Eletrodos armazenadores de energia baseados em compósitos de Polipirrol, Imidazol e Hidróxido de Níquel

Orientador : Prof. Dr. Marcio VidottiCoorientadora : Profª Drª Elisa S. OrthTese (doutorado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Química. Defesa: Curitiba, 20/12/2016Inclui referências : f. 122-136Resumo: O efeito nas propriedades estruturais, eletroquímicas e catalíticas do polipirrol (PPI) foram investigadas na formação de compósitos com imidazol (IMZ) e hidróxido de níquel (Ni(OH)2). Primeiro foram estudadas as alterações nas propriedades capacitivas de eletrodos obtidos por diferentes métodos de eletropolimerização. Esses resultados sugerem que o melhor método para obtenção de eletrodos de PPI para supercapacitores é a eletrodeposição potenciostática. Utilizando esse método, compósitos entre PPI / IMZ foram obtidos em diferentes proporções. O estudo cinético da eletrossíntese de PPI / IMZ permitiu verificar que o IMZ altera o processo de polimerização diminuindo os sítios ativos de crescimento do polímero na superfície do eletrodo. Como consequência alterações morfológicas foram observadas por microscopia eletrônica de varredura (MEV), indicando a formação de estruturas mais organizadas. O desempenho eletroquímico foi avaliado por voltametria cíclica (VC), curvas galvanostáticas de carga e descarga (CGCD) e espectroscopia de impedância eletroquímica (EIS). Foi observado um sinergismo entre o PPI / IMZ, melhorando o valor da capacitância específica do material em 65 %. A caracterização espectroscópica indicou a formação de níveis de oxidação diferentes e a presença de IMZ no material final. Assim, um mecanismo de copolimerização entre o IMZ e o PI foi proposto, segundo o qual, os átomos de nitrogênio do IMZ estão livres e podem atuar como catalisadores nas reações de ésteres de fosfato. Dessa maneira, compósitos entre PPI / IMZ foram obtidos por síntese química e através do estudo cinético foi verificado que o IMZ tem um efeito inibidor, diminuindo a constante de velocidade da reação de polimerização. Esses materiais foram usados como catalisadores na reação de hidrólise de ésteres de fosfato, resultando em um incremento de 5000 vezes em relação a degradação espontânea. Os compósitos entre PPI / Ni(OH)2 foram obtidos na forma de estruturas do tipo core-shell, as quais são constituídas por um núcleo de nanotubos de PPI (PPI-NTs) (core) e revestidas com Ni(OH)2 (shell). As caracterizações espectroscópicas e estruturais confirmam a presença do PPI e Ni(OH)2 no material final, bem como sugerem a formação da fase ?-Ni(OH)2. As imagens de MEV e de microscopia eletrônica de transmissão (MET) evidenciaram que o PPI-NTs foi completamente recoberto com Ni(OH)2 e que a estrutura final tem diâmetro menor que 200 nm. As análises das isotermas de adsorção / dessorção de N2 pelo método de Brunauer, Emmett, Teller (BET) mostraram um aumento significativo da área superficial do material híbrido (PPI-NTs@Ni(OH)2) em relação aos precursores. O desempenho eletroquímico realizado por VCs, CGCD e EIS apresentou melhoras nas propriedades pseudocapacitivas do material PPI-NTs@Ni(OH)2, atribuídas ao sinergismo da combinação das propriedades pseudocapacitivas do PPI com a as reações faradaicas do Ni(OH)2, ao aumento na área superficial e à presença da fase ?-Ni(OH)2. Essas características combinadas facilitam o processo de intercalação iônica na interface eletrodo / solução, além de aumentar a quantidade de carga armazenada. Os valores de energia e potência específica calculados incluem o eletrodo de PPI-NTs@Ni(OH)2 dentre os dispositivos de armazenamento de energia com alto desempenho. Palavras-chave: compósitos; polipirrol; imidazol; hidróxido de níquel; supercapacitores.Abstract: The effect on the structural, electrochemical and catalytic properties of polypyrrole (PPy) were investigated in the composites with imidazole (IMZ) and nickel hydroxide (Ni(OH)2). Firstly, the pseudocapacitive properties of PPy were studied in modified electrodes obtained by different electropolymerization methods. These results suggested that the PPy obtained by potentiostatic condition presents the best supercapacitors electrodes, by this way, this methodology was employed in the development of PPy/IMZ composite modified electrodes. The kinetic studies performed along the electrosynthesis of PPy/IMZ showed that the IMZ changes the polymerization process, diminishing the active sites on the electrode surface. As a result, more organized morphologies were observed by using Scanning Electronic Microscopy (SEM) analyses. The electrochemical performance of the composites modified electrodes was evaluated by cyclic voltammetry (CV), galvanostatic charge and discharge curves (GCDC) and electrochemical impedance spectroscopy (EIS). The synergism between PPy / IMZ enhanced specific capacitance of the material in more than 65%. The spectroscopic characterization, suggests the formation of different oxidation levels of PPy and the presence of IMZ molecules in the polymer chain. Also, a mechanism of copolymerization between IMZ and Py is proposed. In addition, the PPy/IMZ composites were also obtained by chemical synthesis. The kinetic studies showed that the inhibition effect of IMZ, diminishing the polymerization rate. These materials were used as catalyst in the hydrolysis reaction of phosphate esters. The increment of the catalytic constant was found to be 5000-fold higher than the spontaneous degradation. Core-shell nanostructures composed by PPy nanotubes (NTs) and Ni(OH)2were investigated. The spectroscopic and structural characterization confirm the presence of both materials in the final composite, where the presence of ?-Ni(OH)2 phase was found. The SEM and Transmission Electronic Microscopy (TEM) images shows that the PPy-NTs were completely covered with Ni(OH)2, with diameter around 200 nm. The N2 adsorption/desorption experiment was investigated by Brunauer - Emmett - Teller (BET) measurements. It was found a significant increase in the specific surface area of the PPy-NTs@Ni(OH)2 compared with the precursor materials (PPy-NTs and Ni(OH)2). The electrochemical performance was carried out by CVs, GCDCs and EIS. The results showed improvements in the pseudocapacitive behavior due the synergism between PPy and Ni(OH)2. The design of core-shell nanostructures facilitates the ion intercalation on the electrode / electrolyte interface. Also, the combination of PPy pseudocapacitive behavior and Ni(OH)2 faradaic process increases the capacity of charge storage. The specific energy and power values includes the PPy-NTs@Ni(OH)2 amongst the highperformance energy storage materials. Key-words: composites; polypyrrole; imidazole; nickel hydroxide; supercapacitors

Otimização da resposta eletrocatalítica apresentada por eletrodos modificados por ligas Ni/Cu e Ni/Co

Orientador : Prof. Dr. Marcio VidottiCo-orientadora : Profª Drª Noemi NagataDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Química. Defesa: Curitiba, 21/02/2013Inclui referênciasResumo: Este trabalho refere-se a deposição de ligas metálicas de Ni/Cu e Ni/Co sobre a superfície de eletrodos visando o desenvolvimento de materiais eletrocatalíticos. As ligas Ni/Cu foram obtidas por dois métodos diferentes: na primeira a deposição foi realizada sobre eletrodos de cobre, sendo este a fonte de íons Cu2+ em uma solução eletrolítica contendo íons Ni2+, e a segunda, ocorre por redução direta dos íons sobre superfície de eletrodo de platina a partir de sais de sulfato. A conversão das ligas metálicas para a forma eletrocatalítica do material foi realizada por voltametrias cíclicas em meio alcalino. Diferentes parâmetros experimentais foram estudados, tais como, tempo de deposição e proporção de níquel e cobre ou níquel e cobalto na formação das ligas. Os eletrodos modificados foram caracterizados por técnicas eletroquímicas e espectroscópicas, além de MEV. O desempenho eletrocatalítico dos eletrodos modificados foi estudado utilizando a glicose como substrato. Eletrodos modificados por Ni/Co também foram estudados, empregando a otimização multivariada, através de um planejamento fatorial 22 com ponto central, que possibilitou determinar o melhor material nessa região de estudo para determinação de glicose, sendo o tempo de deposição de três segundos na proporção 55 Ni:45 Co mol/mol. A caracterização eletroquímica mostrou que a formação de ligas Ni/Co apresenta deslocamento significativo do potencial de obtenção da forma eletrocatalítica para 0,35 V comparado a materiais formados por ligas Ni/Cu que ocorre em torno de 0,6 V. As propriedades estruturais e morfológicas dos óxidos mistos via síntese química foram caracterizadas por infravermelho e raio-X, sugerindo que o material formado não é apenas uma simples mistura de óxidos de níquel e cobre ou níquel e cobalto, essas análises sugerem a formação de compósitos formados por óxidos de Ni/Cu e Ni/Co. As imagens de MEV mostraram a formação de nanocompósitos metálicos constituídas por ligas Ni/Cu e Ni/Co. Os eletrodos modificados exibiram propriedades eletrocatalíticas notáveis na determinação de carboidratos, apresentando sensibilidade de 195.3 ? 9.5; 262.0 ? 2.0 e 139.5 ? 1.5 ?A mmol L-1 cm-2 para eletrodos de cobre modificados por ligas Ni/Cu com tempo de oxidação de 10 s, eletrodos de platina modificados por ligas 50Ni:50Cu (mol/mol) e 55Ni:45Co (mol/mol), respectivamente, indicando sua aplicação no desenvolvimento de sensores eletroquímicos.Abstract: This work concerns the deposition of Ni/Cu and Ni/Co metal alloys on the electrode surface aiming the development of high performance electrocatalytic materials. The Ni/Cu alloys were obtained by two different methodologies: the first one comprises the deposition on copper electrodes playing role as the source of Cu2+ and the second one the direct reduction of the metallic ions on the platinum electrode surface from sulfate salts. The conversion from the metallic alloys to the electrocatalytic material was done by cyclic voltammetry in alkaline media. Different experimental parameters were studied, such as deposition time and proportion of Nickel and Cobalt or Nickel and Copper in the alloy formation. The modified electrodes were characterized by electrochemical and spectroscopic techniques besides SEM. The electrocatalytic performance of the modified electrodes were studied by employing glucose as electrochemical probe. Ni/Co modified electrodes were also studied by employing the multivariate optimization by using the factorial design 22 with center point that possibilited determine the great material this study region for glucose determination, being three seconds deposition time in the 55 Ni : 45 Co mol/mol. The electrochemical characterization showed the Ni/Co alloys formation presents significant potential shifted for way electrocatalyctic form 0.35 V compared to materials Ni/Cu alloys formed thats occurs arround 0.6 V. The structural and morphological properties of chemically synthesized mixed oxides were characterized infrared and X-ray diffraction suggesting that material formed is not simple misture between nickel and copper oxides or nickel and cobalt, this analysis propose the formation of composites by Ni/Cu and Ni/Co oxides formed. The SEM images showed the formation of metal nanocomposites formed by Ni/Cu and Ni/Co alloys. The modified electrodes showed notable electrocatalytic properties in the carbohydrates, apresented sensibility of 195.3 ? 9.5; 262.0 ? 2.0 e 139.5 ? 1.5 ?A mmol L-1 cm-2 for copper modified electrodes by Ni/Cu alloys with ten seconds oxidation time, platinum modified electrodes by 50Ni:50Cu (mol/mol) alloys at ten seconds depositon time and 55Ni:45Co (mol/mol) alloys at three seconds deposition time, respectively, indicating its application for the development of electrochemical sensors

Enhancement of organophosphate degradation by electroactive pyrrole and imidazole copolymers

Many chemical warfare agents and agrochemicals are composed by organophosphates, that present high toxicity and difficult spontaneous degradation. Amongst the different catalysts to degrade these compounds, heterogeneous systems stand out since they provide easy recovery of the catalyst. However, the limited diffusion of the substrate decreases the rate of the reactions when compared to homogeneous catalysis. To reach a good efficiency in the dephosphorylation, we created heterogeneous catalysts based on pyrrole and imidazole that can enhance the degradation by different effects; both catalytic activity of imidazole and electroactivity of polypyrrole were evaluated. Spectroelectrochemical studies evidenced that the rate constant changes with the applied potential, indicating different reaction mechanisms with the material in the oxidized and neutral states. In summary, a new perspective allying conducting polymers with chemical catalysts was explored. This cooperative effect should be considered in future works concerning the search for new materials to monitor and eliminate organophosphates

Direct electrodeposition of imidazole modified poly(pyrrole) copolymers : synthesis, characterization and supercapacitive properties

Altres ajuts: Beatriu de Pinós (BP-DGR-2013)In this manuscript we report the direct electrosynthesis of a new conducting copolymer based on the incorporation of imidazole molecules within the polypyrrole chain. Different proportions of the monomers were tested during the direct electropolymerization of the copolymer. The resulting materials were characterized by electrochemical and spectroscopic techniques (Raman and XPS) and a mechanism of polymerization is proposed. Our findings showed that imidazole acts as an inhibitor of the polymerization process, decreasing the overall number of actives sites for the polymerization on the electrode surface producing a polymeric morphology very different compared with pure polypyrrole, as observed by Scanning Electron Microscopy images and corroborated by Electrochemical Impedance Spectroscopy. This behavior significantly affects the supercapacitive performance of the resulting p(Py-IMZ) modified electrodes where the specific capacitance of the material increased from 122 to 201 Fg (64%) at 10 mV s. Furthermore, a unique pseudo-capacitive behavior described herein emphasizes the role of the imidazole as inductor of the morphology and co-monomer in the unique electrochemical signature of the material. The results suggest that the incorporation of IMZ increases the specific capacitance of PPy electrode by around 64%

Synthetic approach from polypyrrole nanotubes to nitrogen doped pyrolyzed carbon nanotubes for asymmetric supercapacitors

Pseudocapacitive materials are highly capable to achieve high energy density integrated with high power electrostatic capacitive materials. However, finding a suitable electrostatic capacitive material to integrate with pseudocapacitive material in order to achieve high energy density with good rate capability is still a challenge. Herein, we are providing a novel synthetic approach starting from the synthesis of polypyrrole nanotubes (PPy-NTs) and ending up at the carbonization of PPy-NTs to obtain N-doped carbon nanotubes (N-CNTs). With highly porous nature of PPy-NTs and great graphitic texture with copious heteroatom functionalities, N-CNTs significantly promoted the faradic pseudo-capacitors, demonstrating high single-electrode capacitance over 332 F/g and 228 F/g in 1 M HSO aqueous solution. Further, a novel asymmetric supercapacitor with PPy-NTs as positive and N-CNTs as negative electrode has been fabricated. This PPy-NTs//N-CNTs cell effectively provides high operation voltage (1.4 V) and hence high energy density over 28.95 W h/kg (0.41 mW h/cm) with a high power density of 7.75 kW/kg (113 mW/cm) and cyclic stability of 89.98% after 2000 cycles

Otimização da resposta eletrocatalítica apresentada por eletrodos modificados por ligas Ni/Cu e Ni/Co

Orientador : Prof. Dr. Marcio VidottiCo-orientadora : Profª Drª Noemi NagataDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Química. Defesa: Curitiba, 21/02/2013Inclui referênciasResumo: Este trabalho refere-se a deposição de ligas metálicas de Ni/Cu e Ni/Co sobre a superfície de eletrodos visando o desenvolvimento de materiais eletrocatalíticos. As ligas Ni/Cu foram obtidas por dois métodos diferentes: na primeira a deposição foi realizada sobre eletrodos de cobre, sendo este a fonte de íons Cu2+ em uma solução eletrolítica contendo íons Ni2+, e a segunda, ocorre por redução direta dos íons sobre superfície de eletrodo de platina a partir de sais de sulfato. A conversão das ligas metálicas para a forma eletrocatalítica do material foi realizada por voltametrias cíclicas em meio alcalino. Diferentes parâmetros experimentais foram estudados, tais como, tempo de deposição e proporção de níquel e cobre ou níquel e cobalto na formação das ligas. Os eletrodos modificados foram caracterizados por técnicas eletroquímicas e espectroscópicas, além de MEV. O desempenho eletrocatalítico dos eletrodos modificados foi estudado utilizando a glicose como substrato. Eletrodos modificados por Ni/Co também foram estudados, empregando a otimização multivariada, através de um planejamento fatorial 22 com ponto central, que possibilitou determinar o melhor material nessa região de estudo para determinação de glicose, sendo o tempo de deposição de três segundos na proporção 55 Ni:45 Co mol/mol. A caracterização eletroquímica mostrou que a formação de ligas Ni/Co apresenta deslocamento significativo do potencial de obtenção da forma eletrocatalítica para 0,35 V comparado a materiais formados por ligas Ni/Cu que ocorre em torno de 0,6 V. As propriedades estruturais e morfológicas dos óxidos mistos via síntese química foram caracterizadas por infravermelho e raio-X, sugerindo que o material formado não é apenas uma simples mistura de óxidos de níquel e cobre ou níquel e cobalto, essas análises sugerem a formação de compósitos formados por óxidos de Ni/Cu e Ni/Co. As imagens de MEV mostraram a formação de nanocompósitos metálicos constituídas por ligas Ni/Cu e Ni/Co. Os eletrodos modificados exibiram propriedades eletrocatalíticas notáveis na determinação de carboidratos, apresentando sensibilidade de 195.3 ? 9.5; 262.0 ? 2.0 e 139.5 ? 1.5 ?A mmol L-1 cm-2 para eletrodos de cobre modificados por ligas Ni/Cu com tempo de oxidação de 10 s, eletrodos de platina modificados por ligas 50Ni:50Cu (mol/mol) e 55Ni:45Co (mol/mol), respectivamente, indicando sua aplicação no desenvolvimento de sensores eletroquímicos.Abstract: This work concerns the deposition of Ni/Cu and Ni/Co metal alloys on the electrode surface aiming the development of high performance electrocatalytic materials. The Ni/Cu alloys were obtained by two different methodologies: the first one comprises the deposition on copper electrodes playing role as the source of Cu2+ and the second one the direct reduction of the metallic ions on the platinum electrode surface from sulfate salts. The conversion from the metallic alloys to the electrocatalytic material was done by cyclic voltammetry in alkaline media. Different experimental parameters were studied, such as deposition time and proportion of Nickel and Cobalt or Nickel and Copper in the alloy formation. The modified electrodes were characterized by electrochemical and spectroscopic techniques besides SEM. The electrocatalytic performance of the modified electrodes were studied by employing glucose as electrochemical probe. Ni/Co modified electrodes were also studied by employing the multivariate optimization by using the factorial design 22 with center point that possibilited determine the great material this study region for glucose determination, being three seconds deposition time in the 55 Ni : 45 Co mol/mol. The electrochemical characterization showed the Ni/Co alloys formation presents significant potential shifted for way electrocatalyctic form 0.35 V compared to materials Ni/Cu alloys formed thats occurs arround 0.6 V. The structural and morphological properties of chemically synthesized mixed oxides were characterized infrared and X-ray diffraction suggesting that material formed is not simple misture between nickel and copper oxides or nickel and cobalt, this analysis propose the formation of composites by Ni/Cu and Ni/Co oxides formed. The SEM images showed the formation of metal nanocomposites formed by Ni/Cu and Ni/Co alloys. The modified electrodes showed notable electrocatalytic properties in the carbohydrates, apresented sensibility of 195.3 ? 9.5; 262.0 ? 2.0 e 139.5 ? 1.5 ?A mmol L-1 cm-2 for copper modified electrodes by Ni/Cu alloys with ten seconds oxidation time, platinum modified electrodes by 50Ni:50Cu (mol/mol) alloys at ten seconds depositon time and 55Ni:45Co (mol/mol) alloys at three seconds deposition time, respectively, indicating its application for the development of electrochemical sensors

Hybrid core-shell nanostructured electrodes made of polypyrrole nanotubes coated with Ni(OH)2 nanoflakes for high energy-density supercapacitors

This work describes the design of Ni(OH)@PPy-NTs core-shell nanostructures with potential application as an electrode material for supercapacitors. Initially, one dimensional (1D) polypyrrole nanotubes (PPy-NTs) were synthesized through a chemical oxidation mediated soft template-directed route using as the anion the azo dye methyl orange (MO). Subsequently, three dimensional (3D) Ni(OH) nanoflakes were grown onto PPy-NTs by a simple hydrothermal route. This exclusive Ni(OH)@PPy-NTs nano-architecture helps to improve the overall electrochemical performance of the electrode, due to the high surface area provided by 3D nanoflakes and excellent electronic/ionic conductivity of 1D nanotubes. The maximum specific capacitance obtained for Ni(OH)@PPy-NTs was 536 F g with good capacity retention after 1000 charge/discharge cycles. Last but not least, EIS technique showed a low electrochemical series resistance for Ni(OH)@PPy-NTs confirming their promise as a high-performance energy storage material.The authors acknowledge the financial support of the CAPES Foundation, Ministry of Education of Brazil: Process BEX 3196/14-3. Authors appreciate the award to DPD with the support of the Secretary for Universities and Research of the Ministry of Economy and Knowledge of the Government of Catalonia and the Co-fund programme of the Marie Curie Actions of the 7th R&D Framework Programme of the European Union. Partial funding from Spanish Grant MAT2012-39199-C02-01 is acknowledged. ICN2 acknowledges support of the Spanish MINECO through the Severo Ochoa Centers of Excellence Program under Grant SEV-2013-0295.Peer Reviewe

Core-shell hybrid nanostructure based on polypyrrole nanotubes coated with Ni(OH)2 for high performance supercapacitors

Resumen del trabajo presentado a la 49th IUPAC General Assembly, celebrada en Sao Paulo (Brasil) del 7 al 13 de julio de 2017.The design of Ni(OH)2@PPy-NTs core–shell nanostructures with potential application as an electrode material for supercapacitors were developed. Firstly, one dimensional polypyrrole nanotubes (PPy-NTs) were synthesized through a chemical oxidation mediated soft templatedirected route using as the anion the azo dye methyl orange. Afterwards, three dimensional Ni(OH)2 nanoflakes were grown onto PPy-NTs by a simple hydrothermal route. The scanning electronic microscopy (SEM) and transmission electronic microscopy (TEM) images of the PPyNTs showed the nanotubes are randomly spread with well-developed, highly open and porous structure (Figure 1(a-b)). Figure 1(c-d) display the SEM and TEM images of the Ni(OH)2@PPyNTs, which it is possible to see that no Ni(OH)2 is packed in the interspaces of the nanotubes, suggesting that Ni(OH)2 nanoflakes are preferentially deposited onto the PPy-NTs surface. Spectroscopic characterization by X-ray photoelectron spectroscopy (XPS) confirm the presence of the both PPy and Ni(OH)2 in the final composite. The XRD patterns of the hybrid material indicated the formation of the α-Ni(OH)2 polymorph which can improve the electrochemical properties of the electrode. The specific surface area of the materials were investigated using N2 adsorption / desorption isotherms. The values obtained were 27.1, 43.2 and 77.0 m2g-1 for Ni(OH)2, PPy-NTs and Ni(OH)2@PPy-NTs, respectively. The unique core–shell heterostructured Ni(OH)2@PPy-NTs configuration helps to improve the electrochemical performance of the electrode, due to the high surface area and synergistic effects of the combined pseudocapacitive behavior from the PPy-NTs and the faradaic process of the Ni(OH)2 (Figure 1(e)). The maximum specific capacitance obtained for Ni(OH)2@PPy-NTs was 536 F g-1 (Figure 1(f)) with 90.4 % of capacity retention after 1000 galvanostatic charge/discharge cycles (GCDC). The specific energy (12 Wh kg-1) and power (1143 W kg-1) values includes de Ni(OH)2@PPy-NTs amongst the high performance energy storage materials.Peer reviewe

Enhancement of organophosphate degradation by electroactive pyrrole and imidazole copolymers

Many chemical warfare agents and agrochemicals are composed by organophosphates, that present high toxicity and difficult spontaneous degradation. Amongst the different catalysts to degrade these compounds, heterogeneous systems stand out since they provide easy recovery of the catalyst. However, the limited diffusion of the substrate decreases the rate of the reactions when compared to homogeneous catalysis. To reach a good efficiency in the dephosphorylation, we created heterogeneous catalysts based on pyrrole and imidazole that can enhance the degradation by different effects; both catalytic activity of imidazole and electroactivity of polypyrrole were evaluated. Spectroelectrochemical studies evidenced that the rate constant changes with the applied potential, indicating different reaction mechanisms with the material in the oxidized and neutral states. In summary, a new perspective allying conducting polymers with chemical catalysts was explored. This cooperative effect should be considered in future works concerning the search for new materials to monitor and eliminate organophosphates

Electrochemical supercapacitive properties of polypyrrole thin films: influence of the electropolymerization methods

A detailed study of the effects of different electropolymerization methods on the supercapacitive properties of polypyrrole (PPy) thin films deposited on carbon cloth is reported. Deposition mechanisms of PPy thin films through cyclic voltammetry (CV), potentiostatic (PS), and galvanostatic (GS) modes have been analyzed. The resulting PPy thin films have been characterized by X-ray photoelectron spectroscopy (XPS), SEM, and TEM. The electrochemical properties of PPy thin films were investigated by cyclic voltammetry and galvanostatic charge/discharge. The results showed that the different electrodeposition modes of synthesis significantly affect the supercapacitive properties of PPy thin films. Among different modes of electrodeposition, PPy synthesized by a potentiostatic mode exhibits maximum specific capacitance of 166 F/g with specific energy of 13 Wh/kg; this is attributed to equivalent proportions of the oxidized and neutral states of PPy. Thus, these results provide a useful orientation for the use of optimized electrodeposition modes for the growth of PPy thin films to be applied as electrode material in supercapacitors.CAPES Foundation, Ministry of Education of Brazil: Process BEX 3196/14-3. Spanish grant MAT2012-39199-C02-01 is also acknowledged.Peer Reviewe