Electrochemical studies on cells M/YSZ/Pt (M=Pt, Pt–Ga2O3) in NO, O2, N2 gas mixtures

The cathodic process of the Pt(Ga2O3)/YSZ electrode in O2, N2 gas mixtures with and without NO is studied by electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV) in a wide range of gas composition at temperature range 450–800 °C in order to investigate its electrocatalytic activity for the electrochemical reduction of oxygen and NO, respectively. The results of the impedance spectra and jc–ηc polarisation curves suggest different cathodic mechanisms at two temperature regions. For temperatures <650 °C, the cathodic O2 reduction occurs in two consecutive one-electron transfer steps. At ϑ>650 °C, O2 reduction follows a two-electron transfer step. The electrocatalytic activity of the Pt/YSZ electrode is enhanced due to presence of NO in the gas mixture leading to a decrease of the apparent activation energy and an increase of the exchange current density. The admixture of Ga2O3 to Pt/YSZ shows an inhibitor effect on the cathodic O2 reduction at low temperature. Aside from this, it has decreased the electrocatalytic efficiency of the Pt/YSZ electrode for cathodic NO reduction.