The effect of transition-metal addition on the non-equilibrium EMF-type gas sensor

Abstract

In this study, we made single chamber gas sensor which had two SnO2 electrodes pasted onto either side of zirconia electrolyte. Transition metal (TM) was added in one of two SnO2 electrodes to induce and thus confirm the catalytic effect of transition-metal. Since 1 mol% TM-doped SnO2 showed the negligible change in microstructure, the effect of microstructure change could be ignored. The Co addition increased the e.m.f. of working electrode (TM-added SnO2) in air, implying the enhanced oxygen adsorption. The addition of TM to SnO2 was also effective in changing the e.m.f. values in H-2 balanced by air. Fe and Ni addition exhibited decreased e.m.f. in H-2 from that in air. Thus, Fe and Ni addition improved the catalytic activity for H-2 oxidation. Cu addition slightly improved the catalytic activity for CO oxidation. The results show that Co is expected to be a good additive for the cathode of solid-oxide-fuel-cell (SOFC) at low temperature. On the other hand, Fe, Cu, or Ni is good additives for anode.