Mechanism insights into salt tolerance strengthened by CoCe encapsulated N-doped CNTs cathode in microbial fuel cell

Abstract

To address the challenges of bioanode deactivation and instability of cathode catalysts in the treatment of high-salt organic wastewater using microbial fuel cells (MFCs), a series of CoCe catalysts encapsulated within nitrogen-doped carbon nanotubes (CoCe@NCNTs) was synthesized using a one-pot calcination method. Among the synthesized catalysts, CoCe0.5@NCNTs demonstrated outstanding and stable electrochemical performance in a high-salt environment with 600 mM NaCl, achieving a power density of 144.29 mW m−2, which was 2.7 times higher than that of Co@NCNTs. Notably, the characterization of the catalyst revealed that the addition of Ce element enhanced the stability of the Co crystal structure, mitigated Co leaching, and facilitated the retention of a higher valence state of the Co species after the reaction under high salt conditions. Specifically, the Co3+/(Co2+ + Co3+) ratio in CoCe0.5@NCNTs was 2.82 times larger than that of Co@NCNTs, signifying the favorable influence of the mutual electron conversion between the bimetallic Ce and Co on the performance and stability of catalyst in a high-salt environment. Furthermore, the study assessed the removal efficiency of norfloxacin (NOR), NAD+/NADH ratios, and microbial diversity in conjunction with the stability of cathode electrochemical performance, demonstrating the interconnection between cathode and anode. By considering the practical challenges in treating high-salinity wastewater and the principles of bioelectrochemistry, this paper proposes a mechanism for enhancing anode performance through cathode linkage, thereby providing a novel strategy for MFCs to treat high-salinity organic wastewater treatment.