Scholarly article on topic 'Electrochemistry Preparation of Electrodes based on Polypyrrole and polymethylpyrrole/Manganese Dioxide Particles'

Electrochemistry Preparation of Electrodes based on Polypyrrole and polymethylpyrrole/Manganese Dioxide Particles Academic research paper on "Chemical sciences"

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Abstract of research paper on Chemical sciences, author of scientific article — Ahmed Tabchouche, Ali Ourari, Nawal Zoubeidi, Djamal zerrouki

Abstract In the present work, we study the electrochemical behavior of Polypyrrole and methylpyrrole modified with incorporation of manganese microparticles. Two methods used for the incorpotation of the particle into the PPy film. the first one it's by suspension,The PPy electrodeposition was performed using acetonitrile and tetrabutylammonium perchlorate (TBAP) in the presence of MnO2 microparticle, the second method have been performed in two step after that the PPy films was formed in the electrodes surface, this was immersed in aqueous chloride solution,containing Mn2+ (for manganese incorporation) by electro oxidation

Academic research paper on topic "Electrochemistry Preparation of Electrodes based on Polypyrrole and polymethylpyrrole/Manganese Dioxide Particles"

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Energy Procedia 36 (2013) 1009 - 1017

TerraGreen 13 International Conference 2013 - Advancements in Renewable Energy and Clean

Environment

Electrochemistry preparation of electrodes based on polypyrrole and polymethylpyrrole/manganese dioxide particles

Ahmed Tabchoucheab*, Ali Ourarib, Nawal Zoubeidib,c and Djamal zerroukia

a) Université Kasdi Merbah Ouargla, Laboratoire Dynamiques interaction et réactivité des système, Faculté des Sciences et Technologies

et des Sciences de le Matière, Ouargla 30000 Algérie. b) Université Ferhat Abbas Sétif, Laboratoire d'Electrochimie, d'Ingénierie Moléculaire et de Catalyse Redox (LEIMCR), Faculté de

technologie, Sétif19000 Algérie.

c) Université Kasdi Merbah Ouargla, Département des Sciences de la Matière, Faculté des Sciences et Technologies et des Sciences de le

Matière, Ouargla 30000 Algérie

Abstract

In the present work, we study the electrochemical behavior of Polypyrrole and methylpyrrole modified with incorporation of manganese microparticles. Two methods used for the incorpotation of the particle into the PPy film. the first one it's by suspension ,The PPy electrodeposition was performed using acetonitrile and tetrabutylammonium perchlorate (TBAP) in the presence of MnO2 microparticle , the second method have been performed in two step after that the PPy films was formed in the electrodes surface, this was immersed in aqueous chloride solution ,containing Mn2+ (for manganese incorporation) by electro oxidation

© 2013 The Authors. Published by Elsevier Ltd.

Selection and/or peer-review under responsibility of the TerraGreen Academy Keywords: modified electrode, polypyrrole, manganese micro particles. ;

1. Introduction

The use of modified electrodes as synthesis tool has saved considerable momentum over the past two decades, giving a major boost to the electrocatalysis that has not stopped growing since the 80s when Diaz et al [1,2] highlighted conducting polymers. In this work, we are interested in the modification of the glassy carbon electrode with a film of polypyrrole [3] or poly (methyl-pyrrole) doped by manganese dioxide particles for use as an anode for oxidizing primary and secondary alcohols.

The advantages of using these electrode materials commonly called modified electrodes [5,6] offer the possibility of heterogeneous catalysis for the use of low catalyst concentrations and facilitating the separation of reaction products from the catalyst itself. This has the effect of increasing significantly the lifetime of the catalyst and, by elimination of oxidant-species interactions of oxidative reactions leading to oxidative damage that minimize greatly the life of catalyst particularly in homogeneous catalysis[7,8,9].

The incorporation of metal particles onto polymer-modified films [10,11,12] found to be useful in the field of electro catalysis.

* tabchouche ahmed Tel.: 00213(0)663978980. E-mail address: tabchouche.ah@univ-ouargla.dz

1876-6102 © 2013 The Authors. Published by Elsevier Ltd.

Selection and/or peer-review under responsibility of the TerraGreen Academy

doi:10.1016/j.egypro.2013.07.115

The prepared PPy-electrod [13], and PPY-particle- Mn Particle electrodes were characterized by cyclic voltammetry and atomic absorption spectroscopy. The results explained in terms of the modification of the electrochemical properties of the polymer films caused by the incorporation.

2. Experimental section

All chemical used were of analytical reagent grade from Aldrich-Sigma and were used without further purification. Acetronitrile (CH3CN), Tetra-n-butylammonium perchlorate (TBAP), Manganese dichloride MnCl2, pyrrole (C4H5N) , Le methylpyrrole (C5H8N) were purchased from Sigma and used without further purification except for the acetonitrile purified with double distillation under P2O5 and desyherated under molecular sieve The solutions were obtained by solving substances in ultra-pure water (Milli-Q Millipore).

Cyclic voltammetric study performed in a three-electrode cell Taccussel. The working electrode was a disc of glassy carbon (3mm diameter), the counter electrode was a platinumwire (6mm diameter),and the reference electrode was a saturated calomel electrode (SCE), and all results are given versus SCE. Against the electrode is a platinum plate .The-working electrode cleaned by polishing using micro cloth polished pad with emery paper of small particle size. It is then rinsed with double distilled water and then with acetone and finally dried, before each manipulation. All of the electrochemical measurements were performed at room temperature using a potentiostat/galvanostat ((Taccussel, model PJT 120-06)) and recorded on a tracing table

Tow monomers been used to modify the electrode pyrrole and methylpyrrole before studying the behavior of these tow monomers, we used the votammogram to study the behavior of the electrolyte solution.

2.1- Resultant and discussion

Before studying the electrochemical behavior of pyrrole and methyl pyrrole monomers, we conducted a study by Cyclic voltammetry in acetonitrile solution in 0.1 M tetrabutylammonium perchlorat (TBAP) as electrolyte solution on a glassy carbon electrode (0 = 3 cm) under an atmosphere of nitrogen. The figure 1 show the stability of the electrolyte, the stability domain is very broad and ranges between (1.8 Vand - 2.4 V).

Fig. 1 Voltammogram show the stability domain of electrolyte acetonitrile 0.1M and TBAP

The figure 1 show a strong positive current when we exceeds the potential of 1.8 V, which is characteristic of the oxidation of the acetonitrile, the stability range checked before each experiment.

a) Preparation of modified electrode

The electrodes are prepared in two stages, the first being the deposition of the polymer by electro polymerization, the second is the incorporation of particles of manganese dioxide. the electrode prepared by electro polymerization : the figure2 represent the voltammogram of pyrrole and methylpyrrole , show an oxidation peak at 0.9V for polypyrrole and 0.7 V for methylpyrrole, This oxidation results in the formation of a polypyrrole and polymethylpyrrole. The appearance of a cathodic wave at 0.2 V for pyrrole and to 0.02 V for the methylpyrrole in return scan also shows the formation of a polymeric film.

Fig. 2 Voltammogram of pyrrole A and methylpyrrole B in electrolyte solution

a.1. Effect of the scan rate on the polymerization

The values of E1/2 were determined to the same value of the current intensity (120 ^A) which corresponds to the oxidation of the same amount of pyrrole and methylpyrrole. We note that the potential of the polymerization increases with as the scan rate increases.

From these voltammograms represented in figure3 were drawn up the potential of the wave corresponding to the beginning of oxidation. This study was carried out at different scan rates (100, 50, 25, 10.5 mV / s)

—. 0,70-W

LLJ 0,68 ->

UJE 0,66 -

■ pyrrol methyl-pyrrol

0,640,620,600,58-

20 40 60 80

Slew Rate (mV/s)

Fig. 3 Effect of scan speed on the potential of oxidation

The values of E1/2 were determined to the same value of the current intensity (120 ^ A) which corresponds to the oxidation of the same amount of monomer's. We note that the starting oxidative potential increases with increasing the scan rate speed.

The deposition of a film on the electrode can realized either by scanning successive potential or by controlled potential oxidation.

a.2. Film deposition by controlled potential oxidation

Oxidation selected potential from 0.63V and 0.7V, also allows polymers films deposition at the surface of the electrode.

a.3. Effect of electrical charge on the film thickness ofpolypyrrole

Figure 4 shows that the amount of polymer deposited on the electrode increases with the increase of the charge passed for the electropolymerization of polypyrrole and polymethylpyrrole. For the same charge passed it incorporates a different amount for the two polymers. We remark after anodic peak integration that the amount deposited polypyrrole is always less than that of polymethylpyrrole.

Fig. 4 Effect of the electrical charge on the polymeric film thickness

Fig. 5 Voltammogram of the electro deposition of the monomer pyrrole and methylpyrrole

b) Electrochemistry characterization of the electrodeposition

The modified electrodes, transferred to a monomer-free electrolyte have a reversible oxidation characteristic wave of a deposit irreversible a polypyrrole and polymethylpyrrole to the surface of a glassy carbon electrode. The load measured by integration of the current wave in the anode or cathode, low scan rate, to determine the amount of polymer deposited or the film thickness which is characterized by a magnitude r which is the apparent concentration per unit area . This quantity is calculated using the formula r = Q / NFA, and considering that the polypyrrole (poly methylpyrrole) is oxidized in an amount of an electron to three pyrrole (n = 0.3), A is the area of the electrode and F the number of faraday.

The figure 6 Voltammogram cyclic curve of glassy carbon electrode (O = 3mm) modified by a polymer film drawn after transfer of the electrode in an electrolyte not containing the monomer v = 5 mV / s (A) electrode A modified poly (B) modified electrode poly B

Fig. 6 Voltammamperometric cyclic curve of glassy carbon electrode (O = 3mm) modified by a polymer film (A) modified polypyrrole (B) modified polymethylpyrrole

c) Incorporation of manganese dioxide particles in polymer films

The electrochemical behavior of manganese dioxide has been studied by cyclic volt amperometry on a glassy carbon electrode (0 = 3mm) in aqueous solutions containing 10-3M MnCl2 at different pH (4, 7, 10) and at different speeds scanning (100, 50, 25, 10, 5 mV / s).

The cyclic voltammograms recorded at a scanning speed equal to 100 mV / s in a potential range of 0 to 1500 mV ,show when scanning potential peak positive oxidation of Mn2+ to Mn4+ (MnO2) observed at a potential E = 0.98 V for the solution of pH = 4, E = 0.79 V for the solution of pH = 7 and no oxidation peak was observed for a solution of pH = 10. (Figure7).

E ( V /ECS)

Fig.7 Cyclic voltammograms at different pH value

Oxydation on glassy carbon at E=0.7 V pyrrole (A)

Glassy carbon polymer's A or B

ClO4- ^ Immersion in free monomer's ClO4-

Glassy carbon polymer's A or B

C poly A or poly B

Glassy carbon polymer's A or

Fig. 8 Diagram show the preparation steps of the modified electrode by electro polymerization followed by incorporation by direct oxidation technique (C: glassy carbon)

Monomers

The incorporated amount of MnO2 measured by coulometry and atomic absorption spectroscopy (AAS), knowing that the recovery was carried out in concentrated and hot hydrochloric acid table 1 to 4.

Table 1 Polyopyrrole film at pH= 4 polypyrrole film at pH=7

Qexp(mC) rexp 10+7 (mole/cm2) Qinc(mC) r'(coulometry) 10+8 (mole/l) r' (SAA) 10+8

0.8 3.58 0.076 3.93 3.68

1.8 8.07 0.15 7.77 5.38

2.48 11.1 0.51 2.64 6.19

2.65 11.8 0.66 3.41 8.37

4.9 21.9 0.8 4.14 7.36

Table 2 Polyopyrrole film at pH= 7

polymethylpyrrole film at pH=4

Qth (mC) Qexp (mC) rexp 10+7 (mole/cm2) Qinc (mC) r'(Coulometry) 10+" (mole/l) r'(sAA) 10+8 (mole/l)

10 1 4.48 0.13 7.15 6.72

20 2.05 9.19 0.19 9.84 7.52

30 3.34 14.9 0.29 15.02 7.05

40 4.6 20.6 0.57 29.5 7.06

50 5.3 23.7 0.18 9.63 7.08

Table 3 Polymethylpyrrole film at pH= 4

polymethylpyrrole film at pH=7

Qexp(mC) rexp 10+7 (mole/cm2) Qinc(mC) r'(coulometry) 10+8 (mole/l) r' ,saa) 10+8 (mole/l)

1.1 4.93 0.054 2.79 2.11

2.2 9.86 0.069 3.57 3.24

3.2 14.3 0.087 4.5 4.29

4.7 21.0 0.102 5.28 4.55

5.4 24.2 0.078 4.03 3.57

Table 4 Polymethylpyrrole film at pH= 7 polypyrrole film at pH=4

Qth (mC) Qexp (mC) rexp 10+7 (mole/cm2) Qinc (mC) r'(Coulometry) 10+8 (mole/l) r'(SAA) 10+8 (mole/l)

10 09 4.03 0.093 4~81 4.08

20 2.24 10.0 0.129 6.68 5.10

30 3 13.4 0.162 8.39 8.07

40 3.06 13.7 0.135 6.99 6.41

50 4.9 21.9 0.132 6.83 5.43

Electrical Charge (mC)

Fig. 9 Effect of pH on incorporated quantity manganese dioxide

d) Incorporation in suspension

The glassy carbon electrode was immersed in an acetonitrile solution containing pyrrole in TBAP or methylepyrrole and manganese dioxide (y MnO2 natural or 10-3 M). The deposition of MnO2 occurs simultaneously with the formation of polymer film controlled potential between 0.63 and 0.7V and different charge passed. The amount of incorporated MnO2 is estimated by atomic absorption (AAS) table 5.

Ahmed Tabchouche et al. / Energy Procedía 36 (2013) 1009 - 1017 Table 5 The amount of incorporated MnO2 (moles/l) estimated by atomic absorption(AAS)

incorporated Quantity (moles/l)

Polypyrrole

Polymethylpyrrole

N- MnO2 Y MnO2 N- MnO2 Y MnO2

10 5.12 x10-8 -- 6.19 x10-8 5.05x10-8

20 5.39 x10-8 -- 5.22 x10-8 5.55 x10-8

30 5.55 x10-8 5.01 x10-8 5.07 x10-8 5.87 x10-8

40 5.39 x10-8 5.31 x10-8 6.76 x10-8 4.83 x10-8

50 5.71 x10-8 5.95 x10-8 5.12 x10-8 5.79 10-8

3. Conclusion

In the case of inclusion of particles of MnO2 at the film formation polypyrrole and polymethylpyrrole whatever for the natural form or in the у MnO2 form, there substantially varying the amount of MnO2 incorporated. This may depend on the concentration of the pyrrolic monomer; the MnO2 particles. Worked with the same concentrations, the amount of MnO2 particles incorporated is almost constant as a function of the quantity of electricity passed.

The electrochemical study of the incorporation of these particles (MnO2) was investigated as a function of pH. It turned out that at pH = 4, is formed over MnO2 due to the abundance of Mn2 + ions subjected to anodic oxidation polentiel; E = 0.98 V , at pH = 7 represents neutrality, there is less formation of MnO2 due to the decrease in the concentration of Mn2 + ions that are partially in the hydroxylated form Mn(OH)2 , Mn(OH)4 which has a low solubility in aqueous media or it precipitates which explains the decrease in the concentration of these ions (Mn2 +). Regarding the amount of MnO2 incorporated, there is a gradual grow of MnO2 incorporated depending on the film thickness and the polypyrrole pH of the solution containing the chloride salt of manganese. In this case, there is a unexpected decrease in the amount incorporated MnO2 at 50 mC and recovery rate equal to 2.37x10-6 moles/cm2 for pH = 4 and 2.42x10-6 moles/cm2 for pH = 7. This decrease in the rate of incorporation of MnO2 particles in the films of poly methylpyrrolee could probably be associated with the increase in the hydrophobic character of this film poly methyl pyrrole would tend to keep away ions Mn2 + and that despite of the pH knowing this result was obtained both at pH = 4 and pH = 7. Also, we observed an increase in the amount of MnO2 films incorporated into poly pyrrole gradually as the thickness increases. This phenomenon is reproducible at pH 7, but the amount of incorporated MnO2 drops unexpectedly to a lower charge (40 mC) as mentioned above for the films of polymethylpyrrole.

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