Enhancing electron transfer in anaerobic process by supercapacitor materials: Polyaniline functionated activated carbon

[Display omitted] •Supercapacitor material (AC-PANi) was prepared and applied to the AD process.•Incorporation of AC-PANi significantly increased the methane production.•AC-PANi relieved metabolic imbalance between acetate-producing and methanogenesis.•AC-PANi promoted DIET between acetate-producing bacteria and methanogens. Strengthening the direct interspecies electron transfer (DIET) is an effective strategy to improve the performance of anaerobic digestion (AD) process. In this study, the polyaniline functionated activated carbon (AC-PANi) was prepared by chemical oxidative polymerization. This material possessed pseudo-capacitance properties as well as excellent charge transfer capability. The experimental results demonstrated that the incorporation of AC-PANi in AD process could efficiently increase the chemical oxygen demand (COD) removal (18.6 %) and daily methane production rate (35.3 %). The AC-PANi can also act as an extracellular acceptor to promote the synthesis of adenosine triphosphate (ATP) and secretion of extracellular enzymes as well as cytochrome C (Cyt-C). The content of coenzyme F420 on methanogens was also shown to be increased by 60.9 % with the addition of AC-PANi in AD reactor. Overall, this work provides an easy but feasible way to enhance AD performance by promoting DIET between acetate-producing bacteria and methanogens.