Enhancing CO2 reduction in microbial electrosynthesis with a multifunctional PANI/ZIF-67/MXene composite cathode catalyst

Microbial electrosynthesis (MES) provides a sustainable solution for converting CO 2 into value-added products, but the weak contact between biofilms and the cathode surface often limits its efficiency. MES systems often have low product yields because of inefficient electron transfer and poor microbial attachment. To address this limitation, the design of advanced cathode materials is crucial for strengthening microbe-electrode interactions. The performance of MXene and its composites with polyaniline (PANI) and zeolite imidazolate frameworks (ZIF-67), specifically PANI/MXene, ZIF‑67/MXene, and PANI/ZIF‑67/MXene composite, is systematically evaluated as cathode catalysts for MES. Superior catalytic activity was observed for the PANI/ZIF-67/MXene composite, as evidenced by its lower hydrogen evolution overpotential (−0.52 V) and significantly reduced charge transfer resistance (30.16 Ω) relative to unmodified carbon felt (−0.94 V and 200.28 Ω, respectively). This improved electrochemical performance shows superior bioelectrochemical activity, with the PANI/ZIF-67/MXene composite yielding a 2.63-fold increase in acetate production over the control. This outperforms the improvements achieved by PANI/MXene (2.37-fold), ZIF-67/MXene (2.19-fold), and MXene (1.69-fold) alone. Reactors equipped with the PANI/ZIF-67/MXene cathode achieved a 2.07-fold acetate synthesis rate enhancement, accompanied by observed enhanced microbial growth on the electrode surface. These findings indicated that the PANI/ZIF-67/MXene cathode can effectively overcome key productivity bottlenecks in MES.