Density functional theory calculations and analysis for the reduction of NO by H2 on Pd6/TiO2

Periodic density functional theory (DFT) calculations have been carried out to reveal the mechanism of NO reduction by H-2 on the Pd-6/TiO2 catalyst. The favorable route for N-2 formation is NO -> HNO -> NHOH -> N -> N-2, and the rate-determining step is the formation of intermediate HNO via NO hydrogenation with an energy barrier of 103.0 kJ.mol(-1). The energy barriers of rate-determining steps for the formation of N2O and NH3 are 149.9 and 128.4 kJ.mol(-1), which are higher than that for N-2 formation, indicating that N-2 is the main product. Comparing with the reduction of NO on the Pd(2 1 1) surface, the reaction energy barrier for generating N-2 is obviously reduced, while the energy barrier for generating NH3 has a little difference, which implies that Pd-6/TiO2 shows better selectivity to N-2.