Fe–N-doped carbon nanoparticles from coal tar soot and its novel application as a high performance air-cathode catalyst for microbial fuel cells

Abstract

Coal tar soot (CTS), which is an industrial product of the incomplete combustion of coal tars or heavy oil, is a low-value additive for the production of cement, ink, oil paint, etc. However, it has considerable potential as the catalyst support for oxygen reduction reactions (ORRs) because of its abundant oxygen-containing functional groups and interconnected porous structure. Herein, we proposed a one-pot strategy for synthesizing the high ORR performance catalyst (FePc@CTS) by simultaneously incorporating Fe and N into the carbon matrix of CTS and modifying the textural properties of CTS by using solvothermal treatment with iron phthalocyanine (FePc) and CTS in n-hexane. Electron microscopy investigation shows that the solvothermal treatment produces FePc@CTS with a spherical shape and a rather narrow particle size distribution. X-ray photoelectron spectroscopy and elemental analysis indicate that the FePc@CTS has a high Fe and N content. Due to the interconnected macroporous structure and the abundant ORR active sites, the FePc@CTS sample had the most positive half-wave potential (0.057 V vs. Ag/Cl) and the highest limiting current density (5.63 mA cm−2) among the prepared samples. An air-cathode microbial fuel cell (MFC) with FePc@CTS delivered a peak power density of 2026 ± 160 mW m−2, which was much higher than that of a cell with Pt/C (1337 ± 179 mW m−2). This work provides a facile pathway to convert low-value soot into interesting nano-structured ORR catalyst for MFCs to recover energy from wastewater.