CNFs@MnO2 nanofiber as anode material for improving the extracellular electron transfer of microbial fuel cells

Abstract

The relatively low microbial loading, low extracellular electron transfer efficiency, and poor electrocatalytic activity at the anode interface of microbial fuel cells limit their power generation efficiency. Based on this, using the high electrochemical specific surface area, high porosity, facile loading, and flexible support of electrospinning as well as the superior energy storage capability of MnO₂, we successfully constructed two distinct morphologies of carbon nanofiber-loaded manganese dioxide electrocatalysts. The effects of carbon nanofiber-loaded nanoflower-shaped (CNF@MnO₂-S) and nanorod-shaped (CNF@MnO₂-R) manganese dioxide on the electrochemical performance of the anode, microbial fuel cell power generation and pollutant purification performance were comprehensively investigated. The impact of the two electrocatalysts on the anode biofilm was analyzed, revealing the mechanism for improving the performance of microbial fuel cells. The results show that compared to pure carbon cloth and carbon nanofiber-modified carbon cloth, the CNF@MnO₂-R modified carbon cloth anode exhibits the best power generation performance. An outstanding performance improvement of about 27.9% highest output voltage (0.645 V), 27.9% maximum output power (821.549 mW m⁻²), 1.5 times and 2 times higher specific capacitance (5.93 mF cm⁻²), and 31.9% higher chemical oxygen demand (COD) removal rate (84.35%) were achieved, compared to that of the pure carbon cloth anode. The performance improvement can be mainly attributed to the rough surface, high porosity, and excellent electrocatalytic performance of CNF@MnO₂-R. It not only increases the electrochemical specific surface area and bio-affinity at the anode interface but also promotes microbial adhesion and reproduction and regulates the electron transfer and information exchange process between the biofilm and the anode, thereby enhancing the power generation performance and organic matter removal rate of microbial fuel cells.