In situ spectroscopic studies of the effect of water on the redox cycle of Cu ions in Cu-SSZ-13 during selective catalytic reduction of NO x .

The effect of water on the NH 3 -assisted selective catalytic reduction of NO x (NH 3 -SCR) has been largely neglected, despite the inevitable presence of water vapor in real emissions produced by fuel combustion. In this work, we investigated the role of water in the behavior of active Cu 2+ ions in Cu-SSZ-13 in the NH 3 -SCR reaction. The addition of water to the reactant feed leads to significantly increased NO x reduction over the catalyst. By combining in situ DRIFTS and XANES analyses during the NH 3 -SCR reaction, we found that the redox cycle of Cu ions is promoted by the presence of water.