NO reduction with CO over a highly dispersed Mn/TiO 2 catalyst at low temperature: a combined experimental and theoretical study

Abstract A highly dispersed Mn/TiO 2 catalyst, which has high efficiency for NO conversion with CO and almost completed N 2 selectivity at a low-temperature range (350–550 K), was investigated using experimental and DFT theoretical calculation. The characterization results illustrated that the catalyst assembled with nanoparticles and the Mn doping into the TiO 2 surface lattice led to the formation of Mn–O–Ti configuration, which enhanced the dispersion of Mn on the body of TiO 2 . The DFT study mapped out the complete catalytic cycle, including reactants adsorption, oxygen vacancy generation, N 2 O intermediates formation, N 2 formation in Eley−Rideal (ER), Langmuir−Hinshelwood, and termolecular Eley−Rideal mechanisms. With thermodynamic and kinetic analysis combined with experimental results, the ER reaction process was considered to be the fundamental mechanism over the highly dispersed Mn/TiO 2 catalyst. The calculation results indicated that N 2 O was a significant intermediate. However, the rapid N 2 O reduction process led to high N 2 selectivity. The rate-limiting step was the deoxygenation step of NO−MnO v /TiO 2 from N−O bond scission. The active site Mn−O v pair embedded in Mn/TiO 2 was responsible not only for the formation of N−Mn/TiO 2 in the ER-1 step but also for the N 2 O deoxygenation process to make the final product N 2 in the ER-2 step. The synergetic effect between Mn 3d electron and the oxygen vacancy of TiO 2 were responsible for the catalytic activity of Mn/TiO 2 .