Engineering conducting polymer-based interfaces for high-performance microbial electrochemical systems

Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) is a widely recognized conducting polymer, especially in the field of electromicrobiology. Nonetheless, its inherently moderately hydrophobic and smooth surface poses a challenge for bacterial adhesion and biofilm formation, thereby restricting the growth and charge transfer of electroactive bacteria. To overcome these limitations, PEDOT:PSS films were modified with selected salts (FeCl₃, MgSO₄, MnCl₂, CaCl₂, BaCl₂) to improve bacterial attachment, biofilm formation and electrochemical performance, including charge storage capacity and charge transfer efficiency. Among the formed coatings, PEDOT:PSS@Ca demonstrated the highest charge storage capacity of 5.1 ± 1.0 mC/cm² in the presence of S. oneidensis MR-1, representing a three orders of magnitude increase when compared with pristine PEDOT:PSS. The improvement in biofilm formation was significant, with PEDOT:PSS@Ca attaining 55.0 ± 1.3 % biofilm formation and 92.8 ± 3.1 % bacterial viability, representing a considerable increase compared to unmodified PEDOT:PSS (4.1 ± 1.2 % biofilm formation and 63.1 ± 7.2 % viability). Calcium modification notably enhanced electron transfer by decreasing the charge transfer resistance, thereby promoting more effective electron exchange at the electrode interface. The findings indicate that functionalization of PEDOT:PSS with metal salts, and particularly CaCl₂, is an effective approach for enhancing microbial fuel cell performance.