Electrochemical study of screen-printed electrodes modified with electropolymerized polyaniline films grafted with low mass ratio of graphene oxide

Homemade screen-printed electrodes (SPEs) were produced using conductive inks with graphite and alkyd resin and were modified with electropolymerized films of polyaniline (PAni) grafted with 2.5 and 5.0 (m:m) of graphene oxide (GO) obtained by the chemical oxidation of graphite. The SPEs were characterized by Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The CV results showed similar redox behavior for all SPE, characteristic of PAni films in an acidic medium (0.5 mol L⁻¹ H₂SO₄). However, the EIS results showed a decrease in the charge-transfer resistance (R_ct), from 1064 Ω for SPE/PAni to 364 Ω for SPE/PAni-2.5%GO (about 3 times) and to 113 Ω for SPE/PAni-5%GO (about 10 times) compared to the unmodified counterpart SPE/PAni. Additionally, an increase in the constant phase element (CPE₂) value was also observed, from 459 µS s^α cm⁻² for SPE/PAni to 838 µS s^α cm⁻² for SPE/PAni-2.5%GO and to 1560 µS s^α cm⁻² for SPE/PAni-5%GO, indicating lower ion transport for the SPEs modified with the PAni-GO hybrids. This method to produce a homemade SPE modified with the PAni-GO hybrid with improved electrochemical behavior and ionic conductivity is a simple, low-cost, scalable, and interesting alternative for future applications in sensors or charge-storage electrochemical devices.