synthesized by CBD using pyrrole and KMnO4 National conference on ADVANCES IN BIODIVERSITY, SCIENCE, ENGINEERING AND THE ENVIRONMENT ncabsee2016 Cyclic Voltammetric study of K2S4O6 doped PPy : Mn(OH)2 composite thin films synthesized by CBD using pyrrole and KMnO4 V. Thakur, B. J. Lokhande* Solapur University , Solapur

Table of contents Supercapacitors (Idea, types and applications) Materials Why PPy Ppy composites 3. Methods of thin film deposition CBD advantages parameters 4. Materials and sample codes 5. Film Formation mechanism 6. XRD analysis 7. FTIR analysis 8. CV CV of different samples with Molar variations CV of optimized samples for various scan rates 9. Results and conclusions

The metal oxides have been being used as electrode materials The metal oxides have been being used as electrode materials. They store the power electrochemically by means of the fast Faradaic reactions occuring at the electrode surface. Eg. CuO, Co3O4 , RuO2, NiO2, Fe2O3, etc. Generally all the metal oxides show pseudocapacitive nature. The conducting polymers are also being used as the electrode materials They have 1. high conductivity , 2. charge storage throughout the bulk, 3. porosity etc. eg. Polyaniline (PAN), Polyethylene-dioxy-thiophene (PEDOT), Polypyrrole(PPy), Polythiophene (PTh) etc The composites of Metal oxides and polymers gives more specific power and more energy. The enhanced performance of the thin film can be obtained by using the techniques of hybridization in the preparation of supercapacitive electrodes and devices. By preparing the composites we can combine and enhance the desirable features like capacitance, energy density, conductivity, adherence to the substrate etc.

Why Polypyrrole (PPy) Ease of production, Conductivity 2- 100 S/cm2 by means of the shifting of electrons in conjugate pair, Solubility of monomer in aqueous as well as non aqueous media, Low oxidation potential Charge storage throughout the bulk volume But PPy films have following ambiguities Less adherence to the substrate, Poor electrochemical stability, Less elasticity of shape hence could not regain their shape once expanded by doping. Further The polymerizaros are affecting the composition by implantaing the species formed during the chemical reactions during the PPy synthesis hence pure PPy is tough to get

The oxidative polyerizer should be such chosen that the metal oxide/hydroxide, chalcogenides etc formed and goes in the PPy matrix must improve the supercapacitive performance , adherence and electrochemical stability. There are different oxidizers viz. FeCl3, K2Cr2O7, H2O2 etc. Potassium dichrmate is the strongest oxidizer in the acidic media whereas the KMnO4 acts as a strong oxidizor in basic medium. In the present study we tried and achieved the thin films of oxidative polymerization of PPy using acidic KMnO4 The present study equal volumes of, 0.1M Pyrrole (anionic precursor) and different molar variations (20mM to 40mM) of KMnO4 cationic precursor were taken as the initial sources as the precursor feed for the Chemical Bath Deposition.

Advantages of Chemical Bath Deposition over the other methods of thin film deposition No need of highly sophisticated mechatronic arrangements Can work at any temperature (even room temperature) No constraints on the size and shape of substrate It maintains the stoichiometry of the material in the thin film Thin films of different thickness can be deposited No evolution of toxic gases hence eco friendly Set up is easy to build and cost effective

Chemical Bath Deposition Volume of precursor feed Molarity of precursor Volume of precursor feed Substrate material RPM of the solution Deposition time Temperature Chemical Bath Deposition Schematics Table 1 Sample codes for CBD samples with Molar variations in the anionic source Sample Codes Cationic source Anionic source RPM Deposition time Bath temperature Deposition hrs M1 0.1M Pyrrole 0.02 M KMnO4 200 45 min (2700 sec) 315K 2hrs (7200 sec) M2 0.03M KMnO4 45min (2700 sec) M3 0.04M KMnO4

Reaction mechanism

Schematics of Xray diffractometer

X-Ray diffraction pattern of the sample with optimum parameters Peak details and calculated parameters for K2 S4O6 as per JCPDS card 790505 Peak details and calculated parameters for Mn(OH)2 as per JCPDS card 120696 Obs 2θ Std 2θ Obs. d Std. d hkl 18.11 18.081 4.8943 4.902 2 2 2 23.57 23.44 3.7715 3.7816 5 1 0/ 5 1 1 27.36 27.37 3.257 2.6528 6 0 2 28.69 28.717 3.109 3.1005 1 1 3 32.77 32.74 2.7306 2.733 7 1 2 33.96 33.84 2.6376 2.6465 1 3 0 Obs 2θ Std 2θ Obs. d Std. d hkl 36.25 36.63 2.4761 2.453 1 0 1 49.78 49.97 1.8302 1.825 1 0 2

FTIR spectrograph of the sample M1 C-C, C=C bonds and streching vibrations, N-H streching and vibrations C-H strechings and ring vibrations confirm the formation of PPy

Schematics of Cyclic voltammetry set up Actual set up of Cyclic Voltammetry Schematics of Cyclic voltammetry set up Electrode conncetions

Cyclic voltammogram of samples M1, M2 and M3 at 5mV/S Cyclic Voltammograms of samples with different molarity at the scan rate 2mVSec-1 Specific capacitances of different samples at the scan rate 2mVSec-1 Samples Specific capacitance SC (F/g) M1 271.4510 M2 197.7000 M3 128.9383

Cyclic voltammograms of M1 at different scan rates. Cyclic voltammograms for sample M1 at different scan rate Variation of C, SC and IFC for sample M1 with scan rate Scan rate (mVSec-1) Capacitance C (F) Specific capacitance SC (Fg-1) Interfacial capacitance IFC (Fcm-2) 2 10.8580 271.45 5.4289 5 8.7254 218.13 4.3626 10 9.0021 225.05 4.5009 20 9.7044 242.61 4.8521 25 5.4643 136.60 2.7321 50 7.1727 179.31 3.5863 100 5.5364 143.41 2.8680

Plausible cell reactions during the Cyclic Voltammetric study The reaction during anodic positive sweep is responsible for the reduction S from (+5 state to +4 state) corresponding to reduction peak. During the anodic negative sweep, the recombination of SO2 and O2 to give S4O6– is not possible The only possible reactions are Dedoping of PPy and Oxidation of Mn(OH)2 to MnO2 Neither the de-doping nor the oxidation of Mn hydroxide to oxide is responsible for the pseudocapacitance hence no peaks are observed on the oxidation sweep.

Tetrathionate ion

Result and conclusion Potassium tetrathionate doped PPy : Mn(OH) thin flims were deposited on the SS substrate using Chemical Bath deposition method. 2. The optimized sample shows irreversible behavior. 3. Though the area under curve on CV plot goes on increasing with increase in scan rate , the capacitance, specific capacitance and interfacial capacitance goes on decreasing as the number of intercalations- deintercalations do not increase in the same proportion.