Carbon oxides free fuel processing for fuel cell applications

Fuel processing represents a very important aspect of fuel cell technology. The widespread utilization of fuel cells will only be possible if CO _x-free hydrogen producing technologies are developed. Towards this objective, step-wise reforming of hydrocarbons and catalytic decomposition of ammonia were investigated for hydrogen production. Also, novel Au-based catalysts were synthesized for preferentially eliminating CO in the presence of excess hydrogen.; The step-wise reforming of hydrocarbons was investigated for production of CO-free hydrogen for proton exchange membrane fuel cells. Proof of concept pulse reactor experiments employing Ni-based catalysts clearly showed the feasibility of the cyclic step-wise reforming process for clean hydrogen production. Under optimum conditions the CO content in the hydrogen was found to be less than 20 ppm by this process (a large amount of CO is obtained as a by-product from conventional methods of hydrogen production). The step-wise reforming process thus greatly simplifies fuel reforming, as expensive and circuitous post-reforming hydrogen purification processes are eliminated. The process was profoundly influenced by the operating temperature, space velocity and nature of the catalyst support.; Catalytic ammonia decomposition was investigated for CO_x-free hydrogen production for alkaline fuel cells. These studies revealed that Ru, Ir and Ni-based catalysts were active for the process with Ru being the most active and Ni the least. The catalyst supports played a decisive role in determining the ammonia decomposition activity. Partial pressure dependence studies of the reaction rate on model Ir (100) catalysts yielded a positive order (0.9 ± 0.l) with respect to ammonia and negative order (−0.7 ± 0.l) with respect to hydrogen. The negative order with respect to hydrogen was attributed to the enhancement in the reverse of the ammonia decomposition reaction in the presence of surface hydrogen atoms.; Novel nano-Au catalysts from Au-phosphine complexes were developed for the preferential oxidation of CO in the presence of excess hydrogen. Under specific pre-treatment conditions, the catalysts were found to be highly active and stable for CO oxidation. These catalysts were found to be extremely promising for trace CO clean up in hydrogen streams for proton exchange membrane fuel cells.