Effect of Subsurface Oxygen on Selective Catalytic Reduction of NO by H2 on Pt(100): A First-Principles Study

The mechanisms of NO reduction by H-2 on the Pt(100) surface and the surface modified with subsurface oxygen atoms (Md-Pt(100)) are studied by first-principles calculations. Similar catalytic activity toward NO dissociation is found on both surfaces with barriers of 0.86 and 0.96 eV, respectively. The pathway of N + N -> N-2 rather than NO + N -> N-2 + O is the N-2 formation pathway on the Pt(100) surface, while these two pathways are competitive on the Md-Pt(100) surface. The NH3 formation is almost negligible, and reductant hydrogen can effectively remove the surface oxygen on both surfaces. The microkinetic analysis further confirms that, compared to the high selectivity toward N2O (almost 100% at 300-500 K) on the clean surface, higher N-2 low-temperature selectivity (larger than 90%) is achieved on the Md-Pt(100) surface under lower pressure. The present study shows that subsurface oxygen has an enhanced effect for improving the N-2 selectivity of NO reduction on Pt catalysts.