The electrochemical properties of polyaniline-tungsten composites

In this study, we investigate the applications of composite PANI and tungsten oxide species WO₄²⁻ through the structure–property–performance relationships in supercapacitor and asymmetric supercapacitor (pseudocapacitor//EDLC). PANI was chemically synthesized using oxidative polymerization, and PANI/WO4 composites were fabricated from sodium tungstate (Na₂WO₄·2H₂O) precursor. Structural and chemical characterization were verified using XRD, FTIR, EDX NMR, and STEM analyses. Conversely, CV-GCD-EIS were employed to study the electrochemical performance in three-electrode (PANI/WO4) versus two-electrode (PANI/WO₄ // AC) configurations. The XRD patterns showed that the PANI/WO4 composite was amorphous, which was in agreement with the FTIR and NMR results for PANI-WO₄²⁻ interaction. Morphological changes resulting from composite formation were evident in the STEM images. In the three-electrode system, an areal capacitance of ca. 201.2 mF·cm ⁻² was reached at a current density of 0.5 mA·cm ⁻². As the current density increased, the capacity of the two-electrode device decreased. After 10,000 cycles, 96% of capacity is retained. Relatively low Rs and Rct values obtained in EIS analysis suggest a high degree of charge transfer. Based on Ragone's analysis, the gravimetric energy density is estimated to be 0.15–1.55 Wh·kg ⁻¹ , while the power density is 10–30 W·kg ⁻¹ . For areal specifications, the energy density as per areal value was computed to lie between 5.69 and 58.2 µWh·cm ⁻², whereas power density was estimated to be between 0.375 and 1.125 mW·cm ⁻². The reduced crystallinity/amorphous character inferred from XRD may contribute to the decreased charge-transfer resistance. The charge-transfer resistance was 38.22 Ω for the PANI–WO₄ composite, and 96% of the capacity was retained after 10,000 cycles.