Electrochimica Acta 54 (2009) 7476–7482 Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta Improved performance of PEM fuel cell using carbon paper electrode prepared with CNT coated carbon fibers Priyanka H. Maheshwari, R.B. Mathur ∗ Carbon Technology Unit, Division of Engineering Materials, National Physical Laboratory, New Delhi 110012, India article info Article history: Received 1 July 2009 Received in revised form 30 July 2009 Accepted 30 July 2009 Available online 7 August 2009 Keywords: Carbon fiber Fuel cell Power density Polarization Porosity abstract Porous conducting carbon paper has been identified as the most suitable material to be used as a backing material for the fuel cell electrode. The surface of carbon fiber, the major constituent of the carbon paper was modified by: (1) removing the functional groups by heat cleaning process and (2) coating the non-functionalized carbon fiber with multi-walled carbon nanotubes (MWCNTs). This has a marked influence on the fiber–matrix interactions during later stages of processing of carbon paper that helped in controlling its various characteristic properties. Using the carbon paper formed with CNT coated carbon fiber as electrode, the maximum power density achieved from a unit fuel cell was found to be 783 mW/cm 2 as compared to 630 mW/cm 2 when the paper was formed with normal fiber. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Fuel cells have gained attention in the last few years not only due to depleting energy resources but also due to growing concern about urban air pollution and consequent environmental problems. These are electrochemical cells that use hydrogen and oxygen/air as the fuel and oxidant respectively, generating energy and water as the only by-products. Because of their capability of directly convert- ing chemical energy into electrical energy, they have high efficiency [1,2]. Among all the fuel cells PEM fuel cell is much preferred because of its high power density, favorable stability of cell voltage during lifetime, absence of corrosive liquid electrolyte, favorable efficiency and low operating temperature. The electrode substrate also known as gas diffusion layer provides mechanical support for the electrocatalysts. It allows dif- fusion of gaseous reactants from the bulk flow streams to the reaction site within the catalyst layer and removal of the product water from the reaction site to the bulk flow streams. It transfers heat and electrons through the cells and maintains a uniform con- tact pressure between the catalyst layer and the matrix containing the electrolyte. Because of its critical role in fuel cell performance, much effort has been guided towards optimizing its properties [3–10]. Porous conducting carbon paper has been identified as the ∗ Corresponding author. Tel.: +91 11 45608426; fax: +91 11 45609310. E-mail address: rbmathur@mail.nplindia.ernet.in (R.B. Mathur). most promising material as a GDL, not only because of its high con- ductivity that allows easy flow of electrons but also because of its fine porosity that allows uniform distribution of the reactant gases over its surface. The high mechanical strength of the carbon paper provides mechanical integrity to the MEA. In their previous studies the authors have reported the pro- cess of making porous conducting carbon paper by first making carbon fiber preform by paper making technology followed by its subsequent impregnation with resin, compression molding and carbonization [9]. Because of the strong fiber matrix interaction during the curing and carbonization cycles (with the commercially available fibers), large volume shrinkage occurred along the thick- ness of the sample which not only resulted in the decrease in the porosity of the samples but also in a non-uniform pore size distribu- tion (PSD). In the present study we report two different approaches of controlling the fiber–matrix interactions (and hence the poros- ity and pore size distribution) by modifying the surface of carbon fibers. In the first case by using surface cleaned carbon fibers along with the neat fibers (as received commercial fibers) in varying pro- portions, while in the second case the surface of the carbon fiber has been further modified by MWCNTs coating. References have been cited whereby CNTs have been effectively used as a catalyst support for better utilization of the later, which in turn leads to increased performance [11–15] and durability [16] of fuel cell. We report here significant improvement in the physical and electrical properties of the carbon paper (produced by this new technique), which in turn contributes to the enhanced performance of the fuel cell. 0013-4686/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2009.07.085