Reduction of nitrogen oxides over Ir/YSZ electrochemical catalysts

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 N2 yield higher than 80% between 350 and 500 °C. However, iridium films require on-stream treatment at 500 °C in order to develop their catalytic efficiency by increasing Ir particles size and establishing an ideal Ir0/IrO2 ratio. Under lean-burn conditions, the same sample presents high and durable NO conversion at 500 °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.