Improved Electrocatalysts for Ammonia Fuel Cell Anodes

Abstract

Electrocatalysts containing ir idium and plat inum-ir id ium alloys have shown very encouraging levels of performance when used as anodes in ammonia fuel cells. These materials were appreciably more active than plat inum alone, and the open-circuit voltage and polarization under load generally improved with increasing ir idium content. Data are presented for ammonia/oxygen cells at 100~176 using 54 % potassium hydroxide as electrolyte and plat-inum-ir id ium blacks and Pt / I r supported on boron carbide and graphite as anodes. The observed electrochemical activity of ir idium appears to be related to the unique activity of this metal in the gas phase catalytic decompo-sition of ammonia. Supported ir idium catalysts were also found to be effective in an external cracking unit maintained at 350~176 and coupled to a hydro-gen fuel cell system. In this case enhanced performance was observed when small amounts of oxygen were introduced with the ammonia into the catalytic reactor.