Hollow-spherical Co/N-C nanoparticle as an efficient electrocatalyst used in air cathode microbial fuel cell

The hollow-spherical Co/N-C nanoparticle, which is synthesized via a simple hydrothermal reaction followed by heat treatment, is firstly used as electrocatalyst for oxygen reduction reaction (ORR) in air cathode microbial fuel cell (MFC). The maximum power density of MFC with 10% Co/N-C air-cathode is as high as 2514 +/- 59 mW m(-2), which is almost 174% higher than the control. The exchange current density (i(o)) of cathode equipped with 10% Co/N-C is 238% higher than that of untreated AC. While the total resistance of treated samples decreases from 13.017 to 10.255 Omega. The intensity ratio of Raman D to G band (I-D/I-G) decreases from 0.93 (N-C) to 0.73 (Co/N-C), indicating the catalyst forms graphite structure. Both XRD and XPS testify that Co is bonded to N within graphitic sheets and serves as the active sites in ORR. The four-electron pathway of the Co/N-C also plays a crucial role in electrochemical catalytic activity. As a result, it can be expected that the as-synthesized Co/N-C, with extraordinary electro-catalytic performance towards ORR, will be a promising alternative to the state-of-the-art non-precious metal ORR electro-catalysts for electrochemical energy applications. (C) 2016 Elsevier B.V. All rights reserved.