An electromethanogenesis system incorporating CO 2reducing microorganisms and a cathode material offers a promising approach for CO 2 fixation with improved thermodynamic efficiencies. However, low electron transfer rates at microorganism−cathode interfaces can limit CO 2 conversion efficiency. A nanoarrays/bacteria hybrid system was proposed for bioelectrochemical reduction of CO 2 to CH 4 . The hierarchical nanoarrays derived from metal−organic frameworks enhanced the CO 2 conversion rate with the optimization of both a local electric field and Ni/Co dual metal active sites. Optimizing the electric field intensity (∼1.25-fold compared to bare CF) and introducing a heterojunction on the cathode material boosted the electron transfer and achieved a higher current density (maximum 10 A/m 2 ) at −0.9 V (vs Ag/AgCl) for 9.6-fold CH 4 production (697.9 mmol•day −1 •m −2 ) compared to the control. The dual metal active sites provided extra electron shuttles from a cathode to a microorganism to boost the electron transfer for methane production with a thicker (∼1.3-fold) and enhanced conductive EPS production (∼1.68-fold). A decreased internal resistance, a reconstituted microbial community, and an enhanced methane production rate indicated an increase in the microbial electron transfer between Methanobacterium and Clostridia, resulting in a selective bioelectroreduction (84%) of CO 2 to CH 4 . This study suggests that nanointerface engineering in electromethanogenesis systems can effectively regulate selective CO 2 reduction for new generation biogas projects.
A nanomaterial−living cell biohybrid system is an efficient energy conversion method due to enhanced interactions between inorganic materials and bacteria. However, inefficient electron transfer at the interface of the biohybrid remains as a limiting factor. Herein, an inorganic−biologic hybrid was proposed by combining a typical electroactive bacterium, Geobacter sulfurreducens, and a highly conductive N-doped Fe 3 O 4 with a carbon dot shell (Fe 3 O 4 @CD) to boost energy conversion in bioelectrochemical systems (including microbial electrolytic cells and electro-methanogenesis). One-potsynthesized Fe 3 O 4 @CDs enhanced extracellular electron transfer in the biohybrid system by forming an interaction network with conductive proteins inside and outside G. sulfurreducens. In the microbial electrolytic cell, the maximum current of Fe 3 O 4 @CDs-fed cells was 6.37 times higher than that of the control group without nanoparticle addition. This enhanced performance was accompanied with higher bioactivity, higher cellular adhesion, and lower biofilm resistance. The G. sulfurreducens−Fe 3 O 4 @CDs biohybrids supplemented during electro-methanogenesis remained stable on anodes, which promoted microbial syntrophy. The metabolic methanogenesis pathways are strongly related to the electron transfer ability of G. sulfurreducens, which demonstrates a new strategy to promote extracellular electron transfer through the constructed biohybrid system.
Bio-electrochemical CO2 fixation represents a promising strategy for CO2-to-chemical conversion, yet suffers from a low CO2-reducing rate. Limited microorganism attachment and unfavorable charge extraction at the bioinorganic interface are the...
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