Activation of Lattice Oxygen in Ceria by Plasma Exsolution of MoO_x with Atomic Dispersion for NO_x Abatement

Abstract

The rational control of lattice oxygen activity at the metal oxide surface remains a great challenge. Herein, an O 2 plasma-assisted method was implemented to enable activation of lattice oxygen by exsolution of Mo from ceria lattice to the external surface with atomic dispersion. The obtained surface-loaded MoO x /CeO 2 exhibited a superior turnover frequency of 1.33 × 10 −3 s −1 at 200 °C for NO x abatement, far beyond the commercially available or reported NH 3 -SCR catalysts. The mechanism study revealed that the SCR reaction followed the Mars−van Krevelen pathway with dehydroxylation (release of the lattice oxygen) as the rate-determining step. The hybridization of Mo 4d x 2 −y 2 and O 2p orbitals gave rise to a unique 5-coordinated Mo site that facilitated the interfacial Mo−O−Ce lattice oxygen dehydration and subsequent nucleophilic O 2 filling, which accounted for its higher activity. This work highlights the great potential of plasma treatment to promote the lattice oxygen reactivity of ceria-supported atomically dispersed catalysts and provides valuable insights into the intrinsic understanding of the enhancement.

Catalytic Ozonation of Low Concentration Toluene over MnFeOx-USY Catalyst: Effects of Interactions between Catalytic Components and Introduction of Gas Phase NOx

“…As shown in Figure a, there existed different IR bands on different catalyst surface. On the surface of MnFeO x -USY, the adsorption peaks at ∼1410 and 1150 cm –1 were assigned to bulk ionicnitrate and bridged nitrate species, respectively, ,− and the bands at near 1260 and 1550 cm –1 were attributed to monodentate nitrate species. ,, The vibration peak of bidentate nitrate species at 1600 cm –1 appeared on the surface of other four catalysts except MnFeO x -USY, , and the peak intensity followed the order of MnFeO x > FeO x -USY > MnO x -USY > USY. What’s more, apart from bidentate nitrate species, there were other kinds of nitrate species on the MnFeO x and FeO x -USY surface.…”