A Co atom enhances the HER activity of monolayer MoS2 whereas a Ni atom exhibits the opposite effect on the same basal site.

There has been an intense research to develop 2-H MoS2 based catalysts to reduce or eliminate the use of Pt/C at higher metal loading for hydrogen evolution reaction (HER) in catalytic hydrolysis of water, which enables the capture of renewable energy sources as fuel and chemical. However, the study of its uncommon polymorph, 1T-MoS2 and particularly the doping effect with transition metal (TM) is rather limited due to the instability of this phase. Here we report a simple ambient temperature modification method using sonication to dope the single layer 1T-S MoS2 with various TM precursors. It is found that 1-T S MoS2 is more superior than corresponding 2H-S MoS2 and the inclusion of 3 wt% Pt or Pd can also further enhance the HER activity. STEM-EELS and XAS show the active single TM atom doping on this surface is to account for the high activity. Kinetic and DFT analyses also illustrate that the metallic nature of 1T-S MoS2 greatly facilitates the first proton reduction step from water, rendering it non-rate limiting as contrast to that of 2H-S MoS2. The inclusion of TM single doper such as Pd, despite at low loading, can offer the dramatic acceleration on the rate limiting recombination of H to H2. As a result, a bifunctional catalysis for HER over this tailored composite structure is demonstrated which outperforms most reported catalysts in this area.

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A long-term deviation from the natural species composition of our forests resulted in marked changes in the relative tree species composition where coniferous species began to predominate in the species composition at the expense of broadleaved species. The changes mostly affected the natural distribution of beech, the proportion of which decreased from the original 40.2% to the present 6.9%. On the other hand, the proportion of spruce increased from the original 11.2% to the present 52.8% (MZE 2008).Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) is evidently rightly considered to be the most important and perspective introduced species in the Czech Republic. It is given by more than 150-year tradition of its growing in this country and its potential to grow up very well at acid, mesotrophic and gleyed sites of the 2 nd to the 5 th forest vegetation zone. As a rule, Douglas fir also naturally regenerates there creating mixtures with a number of autochthonous species. For its dynamic intensive growth (Bušina 2007) it is an optimum species for repair or enrichment planting already at an early age. Above all, it is necessary to stress its quite exceptional production potential markedly exceeding all domestic conifers AbsTRAcT: The paper presented evaluates reserves and chemical composition of forest floor of three stands of Douglas fir, spruce and spruce with beech at acid sites (3K) in the Hůrky Training Forest District (TFD) and at a mesotrophic site (4H) in the Křtiny Training Forest Enterprise (TFE). The aim of the study was to evaluate: (i) reserves of forest floor, (ii) soil reaction, (iii) total content of carbon and nitrogen for the forest floor layers, (iv) C/N ratio, and (v) the content of dissolved organic carbon (DOC). The lowest reserve occurs in the Douglas fir stand at a mesotrophic site (25.0 t/ha), the highest accumulation occurs in the spruce stand and in the spruce/beech stand at an acid site (79.4-79.6 t/ha). The soil reaction is strongly acid to acid. The most favourable values of pH for forest floor and soil at acid (4.6 ± 0.4) and mesotrophic sites (5.2 ± 0.4) occur in the Douglas fir stand. It also corresponds to C/N ratio (23-26). The highest reserve of carbon in forest floor occurs at the acid site 34.7 t/ha (1.3 t/ha nitrogen). The lowest reserve of carbon in forest floor at the mesotrophic site amounts to 8.5 t/ha (0.4 t/ha nitrogen). The higher content of DOC in stands at acid sites can result in a higher risk of soil acidification.

The utility of carbon materials in applications as diverse as drug delivery and photocatalysis is often undermined by the complexity of their surface chemistry; different sources of carbon give rise to a varied mixture of functional groups and hence different properties. Considerable efforts have been made to identify specific groups at these surfaces and elucidate the complex interactions that take place but even on materials such as graphene and carbon nanotubes there remains uncertainty about the nature of the components present and their role in the nucleation of other functional materials at the surface. The present study uses highly ordered pyrolytic graphite (HOPG) as a model on which the fundamental properties of specific functional groups and their interactions with deposited nanoparticles can be characterised. We have shown that treatment of HOPG surfaces with low concentrations of hydrochloric acid results in significant topographic changes to the surface and a low concentration of oxygen containing species. From selective derivatization and a comparison of their XP spectra, the latter can be unambiguously identified as surface hydroxyls. DFT calculations have shown that these groups are stable in close proximity to each other. Heating to 573 K leads to conversion of the hydroxyls to mixture of two states, one of which is identified as a ketone whilst the other is proposed to be an ether. Gold deposition on the surface from aqueous solutions of chloroauric acid is shown to be strongly influenced by the nature of the oxygen species present.

Highly oriented pyrolytic graphite (HOPG) samples were investigated as model catalyst supports. The surfaces were treated with dilute HCl and HNO 3 under ambient conditions and examined with atomic force microscopy and scanning tunnelling microscopy (STM) and Xray photoelectron spectroscopy (XPS). Raised features were formed on the HOPG surface after acid treatment. These protrusions were typically 4-6 nm in height and between 10 to 100 nm in width, covering 5% to 20% of the substrate for acid concentrations between 0.01 and 0.2 M. Both width and surface density of the features increases with acid concentration but the heights are not affected. STM images show that the graphite lattice extends over the protrusions indicating that the features are "blisters" on the surface rather than deposited material, a view that is supported by the XPS which shows no other significant adsorbates except for oxygen in the case of the nitric acid. We propose that penetration of the acid at defective sites leads to a decrease in the interplanar van der Waals forces and a local delamination similar to the "bubbles" reported between exfoliated graphene sheets and a substrate. These findings are important in the context of understanding how carbon supports stabilise active components in heterogeneous catalysts.

Mineral nutrition represents the uptake, transport, metabolism and utilization of nutrients by the forest stand. These processes influence all physiological functions of trees. A specific minimum amount of all nutrients is necessary for the healthy development and growth of forest trees. The uptake of nutrients is influenced not only by natural conditions but also by anthropogenic activities. During the period of 2000-2005 the mineral nutrition of mountain Norway spruce stands was studied at the study site Bílý Kříž (Moravian-Silesian Beskids Mts., Czech Republic). Research was carried out in a spruce stand that was limed in the past years (in 1983, 1985 and 1987) and in a spruce stand that was not limed in order to compare the liming effect on the mineral nutrition of spruce stands. A positive liming effect was detected in the calcium, magnesium and phosphorus nutrition because their contents in current needles were higher on the limed plots. No liming effect was determined in the nitrogen, potassium and microelement (Fe, Mn, Cu, Zn, Al) content in current needles. Sufficient nutrition of spruce stands only with calcium was recorded on all studied plots.

The main reason for the transformation of spruce monocultures at sites of mixed broadleaved forests is to create more natural relationships between the species structure of a stand and soil processes. The presented study compares humus conditions and basic growth characteristics of two mixed stands (spruce with beech and larch with beech) aged 25 years with a beech stand (aged 40 years) and spruce stand (aged 30 years). The purpose of the study is to evaluate (<I>i</I>) forms of forest floor, (<I>ii</I>) soil reaction, (<I>iii</I>) the content and total reserves of carbon, nitrogen and C/N ratio, (<I>iv</I>) dissolved organic carbon (DOC) in relation to stand characteristics. The highest reserve of forest floor is detected in the mixed stand of larch with beech (52.6 t/ha), the lowest reserve in a beech stand (21.0 t/ha). The soil reaction of the spruce stand and the beech stand is 4.0 (± 0.3) and 5.1 (± 0.3), respectively. The C/N ratio of the spruce stand is 23.5 (± 1.8) and that of the beech stand 18.8 ± 2.9. The DOC content decreases with layers of surface humus towards depth. Mixed stands represent by their values of soil conditions a mean between spruce and beech stands.