Graphitic carbon micronanofibers asymmetrically dispersed with alumina-nickel nanoparticles: A novel electrode for mediatorless microbial fuel cells Shiv Singh a , Nishith Verma a,b,* a Department of Chemical Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India b Center for Environmental Science and Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India article info Article history: Received 16 January 2015 Received in revised form 27 February 2015 Accepted 4 March 2015 Available online 26 March 2015 Keywords: Microbial fuel cells Electrode Nanoparticles Carbon nanofibers Escherichia coli Power density abstract A novel architecture of alumina (AA) and nickel (Ni) nanoparticles (NPs)-dispersed multi- scale web of carbon micro nanofibers (ACFs/CNFs) is created to produce a stable and high performing electrode material for mediatorless microbial fuel cells (MFCs). The electrode material is produced by impregnating an ACF substrate with the (Al:Ni) bimetal salts fol- lowed by calcination, hydrogen reduction, and chemical vapor deposition (CVD). The CVD conditions are adjusted such that the Ni NPs catalyze the growth of the CNFs on ACF via the tip growth mechanism, whereas the AA NPs remain adhered at the surface of the ACFs. The MFCs fabricated using the AA:Ni-ACF/CNF electrode exhibit an open circuit potential of ~0.9 V and maximum power density of 1780 mW/m 2 . The AA NPs dispersed in the ACFs increase the conductivity of the material and the Ni NPs at the tips of the CNFs facilitate the transfer of the electrons released by Escherichia coli via the graphitic CNFs. The transition metal-based carbon electrode performs superior to the single metal-based electrode and is a potential candidate for an inexpensive but efficient electrode for MFC. Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Introduction At present, there is an increasing concern regarding the decrease in the supply of fossil fuels and their adverse effects on climate change, particularly global warming. A microbial fuel cell (MFC) is an environmentally benign device that can generate bioelectricity from organic and inorganic matter present in wastewater. MFCs simultaneously serve as a renewable energy source and wastewater treatment. There- fore, besides generating electricity, MFCs can be used in wastewater treatment for removing harmful inorganic ele- ments and compounds, such as zinc, cadmium, chromium, copper (Cu), vanadium, mercury, sulfur, ammonia and methylene blue dye [1e5]. Biodegradable organic materials are electrochemically catalyzed by bioactive agents in the anode chamber of MFCs, generating electrons and protons. The electrons are trans- ferred to the anode (electron acceptor) and subsequently to the cathode through an external circuit, while protons diffuse via a proton exchange membrane (PEM) into the cathode chamber. In the cathode chamber, the protons and electrons * Corresponding author. Department of Chemical Engineering and Center for Environmental Science and Engineering, Indian Institute of Technology Kanpur, Kanpur 208016, India. Tel.: þ91 512 259 7704; fax: þ91 512 259 0104. E-mail addresses: vermanishith@gmail.com, nishith@iitk.ac.in (N. Verma). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 40 (2015) 5928 e5938 http://dx.doi.org/10.1016/j.ijhydene.2015.03.010 0360-3199/Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.