Novel Catalysts with Substantially Reduced Metal Content and Undiminished Activity
Researchers at Tufts University have discovered a novel method to make effective catalysts for fuel cells using only a fraction of the precious metals typically used, substantially lowering manufacturing costs. The resulting catalyst is virtually free of microcrystalline metal particles and just as efficient as traditional catalysts.
Fuel cells produce energy in the form of electricity through the conversion of hydrogen fuel and oxygen to water. Reformate gas produced by fuel cells generally includes hydrogen (H2), carbon monoxide (CO), carbon dioxide (CO2), water (H2O) and small quantities of methane (CH4). It is necessary to completely remove the CO component. CO poisons the anode catalyst, degrading fuel cell performance, and constitutes a criterion pollutant.
CO is eliminated through the low-temperature water-gas shift (LTS) reaction (CO + H2O <---> CO2 + H2). It converts carbon monoxide with water vapor to carbon dioxide and hydrogen. Gold and platinum nanoparticles are used to catalyze the reaction.
Current research indicates that LTS catalysts based on cerium oxide (ceria) hold great promise. Only a minute quantity of gold or platinum in non-metallic form (a loading of 1-10 wt%) is needed to create an active catalyst. The current invention demonstrates that stripping this precious metal of most of its metallic crystalline structure with a cyanide solution still exhibits normal catalytic activity. This discovery demonstrates that the amount of precious metal needed for catalysis may be reduced by up to 90%.
Advantages and Applications
The current invention describes methods to remove the majority of the metallic constituents on catalytic substrates. The removal does not compromise the catalytic nature of the material and offers substantial reductions in manufacturing costs.
Fuel cells have a wide range of environmentally friendly applications and reduce our reliance on fossil fuels for energy. They can augment or replace internal combustion engines in cars, trucks and buses while meeting the most stringent emission regulations. Fuel cells may also have stationary power generation applications in residential, commercial and industrial settings.
US Patent No. 8,053,387, Issued November 8, 2011