Bioelectrochemical systems (BESs) enable simultaneous wastewater treatment and energy/resource recovery by coupling microorganisms with electrodes. However, sluggish extracellular electron transfer (EET) at the biotic-electrode interface, remains a major bottleneck limiting power output, startup, and long-term stability. This review summarizes the current mechanistic understanding of direct and mediated EET pathways and translates these insights into interface design principles. With primary emphasis on anodic interfaces, we discuss three complementary engineering strategies: structural engineering to construct hierarchical porous architectures for biofilm accommodation and mass transport; chemical modification to regulate conductivity, redox properties, and catalytic sites; and surface functionalization to optimize wettability, charge, microbial adhesion, and interfacial contact. We further compare electrochemical and system-level metrics used to evaluate modified electrodes and relate performance gains to specific interfacial bottlenecks across different BES configurations. Finally, we outline future priorities, including standardized evaluation, mixed-community systems, multiscale design, and integration with synthetic biology and advanced materials. This review provides a mechanism-guided framework for designing high-performance microbial electrodes for sustainable energy and environmental applications.
Yang et al. (Sun,) studied this question.