Additive manufacturing of polyaniline electrodes for electrochemical applications

Polyaniline (PANI), particularly in its emeraldine salt form (PANI-ES), possesses several desirable properties such as high tuneable conductivity, pseudocapacitance and chemical stability, which make PANI a promising material for a wide range of electrochemical applications. However, its use is severely limited by its poor processability due to its non-thermoformable nature. In this work, a novel additive manufacturing method to process PANI is introduced, which enables the fabrication of electrodes with complex geometries exhibiting conductivities of up to 20000 mS/cm. This novel additive manufacturing process is based on the thermal doping of PANI in its low-conductive emeraldine base form (PANI-EB) with dodecyl benzene sulfonic acid (DBSA). For this purpose, a commercially available 3D printer was modified with a custom-made syringe extrusion system to enable the extrusion of a viscous PANI-EB/DBSA paste. The influence of the additive manufacturing process parameters on the conductivity of printed electrodes was evaluated, and the resulting printed materials were characterised by Fourier-transform infrared spectroscopy – attenuated total reflection, X-ray powder diffraction, thermo-gravimetric analysis and scanning electron microscopy. The feasibility of the 3D printed PANI-ES/DBSA electrodes was studied by conducting a proof-of-concept electrochemical study of 3D printed interdigitated symmetric electrochemical capacitors, demonstrating how the printed structures could be easily integrated in prototypes of electrochemical devices. Although the fabricated devices did not exhibit superior capacitance, they presented a memristive behaviour with a potential for other applications such as artificial neural networks. Moreover, the results of this proof-of-concept study illustrate the significant importance of the conductivity of the printed electrodes, hence the importance of the additive manufacturing process parameters on the electrochemical performance.