Hydrogen sensor based on antimonium pentoxide phosphoric acid solid electrolyte

A solid composite electrolyte with high proton conductivity based on antimonium pentoxide with additives of phosphoric acid has been obtained. A potentiometric solid-state gas sensor using this electrolyte has been developed for detecting small amounts of hydrogen (10-2000 ppm) in gas mixtures at ambient temperature. The sensor consists of the reference electrode: Ag or Ag/(Ag + Ag2SO4), the solid composite electrolyte and H-2-sensitive electrode: Pt or Pd. The electromotive force (e.m.f.) of the sensor varies logarithmically with H-2 concentration for hydrogen partial pressures in the range 100-2000 ppm and depends on the oxygen partial pressure. The slope of e.m.f.-log(pH(2)) dependence is 170 and 200 mV for Pt and Pd, respectively, which exceeds the Nernst value, presumably due to the formation of a mixed potential. The sensor can operate at a wide range (20-95%) of a relative humidity. (C) 1997 Elsevier Science S.A.