Copper foam supported g-C 3 N 4 -metal-organic framework bacteria biohybrid cathode catalyst for CO 2 reduction in microbial electrosynthesis.

Microbial electrosynthesis (MES) presents a versatile approach for efficiently converting carbon dioxide (CO ₂ ) into valuable products. However, poor electron uptake by the microorganisms from the cathode severely limits the performance of MES. In this study, a graphitic carbon nitride (g-C ₃ N ₄ )-metal-organic framework (MOF) i.e. HKUST-1 composite was newly designed and synthesized as the cathode catalyst for MES operations. The physiochemical analysis such as X-ray diffraction, scanning electron microscopy (SEM), and X-ray fluorescence spectroscopy showed the successful synthesis of g-C ₃ N ₄ -HKUST-1, whereas electrochemical assessments revealed its enhanced kinetics for redox reactions. The g-C ₃ N ₄ -HKUST-1 composite displayed excellent biocompatibility to develop electroactive biohybrid catalyst for CO ₂ reduction. The MES with g-C ₃ N ₄ -HKUST-1 biohybrid demonstrated an excellent current uptake of 1.7 mA/cm ² , which was noted higher as compared to the MES using g-C ₃ N ₄ biohybrid (1.1 mA/cm ² ). Both the MESs could convert CO ₂ into acetic and isobutyric acid with a significantly higher yield of 0.46 g/L.d and 0.14 g/L.d respectively in MES with g-C ₃ N ₄ -HKUST-1 biohybrid and 0.27 g/L.d and 0.06 g/L.d, respectively in MES with g-C ₃ N ₄ biohybrid. The findings of this study suggest that g-C ₃ N ₄ -HKUST-1 is a highly efficient catalytic material for biocathodes in MESs to significantly enhance the CO ₂ conversion.
(© 2023. The Author(s).)