Electron pool effect: iron-quinone coordination polymer boosts anaerobic digestion by accelerating interfacial...

Methane production in microbial electrolysis cell-anaerobic digestion (MEC-AD) systems is limited by inefficient interfacial electron transfer (IET), which depends on the slow formation of a conductive microbial biofilm. In this study, a novel material with Fe (III) ions as the metal centers and the redox-active 2,5-dihydroxy-1,4-benzoquinone (dhbq) as the organic ligand (Fe@dhbq) was designed to act as an efficient "electron pool" that mediated electron transfer between the cathode and electroactive methanogens, which helped establish an efficient IET network by accelerating the maturation of electroactive biofilms. The results demonstrated that the electron transfer capacity of the CC/Fe@dhbq biofilm increased by an order of magnitude, and the current was 4.2 times higher than the control. Correspondingly, direct electron transfer (DET) pathway was formed to increase methane production by 35 %. This work provides a new strategy for enhancing methanogenesis via DET in electro-enhanced anaerobic digestion.