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

The activities of Pt/YSZ, PtAu/YSZ and RhPtAu/YSZ thick film electrodes in O2, N2 and NO, N2 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 O2 reduction at both multi-metallic electrodes is strongly inhibited, which is confirmed by charge transfer resistance for cathodic O2 reduction as follows: Rct(Pt/YSZ) < Rct(PtAu/YSZ) < Rct(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, O2, N2, resulting in a linear response to the NO concentration, which is nearly independent of the O2 concentration.