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

Abstract

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...

Revealing Co‐N4@Co‐NP Bridge‐Enabled Fast Charge Transfer and Active Intracellular Methanogenesis in Bio‐Electrochemical CO2‐Conversion with Methanosarcina Barkeri

“…Co‐N 4 @Co‐NP bridge‐based nanosheet matrix was prepared according to our previous study. [ 23 ] First, Co‐doped zeolitic imidazolate framework‐67 (ZIF‐67) was synthesized in situ on carbon felt (CF) to form a stable nanosheet‐based structure (Figure S1, Supporting Information), which is supposed to facilitate microbe enrichment during biohybrid construction. The as‐prepared frameworks were then subjected to pyrolysis to form atomic Co‐N 4 sites (Figure 1b) within carbonized ZIF‐67, during which the excess Co species precipitated and agglomerated under the nanosheets as Co nanoparticles (Figure 1c), leading to the formation of Co‐N 4 @Co‐NP bridge‐based nanosheet electrode.…”

“…Meanwhile, the electrostatic interactions between the microbes and the electrode matrix are enhanced because of the increased surface electric intensity resulting from Co species. [ 23 ] As depicted in Figure 1e, the X‐ray absorption spectrum (XAS) of Co shows that after the loading of M. barkeri , the absorption near edge of the Co species demonstrates a shift from Co foil toward phthalocyanine‐cobalt (Co‐Pc), suggesting an increased average valence state of the Co species resulting from the corresponding charge migration from Co element. Besides, the EXAFS spectra show a shift of Co–N 4 coordination from 1.7 to 1.8 Å with M. barkeri adsorption, indicating the distortion of the Co–N 4 coordination (Figure S7, Supporting Information).…”

“…[40,41] This preference is in agreement with the charge density differences study where an electron-deficient metal (Co) and electron-rich nitrogen-doped carbons are observed in atomic metal-doped carbon nanosheets. [23,42] Besides, the (Δd−p) of N-Fe for Co-N 4 @Co-NP decreases to ≈2.7 eV from ≈3.8 eV for that of Co-N 4 , indicating that the Co nanoparticles in the Co-N 4 @Co-NP bridge effectively fill up the electronic states gap between Co-N 4 and Fe-TCCP via tailoring the electronic structure of the Co-N 4 sites. This decreased energy band gap further reduces the charge transfer barrier between Fe-TCCP and the Co-N 4 active sites, which in turn strengthens the direct transmembrane electron transfer.…”

“…The Co‐based atomic‐nanoparticle bridge (Co‐N 4 @Co‐NP) developed in our previous study provides a robust platform to investigate the bio‐interfacial electro‐interaction as the atomic Co‐N 4 sites act as the target interaction sites and the underneath Co nanoparticles afford further convenient modification of the interfacial interaction. [ 23 ] Yet, the adoption of a mixed microbiome in that work complicates the microbial electron receptors, making it impracticable to scrutinize the pivotal role of Co‐N 4 @Co‐NP electrode in promoting the extracellular electron transfer and intracellular methanogenesis for specific methanogens. [ 23 ] Herein, a model methanogen Methanosarcina barkeri ( M. barkeri ) is selected to combine with the efficient Co‐N 4 @Co‐NP bridge‐based nanosheet electrode for systematically interrogating the charge transfer mechanisms at the biotic–abiotic interface and the structural effects of the electrode on intracellular metabolism for CO 2 ‐to‐CH 4 .…”

“…[ 23 ] Yet, the adoption of a mixed microbiome in that work complicates the microbial electron receptors, making it impracticable to scrutinize the pivotal role of Co‐N 4 @Co‐NP electrode in promoting the extracellular electron transfer and intracellular methanogenesis for specific methanogens. [ 23 ] Herein, a model methanogen Methanosarcina barkeri ( M. barkeri ) is selected to combine with the efficient Co‐N 4 @Co‐NP bridge‐based nanosheet electrode for systematically interrogating the charge transfer mechanisms at the biotic–abiotic interface and the structural effects of the electrode on intracellular metabolism for CO 2 ‐to‐CH 4 . Interfacial direct electron transfer pathway from electrode matrix to iron porphyrin (Fe‐TCPP), which is the center molecule of conductive cytochrome b (Cytb), as well as mediated electron transfer via the redox reaction of riboflavin—the center molecule of coenzyme F 420 —were carefully interrogated at different applied potentials to reveal the function of Co‐N 4 sites and the underneath Co nanoparticles.…”