Nitrogen-Doped Ordered Mesoporous Carbon as Metal-Free Catalyst for Power Generation in Single Chamber Microbial Fuel Cells

Abstract

Metal-free materials derived from the pyrolysis of the low-cost industrial melamine and ordered mesoporous carbon (OMC) were studied for the first time as cathode catalysts in single chamber microbial fuel cells (SCMFCs). The correlation between the instinct structure of three N-doped ordered mesoporous carbon-based catalysts (Nx-OMC) and power generation in SCMFCs was determined. Nx-OMC with different nitrogen contents were synthesized by varying the initial mass ratio (x) of melamine to OMC (10, 50 and 70). The changes in the chemical composition, morphology and structural properties after nitrogen doping were systematically characterized by the transmission electron microscopy (TEM), scanning electron microscopy (SEM), nitrogen adsorption-desorption isotherms, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The performance of Nx-OMC-based cathodes in SCMFC were compared to a Pt-based cathode used as a positive control. The SCMFC catalyzed by N50-OMC generated the maximum power density of 553 ± 11 mW m−2, which was comparable to that of Pt-based carbon cloth cathode containing 0.5 mg Pt cm−2 (530 ± 7 mW m−2). The enhanced power density of N50-OMC was attributed to its high amount of graphitic nitrogen functionality, high structural defect degree, high surface area and low charge transfer resistance. In addition, the performance of the SCMFC equipped with N50-OMC presented excellent stability over time. After approximately 2 months of SCMFC tests, the voltage dropped only by 7% compared with 10% for the Pt/C. This study reveals the great potential of N50-OMC catalysts as stable cost-benefit catalysts for MFC scale-up.