Electrochemical reduction of NO by alternating current electrolysis using yttria-stabilized zirconia as the solid electrolyte: Part II. Modification of Pd electrode by coating with Rh

The electrochemical promotion of the decomposition of NO by applying an AC voltage to a YSZ cell having two Pd electrodes has been modified by calcining the Pd electrode at 1450°C and then coating the obtained Pd electrode with Rh metal. The calcination of the Pd electrode at 1450°C depressed the oxidation of Pd to PdO at temperatures lower than 800°C. The coating of the Pd electrode with Rh increased the catalytic activity for the decomposition of NO at temperatures lower than 800°C. As a result, these modifications enhanced the current efficiency for the decomposition of NO at low temperatures from 650 to 450°C and at high concentrations of O2 from 2 to 13%. No negative effect on the decomposition of NO was observed in the presence of 5% water vapor and 5% CO2, while a positive effect on this reaction was found for the presence of 500 ppm CH4, C3H8 and C5H12. Based on the measurements of the selectivity for N2 over N2O and the decomposition of N2O, it was concluded that NO is reduced to N2 via intermediate N2O, especially at low temperatures.