Tandem Acidic CO2 Electrolysis Coupled with Syngas Fermentation: A Two-Stage Process for Producing Medium-Chain Fatty Acids.

The tandem application of CO2 electrolysis with syngas fermentation holds promise for achieving heightened production rates and improved product quality. However, the significant impact of syngas composition on mixed culture-based microbial chain elongation remains unclear. Additionally, effective methods for generating syngas with an adjustable composition from acidic CO2 electrolysis are currently lacking. This study successfully demonstrated the production of medium-chain fatty acids from CO2 through tandem acidic electrolysis with syngas fermentation. CO could serve as the sole energy source or as the electron donor (when cofed with acetate) for caproate generation. Furthermore, the results of gas diffusion electrode structure engineering highlighted that the use of carbon black, either alone or in combination with graphite, enabled consistent syngas generation with an adjustable composition from acidic CO2 electrolysis (pH 1). The carbon black layer significantly improved the CO selectivity, increasing from 0% to 43.5% (0.05 M K+) and further to 92.4% (0.5 M K+). This enhancement in performance was attributed to the promotion of K+ accumulation, stabilizing catalytically active sites, rather than creating a localized alkaline environment for CO2-to-CO conversion. This research contributes to the advancement of hybrid technology for sustainable CO2 reduction and chemical production.

Delineating cathodic extracellular electron transfer pathways in microbial electrosynthesis: Modulation of polarized potential and Pt@C addition.

Microbial electrosynthesis (MES) is an innovative technology that employs microbes to synthesize chemicals by reducing CO2. A comprehensive understanding of cathodic extracellular electron transfer (CEET) is essential for the advancement of this technology. This study explores the impact of different cathodic potentials on CEET and its response to introduction of hydrogen evolution materials (Pt@C). Without the addition of Pt@C, H2-mediated CEET contributed up to 94.4 % at -1.05 V. With the addition of Pt@C, H2-mediated CEET contributions were 76.6 % (-1.05 V) and 19.9 % (-0.85 V), respectively. BRH-c20a was enriched as the dominated microbe (>80 %), and its relative abundance was largely affected by the addition of Pt@C NPs. This study highlights the tunability of MES performance through cathodic potential control and the addition of metal nanoparticles.

Surface coating combined with in situ cyclic voltammetry to enhance the stability of gas diffusion electrodes for electrochemical CO2 reduction.

Electrochemical CO2 reduction (CO2RR), fueled by clean and renewable energy, presents a promising method for utilizing CO2 effectively. The electrocatalytic reduction of CO2 to CO using a gas diffusion electrode (GDE) has shown great potential for industrial applications due to its high reaction rate and selectivity. However, guaranteeing its long-term stability still poses a significant challenge. In this study, we conducted a comprehensive investigation into various strategies to enhance the stability of the GDE. These strategies involved modifying the structure of the substrate, such as the gas diffusion layer (GDL) and the back side of the GDL (macroporous layer side). Additionally, we explored modifications to the catalyst layer (CL) and the front of the CL. To address these stability concerns, we proposed a practical approach that involved surface coating using carbon black in combination with in situ cyclic voltammetry (CV) cycles on Ag/Ag300/polytetrafluoroethylene (PTFE). The partial Faradaic efficiency exceeded 80 % within a span of 70 h. Electron microscopy and electrochemical characterization revealed that the implementation of in situ CV led to a reduction in catalyst particle size and the formation of a porous surface structure. By enhancing the stability of the GDE, this research opens up possibilities for the advancement of hybrid systems that focus on the production and utilization of syngas.

Refining microbial potentiometric sensor performance with unique cathodic catalytic properties for targeted application scenarios.

Traditional microbial electrochemical sensors encounter challenges due to their inherent complexity. In response to these challenges, the microbial potentiometric sensor (MPS) technology was introduced, featuring a straightforward high-impedance measurement circuit tailored for environmental monitoring. Nonetheless, the practical implementation of conventional MPS is constrained by issues such as the exposure of the reference electrode to the monitored water and the absence of methodologies to stimulate microbial metabolism. In this study, our objective was to enhance MPS performance by imbuing it with unique cathodic catalytic properties, specifically tailored for distinct application scenarios. Notably, the anodic region served as the sensing element, with both the cathodic region and reference electrode physically isolated from the analyzed water sample. In the realm of organic monitoring, the sensor without Pt/C coated in the cathodic region exhibited a faster response time (1 h) and lower detection limits (1 mg L-1 BOD, 1 mM acetic acid). Conversely, when monitoring toxic substances, the sensor with Pt/C showcased a lower detection limit (0.004% formaldehyde), while the Pt/C-free sensor demonstrated superior reusability. The sensor with Pt/C displayed a heightened anode biofilm thickness and coverage, predominantly composed of Rhodococcus. In conclusion, this study introduces simple, cost-effective, and tailorable biosensors holding substantial promise for water quality monitoring.