What is gas diffusion layer made of?
Gas diffusion layers are a porous material composed of a dense array of carbon fibers, which also provides an electrically conductive pathway for current collection. GDL plays an important role of electronic connection between the bipolar plate with channel-land structure and the electrode.
What is the function of gas diffusion layer in APM fuel cell?
In fuel cells, this thin, porous sheet must provide high electrical and thermal conductivity and chemical / corrosion resistance, in addition to controlling the proper flow of reactant gases (hydrogen and air) and managing the water transport out of the membrane electrode assembly (MEA).
What is the primary purpose of the diffusion media in PEM fuel cells?
The GDL manages the water in PEM fuel cells by only allowing a certain amount of water to contact the membrane/electrode assembly to keep the membrane humidified. Also, the GDL promotes the exit of liquid water from the cathode to help eliminate flooding.
What is MEA in fuel cell?
The heart of a PEM fuel cell is the membrane electrode assembly (MEA), which includes the membrane, the catalyst layers, and gas diffusion layers (GDLs).
What is catalyst layer?
Catalyst layers (CLs) are critical components within fuel cells as they are the sites at which the electrochemical reaction occurs. Their relevance for water management has become recognized in recent years [16–18,21,96–99].
What is a bipolar plate?
Bipolar plates (BPs) are a key component of proton exchange membrane (PEM) fuel cells with multifunctional character. They uniformly distribute fuel gas and air, conduct electrical current from cell to cell, remove heat from the active area, and prevent leakage of gases and coolant.
Why is diffusion important in fuel cells?
Gas Diffusion Layers serve to provide conductivity in the cell and control the contact between the reactant gases and the catalyst. Another essential function of a GDL is to provide a connection between the membrane electrode assembly and graphite plates in the fuel cell stack.
Why platinum is used as a catalyst in fuel cell?
A good catalyst should be able to split up oxygen molecules into atoms but should not bind too strongly with the free atoms; the shorter distance between platinum atoms in the new material makes it a more effective catalyst because it binds even more weakly with the oxygen atoms.
What is PEM technology?
Polymer electrolyte membrane (PEM) electrolysis is the electrolysis of water in a cell equipped with a solid polymer electrolyte (SPE) that is responsible for the conduction of protons, separation of product gases, and electrical insulation of the electrodes.
Why do we have pressure drop in bipolar plates?
The pressure between the inlet and outlet changes primarily due to the amount of friction that the fluid encounters with the channel walls. This difference in pressure between the inlet and outlet of the channel drives the fluid flow.
Why Pt is used as a catalyst?
Platinum works as a catalyst by collecting oxygen atoms (O), and letting them bind with the toxic carbon monoxide (CO), to create the less harmful carbon dioxide (CO2).
Why is PT a good catalyst?
What is the purpose of a gas diffusion layer (GDL)?
Gas Diffusion Layer. The GDLs or the PTL might play the most critical and least appreciated role of all. As the name implies, the main purpose of the GDL is to distribute the reactants from the gas flow channels uniformly along the active surface of the catalyst layer.
How does diffusion take place on gases?
Gases flow using DIFFUSION.
How large can a Nernst diffusion layer be?
How large can a Nernst diffusion layer be? Question. May 2016; In the literature, Nernst diffusion layers are often reported as being 0.01 cm thick or even smaller. This is mostly due to RDEs
What is layer of air has greatest density of gases?
LAYERS OF THE ATMOSPHERE. The troposphere is the lowest layer of the atmosphere and contains 75 per cent of all its gases. Above is the stratosphere, which includes the ozone layer. Higher still is the thin air of the mesosphere, where meteors burn up. The thermosphere contains an electrically charged layer that radio waves bounce off.