Application of graphene-based nanomaterials as novel cathode catalysts for improving power generation in single chamber microbial fuel cells Alireza Valipour, Sivasankaran Ayyaru, Youngho Ahn * Department of Civil Engineering, Yeungnam University, Gyeongsan, 38541, South Korea highlights graphical abstract  RGO HI-AcOH and RGO/Ni nanoparticles are studied as MFC cathode catalysts.  HI-AcOH reductant positively in- fluences the formation of RGO frameworks.  Cathode catalyst loading plays a role in the MFC power generation enhancement.  RGO HI-AcOH -DL MFCs (1683 ± 23 mW/ m 2 ) showed higher performance than other non-Pt MFCs.  RGO HI-AcOH could be a cost-effective alternative to Pt-based cathode catalyst. article info Article history: Received 10 March 2016 Received in revised form 23 July 2016 Accepted 25 July 2016 Keywords: Microbial fuel cell Cathodic catalyst Graphene Nickel nanoparticle Nanocomposite abstract The low catalytic activity, limited resources, complexity and costs, and non-environmentally friendly nature are key factors limiting the application of non-precious metals and their composites at the cathode in microbial fuel cells (MFCs). This study evaluated the feasibility of graphene-based nano- materials (RGO HI-AcOH vs. RGO/Ni nanoparticle composite) as novel cathode catalysts in single chamber air-cathode MFCs. A series of MFCs with different catalyst loadings were produced. The electrochemical behavior of the MFCs were evaluated by cyclic voltammetry (CV) and impedance spectroscopy (EIS). As a result, the MFCs with the RGO HI-AcOH cathodes showed greater maximum power densities (>37%) than those with the RGO/Ni nanoparticle cathodes. In the MFCs, the highest maximum power density of 1683 ± 23 mW/m 2 (CE ¼ 72 ± 3%), which covers 77% of that estimated for Pt/C (2201 ± 45 mW/m 2 , CE ¼ 81 ± 4%), was obtained from the double loading RGO HI-AcOH cathodes. Among the MFCs with the RGO/Ni nanoparticle composite cathodes, those loaded with a double catalyst (1015 ± 28 mW/m 2 , CE ¼ 70 ± 2%) showed better power performance than the others. Both CV and EIS showed good agreement with the MFC results. This study suggests that the RGO HI-AcOH cathode, particularly with a double catalyst loading, is promising for sustainable low-cost green materials, stable power generation and the long-term operation of MFCs. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Microbial fuel cells (MFCs) are a novel, environmentally friendly and promising alternative for generating power directly from * Corresponding author. E-mail address: yhahn@ynu.ac.kr (Y. Ahn). Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour http://dx.doi.org/10.1016/j.jpowsour.2016.07.099 0378-7753/© 2016 Elsevier B.V. All rights reserved. Journal of Power Sources 327 (2016) 548e556