ABBREVATIONS. Activated carbon Silver-Silver chloride

Transcription

1 ABBREVATIONS AC Ag/AgCl B.G BaTiO3 BHJ C.B CdS CE CNFs CNT/NiO CNTs CV DALS DMF DMSO DSSC E C EC ECPs EDL EDLC EDOT EDS E F EG EMF EPD Activated carbon Silver-Silver chloride Band gap Barium titanate Bulk Heterojunction Conduction band Cadmium sulfide Counter electrode Carbon nanofibers Carbon nanotube nickel oxide composites Carbon nanotubes Cyclic Voltammetry Double anodized layered structure N, N Dimethyl formamide Dimethyl Sulfoxide Dye sensitized solar cells Conduction band edge Electrochemical capacitor Electronically conducting polymers Electrical Double Layer Electrical Double Layer capacitors Ethlyne dioxythiophene Energy-dispersive X-ray spectrometer Fermi energy level Exfoliated graphite Electro-motive-force Electro phoretic deposition xv

2 FRA FTIR Gr Graphene/NiO HCl HEBM HF HM HOMO i rp IR Isc ITO KOH LiClO 4 LiI Li-ion Li-ion polymer LUMO MnO2 MWNTs NaOH Ni(NO 3 ) 2 NiCd NiMH NiO NT OCV PANI PE PEDOT Frequency response analysis Fourier transform infrared spectroscopy Graphene Graphene nickel oxide composites Hydrochloric acid High energy ball milling Hydrogen Fluoride Hydrothermal method Highest occupied molecular orbital Current corresponding to reduction potential Internal resistance Short circuited current Indium tin oxide Potassium hydroxide Lithium per chlorate Lithium iodide Lithium ion Lithium ion polymer Lowest unoccupied molecular orbital Manganese dioxide Multi-walled carbon nanotubes Sodium hydroxide Nickel nitrate Nickel cadmium Nickel metal hydride Nickel oxide Nanotube Open circuit voltage Poly(aniline) Photoelectrode Poly (3,4-ethylenedioxythiophene) xvi

3 PG stat Ppy Pt PV QDs QDSSC RE RuO 2 S.B S.H.E SALS SC SCE SECM SEM Si SWNTs TCO Ti plates TiO 2 V.B V oc WE XRD ZrO 2 Potentiostat-galvanostat Poly(pyrrole) Platinum Photovoltaic Quantum dots Quantum dot sensitized solar cell Reference Electrode Rutheniumdioxide Schottky barrier Standard hydrogen electrode Single anodized layered structure Super Capacitors Standard calomel Scanning electrochemical microscope Scanning Electron Microscopy Silicon Single walled nanotubes Transparent conducting oxide Titanium plates Titanium dioxide Valance band Open circuit voltage Working electrode X-ray diffraction Zirconia xvii

4 LIST OF FIGURES Figure 1.1: (a) Schematic image of Si solar cell (b) Commercially available Si solar module. Figure 1.2: Schematic diagram of p-n Junction thin film solar cell. Figure 1.3: Commercially available dye sensitized solar cell panel. Figure 1.4: Sketch of Ragone plot for various energy storage and conversion devices [Martin S H et al, 2006]. Figure1.5: Two-electrode sandwich-type structure of the carbon-incorporated photocapacitor [Miyasaka T et al, 2004]. Figure 1.6: Photocharging and discharging characteristics of a photocapacitor [Miyasaka T et al, 2004] (left) Voltage change in the charge process (right) Voltage change in the discharge process. Figure 2.1: Two-electrode sandwich-type structure of the carbon-incorporated photocapacitor (upper) and charge-transfer mechanism in the processes of photo-charging and discharging (lower) [Miyasaka T et al, 2007]. Figure 2.2: Schematic diagrams of 2-electrode phtocapacitor and 3-electrode photo capacitor [Miyasaka T et al, 2007]. Figure 2.3: (a) Schematic illustration of front side illuminated DSSC with capacitor. (b) Voltage variation integrated cell upon photo illumination and self discharge from the capacitor when light turned off. Figure 2.4: Schematic diagram of DSSC. Figure 2.5: (a), (b) schematic representation of integrated structure of DSSC with ZrO2 dielectric capacitor (c) different schemes of integrated structure (i) solar cell scheme (ii) capacitor scheme (iii) integrated scheme. Figure 2.6: (a) Single side anodization set up (b) double side anodization set up. Figure 2.7: (a) SEM image of double side anodized Titanium plate where it is clearly visible that nanotubes grown on either side are almost equal in length (~ µm, 96 hrs) which indirectly shows that the growth rate of nanotube is same because of the equal field distribution (b) & (c) shows the magnified image of TiO2 nanotube and its lateral view. xviii

5 Figure 2.8: XRD pattern of the anodized Ti plate after annealing, symbol A denotes peaks corresponding to anatase face, and Ti denotes peaks for Titanium. Figure 2.9: UV-Visible absorption spectrum of Eosin gelblich dye. Figure 2.10: SEM image of the uniform layer of ZrO 2 on TiO 2 nanotubes. Figure 2.11: Practically assembled structure of integrated solar cell with capacitor. Figure 2.12: I-V characteristics of solar cell with eosin dye, open circuit voltage V oc = 0.42 V and short circuit current density J sc = 970 µa/cm 2. Figure 2.13: Voltage-Time graph of Ti-TiO 2 -ZrO 2 TiO 2 -Ti capacitor at a constant charging and discharging current. Figure 2.14: Schematic representation of the formation of Schottkey barrier upon metal semiconductor contact. Figure 2.15: Cyclic voltammetry of 48 hrs anodized sample in 0.1 M Na 2 SO 4 in a potential window of -1.5 to 1.5 V at a scan rate of 15 mv/s. The reduction potential is found to be at V. Figure 2.16: UV-Vis absorption spectra of 48 hrs anodized TiO 2 nanotube and onset of absorption (corresponding to bandgap) is at 385 nm which corresponds to band gap energy of 3.23 ev. Figure 2.17: Impedance spectra of 48 hrs TiO 2 nanotube on Ti plate. Figure 2.18: I-V behavior of TiO 2 nanotubes in SECM; barrier potential obtained is 0.28 V. Figure 2.19: SEM images of 18 and 48 hrs anodized samples. Figure 2.20: Lateral SEM images of TiO 2 nanotube for different time of anodization (a) 18 hrs (b) 48 hrs (c) 72 hrs Figure 2.21: (a) & (b) Cyclic voltammetry of 18 to 72 hrs anodized samples in 0.1 M Na 2 SO 4 at a scan rate of 15 mv/s (c) UV-Vis absorption spectra of 18 to 72 hrs anodized TiO 2 nanotubes (d) Onset of absorption (corresponding to bandgap) wavelength versus time of anodization plot (e) I-V behaviour of 18 to 72 hrs anodized TiO 2 nanotubes with SECM. Figure 2.22: Impedance spectra of TiO 2 nanotube on Ti plate Figure 2.23: (a) Voltage variation upon photo charging in capacitor. The solar cell was illuminated for 100 seconds and solar cell is disconnected and xix

6 voltage across the capacitor noted for 1500 seconds and found that voltage remains constant (b) shows the current variation with in integrated solar cell time upon illumination. Figure 2.24: Photo charging and discharging of 72 hrs anodized integrated structure. Figure 2.25: I-V characteristics of solar cell with Dye: Eosin, Electrolyte: Iodine/Lithium Iodide (0.3 M), Counter electrode-pt/ito, V oc = 0.38 V, J sc =1.9 ma/cm 2, = 0.25%. Figure 2.26: I-V characteristics of solar cell with Dye: Ruthenium N719, Electrolyte: Iodine/Lithium Iodide (0.3 M), Counter electrode-pt/ito, V oc = 0.47 V, J sc =1.13 ma/cm 2, = 0.45%. Figure 2.27: I-V characteristics of solar cell with Dye: Ruthenium N719, Electrolyte: Iodine/Lithium Iodide (0.3 M), Counter electrode-pt/ito, V oc = 0.62 V, J sc =3 ma/cm 2, = 1%. Figure 2.28: I-V characteristics of solar cell with Dye: Ruthenium N719, Electrolyte: Ionic Iodine/Iodide, Counter electrode-pt/ito, V oc =0.75 V, J sc =9 ma/cm 2, = 3.58%. Figure 2.29: Image of Hydrothermal reactor. Figure 2.30: Schematic illustration of the hydrothermal synthesis of Zirconia. Figure 2.31: SEM images of hydrothermally grown ZrO 2. Figure 2.32: XRD pattern of hydrothermally synthesized ZrO 2 (Top) 48 hrs showing crystalline planes (Bottom) for different time of hydrothermal treatment. Figure 2.33: (a&b) Schematic diagram and charge discharge of Ti/bulk-ZrO 2 /Ti capacitor, (c&d) schematic diagram and v-t graph of anodized Ti/ anodized Ti capacitor without dielectric, (e&f) schematic diagram and charge discharge of capacitor with 12, 24, 48 hrs of anodized and nano-zro 2 dielectric Ti plate with at a constant current of 10µA/cm 2. Figure 2.34: SEM images of Ex- situ grown BaTiO 3 on anodized plate. Figure 2.35: XRD of Ex-situ grown BaTiO 3. Figure 2.36: SEM images of insitu grown BaTiO 3 on anodized plate for (a&b) 3 hrs, (c&d) 6hrs and (e&f) 20 hrs. xx

7 Figure 2.37: XRD of In-situ grown BaTiO 3 for 3 and 20 hrs. Figure 2.38: Charge-discharge of capacitor with in-situ grown BaTiO 3 (a) 3 and (b) 6 hrs at constant current of 100 µa/cm 2. Figure 2.39: Charge-discharge of capacitor with ex-situ grown BaTiO 3 with 48 hrs anodized Ti plate at a constant current of 3 µa/cm 2. Figure 2.40: Photo charging and forced discharging of an integrated structure with Ex- situ prepared BaTiO 3 as dielectric. The applied discharging current is 10 µa/cm 2. Figure 3.1: Schematic representation of poy(pyrrole) and PEDOT. Figure 3.2: SEM image shows the thin film morphology for poly(pyrrole) grown by electropolymerization. Figure 3.3: FTIR spectra of poly(pyrrole). Figure 3.4: UV-Visible spectra of poly(pyrrole), the absorption peak is obtained at a wavelength of 493 nm for a polymerization time of 500 seconds. Figure 3.5: Cyclic voltammetry carried out in different voltage window in aqueous 0.1 M NaOH (b) Platinum electrode when potential window is less than 1.5 V (c) gas evolutions on platinum electrode when applied potential is above 1.5 V. Figure 3.6: Cyclic Voltammetry studies in 0.1 M LiClO 4 in a three electrode set up; Poly(pyrrole) as anode, platinum wire as cathode and saturated calomel electrode as the reference electrode at different scan rate from 10 mv/sec to 100 mv/sec. Figure 3.7: Cyclic voltammetry (CV) variation with time of polymerization for bare poly(pyrrole) film at 10 mv/sec. Figure 3.8: Graph shows the variation in area capacitance with time of polymerization for bare poly(pyrrole) film. Figure 3.9: Cycling studies: 25 cycles of CV carried out for same Ppy electrode. Figure 3.10: The charging and discharging nature of PPY electrode at a constant external current of 1 ma/cm 2. Figure 3.11: Schematic of supercapacitor electrodes synthesized using a graphene/poly(pyrrole) composite. xxi

8 Figure 3.12: SEM images of electro polymerized pyrrole on graphene platelets. Figure 3.13: Raman spectra of graphene. Figure 3.14: Raman spectra of Graphene/Ppy composites. Figure 3.15: Cyclic voltammetry (CV) curves for various scan rates at 1500 seconds polymerization. Figure 3.16: CV of graphene, Ppy, Gr/Ppy composite in 0.1 M LiClO 4 electrolyte. Figure 3.17: (a) CV of Ppy electrode for different time of polymerization from 500 to 3000 sec, (b) A plot of area capacitance versus time of polymerization (or layer thickness) shows a gradual increase of capacitance up to a maximum (1500 sec) and thereafter it reduces and maximum obtained area capacitance is 150 mf/cm 2. Figure 3.18: Cycling studies: 25 times CV cycling the composite electrode. Figure 3.19: Galvanostatic charge discharge (discharge is forced by external current of 1 ma/cm 2 ) studies on the graphene/ppy composite film. Figure 3.20: SEM image of the PEDOT thin film. Figure 3.21: AFM image of electropolymerized EDOT on Ti substrate. Figure 3.22: FTIR spectra of of electropolymerized EDOT Figure 3.23: Raman spectra obtained of PEDOT. Figure 3.24: CV curve of the PEDOT thin film for varying time of polymerization (300 to 2100 sec). Figure 3.25: CV curves at various scan rates for a fixed polymerization time (1800 sec). Figure 3.26: Cycling studies: 30 repeated CV scans of PEDOT film (At a scan rate 40 mvs -1 ). Figure 3.27: SEM image of the composite film electrode formed with 8 minutes of polymerization. Figure 3.28: CV curve of the PEDOT/Graphene composite film for varying time of polymerization (2 minutes to 15 minutes). Figure 3.29: CV of the composite film in 0.1 M LiClO 4 electrolyte for time of polymerization 8 minutes for different scan rate. xxii

9 Figure 3.30: Cycling study: 50 repeated CV scans of PEDOT/Graphene film (40 mvs-1). Figure 4.1: Schematic illustration of a charged double layer capacitor. 1 and 2 current collector; 3 and for electrode material; 5-6 seperator; 6electrolyte; 7-pores in the electrode material; 8-positive charge; 9negative ion; 10-negative charge; 11-positive ion [Obreja V.V.N et al, 2008]. Figure 4.2: SEM image of 4hrs ball milled EPD deposited activated carbon. Figure 4.3: Cyclic Voltammetry of activated carbon at different scan rates. Figure 4.4: Charging and discharging of AC electrode in three electrode system with charging and discharging current of 10 A/cm2. Figure 4.5: Cycling of CV 25 times with same AC electrode in three electrode system. Figure 4.6: SEM images of (a&b) electrophoretically deposited graphene and (c) is the raman spectra of graphene Figure 4.7: (a) Cyclic Voltammetry of Graphene/NiO for different duration of electrophoresis at 10 mv/sec (b) variation in area capacitance with time of electrophoretic deposition. Figure 4.8: Cyclic Voltammetry carried out for Gr/NiO sample for 50 minutes of deposition. Figure 4.9: Nyquist plot of Graphene/NiO film on Ti plate. Figure 4.10: Cycling studies: 25 cycles of CV for Graphene/NiO electrode. Figure 4.11: Voltage Time behaviour of Graphene/NiO electrode upon charging (Ic=5 ma/cm2) and discharging (Id=100 µa/cm2), blue line shows the Current - time behaviour of electrode on charging at 0.57 V w.r.t. SCE. Figure 4.12: (a) Schematic representation of Equivalent circuit of symmetric capacitor with cathode and anode (b) Voltage-Time behaviour of Graphene/NiO symmetrical capacitor upon charging (Ic=5 ma/cm2) and discharging (Id=100 µa/cm2), blue line shows the current-time behaviour of electrode on charging at 2.2 V. Figure 4.13: SEM image of electrophoretically deposited CNTs. xxiii

10 Figure 4.14: Raman signature of CNT using a Raman spectrometer at 488 nm. Figure 4.15: (a) Cyclic voltammetry of CNT/NiO for different duration of electrophoresis at 10 mv/sec and (b) variation in area capacitance with time of electrophoretic deposition. Figure 4.16: Cyclic Voltammetry carried out for Gr/NiO sample for 60 minutes of deposition. Figure 4.17: Nyquist plot of CNT/NiO film on Ti plate. Figure 4.18: Cycling studies: 25 cycles of CV carried out for CNT/NiO electrode. Figure 4.19: Voltage Time behavior of CNT/NiO electrode upon charging(i c =5 ma/cm 2 ) and discharging (I d =500 µa/cm 2 ), blue line shows the Currenttime behavior of electrode on charging at 0.57 V. Figure 4.20: Voltage-Time behavior of CNT/NiO symmetrical capacitor upon charging (I c =5 ma/cm 2 ) and discharging (I d =5 ma/cm 2 ), blue line shows the Current - time behavior of electrode on charging at 2.2 V. Figure 4.21: SEM image of CNT/Ppy composite. Figure 4.22: Cyclic Voltammetry of CNT/Ppy for different duration of electrophoresis at 10 mv/sec, (b) variation in area capacitance with time of electrophoretic deposition and (c) cyclic Voltammetry carried out for CNT/Ppy sample for 2300 seconds of deposition. Figure 4.23: Cycling studies: 25 cycles of CV carried out for CNT/Ppy electrode. Figure 4.24: Voltage-Time behavior of CNT/NiO electrode upon charging (I c =2 ma/cm 2 ) and discharging (I d =1 ma/cm 2 ), blue line shows the Currenttime behavior of electrode on charging at 1.1 V. Figure 4.25: Voltage-Time behavior of CNT/Ppy symmetrical capacitor upon charging (I c =5 ma/cm 2 ) and discharging (I d =10 A/cm 2 ), blue line shows the Current-time behavior of electrode on charging at 7V. Figure 4.26: Schematic illustration of asymmetric capacitor. Figure 4.27: Charge-Discharge of CNT-CNT/Ppy asymmetric capacitor, Charging current of 1mA/cm 2 applied and found that it reaches maximum 7.3 V and remains constant. A discjarging current of 10 µa/cm 2 is applied and xxiv

11 found an initial voltage drop to 4.1 V and remaining voltage drops in 1000 seconds. Figure 4.28: Photo-charging of CNT/KOH symmetric capacitor from DSSC (a) voltage variation across the capacitor and (b) voltage variation while discharging current of 10 µa current applied. xxv

12 LIST OF TABLES Table 2.1: Shows the change in absorption wave length, band gap, conduction band width and valance band gap with time of anodization. Table 2.2: Shows the variation in reduction potential and fermilevel alignments for 18 hrs to 72 hrs anodized sample. Table 2.3: Variation of capacitance with size of ZrO 2. Table 2.4: Shows the variation in capacitance with length of nanotube. Table 4.1: Shows the capacitance and operating voltage variation with electrode. xxvi