Spray Coating Proton Exchange Membranes With Platinum Carbon Black Using Ultrasonic Nozzles

Proton Exchange Membrane fuel cells or Polymer Electrolyte Membrane (PEM fuel cells) operate by transforming the energy released from hydrogen and oxygen reactions into electrical energy. The PEM fuel cells start using a membrane, which performs the important function of transmitting protons while hampering the flow of electrons. Platinum acts as a catalyst in hydrogen fuel cells by splitting hydrogen molecules. Platinum blended with carbon black and water is layered onto the fuel cell membrane.

Let us look deeper in to the construction of these fuel cells and how this material is layered onto the membrane. Platinum plays a central role in the operation of a PEM fuel cell; it’s responsible for the oxidation of hydrogen and reduced amount of oxygen hence it needs to cover the most area of the membrane in order to come in contact with the absolute most injected gas. It is also important to maximize the outer lining section of the platinum catalyst particles, polyurea coating using the smallest sized particles possible. Smaller the size, the more area that’s exposed to the injected gas. Lastly, it is important that the platinum particles be layered consistently and in this way as to prevent clumping or agglomeration.

Another objective that really needs to be observed in the construction of the PEM fuel cell is the even thickness of the platinum catalyst coating. It is imperative to create a leveled or uniform film thickness so that there is an equal amount of hydrogen oxidation over the film. If there must be an inconsistent layer of platinum, the less dense section would achieve a diminished rate of oxidation while a thicker than normal layer may cause other problems. Hence, determining the proper density of the platinum film is just a critical issue so it is important that the platinum carbon black coating on the fuel cell’s membrane be highly uniform for optimum hydrogen conversion. The platinum density acts as an important element in determining the total amount of gas that reaches the membrane of the hydrogen fuel cell. The platinum carbon black combination must certanly be such as for example allowing a permissible amount of contact between the gas and the membrane. A heavy layer would obviously supply a way of measuring resistance leading to a diminished rate of contact between the platinum and the gas, and subsequently an inferior rate of chemical reaction. A less dense layer would result in hot spots and other problems. Thus uniformity, both in the layering of platinum and the carbon web is just a necessity.

Pressing, knife-edge and printing methods are found to produce these non-uniform coating thicknesses and/or hot spots on fuel cell membranes. Ultrasonic spray technology is a perfect solution for applying a coating of platinum catalyst to the polymer membrane. First, platinum is needless to say a costly material and ultrasonic spray nozzles because of the soft or low forward velocity, minimize bounce or over spray. Secondly, coating applications must certanly be extremely precise to facilitate optimal results, which is often achieved with ultrasonics. Lastly, the coating process shouldn’t damage what it’s you are trying to coat. By press methods, the internal apparatus may be harmed by prolonged contact with the environment. Whereas the rolling processes, also subjected to prolonged contact with the surroundings, may cause platinum particles to agglomerate. The hydraulic spraying process is far considerably better but it’s its many pitfalls as well. Dispersion via hydraulic spraying is usually inconsistent, that may result in hot spots. There’s also unnecessary waste of platinum due to the high-pressure velocity of the fluid leading to fluid “bounce.”

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