Decomposition pathways of NO on carbide and oxycarbide-modified W(1 1 1) surfaces

The decomposition of NO has been studied on clean W(1 1 1), carbide-modified W(1 1 1), and oxycarbide-modified W(1 1 1) surfaces. The decomposition pathways are investigated using a combination of temperature programmed desorption, Auger electron spectroscopy, high-resolution electron energy loss spectroscopy, and soft X-ray photoelectron spectroscopy. All these surfaces exhibit high activity toward the decomposition of NO, and the only N-containing products are N2 and N2O. Furthermore, all three surfaces preferentially produce N2 over N2O from the decomposition of NO. Oxygen atoms, produced from the decomposition of NO, react with carbide surfaces to produce gas-phase CO at high temperatures. In addition, our results demonstrate that cycles of alternate NO/hydrocarbon treatments can regenerate the carbide overlayer on W(1 1 1), and the regenerated C/W(1 1 1) surface remains active in the decomposition of NO.