Dual Metal Active Sites and an Enhanced Electric Field Boosting CO₂ Reduction to CH₄ in an Electromethanogenesis System

Abstract

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.

Upgrading CO2 into acetate on Bi2O3@carbon felt integrated electrode via coupling electrocatalysis with microbial synthesis

“…By contrast, in the case of Bi 2 O 3 /CF and bare CF, CLSM images (Figure 6B,C) exhibit a large area of yellow fluorescence, accompanied with some fractions of red fluorescence and pale green fluorescence. The yellow signal originated from the overlapping of green and red fluorescence 55,56 . Especially, CLSM observation revealed that abundant cells died within 2 weeks of operation in the absence of Bi 2 O 3 .…”

Tailoring interfacial microbiome and charge dynamics via a rationally designed atomic-nanoparticle bridge for bio-electrochemical CO2-fixation

“…The high- and low-frequency response arcs of the impedance spectra are ascribed to biofilm resistance ( R bio ) and extracellular electron transfer resistance ( R ct ), respectively. 34 R bio is much smaller than R ct (Fig. 4(F) and Fig.…”

“…The increased current densities demonstrated that the original electrochemical process matched the microbial extracellular electron utilization process, indicating an efficient charge transfer to the electroactive microbes for CO 2 conversion. 34 The CV of the groups without microbes revealed a near-rectangular shape, manifesting an electric double-layer-based capacitive response (Fig. 3(B)).…”

“…It is worth noting that the specifical interfacial coordination for improving charge extraction remains unrevealed due to complicated interaction sites and unclear electron transfer pathways in mixed microbiome systems. 33,34 The ability to simultaneously enhance interfacial biocompatibility and charge extraction via revealing the correlation between the catalytic characteristics of the electrode and the metabolic process of microbes represents an important endeavor toward high-efficiency bio-electrochemical CO 2 fixation. This, however, has yet to be explored.…”

Self-Supporting Metal-Organic Framework-Based Nanoarrays for Electrocatalysis

“…The advantages of high porosity and abundant metal sites make MOFs well capable to establish an ideal catalytic environment for CO 2 RR. − Among them, self-supporting MOF-based nanoarrays are specifically prominent with good CO 2 RR performance. , For example, Zhang et al prepared bismuth nanosheet arrays (Bi/CC-17) by an in situ electrochemical conversion strategy using Bi-based MOFs (CAU-17) as precursors (Figure a) . As shown in Figure b, Bi/CC-17 presented a porous and hierarchical morphology, exposing a large number of marginal active sites and accelerating the mass transfer.…”