Microbial electrosynthesis (MES) is an electrochemical reduction technique where microorganisms attached to electrodes are used as catalysts for CO2 reduction into chemicals. In situ grown molybdenum carbide (Mo2C) without binder-modified electrodes for MES was constructed in different layer numbers. Results showed that the hydrogen evolution reaction activity of carbon felt (CF) with Mo2C was higher than that of bare CF. The volumetric acetate production rate of MES with in situ grown Mo2C through a single electrostatic self-assembly method was 0.15 +/- 0.01 g L-1 day(-1), which was 1.8 times that of the control. The final acetate concentration reached 4.56 +/- 0.1 g L-1 within 30 days, and the coulomb efficiency was 50 +/- 0.3%. In addition, scanning electron microscopy and microbial community analyses showed that Mo2C with a single layer was conducive to the attachment of microorganisms, improved the enrichment of Acetobacterium and Arcobacter, and inhibited the abundance of Sulfurospirillum. In situ grown Mo2C-modified cathode is an effective strategy for improving MES efficiency.