A wearable system based on core-shell structured peptide- Co 9 S 8 supercapacitor and triboelectric nanogenerator Wei Xiong [a,b] 1 , Kuan Hu [b,c] 1 , Zhe Li [b] 1 , Yixiang Jiang [c] , Zigang Li [c,d] , * Zhou Li [b] , * and Xinwei Wang [a] * [a] School of Advanced Materials, Shenzhen Graduate School, Peking University, Shenzhen, 518055, China *E-mail: [email protected][b] Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing, 100083, China *E-mail: [email protected][c] Key Laboratory of Chemical Genomics, School of Chemical Biology and Biotechnology, Shenzhen Graduate
Transcript
A wearable system based on core-shell structured peptide-Co9S8 supercapacitor and triboelectric nanogenerator
Experimental SectionSynthesis of peptide nanobricks: The cyclic peptide of Ac-CAAAS5(phenyl) was synthesized based on our previous reports.[1, 2] To achieve high yield and high purity, enantiomeric-pure unnatural amino acids were used for the peptide synthesis. The synthesis completed in half a day by a semi-automatic solid-phase peptide synthesizer. Notably, all the unnatural amino acids are commercially available and the associated synthesis and purification methods are also well-documented, and therefore the synthesis of the cyclic peptide could be scaled up with a reasonable cost. The synthesized product of the cyclic peptide was lyophilized as white-color solid powder. A reported sonication method was used to self-assemble the peptide monomers into nanostructures.[3]
Preparation of polypyrrole (PPy) nanowire electrode:[4] the PPy nanowires were grown on a glass carbon (GC) electrode by electrochemical polymerization from a solution (200 mL) containing Na2HPO4∙12H2O (15.40 g), NaH2PO4∙2H2O (6.24 g), p-toluenesulfonyl (3.88 g), and pyrrole (1.38 mL, 98%). The GC electrode (3 mm in diameter) was pre- coated with nano-island Pt catalyst by sputtering (Leica EM ACE200, 40 mA for 10 s), and then inserted into the above solution as the working electrode to electrochemically grow PPy nanowires on the electrode. A Pt plate electrode (1×1 cm2) and a saturated calomel electrode (SCE) were used as the counter and reference electrodes, respectively. The electrochemical polymerization was conducted with an electrochemical workstation (CHI660E) using a constant current of 2 mA for 1 h. The resultant mass loading of the PPy nanowires on the GC electrode was 0.60 mg/cm2.
Preparation of polyaniline (PANI) nanowire electrode:[5] 146 μL of aniline was added into 40 mL of DI water, and the obtained suspension was stirred for 30 min in an ice bath. Then, into the suspension was inserted a GC electrode and added 0.24 g (NH4)2S2O8. The obtained suspension was then stirred continuously for 12 h in the ice bath to grow PANI nanowires on the GC electrode. The resultant PANI nanowire electrode was carefully washed by DI water and then dried at 60 °C, which afforded a mass loading of 0.57 mg/cm2 for PANI nanowires on the GC electrode.
Preparation of CNTs electrode: A glass carbon (GC) electrode (3 mm in diameter) was polished, using 0.05 μm alumina particles, to be mirror-like and then drop-cast with a suspension ink containing the peptide material. The ink was prepared by dispersing 1 mg CNTs in 1 mL DI water, followed by adding 80 μL Nafion (5 wt%, Electrochem Inc.) solution and sonicating for 10 min. 5 μL of the ink was drop-cast onto the GC electrode and then dried to afford a mass loading of 0.5 mg/cm2 for the CNTs electrode.
Preparation of peptide electrode: A glass carbon (GC) electrode (3 mm in diameter) was polished, using 0.05 μm alumina particles, to be mirror-like and then drop-cast
with a suspension ink containing the peptide material. The ink was prepared by dispersing 1 mg peptide nanobricks in 1 mL DI water, followed by adding 80 μL Nafion solution (5 wt%, Electrochem Inc.) and sonicating for 10 min. 5 μL of the ink was drop-cast onto the GC electrode and then dried to afford a mass loading of 0.5 mg/cm2 for the peptide nanobricks.
Preparation of peptide-Co9S8 electrode:[6] The above mentioned peptide electrode was coated with a Co9S8 layer by ALD, using bis(N,N’-diisopropylacetamidinato)cobalt(II) as the cobalt precursor and H2S as the coreactant gas. The cobalt precursor was kept in a glass container and heated to 75 °C during the deposition. The precursor vapor was delivered into the deposition chamber with the assist of purified N2 gas (through a Gatekeeper inert gas purifier) as the carrier gas. The deposition temperature was 120 °C, and the Co9S8 ALD growth rate at 120 °C was 0.27Å/cycle. The thickness of the Co9S8 coating layer was controlled by digitally setting up the total ALD cycles.
Preparation of solid-state asymmetric supercapacitor (SC): Pieces of carbon cloth (2 cm × 4 cm × 0.35 mm) were used as the charge collectors for the supercapacitor electrodes. For the cathode electrode, the carbon cloth was first loaded with peptide nanobricks and then subjected to the ALD of Co9S8 to afford the peptide-Co9S8
electrode. The mass of the loaded peptide-Co9S8 was 6 mg. For the anode electrode, activated carbon (AC) was loaded as the active material onto the carbon cloth, and the mass of the loaded AC was approximately 4.8 mg in order to balance the charge of the cathode electrode. Poly(vinyl alcohol) (PVA)/KOH polymer gel was used as the solid electrolyte. The gel was prepared by a solution-casting method, where 3 g PVA and 1.68 g KOH were first dissolved in 30 mL deionized water at 85 °C and the afforded solution was then poured into a Petri dish at room temperature to afford the gel.
Fabrication of TENG: The as-fabricated TENG is of classical contact-separation mode, which contained the three parts of the triboelectric layer, electrode layer and encapsulation layer. Nanostructured polytetrafluoroethylene (n-PTFE) and rough Al sheet (Figure S10) were employed as the triboelectric layer. The n-PTFE film was adhered to a Kapton substrate, and then Au film was deposited on the Kapton substrate to afford the electrode layer. Note that a thick layer of polydimethylsiloxane (PDMS) was used as the spacer and an elastic titanium strip was integrated on the Kapton film to ensure the separation and contact of the friction layers. Finally, the structure was encapsulated. First, an n-PTFE/PDMS layer, to enhance the sealing capability, and then a PDMS/parylene layer to further enhance the stability of the device and avoid potential erosion by environment.
Test of the electrical performance of TENG: A liner motor was employed as the external force to drive TENG (operating distance = 50 mm; maximum speed = 1 m/s; acceleration = 1 m/s2; and deceleration = 1 m/s2). The trace of the output voltage was acquired by an oscilloscope (HDO6104), and the trace of the output current was
acquired by an electrometer (Keithley 6517B).
Preparation of nanostructured PTFE film: A PTFE film (3.0 cm × 2.3 cm × 0.1cm) was first cleaned with acetone, ethanol and deionized water for three times and then blown dry with nitrogen gas to remove any adsorbed moisture. Subsequently, the processed PTFE film was etched by inductively coupled plasma reactive-ion etching system (SENTECH/SI500, Germany) for 15 s with a density plasma generator (400 W) and plasma-ion acceleration (100 W) to obtain the nanostructured PTFE film. The reaction gas was 15.0 sccm Ar, 15.0 sccm O2 and 25.0 sccm CF4.
Preparation of rough Al sheet: Al sheet (3.0 cm × 2.3 cm × 0.1 cm) was sequentially cleaned with acetone, ethanol and deionized water for three times. After blown dry with compressed nitrogen gas, the Al film was polished by sandpaper to obtain rough structures. The fabricated Al film served as both the friction layer and the electrode of TENG.
Integrating TENG with supercapacitor: The TENG, transformer, rectifier, and all-solid asymmetric supercapacitor were connected in series. The output voltage and current produced by TENG could be used to charge the supercapacitor through the transformer and rectifier. The voltage of the supercapacitor was measured using an electrometer (Keithley 6517B, USA).
Characterizations FTIR spectra were measured by a Bruker Vertex 70 FTIR spectrometer. XRD
patterns were acquired by an Oxford Instruments Gemini X-ray diffractometer using Cu Kα radiation. Scanning electron microscopy (SEM) (Zeiss, SUPRA 55) and transmission electron microscopy (TEM) (JEM-100F) were used to examine the sample morphology. For X-ray photoelectron spectroscopy (XPS) (thermo Scientific, Escalab 250Xi) experiments, the sample was loading on the copper tape, a monochromatic Al Kα X-ray source was used, and the binding energy was referenced to Au 4f7/2 (83.96 eV). The high-resolution XPS spectra were acquired using a pass energy of 20 eV.
Electrochemical measurementAll the electrochemical measurements were carried out on a CHI660E
electrochemical workstation using a standard three-electrode configuration. 1 M KOH aqueous solution was used as the electrolyte, and an Hg/HgO electrode and a Pt wire were used as the reference and counter electrodes, respectively. Electrochemical impedance spectra (EIS) were measured at open-circuit potential with ac frequency ranging from 0.1 Hz to 10 kHz.
Figure S1. SEM images of (a) PPy nanowires, (b) PANI nanowires, and (c) CNTs.
Figure S2. CV curves for the (a) CNTs, (c) peptide nanobricks, (e) PPy nanowires, and (g) PANI nanowires electrodes measured at various voltage scan rates ranging from 10 to 80 mV/s. (b,d,f,h) The corresponding charge-discharge curves at various current densities. (i) Plot of the areal capacitance with respect to the current density. (j) EIS results showing the complex-plane plot of the impedance. Inset shows the plot of phase angle versus frequency and the equivalent circuit model used for fitting.
Table S1. Summary of the areal capacitances and series resistances (Rs) for the peptide nanobricks, CNTs, PPy nanowires, and PANi nanowires electrodes.
Areal capacitance
(at 0.05 mA/cm2)Rs (fitting error)
peptide 5.5 mF/cm2 7.4 (±0.1) Ω
CNTs 7.3 mF/cm2 6.4 (±0.1) Ω
PPy 1.4 mF/cm2 10.0 (±0.2) Ω
PANi 0.9 mF/cm2 10.8 (±0.1) Ω
Figure S3. SEM images of (a) the uncoated peptide nanobricks after 500 charge-discharge cycles and (b) the peptide-Co9S8 nanobricks after 5000 charge-discharge cycles.
Figure S4. Galvanostatic charge-discharge curves at various current densities.
Figure S5. Specific capacitance of the peptide-Co9S8//AC supercapacitor with respect to discharge current density.
Figure S6. (a) Comparison of the volumetric energy and power densities of the peptide-Co9S8//AC supercapacitor with other solid-state energy storage devices.[7-11] (b) Measurement of the leakage current of the peptide-Co9S8//AC supercapacitor. The supercapacitor was first charged to 1.0 V at 2 mA and then kept at 1.0 V for 2 h, during which the current trace (i.e. leakage current) was recorded. As shown in (b), the current quickly stabilized at 9.1 μA, which was the leakage current of the supercapacitor.[12, 13]
Figure S7. Schematic illustration of the working principle of the TENG.
a b c
Figure S8. Photographs of TENG
a b
Figure S9. (a,b) Enlarged views of the olive-color areas in Figure 5b,c
Figure S10. SEM images of the (a) nanostructured PTFE film and (b) rough Al sheet
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