Experimental Study on the Effects of Oxidant for the Performance of Polymer Electrolyte Membrane Fuel Cell System Hong Gun Kim 1, a , Yoo Shin Kim 2,b and Hong Youl Kim 3,c 1,2 Department of Mechanical & Automotive Engineering, Jeonju University, 1200 Hyojadong 3ga, Wansanku, Jeonju, 560-759, Korea 2 Institute for Engineering & Technology, Jeonju University, 1200 Hyojadong 3ga, Wansanku, Jeonju, 560-759, Korea a hkim@jj.ac.kr, b generalshin@chol.com, c perc@skku.edu Keywords: Polymer, Membrane, Fuel Cell, Performance Analysis, SEM(Scanning Electron Mircoscope) Abstract. Characteristics of fuel cell depend highly on the conditions such as gas pressure, temperature, supplied oxidant type (Hydrogen/Oxygen) and H 2 O management. Oxidant supply such as highly pure hydrogen and air is one of the most important factors to enhance the performance of fuel cell. To enhance the cell performance, in this paper, simulation is carried out to give the standard for the comparison of which conditions obtain better output voltage and current density. Furthermore, experimental study is carried out to investigate the performance and efficiency for the different oxidants, such as air or oxygen in a fuel cell system. SEM(Scanning Electron Microscope) analysis is used to investigate the characteristics of MEA(Membrane Electrode Assembly). Testing condition is fixed at 60sccm and 70℃ in anode and cathode, respectively. As a result of the test, it is found that current density is increased significantly when pure hydrogen gas is provided as a oxidant and oxygen compared to the ambient air. Introduction Fuel cells are a rapidly developing energy conversion technology. Offering higher efficiencies and significantly lower emissions than conventional technologies, they also operate quietly and have a modular construction that is easily scaleable [1,2]. These features mean that fuel cells are attractive for a range of potential applications, including combined heat and power, distributed power generation and transport. In the longer term, fuel cells may also be used for large scale power generation, probably in combination with gas turbines. Fuel cells are electrochemical devices which convert the energy of a chemical reaction directly into electricity, with heat as a by-product. They are similar in principle to primary batteries except that the fuel and oxidant (oxygen or air) are stored externally, enabling them to continue operating as long as fuel and oxidant are supplied [3-5]. Due to their high-energy efficiency, a low temperature (60~80℃) operation, a pollution-free characteristic, and a relatively simple design, the PEM fuel cells are currently being considered as an alternative source of power in the electric vehicles. However, further improvements in the efficiency and the cost are needed before the PEM fuel cells can begin to successfully compete with the traditional internal combustion engines. This work is also included unit cell experiment in addition to the fuel cell simulation. Finally, the experiment and simulation is reevaluated to compare the current density vs. potential results. Analysis One of the most promising fuel cells is the so-called polymer electrolyte membrane or proton exchange membrane (PEM) fuel cells. A schematic of the PEM fuel cell is given in Fig.1. The anode and the cathode (the electrodes) are porous and made of an electrically conductive material, typically carbon. The faces of the electrodes in contact with the membrane (generally referred to as the active layers) contain, in addition to carbon, polymer electrolyte and a platinum-based catalyst