWs (This study)

0

1600

4

8

12

16

20

24

Energy (mJ

cm2)

Figure 5


28

cm-2)

32

36

Page 27 of 28

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


Figure 6



PEDOT-Diamond@SiNWs j (mA cm-2)

0.60

) 2N

F (C

0.20 0.00 -0.20

-0.40 -0.60 -2.00

-1.50

-1.00

-0.50

0.00

Voltage (V)

0.50

1.00

SO F3 (C

N

S 3

O2

0.40

N ) 2N

2

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

Page 28 of 28


Designing 3D Multihierarchical Heteronanostructures for High

Recommend Documents