Plasticstrends

If you hear it, you heard it. Fuel cell is just not another hype-filled innovation - it is the future for power generation in our daily life. Reasons are pretty straightforward: energy independence and cleaner air. No wonder why researchers are upbeat and so are the industries, research institutions, governments and investors.

In principle, fuel cells convert chemical energy into electrical energy without using combustion process and run on hydrogen. Hydrogen combines with oxygen to produce electricity, water, heat and no emission (ideally). Of course, the oxygen comes from the air. Interestingly, plastic provides the key ingredient to this hot technology: we are talking about popular Polymer Exchange Membrane or Polymer Electrolyte Membrane (PEM) fuel cell technology.
What makes the PEM fuel cell structure being preferred for vehicle, home power generation and portable electronics? The structure consists of a "Fuel reformer", a "Fuel cell stack" and a "Power conditioner". Ideally, there is no need of a fuel reformer if we could get hydrogen from gas stations. Since we do not have hydrogen fuelling infrastructure and distribution, a variety of optional hydrogen producing sources are utilised such as methanol, natural gas, biogas, gasoline, etc. Whereas a reformer converts methanol or hydrocarbons into hydrogen, which then goes to a fuel cell stack. To produce electricity in large amounts, many cells are combined into a fuel cell stack. Bipolar plates separate neighbouring cells and serve as the anode for one fuel cell and the cathode for the adjacent one. What is needed now is a plastic thin film (membrane), the heart of a PEM fuel cell, coated with a platinum (and / or ruthenium) catalyst on both sides. When hydrogen or hydrogen rich gas from the reformer gets to the coated plastic membrane, hydrogen molecules are broken into protons & electrons. The protons penetrate the membrane and combine with oxygen to produce water and heat. However, the membrane does not allow the electrons to pass through. When electrons get around the membrane, they generate direct current (DC). A power conditioner then transforms the DC power to AC power, reducing voltage spikes and thereby completing the PEM fuel cell structure.
The idea may appear simple but finding a plastic membrane that can work in extreme environment is a real challenge. At present commercially available plastic membrane is a sulfonated fluoropolymer manufactured by Dupont called Nafion^®. The problem with Nafion® is that above 800C, its conductivity is greatly reduced. This happens due to lack of humidity and high degree of methanol crossover through the plastic membrane. Similar problem faces sulfonated ethylene styrene interpolymer (Dow's ESI). Researchers at Virginia Polytechnique Institute at Blacksburg, USA are working on composites and aromatic polyimide membranes to address these problems and will present their finding at ACS, Spring meeting (April 2002) in Orlando, Florida.
Plastic membrane is not the only involvement of plastic in PEM fuel cell. End plates holding the PEM fuel cell stack are also made of plastics. Plug Power Inc., producer of PEM fuel cell for home power generation, uses highly graphite loaded vinyl ester polymeric bulk compounds (BMC 940) for its end plates. The potentials for plastic usage in making fuel cells represent future challenges for scientists and engineers alike. Developing lower cost membrane, greater operating temperature ranges, without wet environment, injection moldable end plates by bulk volume, and hydrogen storage tanks are among those challenges. Interests from raw material suppliers (Bulk molding compounds, Dow, DuPont, Celanese, Dais-Analytic, Victrex etc.) to PEM cell manufacturers (H Power Corp., Plug Power, Ballard Power Systems, Proton Energy Systems, ZTEK, Idatech, DCH Technology etc.) to users (General Electric, General Motors, Daimler Chrysler, Toyoto Motor Co., ABB, Naps Systems Oy, etc.) are encouraging. Thanks to plastic membranes and its developers.