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• Multi-physics simulation guided the design and optimization of BES anodes. • Binary carbon anode was spatially assembled with carbon mesh skeleton and GAC. • Directional electron transfer and enhanced microbe accommodation were synergized. • Binary carbon anode improved wastewater energy conversion with cost-effectiveness. Bioelectrochemical systems (BESs) hold prospects in wastewater energy and resource recovery. Anode optimization is important for simultaneous enhancement of wastewater energy conversion and effluent quality in BESs. In this study, a multi-physics model coupling fluid flow, organic degradation and electrochemical process was constructed to guide the design and optimization of BES anodes. Based on the multi-physics simulation, spatially-assembled binary carbon anodes composed of three-dimensional carbon mesh skeleton and granular activated carbon were proposed and established. The granular activated carbon conducive to microbe accommodation played a vital role in improving effluent water quality, while the carbon mesh skeleton favoring electron collection and transfer could enhance the bioelectricity output. With an average chemical oxygen demand (COD) removal rate of 0.442 kg m−3 d−1, a maximum power density of 20.6 W m−3 was achieved in the optimized composite anode BES, which was 25% and 154% higher than carbon mesh skeleton BES and granular activated carbon BES. Electroactive bacteria were enriched in composite anodes and performed important functions related to microbial metabolism and energy production. The spatially-assembled binary carbon anode with low carbon mesh packing density was more cost-effective with a daily energy output per anode cost of 221 J d−1 RMB−1. This study not only provides a cost-efficient alternative anode to simultaneously improve organic degradation and power generation performance, but also demonstrates the potential of multi-physics simulation in offering theoretical support and prediction for BES configuration design as well as optimization. [Display omitted] [ABSTRACT FROM AUTHOR]

[Display omitted] • Biomimetic membrane anode with electroactive atomically-dispersed Fe was designed. • Fe-NCM availed biofilm colonization and microbe-electrode interfacial interaction. • Fe-NCM anode intensified wastewater treatment and energy conversion in BESs. • Intracellular electron production and extracellular electron transfer were elevated. Bioelectrochemical systems (BESs) are promising for future wastewater treatment towards carbon neutrality. Hemes, as the active centers of outer-membrane c-type cytochromes, play an important role in anodic electron transfer. In this work, a biomimetic Fe–N x incorporated carbon membrane (Fe-NCM) mimicking the heme active center was proposed based on a nanocage confinement-electrospinning strategy and applied as the anode in BESs. The aligned carbon fibers with high electrical conductivity could serve as the electron "expressway" for swift electron transfer while the Fe–N x nexus served as the "gas station" and endowed the membrane anode with boosted redox activity. The Fe-NCM anode featuring great biocompatibility and electrochemical activity was conducive to microbe adhesion and biotic-abiotic interfacial interaction. The power output and chemical oxygen demand (COD) removal rate constant in the BES with this Fe-NCM anode reached 1406 ± 44 mW m−2 and 0.42 ± 0.01 h−1 under filtration operation mode, which were 156% and 191% as high as those of the pristine carbon membrane. The introduction of Fe–N x species exerted a significant influence on the anodic biofilm property, composition and function, which were of importance to bolstering wastewater energy conversion. Metagenomics unveiled that simultaneous intensification of intracellular electron production and extracellular electron transfer processes was achieved in the Fe-NCM BES. The Fe-NCM anode with electroactive Fe–N x sites facilitated the biotic-abiotic interfacial interaction in BESs and highlighted the rational design of anodes for efficient wastewater treatment and energy conversion. [ABSTRACT FROM AUTHOR]

• Fe-CFM has high electrochemical activity and electron transfer efficiency. • Fe-CFM exhibits superior microbial adhesion and forms highly active biofilms. • The iron element is distributed stably in the form of iron oxide inside Fe-CFM. • The Fe-CFM anode has high wastewater energy conversion efficiency in BESs. • Bioelectricity generation is greatly affected by the amount of iron. Bioelectrochemical systems (BESs) can achieve energy and resource recovery from wastewater. Accelerating electron transfer at the microbe-anode interface is vital for high-efficient wastewater energy conversion in BESs. Here, we fabricated an iron-doped carbon fiber membrane (Fe-CFM) anode with the stable and uniform distribution of iron oxides to boost electron transfer and microbial adhesion. This Fe-CEM anode efficiently accelerated the electron transfer with a small charge transfer resistance of 2.3 Ω. It achieved excellent energy conversion with a maximum power density of 3222 ± 384 mW m−2 and a maximum current density of 20.4 A m−2 assembled with the filtration composite anode and Co single atom air cathode in BES, which were 28% and 58% higher than those of the commercial carbon fiber cloth anode. The electricity generation could be significantly improved with the appropriate iron content. Our results demonstrate that this Fe-CFM has remarkable application potential in wastewater energy conversion. [Display omitted] [ABSTRACT FROM AUTHOR]

Bioelectrochemical system (BES) is promising technology to simultaneously treat wastewater and recover energy, and electrode material is important for the system performance. Microbial fuel cell (MFC) is one of typical BES to be applied in wastewater treatment. How to improve the electrode material is significant to improve wastewater treatment, energy recovery and cost effectiveness. In this study, 3D-weaved carbon electrode entity, assembled by multiple pieces of carbon mesh (CM), was proposed to combine all electrode components as entity to facilitate electron conduction and ionic migration, compared with carbon brush (CB) and granular activated carbon (GAC). The result showed that current density and internal resistance of MFC using 3D-weaved CM as horizontally extended inside anode (CM(T)) were 30.9 A m-3 and 4.5 Ω, respectively, with higher output than traditional GAC (22.6 A m-3 and 6.2 Ω). Though GAC had greater electrode filling and surface area for biomass growth, the electron transfer efficiency per unit electrode biomass was only at 0.0019 ± 0.0002 mol g-1 d-1, much lower than CM(T) at 0.0077 ± 0.0009 mol g-1 day-1. Higher ionic migration rate of CM(T) suggested the assisting effect of composite electrode to enhance ionic transportation towards the cathode. Microbial analysis further indicated that 3D-CM electrode network could simultaneously enhance Geobacter abundance and methanogen activity, suggesting the importance of electrode network on electricigens. Furthermore, CM(T) could obtain 10 times higher energy output efficiency than traditional GAC when applied inside anode chamber. This study proved that network construction of anode electrode could promote the electrode performance and cost effectiveness, suggesting the future development of reactor design of bioelectrochemical system. Image 1 • Anode configuration impacted biomass growth and electron conduction. • 3D carbon mesh constructed as electron network entity for conducting facility. • Electrode entity construction greatly benefited electron generation efficiency. • 3D carbon mesh stimulated microbial activity and Geobacter growth. • Massive cost optimization achieved by 3D carbon mesh. [ABSTRACT FROM AUTHOR]