Fabrication of polymer electrolyte fuel cell (PEFC) H2 sensors

Abstract

Galvanic cell-type PEFC (polymer electrolyte fuel cell) gas sensors have been fabricated. Their sensing behaviors to H 2 are examined. The sensing elements, Pt/Naflon composite electrodes, are prepared by first ion exchanging Pt(NH3)4 2+ ions and ",hen chemical with NaBH4 solution. Among the preparation variables for the composite electrodes, the NaBH4 solution flux has the most significant effect on the microstmcmre of the Pt deposits and therefore on the sensing characteristics of the resulting sensors. Submieron-sized Pt deposits arc dispersed evenly in the deeper region of the membrane surface under a high-flux condifion, while densely clustered Pt particles are depnsi¢~l mainly on the external surface of the membrane when the flux is low. The current intensifies are well correlated with the effective surface area of the Pt deposits, but not with the layer thickness. The current intensities and linearly cesponding H2 concentration range are also influenced by the size of the capillary-type diffusion barrier.