Polymer Exchange Membrane (PEM) Fuel Cell: A Review

1 International Journal of Current Engineering and Technology, , (March 2012) ISSN 2277 - 4106. Review Article Polymer Exchange Membrane (PEM) fuel Cell: A Review Shikha Bhatta, Bhupendra Guptaa*, V. K. Sethib, Mukesh Pandeyb a Jabalpur Engineering College, Jabalpur, b UIT, RGPV, Bhopal, Accepted 22 March 2012, Available online 28 March 2012. Abstract The Review paper includes introduction, working principle of the PEM fuel cell and Description of water management problem in PEM fuel cell. The discussions are based on elimination of water management problem by proper design of fuel cell. The paper shows the various types of efficiency, polarization characteristics and power characteristics.

2 It also describes the various parameters (pressure, temperature, stoichiometry ratio and humidity) which affect the performance of fuel cell, its optimum range in which fuel cell operate safely and efficiently. This paper represents the recent work done for improvement of the performance of PEM fuel cell. fuel cell performance is increased by proper water management on the Membrane . Basic parameter which enhances the fuel cell performance is Relative humidity, Flow field design, Temperature, stoichiometric ratio. With the help of this studies, we observe that the fuel cell performance improve by Increasing the relative humidity, temperature, pressure , stoichiometric ratio and using the split serpentine flow field instead of single serpentine flow field.

3 The objective of this study is to explore the research in the field of PEM. fuel cell and to make it cost effective for sustainable power supply. Keywords: PEM fuel cell, Water management, affecting Parameters, Flow Field, Polarization curve, Efficiencies. 1. Introduction consists of an electrolyte with anode (negative electrode). and cathode (positive electrode) on either side, when 1. In 1989 the fuel cell discover by Sir William Grove. H2gas is fed to anode the H2 is split into protons and Proton Exchange Membrane fuel cells were first used by electrons on anode catalyst layer the protons is allow to NASA in 1960's as part of the Gemini space program, and flow through the electrolyte to the cathode side but used on scale, expensive and not commercially affordable.

4 Electrons are not allow to flow though the electrolyte so This fuel cell used pure hydrogen and oxygen as a reactant electrons are flow through the external circuit where gases. NASA interested to future development of fuel electricity (discharge) are produced. When electrons and cells because of the energy crisis in investigate protons flow from anode to cathode simultaneously the the performance of the fuel cell the fundamental model of O2(from air) gas is fed to cathode after then electrons Polymer electrolyte Membrane fuel cell was developed in proton and O2 react at cathode catalyst layer and produce 1990 by Springer. water and heat as a byproduct.

5 The fuel cell is work till the In Polymer electrolyte Membrane fuel cell (PEMFC) ion fuel is supplied continuously. shows the schematic Exchange Membrane (fluorinated sulfonic acid Polymer ) diagram of PEM fuel cell are used as a electrolyte, Membrane has excellent proton conductor. Water management is the critical problem in PEM fuel cell because the conductivity of Membrane is highly depend on the water content the Membrane must be hydrate for efficient performance of fuel cell which depend on the reactant stream humidification , flow field of gas diffusion layer (GDL) and wetting property of GDL and Polymer Membrane . of fuel cell fuel cell is electrochemical device which converts chemical energy of reaction into the electrical energy.

6 It * Corresponding author's email: Schematic of PEM fuel cell 219. Shikha Bhatt et al International Journal of Current Engineering and Technology, , (March 2012). Advantages of PEM fuel cell Highly efficient More electricity per unit of fuel is produce Low CO2 emission Low operating temperature Quick startup of PEM fuel cell (a) Electrolyte Membrane fuel cell Membrane have relatively high proton Schematic of detailed water behavior in a PEM fuel conductivity, it provide a barrier to mixing of fuel and cell reactant gases. It is made of perfluorocarbon-sulfonic acid ionomer (PSA). The main property of the Membrane is Design of cell system proton conductivity which is the function of water content and temperature.

7 Of reactant gases (b) Electrode The proton conductivity of an electrolyte Membrane can be maintained high when the Membrane is fully Electrode is essentially made of a thin catalyst layer humidified. Fully humid Membrane offered low resistance pressed between the ionomer Membrane and a porous to current flow and increase the efficiency of PEM fuel electrically conductive substrate. In this electrode catalyst cell. There are three ways to increase the hydration level layer electrochemical reaction take place. of the Membrane which are internal humidification, external humidification and direct injection. (c) Gas diffusion layer (GDL). Design of flow field GDL plays crucial role in PEM fuel cell, it distribute the reactant gases homogeneously from the flow field to the Flow channel design is play important role in water catalyst layer through it for the electrochemical reaction.

8 It management of fuel cell. It remove the water out of the prevents local hotspot and catalyst flooding by removing cell which transport from the GDL by flow channels, heat and excess water from the electrode. It is made of There are three type of flow channel are used which are carbon fiber material such as carbon fiber paper and Conventional flow field, Serpentine flow field and woven cloths. Interdigitated. Fig 3 shows the schematic diagram of different type of flow field. (d) Bipolar plates The Bipolar separator/collector connect the cell electrically in series in fuel cell stack, it also separate the gases in adjacent cell. It is generally made of two families of material which are graphite composite and metallic.

9 2. Water management in PEM fuel cell Water management play important role to obtain the good performance of PEM fuel cell. Water transport in the PEM. cell done by three processes first is electro osmotic drag by which water molecules is transport from anode to cathode because of potential difference, second is back diffusion from cathode to anode because of concentration Schematic of three types of flow field gradient and last one is because of pressure difference between anode and cathode. Proper management of water (a) Conventional flow field provide well humid Membrane to achieve better proton conductivity simultaneously prevent the flooding at In the conventional flow field transportation of the cathode side.

10 Water management is improving by proper reactants and product is done by diffusion mechanism design of cell system which is described as follows. which reduces the transportation rate of the reactants shows the schematic of detailed water behavior in a PEM because of this excessive accumulation of liquid water and fuel cell. finally arrive flooding problem. 220. Shikha Bhatt et al International Journal of Current Engineering and Technology, , (March 2012). (b) Serpentine flow field If hydrogen is supplied to the cell in excess of that required for the reaction stoichiometry, this excess will The channel cross-section of serpentine flow field is small leave the fuel cell unused.