High-performance solid state supercapacitors based on intrinsically conducting polyaniline/MWCNTs composite electrodes

Preparation of PANI modified TiO2 and characterization under pre- and post- photocatalytic conditions

Polyaniline (PANI) is a promising conducting polymer for surface modification of TiO2 to overcome limitations of the use of visible light and attain increased photocatalytic efficiency for the removal of organic contaminants. In this study, a series of polyaniline modified TiO2 (PANI-TiO2) composites were prepared by using "in-situ" chemical oxidation polymerization method. The composites were systematically characterized by Fourier transform infrared spectroscopy (equipped with an attenuated total reflection accessory, FTIR-ATR), Raman spectroscopy, X-ray diffractometry (XRD), scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDAX), X-ray photoelectron spectroscopy (XPS), ultraviolet-visible diffuse reflectance spectroscopy (UV-DRS), photoluminescence spectroscopy (PL), nitrogen (N2) physisorption (Brunauer - Emmett - Teller surface area (SBET) and Barrett-Joyner-Halenda (BJH) pore size analysis), thermogravimetry-derivative thermogravimetry (TG-DTG) techniques. XRD patterns of PANI-TiO2 composites confirmed both the amorphous phase of PANI and the crystalline character of TiO2. TG/DTG analysis complemented the XRD profiles that the interactions between PANI and TiO2 resulted in a more stable PANI-TiO2 matrix. SEM images displayed the dominant morphology as dandelion-like shapes of PANI being more pronounced with increasing PANI ratios in PANI-TiO2 composites. UV-DRS profiles revealed that the band gap energies of the composites were lower than bare TiO2 expressing a shift to the visible light region. Both PL and UV-DRS analyses confirmed the band-gap reduction phenomenon of PANI modification of TiO2. The incorporation of PANI into TiO2 resulted in a reduction of the surface area of TiO2. The composites were subsequently subjected to photocatalytic activity assessment tests using humic acid (HA) as a model of refractory organic matter (RfOM) under simulated solar irradiation (Uyguner-Demirel et al. Environ Sci Pollut Res 30 85626-85638, 2023). The morphological and structural changes attained upon application of photocatalysis were also evaluated by FTIR-ATR, Raman spectroscopy, XRD, and SEM-EDAX methods in a comparable manner. The FTIR-ATR spectral features of PANI, RfOM and all composites displayed peaks with slight shifts under pre- and post- photocatalytic conditions as well as following dark surface interactions. Besides exhibiting noticeable photocatalytic performance, PANI-TiO2 composites were also proven to maintain stability under non-selective oxidation conditions in the presence of a complex organic matrix. The prepared PANI-TiO2 composites overcoming the limitations of UVA light active bare TiO2 photocatalysis could possibly find a beneficial use as potential catalysts in solar photocatalytic applications.

Fabrication of Textile-Based Flexible Supercapacitor with a Textile Dye on Polyaniline-Based Composite Electrode for Enhanced Energy Storage

Polyaniline (PANI) is a promising conductive polymer for use in energy storage applications. Here, a one-step hydrothermal method of PANI polymerization on carbon felt electrode was synthesized using an azo dye, a bisulfonated dichloro anionic dye molecule to enhance an efficient textile-based flexible supercapacitor electrode material for energy storage applications. The electrode material synthesized at concentration of 2 mM AY17 exhibits 814.1 F g-1 at the scan rate of 5 mV s-1 with multiwall carbon nanotubes (MWCNTs). Due to electrostatic interaction with the polymer, the presence of high electronegativity Cl atoms in the dye molecule significantly improves the PANI structure's electron donor/acceptor properties. A symmetric supercapacitor exhibits an energy density of 11.7 W h kg−1 at a power density of 300 W kg−1, and it is 4.5 W h kg−1 at 1800 W kg−1 in 3.0 M KCl aqueous electrolyte. The capacitance retention performance value of the symmetric supercapacitor exhibited 81.76% after 2500 cycles.