In this work, a series of cesium (Cs) modified metal oxide (Co3O4, CuO, Mn2O3, and NiO) catalysts were synthesized and investigated for N2O catalytic decomposition. More than 95% N2O conversion was obtained with the Cs-supported Co3O4 (Cs/Co) catalyst at 300 °C, but only a slight increase or even suppression was obtained with the other catalysts. The activation energy (E a) varied significantly for Cs modified catalysts. It was found that both of N2O adsorption–dissociation (from N2O-TPD) and O2 desorption capacities (from O2-TPD) were highly correlated with the N2O decomposition activity. Highly optimized N2O activation and O2 desorption capacities contributed to the boosting performance of the Cs/Co catalyst. Moreover, the improved electron transfer property inferred from H2-temperature-programmed reduction and X-ray photoelectron spectroscopy was likely to facilitate the reaction processes and promote N2O catalytic decomposition performance.

Nitrogen isotopes (δ 15 N) can trace sources of major inorganic NO y species (here referring to nitrogen dioxide (NO 2 ), nitric acid (HNO 3 ), and nitrate (NO 3 − )) in the atmosphere. However, δ 15 N variations during transformation and deposition processes of NO y species remain poorly understood. Here, we dissected δ 15 N differences between NO 2 , HNO 3 , particulate NO 3 − , and precipitation NO 3 − by converging observations of their concentrations and δ 15 N from literature sources. δ 15 N values of HNO 3 were higher by 6.9 ± 4.6‰ than those of NO 2 , indicating that the hydroxyl radical pathway dominated the HNO 3 formation. δ 15 N values of particulate NO 3 − were higher by 4.9 ± 4.2‰ than those of HNO 3 , indicating HNO 3 as a main precursor of particulate NO 3 − . δ 15 N values of precipitation NO 3 − were lower than those of HNO 3 (by 2.8 ± 3.3‰) and particulate NO 3 − (by 7.5 ± 3.5‰) but higher than those of NO 2 (by 5.1 ± 4.5‰). Relative contributions of NO 2 , HNO 3 , and particulate NO 3 − to precipitation NO 3 − were estimated as 45 ± 10%, 32 ± 5%, and 23 ± 7%, respectively, which differed from their fractions in ambient atmosphere (57 ± 14%, 14 ± 8%, and 29 ± 11%, respectively). This revealed NO 2 as an important precursor of precipitation NO 3 − and a preferential scavenger of HNO 3 by precipitation. This work is beneficial for more accurate evaluations on sources and processes of atmospheric NO y pollutants.

Selective catalytic reduction of NO x by ammonia (NH 3 -SCR) was affected by HCl, which was widely present in industrial flue gas. In this study, the SCR performances over MO x -WO 3 /TiO 2 (MW/Ti, M = Mn, Ce and V) catalysts after HCl treatment were investigated. It was found that HCl poisoning showed inhibition and promotion in NO x conversion over MnW/Ti and CeW/Ti catalysts, respectively. While the SCR activity over VW/Ti catalyst was hardly affected by HCl. Over MnW/Ti catalyst, the rupture of the MnÀ O bond by the strong MnÀ Cl binding induced the formation of amorphous MnCl 2 species. This Cl-containing species with Mn in a low oxidation state exhibited poorer redox ability and NO activation, resulting in a decrease in lowtemperature SCR activity. However, instead of directly affecting the CeO x and VO x sites, gaseous HCl reacted with NH 3 to form NH 4 Cl species on the surface of CeW/Ti and VW/Ti catalysts. As a result, the SCR activity of VW/Ti catalyst was scarcely influenced by HCl, taking the unchanged redox ability and NH 3 adsorption. With a further accumulation of NH 4 Cl on CeW/Ti catalyst, the NO x conversion at low temperature was evidently enhanced due to the promotion in NO-to-NO 2 conversion (Fast-SCR).

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