Electrochemical investigations on multi-metallic electrodes for amperometric NO gas sensors

Abstract

The activities of Pt/YSZ, PtAu/YSZ and RhPtAu/YSZ thick film electrodes in O 2, N 2 and NO, N 2 gas mixtures at high temperatures were investigated by electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). As compared with the Pt/YSZ electrode the cathodic O 2 reduction at both multi-metallic electrodes is strongly inhibited, which is confirmed by charge transfer resistance for cathodic O 2 reduction as follows: R ct(Pt/YSZ) < R ct(PtAu/YSZ) < R ct(RhPtAu/YSZ). In contrast to that the cathodic NO reduction is accelerated only by the RhPtAu/YSZ electrode, indicating that the RhPtAu mixture is a suitable working electrode material for amperometric NO sensors based on the solid electrolyte (YSZ). A new amperometric NO sensor with only one working electrode made of RhPtAu mixture was tested in simulated gas mixtures containing NO, O 2, N 2, resulting in a linear response to the NO concentration, which is nearly independent of the O 2 concentration.