Novel Porous Nitrogen Doped Graphene/Carbon Black Composites as Efficient Oxygen Reduction Reaction Electrocatalyst for Power Generation in Microbial Fuel Cell.

Yuan Liu,Hong Liu,Meiling Liao,Zhimei Liu

doi:10.3390/nano9060836

Abstract

To improve the power generation of a microbial fuel cell (MFC), a porous nitrogen-doped graphene/carbon black (NG/CB) composite as efficient oxygen reduction reaction (ORR) electrocatalyst was successfully synthesized by pyrolyzing graphene oxide (GO) encapsulated CB with cetyltrimethyl ammonium bromide as a bridge. This concept-to-proof synthesis can be considered as a template-like method. Based on this method, one composite named as NG/CB-10 was acquired using the optimized GO-to-CB mass ratio of 10:1. Electrochemical tests demonstrate that NG/CB-10 can catalyze ORR in neutral-pH medium through a four-electron pathway with positively shifted the onset potential, the enhanced current density and reduced charge transfer resistance. CB addition also prolongs the stability of NG/CB-10. The enhancement in electrochemical performance of NG/CB-10 was attributed to the enlarged surface area, abundant mesopores and high content of pyridinic nitrogen. The maximum power density of MFC equipping NG/CB-10 as cathode electrocatalyst reached 936 mW·m−2, which was 26% higher than that of NG and equal to that of platinum/carbon. The cost of NG/CB-10 was reduced by 25% compared with that of NG. This work provides a novel method to synthesize promising ORR electrocatalyst for MFC in the future.

Highlights

Oxygen reduction reaction (ORR) has become a dominant cathode reaction in microbial fuel cells (MFCs) due to its easy operation and potential for large-scale application [1,2,3,4]
carbon black (CB) addition into nitrogen-doped graphene (NG) is expected to influence the electrochemical performance of nitrogen-doped graphene/carbon black (NG/CB)-x composites, which was investigated by means of RRDE tests
As shown in the polarization curves, the MFC equipped with NG/CB-10 generated an open circuit voltage (OCV) of 0.822 V, which was slightly lower than that of Pt/C (0.880 V) but higher than that of NG (0.748 V)

Summary

Introduction

Oxygen reduction reaction (ORR) has become a dominant cathode reaction in microbial fuel cells (MFCs) due to its easy operation and potential for large-scale application [1,2,3,4]. Heteroatom doping into graphene sheets raises the Fermi energy and provides abundant highly active catalytic sites, which significantly improve the electrocatalytic properties for ORR [14,15,16,17]. Contrary to pristine graphene, the doping of heteroatom into graphene sheets causes structural defects. These defects provide ORR active sites but severely deteriorate the electrical properties of NG [16,18]. On the other hand, restacking of graphene sheets via van der Waals forces reduces the active surface area and accessibility of electrocatalytically active sites, which result in decreased ORR activity [15,19,20]. The suppressed electrocatalytic activity of NG depresses performance of energy-conversion cells

Methods

Results

Conclusion