Fe₃O₄/granular activated carbon as an efficient three-dimensional electrode to enhance the microbial electrosynthesis of acetate from CO₂

Microbial electrosynthesis (MES) allows the transformation of CO₂ into value-added products by coupling with renewable energy. The enhancement in the microbial activity and electron transfer rate via a new electrode modification method is essential for developing MES. Here, three groups of granular activated carbon decorated by Fe₃O₄ (Fe₃O₄/GAC) with mass fractions of 23%, 38% and 50% were prepared and compared with bare GAC. The volumetric acetate production rate of MES with Fe₃O₄/GAC-38% was the highest (0.171 g L^-1 d^-1), which was 1.4 times higher that of the control (bare GAC), and the final acetate concentration reached 5.14 g L^-1 within 30 days. Linear sweep voltammetry and microbial community analyses suggested that Fe₃O₄/GAC facilitates extracellular electron transfer and improves the enrichment of electrochemically active bacteria. Fe₃O₄/GAC is an effective three-dimensional electrode material that enhances biofilm activity on GAC and improves MES efficiency.