This study has shown that Ir/YSZ electrochemical catalysts can reach high catalytic activity for the SCR of NO by propene in the presence of oxygen. Under stoichiometric conditions, porous and thin (about 40 nm) Ir film achieves N-2 yield higher than 80% between 350 and 500 degrees C. However, iridium films require on-stream treatment at 500 degrees C in order to develop their catalytic efficiency by increasing Ir particles size and establishing an ideal Ir-o/IrO2 ratio. Under lean-bum conditions, the same sample presents high and durable NO conversion at 500 degrees C. These results confirm that magnetron sputtering is a suitable technique for synthesis of effective thin catalytic films. Furthermore, it was found that NO reduction by propene can be electrochemically promoted on Ir/YSZ electrochemical catalysts. This promotion exhibits an electrophobic NEMCA effect, the reaction rate increasing when a positive polarisation is applied. The electropromotion efficiency was found to be structure sensitive. (c) 2006 Elsevier B.V. All rights reserved.