Superior Performance of FeWO for the Selective Catalytic Reduction of NO with NH: Interaction between Fe and W.

Novel iron-tungsten catalysts were first developed for the selective catalytic reduction of NO by NH in diesel exhaust, achieving an excellent performance with a wide operating temperature window above 90% NO conversion from 225 or 250 to 450 °C (GHSVs of 30 000 or 50 000 h). It also exhibited a pronounced stability and relatively high NO conversion in the presence of HO, SO and CO. The introduction of W resulted in the formation of α-FeO and FeWO species obtained by HRTEM directly. The synergic effect of two species contributed to the high SCR activity, because of the increased surface acidity and electronic property. The FeWO with octahedral [FeO]/[WO] structure acted as the Brønsted acid sites to form highly active NH species. Combining DFT calculations with XPS and UV-vis results, it was found that the fine electron interaction between α-FeO and FeWO made the electron more easily transfer from W sites to Fe sites, which promoted the formation of NO. Judging by the kinetics and SCR activity studies, the FeWO with an appropriate W amount showed the strongest interaction, and thereby the lowest activation energy of 39 kJ•mol and optimal catalytic activity. These findings would be conducive to the reasonable design of NH-SCR catalysts by adjusting the fabrication.