We show a facile method to prepare surface-clean monodispersed small and stable CuOx nanoparticles with controllable average sizes from below 1 nm up to ~5 nm without using bulk capping agent. Structural and surface characterizations show that the chemical states of CuOx nanoparticles and their interactions with O 2 are dependent on the particle size. To show their relevance to catalysis, the well-defined monodispersed CuOx nanoparticles have been used for oxidative coupling of alkynes. While the generally used CuCl catalysts presents a reaction induction period and agglomerate into CuOx nanoparticles during the reaction, the induction period disappears when monodispersed CuOx nanoparticles (~2 nm) were used as catalyst. Supported CuOx nanoparticles on TiO 2 behave in the same way as monodispersed CuOx nanoparticles. Kinetic, spectroscopic and isotopic studies show that O 2 activation is the rate-controlling step and the nature of the oxygen species formed on supported CuOx nanoparticles are dependent on the size of CuOx and determine the catalytic properties for oxidative coupling of alkynes.

CrV0.95P0.05O4 prepared as a pure crystalline form was found to be highly active for the vapor-phase oxidation of picolines to the corresponding aldehydes and acids in the presence of water.

To determine the source of excess methane in oxic, surface‐water columns often found in freshwater environments, we measured the in situ concentration and stable isotopic compositions (δ13C and δ2H) of methane in Lake Biwa, a mesotrophic lake in Japan. The values from the littoral zone and lake‐floor sediments were determined, besides those in the water column of the pelagic zone. Furthermore, we conducted incubation experiments to measure microbial oxidation rates and alterations in the isotopic signatures of methane. We found significant vertical and seasonal variations in both in situ concentrations and stable isotopic compositions of methane measured in the pelagic zone. We concluded that active microbial oxidation was primarily responsible for the variation in δ13C and δ2H values of methane in the pelagic water column. As a result, we defined a new indicator Δ(2,13) to characterize the sources of dissolved methane, in which variations in both δ13C and δ2H during methane oxidation had been corrected. The excess methane in oxic, surface‐water columns exhibited Δ(2,13) values similar to those in the littoral zone. We concluded that excess methane at the surface of the pelagic zone originated from the littoral zone via lateral transport. Anoxic near sediments and inflowing rivers were responsible for methane enrichment in water of the littoral zone and in the surface water columns of the pelagic zone.

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The catalytic behaviour of CrV 0.95 P 0.05 O 4 has been investigated in the selective oxidations of 2-, 3-and 4picolines by in situ DRIFTS, and the model of picoline adsorption and the oxidation mechanism are proposed. Both Lewis and Brønsted acid sites were detected on the surface of CrV 0.95 P 0.05 O 4 , and the number of the latter increased on the addition of steam in the reaction mixture, resulting in enhanced activity for selective oxidations. The enhanced activity due to water addition is interpreted by the fact that Brønsted acid sites are produced by the hydrolysis of V-O-Cr and activate picoline molecules by withdrawing the electrons of the pyridine ring, and at the same time, enable to accelerate the desorption of the acid products from the catalyst surface. Every 2-, 3-and 4-picoline was adsorbed on the catalyst surface via the N atom donating the electrons to the Brønsted acid sites, and the substituted methyl group was oxidized via hydrogen abstraction by surface oxide ion to form the radical intermediate, followed by oxygen insertion to produce the corresponding aldehyde and then acid. Even in the absence of gaseous oxygen, the oxygenated products were formed and observed over the catalyst surface by in situ DRIFTS. Thus, a Mars and van Krevelen mechanism was suggested for 2-, 3-and 4-picolines oxidations based on the spectral analysis. Both 2-and 4-picolines were more quickly oxidized than 3-picoline due to the inductive hyper-conjugative effect of nitrogen, resulting in an easy leaving of proton from the methyl group. 4-Picoline produced almost quantitatively isonocotinic acid, while 2-picoline afforded 2-picoline aldehyde as the main product due to the unstability of the acid product, i.e., the decarboxylation of picolinic acid took place to form pyridine.