Low-Temperature Reduction of NO₂ on Oxidized Mo(110)

Abstract

The reactions of nitrogen dioxide (NO(2)) were investigated on oxidized Mo(110) containing both chemisorbed oxygen and a thin film oxide. NO(2) reacts on both oxidized Mo(110) surfaces via a combination of reversible adsorption and reduction to NO, N(2), and trace amounts of N(2)O below 200 K. On the surface containing chemisorbed O, there is some complete dissociation of NO(2) to yield N(a) and O(a). N(2) forms at high temperatures through atom combination. On both surfaces, NO is the predominant product of NO(2) reduction. However, the chemisorbed layer which has a low oxidation state, and hence a greater capacity to accept oxygen, more effectively reduces NO(2). The selectivity for N(2) formation over N(2)O is greater for NO(2) as compared with NO on both surfaces studied. The selectivity changes are largely attributed to an increase in the concentration of Mo=O species and a change in the distribution of oxygen on the surface. Notably, more oxygen, in particular Mo=O moieties, is deposited by NO(2) reaction than by O(2) reaction, indicating that NO(2) is a stronger oxidant. The fact that there are several N-containing species on the surface at low temperatures may also affect the product distribution. On both surfaces, N(2)O(4), NO(2), and NO are identified by infrared spectroscopy upon adsorption at 100 K. All N(2)O(4) desorbs by 200 K, leaving only NO(2) and NO on the surface. Infrared spectroscopy of NO(2) on (18)O-labeled surfaces provides evidence for oxygen transfer or exchange between different types of sites even at low temperatures.

In Situ Ambient Pressure Studies of the Chemistry of NO2 and Water on Rutile TiO2(110)

“…Importantly, physisorbed and gas-phase NO 2 or the dimer, N 2 O 4 , are also observed at higher NO 2 pressure simultaneously with the exponential increase of the NO 3 signals. Above 2.5 × 10 −2 torr, a shoulder appears on the N 1s and O 1s peaks at 405.4 and 534.3 eV (ratio 1:2), respectively, which is probably physisorbed N 2 O 4 via comparison to earlier IRAS studies, but it cannot be distinguished from NO 2 by our XPS experiments. At pressures of 200 mtorr of NO 2 , a very weak but distinguishable signal of gas phase NO 2 /N 2 O 4 is measured at 537.6 eV.…”

Effect of Crystallographic Phase (β vs. γ) and Surface Area on Gas Phase Nitroarene Hydrogenation Over Mo2N and Au/Mo2N

“…Hydrogenation selectivity can be attributed to effective polarisation of the N=O group via surface interaction that renders the nitro function susceptible for hydrogen attack [72]. Indeed, -NO 2 adsorptionreduction on Mo has been demonstrated elsewhere [73,74] and Chen and Chen [69] have shown that the addition of Mo to nickel borides promoted selective nitro-group reduction while suppressing the dehalogenation step. A temporal decrease in fractional p-CNB conversion (X p-CNB ) with time on-stream was observed, which can be expressed in terms of the empirical relationship [75]…”

NO dissociation and reduction by H 2 on Pd(1 1 1): A first-principles study

“…What is the main pathway for N 2 formation? In addition, interestingly, (NO) 2 dimer was observed at room temperature by using infrared spectroscopy on Pd(1 1 1) surface recently, as demonstrated in the literature on some other surfaces including Au [4], Ag [26], Cu [27][28][29], Mo [30], Rh [31], Al 2 O 3 [32], MgO [33], and Si-doped graphene [34]. In experiment, N 2 O was observed at low temperature on ZrO 2 -supported Pd nanocatalysts [3].…”