Polymer Membrane Electrolyte Fuel cells

Polymer Membrane Electrolyte Fuel cells

Polymer Membrane Electrolyte Fuel cells

Introduction

Fuel units are electrochemical apparatus that alter chemical energy into electrical energy. They offer cleaner and more-efficient energy than the internal-combustion engine. They have been used to power vehicles, for stationary power generation and portable applications. Hydrogen or hydrogen-rich gas (such as natural gas) or liquid methanol can be used as fuels depending on the fuel-cell type. Many types of fuel cells are now available based on the electrolyte used, including polymer electrolyte membrane fuel cells (PEMFC), direct methanol fuel cells (DMFC), solid oxide fuel cells (SOFC), molten carbonate fuel cells (MCFC) and alkaline fuel cells (AFC). Each has its own electrolyte, cathode and anode as well as fuel type, typically operates in different temperature ranges and caters to different applications - among these, the polymer electrolyte membrane fuel cell is the most widely used.

The Polymer electrolyte membrane fuel cells (PEMFC), also known as proton exchange membrane fuel cells, give very high power density. They have the benefit of low heaviness and volume, compared with other fuel cells. As shown in Figure 1 (Appendix), polymer electrolyte membrane fuel cells use a solid polymer membrane as an electrolyte and porous carbon electrodes coated with a platinum catalyst. They need only hydrogen, oxygen from the air and water to operate and do not require corrosive fluids like some other fuel-cell types (e.g. PAFCs, phosphoric unpleasant fuel cells). Pure hydrogen or hydrogen-rich gas supplied from storage tanks or on-board reformers can be used as fuel for PEMFC.

Purpose of Study

Polymer electrolyte membrane fuel cells (pemfc) operate generally at relatively low temperatures, around 80 °C (176 °F), although some new types of PEMFC can operate at high temperatures as well. Low-temperature operation allows them to start quickly (less warm-up time), resulting in less wear on system components increasing lifetime of the system; however, they require a noble-metal catalyst (typically platinum) to catalyze the reaction of hydrogen with oxygen. The platinum catalyst is also extremely sensitive to CO poisoning, so it may be necessary to use an additional reactor to reduce CO in the fuel gas if the hydrogen is derived from an alcohol or hydrocarbon fuel. Different catalyst systems or different operating conditions have been developed to increase the system's resistance to CO. PEMFC are used primarily for transportation applications and some stationary applications. Due to their fast startup time and favorable power-to-weight ratio, PEMFC are suitable for use in passenger vehicles, such as cars and buses.

During the manufacturing of polymer electrolyte membrane fuel cells, one of the most important parts is the membrane electrode assembly (MEA). The MEA comprises of a proton exchange membrane, catalyst layers and gas diffusion levels (GDL). One method to make an MEA is to print the catalystcontaining ink over the gas diffusion layers - for example, carbon cloth. The carbon cloth is treated to remove solvent, which results in the gas diffusion electrode (GDE). The GDE is then hot pressed with the proton-exchange membrane to form an ...