Fe@NC-hybrid electrode enhancing acetate synthesis from CO2via microenvironment regulation in microbial electrochemical systems.

The practical implementation of CO2 valorization via microbial electrochemical systems (MES) is constrained by its relatively suboptimal production rate. Rational design of electrode-localized microenvironments offers a promising strategy to overcome this bottleneck. This study provided a regulation strategy with metal-microbial hybrid electrode which synergistically enhanced CO2 conversion efficiency and microbial activity in MES. The engineered Fe@NC-hybrid electrode demonstrated exceptional performance in modulating the electrode-suspended sludge interface microenvironment, exhibiting outstanding potential for acetate production. Experimentally, with the effect of Fe@NC-hybrid electrode, the mean cumulative amount of acetate increased by 2.9 times approximately as compared with the control group. Notably, the highest acetate production rate reached 3.7 g/(m2 h) in the Fe@NC- hybrid electrode group, indicating the great potential of the Fe@NC- hybrid electrode in improving the acetate production rate. The novelty of composite architecture of Fe@NC facilitates enhanced electrochemical activity by reducing charge transfer resistance. Additionally, dual functionality in electrocatalytic hydrogen evolution and high-affinity CO2 adsorption capacity of Fe@NC synergistically promote the selective enrichment of Acetobacterium (47.5 %) on the electrode interface. Further analysis of the enzyme activities during the Wood-Ljungdahl pathway demonstrated that Fe@NC-hybrid electrode effectively facilitated both the carbonyl and methyl branches. These findings offer valuable insights into a microenvironment regulation for CO2 utilization and reduction in MES.