The investigation of the electrocatalytic effect of nanocomposites polyaniline films modified with platinum.
الموضوعات :
Nafiseh Hajiabdolah
1
,
Mohammad Yousefi
2
1 - Department of Chemical Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran
2 - Department of Chemical Engineering, Abadan Branch, Islamic Azad University, Abadan, Iran
الکلمات المفتاحية: Polyaniline, electrocatalytic effect, Platinum, Carbon Graphete.,
ملخص المقالة :
Polyaniline (PAni) is relatively stable in the air even at very high temperatures. His indomitable nature is due to its instability, fragility, high pH dependence of the conductivity and electrochemical activity of the environment, and limitation of application. Therefore, efforts to change the structure of PAni have been made to deal with these problems. Between copolymers and composites, the yen has been considered as an important way to improve its properties. The use of conductive polymers as a support for catalytic platinum particles for the oxidation of hydrogen ions and small organic molecules has been the focus of many researchers, usually platinum is used as an ideal catalyst for these processes. The main reason for studying such composite materials is their extraordinary electrocatalytic activity, which is comparable to platinum electrode or even much more.
[1] D. Kumar, R. Sharma, Advances in conductive polymers, European polymer journal 34(8) (1998) 1053-1060.
[2] N.A.M. Radzuan, A.B. Sulong, J. Sahari, A review of electrical conductivity models for conductive polymer composite, International Journal of Hydrogen Energy 42(14) (2017) 9262-9273.
[3] B.C. Hagelüken, Recycling the platinum group metals: A European perspective, Platinum Metals Review 56(1) (2012) 29-35.
[4] J. Pawlak, E. Łodyga-Chruścińska, J. Chrustowicz, Fate of platinum metals in the environment, Journal of Trace elements in Medicine and Biology 28(3) (2014) 247-254.
[5] M. Ashiq, M. Danish, M.A. Mohsin, S. Bari, F. Mukhtar, Chemistry of platinum and palladium metal complexes in homogeneous and heterogeneous catalysis: a mini review, Int. J. Sci. Basic Appl. Res 7(1) (2013) 50-61.
[6] H. Dong, J. Zhao, J. Chen, Y. Wu, B. Li, Recovery of platinum group metals from spent catalysts: a review, International Journal of Mineral Processing 145 (2015) 108-113.
[7] N. Cutillas, G.S. Yellol, C. de Haro, C. Vicente, V. Rodríguez, J. Ruiz, Anticancer cyclometalated complexes of platinum group metals and gold, Coordination chemistry reviews 257(19-20) (2013) 2784-2797.
[8] M. Zorko, B. Jozinović, M. Bele, N. Hodnik, M. Gaberšček, SEM method for direct visual tracking of nanoscale morphological changes of platinum based electrocatalysts on fixed locations upon electrochemical or thermal treatments, Ultramicroscopy 140 (2014) 44-50.
[9] N. Hodnik, M. Zorko, B. Jozinović, M. Bele, G. Dražič, S. Hočevar, M. Gaberšček, Severe accelerated degradation of PEMFC platinum catalyst: A thin film IL-SEM study, Electrochemistry Communications 30 (2013) 75-78.
[10] C.-Y. Liu, K.-C. Huang, P.-H. Chung, C.-C. Wang, C.-Y. Chen, R. Vittal, C.-G. Wu, W.-Y. Chiu, K.-C. Ho, Graphene-modified polyaniline as the catalyst material for the counter electrode of a dye-sensitized solar cell, Journal of Power Sources 217 (2012) 152-157.
[11] J. Zhang, L. Nan, W. Yue, X. Chen, Enhanced methanol electro-oxidation activity of electrochemically exfoliated graphene-Pt through polyaniline modification, Journal of Electroanalytical Chemistry 858 (2020) 113821.
[12] H.G. Lemos, S.F. Santos, E.C. Venancio, Polyaniline-Pt and polypyrrole-Pt nanocomposites: Effect of supporting type and morphology on the nanoparticles size and distribution, Synthetic Metals 203 (2015) 22-30.
[13] P. Boomi, H.G. Prabu, J. Mathiyarasu, Synthesis, characterization and antibacterial activity of polyaniline/Pt–Pd nanocomposite, European journal of medicinal chemistry 72 (2014) 18-25.
[14] J. Hou, M. Yang, C. Ke, G. Wei, C. Priest, Z. Qiao, G. Wu, J. Zhang, Platinum-group-metal catalysts for proton exchange membrane fuel cells: From catalyst design to electrode structure optimization, EnergyChem 2(1) (2020) 100023.
[15] P. Daubinger, J. Kieninger, T. Unmüssig, G.A. Urban, Electrochemical characteristics of nanostructured platinum electrodes–a cyclic voltammetry study, Physical Chemistry Chemical Physics 16(18) (2014) 8392-8399.
[16] M. Khalid, L.T. Quispe, C.C.P. Cid, A. Mello, M.A. Tumelero, A.A. Pasa, The synthesis of highly corrugated graphene and its polyaniline composite for supercapacitors, New Journal of Chemistry 41(11) (2017) 4629-4636.
[17] A. Shahid, Z.N. Kayani, H. Nazli, S. Riaz, S. Naseem, Controllable synthesis of composite electrode material to enhance the electrochemical performance of supercapacitors, Optical Materials 143 (2023) 114264.
[18] A. Kumar, A. Moin, A. Ahmed, H. G Shivakumar, Cashew gum a versatile hydrophyllic polymer: a review, Current Drug Therapy 7(1) (2012) 2-12.
JCRS Journal of Chemical Reactivity and Synthesis 2024: 14(2) 73-82
Research Article
The investigation of the electrocatalytic effect of nanocomposites polyaniline films modified with platinum.
Nafiseh Hajiabdolah, Mohammad Yousefi
Department of Chemical Engineering, Arvand International Branch, Islamic Azad University, Abadan, Iran
ARTICLE INFO: ABSTRACT
Polyaniline (PAni) is relatively stable in the air even at very high temperatures. His indomitable nature is due to its instability, fragility, high pH dependence of the conductivity and electrochemical activity of the environment, and limitation of application. Therefore, efforts to change the structure of PAni have been made to deal with these problems. Between copolymers and composites, the yen has been considered as an important way to improve its properties. The use of conductive polymers as a support for catalytic platinum particles for the oxidation of hydrogen ions and small organic molecules has been the focus of many researchers, usually platinum is used as an ideal catalyst for these processes. The main reason for studying such composite materials is their extraordinary electrocatalytic activity, which is comparable to platinum electrode or even much more
Keywords: Polyaniline; Electrocatalytic effect, Platinum; Carbon Graphete |
Received: 1 December 2024
|
Accepted: 15 January 2025
Available online: 18 January 2025
|
✉: N.Hajiabdolah |
1. Introduction
Electrically conductive polymers are among the most fascinating materials in modern technology due to their natural and diverse doping states. In the meantime, polyaniline has a special feature that may be due to its use in several different branches of technology. Although polyaniline is one of the most important conducting polymers of this era. Basically, polyaniline is known as a redox polymer. Chemical polymerization of aniline is carried out in an acidic environment. The acidic environment helps to dissolve the monomers in the formation of conductive polyaniline [1, 2].
Platinum is an extremely rare metal, Platinum is a shiny gray metal, and when it is pure, it is soft, malleable, and conductive [3]. This element is also used to make the cover of rockets, jet engine fuel. This metal, like palladium, has high hydrogen absorption properties. Platinum is used as a suitable catalyst for sulfuric acid production processes [4, 5]. Platinum is one of the main components of many metal products such as electrodes and is used as a catalyst in some chemical reactions. Platinum is usually used as a medicine in the treatment of cancer. The effects of platinum on health depend on the type of bonds formed and the level of immunity of the person [3, 6, 7].
The purpose of this study is Considering that platinum is an expensive metal, with the consumption of the least amount of platinum, the most analytical use was taken in the electrocatalysis of hydrogen reduction and ethanol oxidation.
2. Experimental
Materials, Equipment, and Method
Aniline is distilled under low pressure in a nitrogen atmosphere and the resulting colorless liquid is kept at 5 degrees Celsius. Ethanol was also used in pure form. Platinum is used in the form of hexachloroplatinic acid hexahydrate H2(PtCl6)6H2O. Mineral salt potassium chloride (KCL) and phosphoric acid (H3PO4)) have been used without purification. All the above items were labeled by the German company Merck.
Potentiostat/galvanostat model compactstat owned by Ivium Technologies, Netherlands was used for the synthesis and identification of nanocomposite. The Vega model electron microscope device of Tscan company (TESCAN) made in the Czech Republic and Slovakia, which has an Energy Dispersive X-ray analyzer, was used to check the morphology and size of the composite particles. The studies were carried out in a typical three-electrode electrochemical cell.
Graphite composite panels CG (1.8mm) 2B composite made by Gaj Educational Institute was used as working electrode and platinum electrode as auxiliary electrode and Ag/AgCl reference electrode. The reference electrode was prepared and used by placing a silver wire in saturated KCL solution along with a platinum electrode and connecting them to a DC current source and applying a voltage of 1.6 to 1.8 volts for 20 to 30 minutes. First, the electrochemical synthesis of polyaniline was performed on the tip of a graphite pencil; Polyaniline was synthesized by 10 ml of 50 mM aniline in 1 M phosphoric acid and 0.5 M potassium chloride solution on the working electrode (graphite pencil tip). The graphite electrode was placed in the above solution and subjected to a potential of -0.4 to 1.2V according to Ag/AgCl reference with a scanning speed of 100 mV/s for 20 cycles by cyclic voltammetry method. Then, by potentiostatic electrochemical method (cyclic voltammetry), aniline-platinum composite (in different concentrations of platinum) was synthesized as a layered black deposit on the graphite electrode.
Electrosynthesis was performed by cyclic voltammetry method at a potential of -0.4 to 1.2V in the presence of silver electrode (Ag/AgCl) with a scanning speed of 100 mV/s.
After the synthesis of the composite films prepared on the graphite electrode, the films were examined by SEM were studied and investigated. Graphite electrodes were placed inside different solutions. Solutions containing 10 ml containing 50 mM aniline in the presence of 0.5 M potassium chloride supporting electrolyte and 1 M phosphoric acid solution were applied to the electrode under a potential of -0.4 to 1.2V, then the above modified electrode (PAni was modified by platinum with different molar fractions of platinum. Then Solutions containing 10 ml, including 50 mM aniline with platinum (with different fractions, from 1 to 7 mM platinum) and in the presence of 0.5 M potassium chloride and 1 M phosphoric acid solution under a potential of – 0.4to 1.2 V were placed on the working electrode (CG). The working electrode (CG graphite) was placed in a 10 ml solution containing 4 mM hexachloroplatinic acid, the current Was applied, then the above electrode was placed in a 10 ml solution of aniline (50 mM) containing 1 M phosphoric acid and 0.5 M potassium chloride was entered. The above methods were used in order to select the best composite film with the highest distribution of platinum on the microlayer level and to study the electrocatalytic effect of that electrode on ethanol. Different molar fractions of monomers were used to examine polymer films for platinum diffusion on the electrode surface by SEM.
Then cyclic voltammetry method was used to measure ethanol in such a way that the above modified electrode was placed in solutions containing (0.5, 1, 2 M) of ethanol and the amount of current was measured according to the potential. The compactstat device was also used here.
3. Results and Discussion
Electrochemical synthesis of polyaniline
Polyaniline was subjected to a potential of -0.4 to 1.2V according to Ag/AgCl reference with a scanning speed of 100 mV/s up to 20 cycles by cyclic voltammetry method. Fig 1 shows cyclic voltammograms of 50 mM aniline in 1 M phosphoric acid containing 0.5 M potassium chloride on the tip of a graphite pencil.
Fig 1. Cyclic voltammograms of PAni with a scanning speed of 100 mV/s
Analysis of surface and structure of polyaniline film
The SEM image (Fig 2) show the polyaniline film obtained from a 50 mM monomer solution in phosphoric acid containing potassium chloride, which proves that polyaniline is doped with ions. It is phosphate [8, 9].
Fig 2. SEM (a) of polyaniline obtained from 50 mM monomer solution in phosphoric acid.
Scanning electron microscope image (SEM) of the electrode surface
When aniline is added together with platinum (simultaneously) to the graphite electrode surface (Fig 3). As can be seen, platinum is placed in the form of spherical circles in the interior of the polymer, but compared to the previous case when platinum was synthesized on the polymer (Pt/PAni), it has less spread and dispersion. Checking and identifying the modified electrode by scanning electron microscope (SEM). The resulting images showed that only aniline polymerization has taken place and there is no trace of platinum particles on the surface.
Fig 3. Scanning electron microscope images of the surface of Pt / PAni /CG
The SEM image taken in the presence of platinum not only proves the formation of the composite, but also shows the formation of nano-sized particles. (The presence of causes the reflection of transparent points on the surface of the microlayer). The results confirmed the presence of platinum in the microlayer [10, 11]. According to the pictures (Fig 4), the presence of platinum in the polymer has been confirmed by SEM, which proves the doping of polyaniline with platinum ions. As can be seen in the resulting images, this state has the highest distribution of platinum at the microlayer level and has a high and uniform distribution on the surface of the modified polyaniline electrode and contains a high percentage of platinum [12, 13].
Fig4.Spreading platinum on the surface of the polyaniline modified electrode
By spreading platinum on the PAni film, the size of the platinum particles reaches less than 100 nm. When the particles reach nanometer dimensions, their contact surface increases significantly. As a result, by distributing platinum on the film, it is possible to cover the surface with a much smaller amount of platinum. More calls were received. With this, the amount of platinum used will reach the lowest level and more platinum level will be available. In addition, due to the reactions between platinum and the substrate, the electronic structure of platinum atoms is probably improved, which can increase the catalytic activity [14, 15].
Electropolymerization of aniline in the presence of platinum by graphite electrode
Solutions containing 10 ml, including 50 mM aniline along with platinum (simultaneously) in the form of hexachloroplatinic acid in the presence of 0.5 M and 1 M potassium chloride Of H3PO4 was placed under a potential of -0.4 to 1.2V by graphite electrode. In all the above cases, the solution was performed by the cyclic voltammetry method at a potential of -0.4 to 1.2V in the presence of Ag/AgCl with a scanning speed of 100 mV/s. The studies showed that increasing the mole fraction of platinum increases the anode peak potential. It can be said that the synthesis of polyaniline was done on the electrode more than platinum.
Fig 5. Cyclic voltammograms of aniline with platinum by a graphite electrode with a scanning speed of 100 mV/s up to 20 cycles
Electrocatalytic effect of modified electrode of ethanol
Fig. 6. Cyclic Voltammetry (CV) shows different concentrations of ethanol by graphite electrode. As it is evident, the potential of anodic peaks by the unmodified graphite pencil tip appears at 0.43 V on the above electrode. Fig 7. Different concentrations of ethanol (2, 1, 0.5 M) in phosphoric acid in the potential range of -0.4 to 1.2V are measured using cyclic voltammetry method using modified CG electrode/PAni/Pt. As it is evident, in case of using the modified CG-PAni-Pt electrode, the anode peaks appeared at 0.27 V, which indicates a negative shift of 0.16 V compared to the unmodified electrode. Meanwhile, the current of anodic peaks is directly proportional to the increase in ethanol concentration and confirms the electrocatalytic effect of the modified CG-PAni-Pt electrode on ethanol [16-18].
Fig 6. Cyclic voltammetry (CV) and linear scan voltammetry (LSV) of different concentrations of ethanol by graphite electrode
Fig 7. Cyclic voltammetry (cv) of different concentrations of ethanol by modified graphite electrode CG/PAni/Pt
As the increase in the current of the anodic peaks is directly proportional to the increase in ethanol concentration and confirms the electrocatalytic effect of the modified CG-PAni-Pt electrode on ethanol.
4. Conclusion
In this research, the electrosynthesis of platinum-modified polyaniline film nanocomposite was carried out on the tip of a graphite pencil (CG-PAni-Pt) in 1 M phosphoric acid environment, which included potassium chloride electrolyte support. The main reason for choosing graphite as a substrate is the unique properties of this material, including: cheap price, high electrical conductivity, high corrosion resistance and good chemical stability.
According to the scans performed and the results obtained from the voltammograms of the modified electrodes, we found that the absence of aniline on the graphite composite substrate causes platinum to not have an electrochemical reaction with graphite, and in other words, the synthesis of metal-based nanocomposite is not possible; According to the images taken from the surface of the micro layer, its presence causes the polymerization process and the uniform distribution of platinum on the surface of the modified polyaniline electrode, which is probably due to the increase in the conductivity of polyaniline compared to graphite.
References
[1] D. Kumar, R. Sharma, Advances in conductive polymers, Europ. Polym. J. 34(8) (1998) 1053-1060.
[2] N.A.M. Radzuan, A.B. Sulong, J. Sahari, A review of electrical conductivity models for conductive polymer composite, Int. J. Hydrogen Energy 42(14) (2017) 9262-9273.
[3] B.C. Hagelüken, Recycling the platinum group metals: A European perspective, Plat. Met. Rev. 56(1) (2012) 29-35.
[4] J. Pawlak, E. Łodyga-Chruścińska, J. Chrustowicz, Fate of platinum metals in the environment, J. Trace. Elem. Med. Biol. 28(3) (2014) 247-254.
[5] M. Ashiq, M. Danish, M.A. Mohsin, S. Bari, F. Mukhtar, Chemistry of platinum and palladium metal complexes in homogeneous and heterogeneous catalysis: a mini review, Int. J. Sci. Basic Appl. Res 7(1) (2013) 50-61.
[6] H. Dong, J. Zhao, J. Chen, Y. Wu, B. Li, Recovery of platinum group metals from spent catalysts: a review, Int.J.Min.Process. 145 (2015) 108-113.
[7] N. Cutillas, G.S. Yellol, C. de Haro, C. Vicente, V. Rodríguez, J. Ruiz, Anticancer cyclometalated complexes of platinum group metals and gold, Coord. Chem. Rev. 257(19-20) (2013) 2784-2797.
[8] M. Zorko, B. Jozinović, M. Bele, N. Hodnik, M. Gaberšček, SEM method for direct visual tracking of nanoscale morphological changes of platinum based electrocatalysts on fixed locations upon electrochemical or thermal treatments, Ultramicroscopy. 140 (2014) 44-50.
[9] N. Hodnik, M. Zorko, B. Jozinović, M. Bele, G. Dražič, S. Hočevar, M. Gaberšček, Severe accelerated degradation of PEMFC platinum catalyst: A thin film IL-SEM study, Electrochem. Commun. 30 (2013) 75-78.
[10] C.-Y. Liu, K.-C. Huang, P.-H. Chung, C.-C. Wang, C.-Y. Chen, R. Vittal, C.-G. Wu, W.-Y. Chiu, K.-C. Ho, Graphene-modified polyaniline as the catalyst material for the counter electrode of a dye-sensitized solar cell, J. Power Sour. 217 (2012) 152-157.
[11] J. Zhang, L. Nan, W. Yue, X. Chen, Enhanced methanol electro-oxidation activity of electrochemically exfoliated graphene-Pt through polyaniline modification, J. Electroanalytical Chem. 858 (2020) 113821.
[12] H.G. Lemos, S.F. Santos, E.C. Venancio, Polyaniline-Pt and polypyrrole-Pt nanocomposites: Effect of supporting type and morphology on the nanoparticles size and distribution, Synth. Met. 203 (2015) 22-30.
[13] P. Boomi, H.G. Prabu, J. Mathiyarasu, Synthesis, characterization and antibacterial activity of polyaniline/Pt–Pd nanocomposite, Euro. J.Med. Chem. 72 (2014) 18-25.
[14] J. Hou, M. Yang, C. Ke, G. Wei, C. Priest, Z. Qiao, G. Wu, J. Zhang, Platinum-group-metal catalysts for proton exchange membrane fuel cells: From catalyst design to electrode structure optimization, Energy .Chem. 2(1) (2020) 100023.
[15] P. Daubinger, J. Kieninger, T. Unmüssig, G.A. Urban, Electrochemical characteristics of nanostructured platinum electrodes–a cyclic voltammetry study, Physical Chem. Chemical. Phys. 16(18) (2014) 8392-8399.
[16] M. Khalid, L.T. Quispe, C.C.P. Cid, A. Mello, M.A. Tumelero, A.A. Pasa, The synthesis of highly corrugated graphene and its polyaniline composite for supercapacitors, New J. Chem. 41(11) (2017) 4629-4636.
[17] A. Shahid, Z.N. Kayani, H. Nazli, S. Riaz, S. Naseem, Controllable synthesis of composite electrode material to enhance the electrochemical performance of supercapacitors, Optical Mat. 143 (2023) 114264.
[18] A. Kumar, A. Moin, A. Ahmed, H. G Shivakumar, Cashew gum a versatile hydrophyllic polymer: a review, Curr. Drug Therapy .7(1) (2012) 2-12.
