Nitrogen doping to atomically match reaction sites in microbial fuel cells

Abstract

Direct electron transfer at microbial anodes offers high energy conversion efficiency but relies on low concentrations of redox centers on bacterium membranes resulting in low power density. Here a heat-treatment is used to delicately tune nitrogen-doping for atomic matching with Flavin (a diffusive mediator) reaction sites resulting in strong adsorption and conversion of diffusive mediators to anchored redox centers. This impregnates highly concentrated fixed redox centers in the microbes-loaded biofilm electrode. This atomic matching enables short electron transfer pathways resulting in fast, direct electrochemistry as shown in Shewanella putrefaciens (S. putrefaciens) based microbial fuel cells (MFCs), showing a maximum power output higher than the conventional non-matched nitrogen-doped anode based MFCs by 21 times. This work sheds a light on diffusion mediation for fast direct electrochemistry, while holding promise for efficient and high power MFCs.

Surface activated natural wood biomass electrode for efficient microbial electrocatalysis: Performance and mechanism

“…Although, there was no linear relationship between the molar concentration and the catalytic current, the huge difference suggested other underlying reasons besides riboflavin concentration were responsible for the MET improvement. It was reported that the size‐matchable nanopores (1‐1.5 nm for riboflavin, 2‐4 nm for nanopores) provided the steric advantages for direct electrochemistry of riboflavin on the electrode surface, 26 which activated the electrode surface for bioelectrochemical catalysis. Although, the carbon or graphite surface was highly conductive, the smooth surface was difficult for direct electrochemistry of flavins or cells.…”

Extracellular electron transfer via multiple electron shuttles in waterborneAeromonas hydrophilafor bioreduction of pollutants

“…Therefore, the significant increase of redox peak current centered at −0.44 V versus Ag/AgCl in “1.2 μM ACNQ + 2 μM Rib + 2 μM FMN” experimental groups than that in “1.2 μM ACNQ + 2 μM Rib” experimental groups should be attributed to the addition of FMN into the bioelectrochemical systems (Figure 2). The redox peak appeared at −0.57 V versus Ag/AgCl should be attributed to the flavin adsorption on the anode surface (X. S. Wu et al, 2020). Moreover, we also found that the Mtr‐like respiratory pathway played an important role in reducing flavins by A. hydrophila ATCC7966 (Figure S4).…”

“…Some special features of waterborne A. hydrophila (Table S2), which differ from S. oneidensis MR‐1 and G. sulfurreducens PCA, make it a promising candidate for environmental applications. A. hydrophila has attracted great interests due to its widespread in the environment and potential applications in the transformation of environmental pollutants (Cao et al, 2010, 2012; Huang et al, 2019; X. S. Wu et al, 2020). Direct EET via outer membrane cytochromes has been confirmed to play a vital role in the reduction of pollutants or Fe/Mn oxides by A. hydrophila (Conley et al, 2018).…”

“…Although the fact that the bulk concentration of ACNQ produced by microorganisms is not high, the local concentration of ACNQ can reach 1000 times higher than the bulk concentration when biofilms are formed (Mevers et al, 2019), which is sufficient for ACNQ to act as an electron shuttle. In addition, ACNQ synthesis by A. hydrophila can also be improved by means of genetic engineering approaches (Min et al, 2017; X. S. Wu, et al, 2020). A. hydrophila possesses an N‐acylhomoserine lactone‐dependent quorum‐sensing system based on the ahyRI locus (Lynch et al, 2002; Zhang et al, 2020).…”

“…Members of the genus Aeromonas prevail in various aquatic habitats (Huang et al, 2019; Huys, 2014; Janda & Abbott, 2010; Nsabimana et al, 2000; Sanglas et al, 2017; VandeWalle et al, 2012) and play important roles in biological wastewater treatment and environmental remediation due to their metabolic diversities (Cao et al, 2012; Chung & Okahe, 2009; Park et al, 2008). They can respire with various organic and inorganic electron acceptors, including chlorinated organic compounds, azo dyes, nitrate, vanadium (V(V)), cobalt (Co(III)), selenium (Se(VI)), chromium (Cr(VI)), and iron oxides (Cao et al, 2012; Knight & Blakemore, 1998; T. X. Liu et al, 2014; X. S. Wu et al, 2020). Some Aeromonas strains can even reduce halogenated organics (Cao et al, 2010, 2012) and are known to prevail in wastewater treatment plants (Chung & Okahe, 2009; Doyle et al, 2017; Kim et al, 2011; Park et al, 2008).…”