Electroactive Materials for Anaerobic Bioenergy and Bioproduct Recovery from Wastewater: Decoding Tripartite Interfaces in Microbial Electron Transfer

Anaerobic wastewater valorization via methanogenesis (bioenergy) and chain elongation (bioproducts) is central to the circular water economy, yet it is fundamentally hindered by thermodynamic constraints and sluggish syntrophic kinetics. While electroactive materials (EAMs) are increasingly deployed to modulate microbial electron transfer (MET), the current understanding remains fragmented and largely phenomenological. This Critical Review establishes a unified multiscale mechanistic framework centered on tripartite interfaces. At the biotic-biotic interface, we demonstrate how EAMs alleviate thermodynamic bottlenecks to steer bidirectional syntrophic fluxes, challenging the oversimplified causal view of direct interspecies electron transfer. At the material-biotic interface, we reframe EAMs from static bioconductors to dynamic mediators, analyzing how their intrinsic solid-state physics and surface redox chemistry govern interfacial charge kinetics. At the intraextracellular interface, we reveal how EAMs regulate transmembrane electron fluxes to reprogram central carbon routing, imposing a biosynthetic trade-off where EAMs replace biological conduits to conserve cellular energy. Critical knowledge gaps are further exposed, spanning biotic/abiotic conductivity confounding, taxonomic overestimation of Geobacter, and material biogeochemical decay. Finally, a roadmap is provided that advocates rational design of self-healing EAMs, synthetic electrogenetic microbiome engineering, artificial intelligence-enabled reactor intensification, and life-cycle sustainability assessments. This Review conceptualizes EAMs as active, adaptive physicochemical regulators, laying the groundwork for programmable material-microbe biohybrids.