Biodegradable rGO-reinforced poly(3-hydroxybutyrate-<i>co</i>-4-hydroxybutyrate) (P3HB4HB) composite membranes for enhanced power generation in microbial fuel cells: a sustainable alternative to commercial PEMs

Microbial fuel cells (MFCs) represent a promising green technology for energy recovery from organic waste. In this study, we developed biodegradable composite proton exchange membranes (PEMs) based on poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P3HB4HB) reinforced with reduced graphene oxide (rGO) using a solution casting method. The membranes were systematically characterized and tested in a dual-chamber MFC system. The membrane doped with 7 wt% rGO showed a proton conductivity of 23.3 mS cm-1 at 80 degrees C, a water uptake of 7.71% and a low oxygen permeability of 2.43 x 10-4 cm s-1. This membrane achieved a power density of 71.3 mW m-2, outperforming the commercial Tion5-W membrane by approximately 50%. The integration of rGO improved thermal, mechanical and electrochemical performance while maintaining the biodegradability of the membrane matrix. These findings highlight the potential of rGO/P3HB4HB membranes as a high-performance and environmentally sustainable alternative to conventional perfluorinated PEMs, especially in decentralized wastewater-to-energy applications.