Boosting cathodic performance of microbial electrosynthesis cell via co-polymerized graphitic carbon nitride

Industrialization and urbanization have substantially contributed to CO₂ generation, which drives climate change. A microbial electrosynthesis cell (MES) is a promising bioelectrochemical system that captures CO₂ and converts it to bio-products like acetate. However, its utilization is limited by the high cathodic overpotential that arises from poor catalytic materials. This study developed graphitic carbon nitride (g-C₃N₄) composites through co-polymerization of urea and melamine and examined their effectiveness in enhancing cathodic reactions for converting carbon into acetate. The results revealed the promising properties (hybrid morphology and tunable energy band gap) of g-CN_50m, demonstrating it as the most promising catalyst for MES. Under light illumination, the co-polymerized g-CN_50m recorded an acetate concentration of 41.77 mg/L with 54.58% coulombic efficiency and 20.07% carbon conversion efficiency, which are higher than the control reactor. The findings suggested that the photogenerated electrons allowed higher electron transfer for carbon reduction into acetate. However, acetate consumption for possible biofilm growth in both light and dark conditions was observed by acetate accumulation, higher voltage, and short acclimation. Future work shall investigate optimal cathodic voltage and acclimation periods to promote microbial growth and charge transfer via g-CN_50m with a strong conductive metal catalyst for optimal acetate production.