T he reduction of CO 2 emissions into the Earth's atmosphere is gaining legislative importance in view of its impact on the climate [1][2][3][4][5] . Reduction of the harmful effect of these emissions through reclamation of CO 2 is made attractive because CO 2 can be a zero-or even negative-cost carbon feedstock 6,7 . The conversion of renewably produced hydrogen and CO 2 into methane, or synthetic natural gas, over Ni is a solution that combines the potential to reduce CO 2 emissions with a direct answer to the temporal mismatch in renewable electricity production capacity and demand [8][9][10][11][12][13][14][15][16][17] . Chemical energy storage in the form of hydrogen production by electrolysis is a relatively mature technology; however, the required costly infrastructure, and inefficiencies in distribution and storage deem it inconvenient for large-scale application in the near future. Point-source CO 2 hydrogenation to methane represents an alternative approach with higher energy density. Furthermore, methane is more easily liquefied and can be stored safely in large quantities through infrastructures that already exist 18,19 . Power-to-gas (in this case methane) is thus actively considered as being capable of balancing electric grid stability, which will allow us to increase the renewable energy supply 20 .The search for fossil fuel alternatives, and application of a process such as that described above can arguably be achieved only with the help of advances in catalysis and the closely related field of nanomaterials. Continuous efforts in both fields have allowed us to make increasingly smaller and catalytically more active (metal) particles. However, it is already known that making progressively smaller supported catalyst particles does not necessarily linearly correspond to higher catalytic activity [21][22][23] . This phenomenon, where not all atoms in a supported metal catalyst have the same activity, is called structure sensitivity and is often attributed to the distinctly different chemistries on different lattice planes for π -bond activation in CO 2 , or σ -bond activation in, for example H 2 dissociation and C-H propagation 21,24 . The availability of stepped (less coordinated) versus terrace (more coordinated) sites on the surface of supported catalyst nanoparticles obviously changes with particle size, and atomic geometries become particularly interesting below 2 nm where, for example, π -bond activation is believed to not be able to occur 21 . While particle-size effects have been extensively studied for CO hydrogenation over Co 23,25 , the understanding of such structure sensitivity effects for these critical smaller metal particle sizes is lacking as sub-2-nm particles prove difficult to synthesize for first-row transition metals (Co, Fe and Ni). However, a particle-size effect for CO 2 hydrogenation is much less well established 26 .Here, we used a unique set of SiO 2 -supported Ni nanoparticles with diameters ranging from 1 to 7 nm in size, and show not only the existence of a distinct pa...

Carbon dioxide is a desired feedstock for platform molecules, such as carbon monoxide or higher hydrocarbons, from which we will be able to make many different useful, value-added chemicals. Its catalytic hydrogenation over abundant metals requires the amalgamation of theoretical knowledge with materials design. Here we leverage a theoretical understanding of structure sensitivity, along with a library of different supports, to tune the selectivity of methanation in the Power-to-Gas concept over nickel. For example, we show that carbon dioxide hydrogenation over nickel can and does form propane, and that activity and selectivity can be tuned by supporting different nickel particle sizes on various oxides. This theoretical and experimental toolbox is not only useful for the highly selective production of methane, but also provides new insights for carbon dioxide activation and subsequent carbon–carbon coupling towards value-added products thereby reducing the deleterious effects of this environmentally harmful molecule.

An innovative BASF catalyst manufacturing technology (NanoSelect TM ) is introduced which allows production of heterogeneous catalysts with excellent control over metal crystallite sizes. NanoSelect TM technology enabled the development of Pd catalysts which are leadfree Lindlar catalyst replacements in alkyne-to-cis-alkene hydrogenations. NanoSelect TM Pt catalysts showed excellent chemoselectivity in substituted nitro-arene hydrogenation reactions without build-up of hydroxylamine intermediates. All NanoSelect TM produced catalysts show markedly higher activity per gram of metal leading to tenfold less use of precious metal.

In recent years, many articles describing the preparation of supported colloidal catalysts have been published. The semi‐hydrogenation of alkynes to yield cis‐alkenes is often used as a test reaction in these publications. Many highly selective catalysts are described. However, a satisfactory explanation for the high reported selectivity has never been shown. Here we report a study on the possible effects that lead to the large selectivity differences between current commercial Pd/C catalysts and our newly developed NanoSelect catalysts. The focus is on differences in chemical composition as well as catalyst characteristics. We use a focused ion beam scanning electron microscope (FIB‐SEM) to locate the metal particle with respect to the surface of the support. FIB‐SEM analysis clearly shows the absence of the active component inside the support material, which could explain the high observed selectivity. Nevertheless, an effect of the stabilizer cannot be ruled out.

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Reducible supports can affect the performance of metal catalysts by the formation of suboxide overlayers upon reduction, a process referred to as the strong metal–support interaction (SMSI). A combination of operando electron microscopy and vibrational spectroscopy revealed that thin TiO x overlayers formed on nickel/titanium dioxide catalysts during 400°C reduction were completely removed under carbon dioxide hydrogenation conditions. Conversely, after 600°C reduction, exposure to carbon dioxide hydrogenation reaction conditions led to only partial reexposure of nickel, forming interfacial sites in contact with TiO x and favoring carbon–carbon coupling by providing a carbon species reservoir. Our findings challenge the conventional understanding of SMSIs and call for more-detailed operando investigations of nanocatalysts at the single-particle level to revisit static models of structure-activity relationships.

Vegetative and reproductive components of litter-fall of hard beech were measured for five years and of silver beech for four years under mature trees in the Orongorongo Valley, near Wellington, New Zealand. Mean annual total litter-fall of hard beech (477 g m -2 ) included 318 g of leaves and 109 g of twigs; that of silver beech (463 g m -2 ) included 295 g of leaves and 164 g of twigs. In one year only (1994/95) both species flowered and seeded prolifically. The two species produced similar numbers of seeds (hard beech 4866 seeds m -2 ; silver beech 5551 seeds m -2 ) but litter from male flowers, seeds, and cupules of hard beech weighed 232 g m -2 compared with only 59 g m-2 for silver beech. Seasonal patterns of leaf-fall of the two species also differed substantially; peak leaf-fall of hard

||This study investigates further the possibility that eruptions of house mice in forests of southern beech (Nothofagus spp ) in New Zealand after mast seedings are triggered by increases in the populations of some arthropods, especially Lepidoptera larvae and spiders that are common foods of mice, rather than by the beech seed It reports on a 5-year study of arthropods of the forest floor in hard beech and silver beech forest in the Orongorongo Valley, near Wellington, in relation to (1) litter and seedfall, and (2) the numbers and diet of mice Litter-feeding larvae of Lepidoptera in both the litter and fermentation layers of the forest floor feed on the fallen male flowers of beech, and most species were more common after heavy flowering of the beeches A few of the common spiders (including Miturga sp , the main spider eaten by mice) were also more abundant after beech seeding Analysis of the long-term records of hard beech seeding, numbers of mice, and numbers of adults of the moth Gymnobathra tholodella (Oecophondae) showed that the number of mice was positively correlated with both the number of beech seeds and the number of moths These results indicate a more complex web of interactions in beech forest than was earlier suggested, but because the intensity of flowering in spring largely determines the numbers of both Lepidoptera larvae and beech seeds, the role of each in the population increase of mice can not be determined