Binary heterogeneous conductive polypyrrole hydrogel as bio-scaffold for optimizing cytochrome-mediated direct extracellular electron transfer process and power generation performance of microbial fuel cell

This study addresses the challenge of high charge transfer resistance and limited bioelectrocatalytic activity in conductive polymers, which hinder their use as bioanode materials in bioelectrochemical systems. The research investigates the use of a MOF-derived matrix (Fe,Zn-NC) to modify polypyrrole (PPy) hydrogel as bioanode, improving its interfacial direct extracellular electron transfer (DET) rate. The charge transfer resistance is reduced from 23.62 Ω (Zn-NC/PPy) to 9.69 Ω in Fe,Zn-NC/PPy, and the maximum power density in microbial fuel cells (MFC) increases by 1.35 times, from 3.65 W/m3 to 4.93 W/m3. Using Fourier-Transformed alternating current voltammetry (FTACV) and distribution of relaxation time (DRT) analysis, we demonstrate that Fe,Zn-NC enhances the interfacial charge transfer rate of electroactive microbes. DFT calculations show that the α-α conjugated structures in the composite hydrogel significantly enhance the adsorption of C-type cytochrome. High-throughput sequencing results and PICRUSt analysis validate the screening characteristics of binary heterogeneous hydrogel on Geobacter (increased from 11.97 % to 33.83 %) and the promotion of flavin related metabolism activity. This research highlights the unique bioelectrocatalytic activity of PPy composite hydrogel and its potential as a bio-functional material in bioelectrochemical systems, offering new insights for the development of non-adhesive materials in bioelectrochemical applications.