When cars produce water instead of exhaust gases

Hydrogen fuel cells are considered a hopeful prospect in the discussion about the vehicle propulsion of the future. Their greatest advantage: water and heat are the only "waste products" they emit. One of the currently biggest disadvantages: the costs, which are not least dependent on the very expensive material platinum used for the catalyst in the fuel cell. Reducing the platinum content in the fuel cell, however, also causes the electrical power generated to decrease even faster. Prof. Dr. Peter Strasser from TU Berlin and his team at the Department of Electro Catalysis and Materials have now succeeded, in cooperation with scientists from BMW, in designing the catalyst carrier material chemically in an automotive-compatible hydrogen fuel cell so that high electrical power is generated despite low platinum usage. Their results have now been published in the renowned journal Nature Materials.

Ultimately, fuel cell vehicles are also electric cars. The difference: the required electricity is not stored in a battery but generated on board as needed during the drive. Hydrogen, which is carried in a special tank in the car, reacts with the oxygen from the ambient air at two separate electrodes of the fuel cell. This produces electricity and water. The generated electricity is consumed or temporarily stored in a small buffer battery. A platinum catalyst is required for the electrochemical reaction at the cathode of the fuel cell. "Even if the currently available fuel cell cars on the market only use 30 grams of platinum per fuel cell, this is still far from the long-term sustainable goal of five grams of platinum per fuel cell car," says Peter Strasser.

The problem: The platinum nanoparticles must be applied to the carbon support material in an extremely uniform distribution with a so-called ionomer, a plastic that conducts hydrogen ions (protons). The less platinum nanoparticles are used, the more important the uniform distribution of the ionomer becomes so that all involved reactants have access to the platinum particles acting as catalysts. An uneven distribution of the ionomer results in high resistance to the transport of oxygen molecules, which in turn leads to a high loss in the generated electrical voltage and power. "In the work now published, we describe the production of a novel, chemically modified carbon support material with tailored surface properties. This has allowed us to achieve an unprecedented uniform distribution of the ionomer on this support material. As a result, we attain high power densities with minimal platinum use," explains the scientist. This tailored catalyst achieved an unprecedented performance and stability in power generation within the fuel cell—at least 50 percent less platinum consumption.

"The special thing about our approach: we worked directly with an automotive-compatible fuel cell, so our results have the chance to be immediately integrated into the next generations of fuel cell cars," Peter Strasser is pleased with the success.

Further information gladly provided by:

Prof. Dr. Peter Strasser
TU Berlin
Department of Technical Chemistry
The electrochemical energy, catalysis, and materials science group
Tel.: 030/314-22261
Email: peter.strasser@tu-berlin.de