Effect of Annealing Temperature on Polypyrrole Super Capacitive Behaviour

Abstract

Polypyrrole was synthesized by using potentiostatic electrodeposition method. Polypyrrole deposits on stainless steel for 25 min and it annealed at 500c, 700c, 1000c and 2000c, the effects of annealing temparature on polypyrrole morphology were studied by using scanning electron morphology technique. Similarly the super capacitive behaviour of polypyrrole was studied using cyclic voltammetry and charging-discharging technique. Maximum specific capacitance 62.87 F/gm is obtained at 700C.

Introduction

I. INTRODUCTION

The conducting polymers, have created a new area of research. Conducting polymers are important and interesting classes of new organic materials that have gained considerable attention in the recent years. These polymers have unique properties which have led to some commercial applications such as manufacturing of printed circuit boards, corrosion protection, electro chromic displays, electrolytic capacitors, rechargeable batteries and conductive coating for textile sensors, light emitting diodes electromagnetic shielding ,etc.[5,8-11].A polymer is a long – chain molecule that compose a large number of repeating units of identical structure. New conducting polymer structures have been developed over the past two decades with the hope of obtaining better properties than polyacetylene .In many researches it is found that polypyrrole is very sensitive to moisture, because this leads to leaching of the counter ion and thus to decrease in conductivity. Annealing makes the chain mobile to acquire a stable morphology and also to enhance the properties by elimination of moisture content. Polypyrrole is one of the most important conducting, easy to synthesize polymer. Due to enormous properties such as chemical, electrical, optical, surface morphological, etc.it used in many application like solar cell, supercapacitor, and biosensor etc. [3] .

Many of researcher studied effect of annealing temparature on polypyrrole. Rashmi Saxsena [5]has reported that polypyrrole phase was changed in range from 1100C-1700C, Sutar Rani[4] reported that around 1000c water gets evaporated from material and its FTIR Spectrum recorded at different temparature are in good agreement with the TG/DTA data, Riza Ansari[6] reported that thermal treatment of PPY membrane did not lead to any improvement.

In this paper, we have synthesized polypyrrole by elctropolymerization technique using 5 sulfosalicylic acid. Then it was annealed at 500 c, 700, 1000, 2000 c and studied supercapacitive behaviour using cyclic voltammetry and charging-discharging techniques. Surface morphology of polypyrrole was studied with the help of SEM, XRD and Raman spectra.

II. EXPERIMENTAL METHOD

For electrodeposition of Polypyrrole we have used 99% pure pyrrole and 5 sulfosalicylic acid. In 0.1M Pyrrole added 0.01 M of 5 sulfosalicylic acid to adjust PH 2.2.We have applied 0.7 volt to the cell for 25 min, after elctrodeposition, annealed Polypyrrole samples at 500c,700c,1000cand 2000c for 3 hours. This electrodeposition is carried out by three electrode system, stainless steel is used as working electrode, graphite is used as counter elctrode and saturated calomel is used as reference electrode. Before deposition, we cleaned stainless steel substrate properly, then we polished Stainless steel with zero grade paper and  then rinsed with acetone and ethanol ;etched in HNo3 for few second and finally cleaned them ultrasonically with distilled water. Electrodeposited polypyrrole are chemically characterized by cyclic voltammetry, charging-discharging and impedance spectroscopic method by using metrohm autolab PGSTAT 204. Confirmation of polypyrrole were confirmed with the help of XRD, Raman spectroscopy and electrochemical impedance technique.

III. RESULT AND ANALYSIS

A. XRD

XRD shows the structure of polypyrrole, figure1 a to d shows amorphous structure of polypyrrole. Peaks are attributed for steel, it is indexed by square. Hump at 20 to 26 degree shows pure amorphous nature of polypyrrole [5]. Water starts its evaporation at around 100 0c and at 2000C it gets completely evaporated from the thin film.

B. Raman Spectra

This is one of the most used technique for confirmation of material. From the above figure2 peak at 929, 933 cm-1 attributes the polypyrrole ring which is absent in 2000c,  peak 970, 977, 984 cm-1attributes C-H Bond, peaks from 1050 cm-1 to 1052 cm-1  shows C-H plane symmetry band, the band from 1235 cm-1  to 1249 cm-1 shows C-H asymmetry plane, which is absent at 2000c. Peaks at 1377 cm-1 and 1378 cm-1 shows  C-N asymmetry plane which are greater than  wave numbers obtained  at 2000c .Peaks from 1582 cm-1 to 1592 cm-1 are obtained because of the C=C backbone stretch of PPY. Around 1000\c water starts its evaporation hence at 2000c water gets completely evaporated, so polypyrrole ring vanishes slowly at increasing temparature.

C.  SEM Image

Surface morphology was studied with the help of scanning electron morphology technique. In figure3 a at 500c  image looks like cauliflower structure and more dense structure is observed somewhat like cabbage , its size is about 2 micro meter, at 700c all particles are uniformly distributed and shows cloud like cluster, its average size is 480 nm, at 1000c particles are agglomerated [3]in spherical shape and are seen distributed non uniformly, surrounded by cauliflower like structure at periphery, at 2000 c particle structure looks like agglomeratedshape[3] and cauliflower structure but, due to reduction of water content some granular like particles are formed on it.

D. Electrochemical Characterization

1. Cyclic Voltammetry: Cyclic Voltammogram is one of the technique which is used to study supercapacitive behaviour of material. Using this technique we have studied supercapacitive behaviour of Polypyrrole in 0.5 M of Na2So4 at voltage range from -0.5 V to 0.4 V at 2mV/sec.

figure4(a) shows temparature at 500 and 700 , area under the curve increase, while at increasing temparature greater than 700 area under the curve reduces, so maximum capacitance is 62.87 F/gm at 70 degree for scan rate of 2mV/sec. At increasing temparature from 1000 C to 2000C polypyrrole shows poor capacity performance.

The figure 4(b) for 700c shows that at increasing scan rate area under the curve increases, for low scan rate electrons enter inside pore of film, so specific capacitance is larger at low scan rate. For fast scan rate with increase in scan rate, specific capacitance (Cs) decreases of all polypyrrole films. Ideally capacitive behaviour of the film is observed from CV curves which depict, increase in current with increases scan rate.

2. Charging- Discharging Curve:  Figure 5 shows the charging-discharging curve for polypyrrole at 500, 700, 1000, 2000C in 0.5 M of Na2So4 at 0.5 mA current. Voltage window for charging- discharging curve is 0 to1 V, it represents pseudocapacitve behaviour of polypyrrole. Maximum specific capacitance from charging-discharging curve is 21.66 F/g. The charging-discharging curve shows asymmetry Nature and maximum energy density and power density are 10.57wh/kg and 292.88W/kg respectively.

Conclusion

Effect of annealing temparature on polypyrrole and its characterization is successfully studied, its supercapacitive was studied in 0.5M of Na2SO4 from cyclic Voltammetry. Film annealed at 700c shows maximum capacitance (62.87 F/gm). At 1000c evaporation of water starts and at 2000c water completely gets evaporated which is observed in raman spectra and some granual particle is form around film and is observed with the help of SEM. Due to low porosity at other annealing temparature film capacitance reduces.

References

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Copyright

Copyright © 2022 Miss. Priti Jadhav, Dr. K. V. Sukhatankar. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.