Direct electrodeposition and superior pseudocapacitive property of ultrahigh porous silver-incorporated polyaniline films
Graphical abstract
Highlights
► Direct electrodeposition of Ag-incorporated polyaniline (Ag/PANI) pseudocapacitor electrode. ► Ag/PANI with ultrahigh porosity accelerates ion transportation. ► Ag introduces good electrical conductivity to the pseudocapacitive composite. ► Ag/PANI has ultrahigh capacitance and excellent cycle stability.
Introduction
Supercapacitors are of interest for portable electronic devices and hybrid electric vehicles since they exhibit high power density, fast charge–discharge rate and high stability [1]. Two storage mechanisms of the supercapacitors are based on electrochemical double layer capacitance (EDLC) at the solid–liquid interface and pseudocapacitance. Pseudocapacitors or redox supercapacitors have fast Faradaic charge-transfer at the electrode materials in addition to EDLC. Pseudocapacitive materials consist of metal oxides (e.g., RuO2, NiO, and MnO2) and conducting polymers (e.g., PANI, polypyrrole, polythiophene, and PEDOT) [2]. Among various pseudocapacitive materials, PANI is recognized as one of the most promising pseudocapacitive materials suitable for the next generation of supercapacitors since it has high theoretical pseudocapacitance, low cost, controllable electrical conductivity, high energy density, environmental friendliness and facile synthesis [3].
However, the specific capacitance of PANI with dense morphology is still limited by low ionic transport through its film while the stability of thin film (a few micrometers in thickness) of PANI is somewhat poor [4]. The conductivity of pure PANI is rather low (2 S cm−1) [5] when compared with polypyrrole (55–100 S cm−1) [6], polythiophene (300–400 S cm−1) [7], and PEDOT (300–500 S cm−1) [7] leading to low charge transfer in PANI pseudocapacitors. Notably, Ag has been recently incorporated to MnO2 [8], [9] and RuO2 [10] for enhancing their electrical conductivity leading to ultrahigh pseudocapacitance. In the present work, we have incorporated Ag to the PANI film by using a one-step electrodeposition method. Ag/PANI composite with good electrical conductivity and high porosity exhibits ultrahigh pseudocapacitance and excellent cycle stability.
Section snippets
Experimental
PANI and Ag/PANI materials were coated onto glassy carbon electrodes using the electrodeposition method. Three electrodes containing a working glassy carbon electrode (1 cm2), a platinum wire counter electrode, and a Ag/AgCl reference electrode, were immersed in the aqueous solution containing 0.2 M aniline and 0–1.5 mM AgNO3 in 0.2 M H2SO4. The electrodeposition potential and time were fixed at 0.4 V vs. Ag/AgCl and 5 min, respectively since these conditions can provide the pseudocapacitive films
Results and discussion
Morphological and elemental analyses: Fig. 1 shows the typical morphology of PANI and Ag/PANI films. PANI clusters found on the glassy carbon electrode were from an agglomeration of small PANI particles (see Fig. 1a). The surface of PANI film is rather rough since the electropolymerization of PANI from aniline monomer is a multi-level growth process [4]. Whilst, Ag/PANI composite in Fig. 1(b) has higher porosity and uniformity with the hollow fibers packed tightly onto the surface of the
Conclusions
Ag/PANI nanocomposites were produced using a direct electrodeposition method. An electroplating solution of 0.2 M aniline monomer in 0.2 M H2SO4 containing diluted AgNO3 can provide ultrahigh porous composite film in lieu of denser PANI film without using AgNO3. AgNO3 concentration plays an important role in the specific capacitance of the composites for which 0.5 mM AgNO3 is satisfactory to be incorporated to PANI film providing high specific capacitance of 420 F g−1 measured in 0.5 M Na2SO4 at the
Acknowledgments
This work was supported in part by grants from the Kasetsart University Research and Development Institute, the Thailand Research Fund (MRG5480195), the Commission on Higher Education, and Ministry of Education (The National Research University Project of Thailand).
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