Conducting polymer films of cross-linked structure and their QCM analysis

Electrochemical performance optimization of the polyaniline electrodeposited on ITO substrate

We have elaborated polyaniline films on ITO substrate (indium tin oxide), by electrochemical process in different electrolytes (HCl, H2SO4, HNO3, and H3BO3), which allowed us to study the effect of the counter ion on electrochemical energy storage performances of polyaniline as electrode material in supercapacitors. The study of the different obtained films performances was carried out by cyclic voltammetry and galvanostatic charge-discharge method and is interpreted by the SEM technique. We found that there is a clear dependence on the specific capacitance of the counter ion. Justified by its porous structure, the PANI/ITO electrode doped with SO42- has the highest specific capacitance, 57.3 mF/cm2 at a current density of 0.2 mA/cm2 and 64.8 mF/cm2 at 5 mV/s. The deep analysis by Dunn's method allowed us to conclude that the faradic process dominates the energy storage in the case of PANI/ITO electrode elaborated in boric acid (99%). On the contrary, the capacitive character is the most contributory in the case of electrodes elaborated in H2SO4, HCl, and HNO3. The study at different potentials (0.80, 0.85, 0.90, 0.95, and 1.0 V/SCE) from 0.2 M monomer aniline showed that the deposition at 0.95 V/SCE leads to higher specific capacitance (24.3 mF/cm2 at scan rate 5 mV/s and 23.6 mF/cm2 at 0.2 mA/cm2) with a coulombic efficiency of 94%. By varying the concentration of the monomer while keeping a potential fixed at 0.95 V/SCE, we also found that the specific capacitance increases with monomeric concentration.

A novel electronic tongue using electropolymerized molecularly imprinted polymers for the simultaneous determination of active pharmaceutical ingredients

The combination of chemometrics and electrochemical sensors modified with molecularly imprinted polymers (MIPs) towards the development of MIP-based electronic tongues (ETs) was explored herein. To demonstrate the potential of such an approach, the simultaneous determination of paracetamol, ascorbic acid and uric acid mixtures in pharmaceutical samples was evaluated. To this aim, MIP-based sensors for the different compounds were prepared by in situ electropolymerization of pyrrole in the presence of p-toluenesulfonate anion (pTS^-), which acted as functional doping ion of the polypyrrole (PPy) MIP backbone. Morphological characterization of the MIPs was done by scanning electron microscopy (SEM), while functionalization of the electrodes was monitored electrochemically. Under the optimized measuring conditions, the developed sensors showed a good performance, with good linearity at the μM level (R² > 0.992, limits of detection between 1 and 24 μM) as well as good repeatability (intra- and inter-day RSD values between 3 and 6% over 30 consecutive measurements). Finally, the quantification of the individual substances in different pharmaceutical samples was achieved by an artificial neural networks (ANNs) model, showing satisfactory agreement between expected and obtained values (R² > 0.987).

Structural Tuning of a Flexible and Porous Polypyrrole Film by a Template-Assisted Method for Enhanced Capacitance for Supercapacitor Applications

Constructing a rational electrode structure for supercapacitors is critical to accelerate the electrochemical kinetics process and thus promote the capacitance. Focusing on the flexible supercapacitor electrode, we synthesized a three-dimensional (3D) porous polypyrrole (PPy) film using a modified vapor phase polymerization method with the use of a porous template (CaCO₃). The porous design provided the PPy film with an improved surface area and pore volume. The porous PPy film electrode was studied as a binder-free electrode for supercapacitors. It was found that the abundant interpenetrated pores created by the CaCO₃ templates within the 3D framework are beneficial to overcoming the diffusion-controlled limit in the overall electrochemical process. It was revealed by electrochemical investigation that a more pseudocapacitive contribution than diffusion-controlled process contribution was observed in the total charge in the redox reaction. The galvanostatic charge/discharge (GCD) measurements showed that the optimized 3D porous PPy film electrode delivered a high capacitance of 313.6 F g^-1 and an areal capacitance of 98.0 mF cm^-2 at 1.0 A g^-1 in a three-electrode configuration, which is nearly three times that of the dense counterpart electrode synthesized in the absence of the CaCO₃ template. A specific capacitance of 62.5 F g^-1 at 0.5 A g^-1 and 31.1 F g^-1 at 10 A g^-1 was obtained in a symmetric capacitor device. In addition, the porous structure provided the PPy film with the attractive capability of accommodating the volume change during the doping/dedoping process. This is essential for the PPy film to maintain a long cycling life in a practical operation for a supercapacitor. It turned out that a high capacitance retention up to 81.3% after 10,000 GCD cycles was obtained for the symmetric supercapacitor device with the 3D porous PPy electrode (57.1% capacitive retention was observed for the dense PPy electrode). The strategy and the insight analysis are expected to provide valuable guidance for the design and the synthesis of flexible and wearable film electrodes with high performance.

Faradaic Electrodes Open a New Era for Capacitive Deionization

Capacitive deionization (CDI) is an emerging desalination technology for effective removal of ionic species from aqueous solutions. Compared to conventional CDI, which is based on carbon electrodes and struggles with high salinity streams due to a limited salt removal capacity by ion electrosorption and excessive co-ion expulsion, the emerging Faradaic electrodes provide unique opportunities to upgrade the CDI performance, i.e., achieving much higher salt removal capacities and energy-efficient desalination for high salinity streams, due to the Faradaic reaction for ion capture. This article presents a comprehensive overview on the current developments of Faradaic electrode materials for CDI. Here, the fundamentals of Faradaic electrode-based CDI are first introduced in detail, including novel CDI cell architectures, key CDI performance metrics, ion capture mechanisms, and the design principles of Faradaic electrode materials. Three main categories of Faradaic electrode materials are summarized and discussed regarding their crystal structure, physicochemical characteristics, and desalination performance. In particular, the ion capture mechanisms in Faradaic electrode materials are highlighted to obtain a better understanding of the CDI process. Moreover, novel tailored applications, including selective ion removal and contaminant removal, are specifically introduced. Finally, the remaining challenges and research directions are also outlined to provide guidelines for future research.

Flexible Energy Storage System—An Introductory Review of Textile-Based Flexible Supercapacitors

Recently, researchers have become interested in exploring applications of rechargeable battery storage technology in different disciplines, which can help our daily life, such as textile-based supercapacitors. This paper briefly describes this development and classification of supercapacitors. Besides, various types of materials which are commonly used to prepare supercapacitors, such as carbons, metal oxides, alkaline earth metal salts and polymers, are introduced. Moreover, applications and methodology to prepare textile materials with supercapacitors are described. Finally, the commonly used non-destructive measuring methods for textile-based supercapacitors are also introduced.

Wood-derived biochar supported polypyrrole nanoparticles as a free-standing supercapacitor electrode

Paulownia wood processing residues were adopted as both a template and precursor for the synthesis of a wood-derived biochar/polypyrrole composite, serving as a free-standing and binder-free supercapacitor electrode.

Chemical versus electrochemical synthesis of carbon nano-onion/polypyrrole composites for supercapacitor electrodes

The development of high-surface-area carbon electrodes with a defined pore size distribution and the incorporation of pseudo-active materials to optimize the overall capacitance and conductivity without destroying the stability are at present important research areas. Composite electrodes of carbon nano-onions (CNOs) and polypyrrole (Ppy) were fabricated to improve the specific capacitance of a supercapacitor. The carbon nanostructures were uniformly coated with Ppy by chemical polymerization or by electrochemical potentiostatic deposition to form homogenous composites or bilayers. The materials were characterized by transmission- and scanning electron microscopy, differential thermogravimetric analyses, FTIR spectroscopy, piezoelectric microgravimetry, and cyclic voltammetry. The composites show higher mechanical and electrochemical stabilities, with high specific capacitances of up to about 800 F g(-1) for the CNOs/SDS/Ppy composites (chemical synthesis) and about 1300 F g(-1) for the CNOs/Ppy bilayer (electrochemical deposition).

Self-doped 3-hexylthiophene-b-sodium styrene sulfonate block copolymer: synthesis and its organization with CdSe quantum dots

A strategy was developed for producing a conjugated polymer with both doped stability during repeated electric cycle and compatibility with inorganic semiconductor materials.

Polymer coated quartz crystal microbalance sensors for detection of volatile organic compounds in gas mixtures

By coating different conducting polymers of thiophene and its derivatives on quartz crystal microbalance (QCM) sensor surfaces, new novel QCM gas sensors have been produced in two simple ways, which could classify testing gas samples of volatile organic compounds (VOCs) gases. Principle components analysis (PCA) has been performed based on the QCM measurement results, which shows that our QCM sensors array has very good utilizing potential on sensing both polar and low-polar/nonpolar VOC gases. The sensitivity, selectivity, reproducibility and detection limit of QCM sensors have also been discussed. Quantitative variation of sensitivity response with the increasing concentration has been studied. (PLS) analysis and prediction of concentrations of single gas in mixtures have been carried out.

An EQCM Study of the Electropolymerization of Benzene in an Ionic Liquid and Ion Exchange Characteristics of the Resulting Polymer Film

The direct electropolymerization of benzene dissolved in the ionic liquid 1-hexyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate was studied at room temperature applying the electrochemical quartz-crystal microbalance technique. Analysis of the damping changes showed that the Sauerbrey equation could be applied for data evaluation. In the polymer, every third to fourth benzene ring carried a positive charge in the oxidized state. During electropolymerization, some ionic liquid was absorbed in the growing polymer. The redox behavior was characterized by wide peaks typical for conducting polymers. Charge neutrality of the polymer during redox cycling was maintained by anion and cation exchange with the ionic liquid. With increasing scan rate, cation exchange became more and more important.