An Exceptionally Efficient Co-Co2 P@N, P-Codoped Carbon Hybrid Catalyst for Visible Light-Driven CO2 -to-CO Conversion.

Artificial photosynthesis has attracted wide attention, particularly the development of efficient solar light-driven methods to reduce CO2 to form energy-rich carbon-based products. Because CO2 reduction is an uphill process with a large energy barrier, suitable catalysts are necessary to achieve this transformation. In addition, CO2 adsorption on a catalyst and proton transfer to CO2 are two important factors for the conversion reaction, and catalysts with high surface area and more active sites are required to improve the efficiency of CO2 reduction. Here, a visible light-driven system for CO2 -to-CO conversion is reported, which consists of a heterogeneous hybrid catalyst of Co and Co2 P nanoparticles embedded in carbon nanolayers codoped with N and P (Co-Co2 P@NPC) and a homogeneous RuII -based complex photosensitizer. The average generation rate of CO of the system was up to 35 000 µmol h-1 g-1 with selectivity of 79.1 % in 3 h. Linear CO production at an exceptionally high rate of 63 000 µmol h-1 g-1 was observed in the first hour of reaction. Inspired by this highly active catalyst, Co@NC and Co2 P@NPC materials were also synthesized and their structure, morphology, and catalytic properties for CO2 photoreduction were explored. The results showed that the nanoparticle size, partially adsorbed H2 O molecules on the catalyst surface, and the hybrid nature of the systems influenced their photocatalytic CO2 reduction performance.

Highly Efficient Photocatalytic System Constructed from CoP/Carbon Nanotubes or Graphene for Visible-Light-Driven CO2 Reduction.

Visible-light-driven conversion of CO2 to CO and high-value-added carbon products is a promising strategy for mitigating CO2 emissions and reserving solar energy in chemical form. We report an efficient system for CO2 transformation to CO catalyzed by bare CoP, hybrid CoP/carbon nanotubes (CNTs), and CoP/reduced graphene oxide (rGO) in mixed aqueous solutions containing a Ru-based photosensitizer, under visible-light irradiation. The in situ prepared hybrid catalysts CoP/CNT and CoP/rGO show excellent catalytic activities in CO2 reduction to CO, with a catalytic rates of up to 39 510 and 47 330 µmol h-1 g-1 in the first 2 h of reaction, respectively; a high CO selectivity of 73.1 % for the former was achieved in parallel competing reactions in the photoreduction of CO2 and H2 O. A combination of experimental and computational studies clearly shows that strong interactions between CoP and carbon-supported materials and partially adsorbed H2 O molecules on the catalyst surface significantly improve CO-generating rates.

MOF-derived Co1.11Te2 with half-metallic character for efficient photochemical conversion of CO2 under visible-light irradiation.

The Co1.11Te2 material, prepared by using an MOF as the self-template, showed excellent catalytic performance in the photoconversion of CO2 to CO. Experimental and theoretical evidence demonstrate that Co1.11Te2 has half-metallic nature, which is conducive to transferring electrons and enhancing the catalytic reduction activity.

Response of soil fauna to simulated nitrogen deposition: a nursery experiment in subtropical China.

We studied the responses of soil fauna to a simulated nitrogen deposition in nursery experimental plots in Subtropical China. Dissolved NH4NO3 was applied to the soil by spraying twice per month for 16 months, starting in January 2003 with treatments of 0, 5, 10, 15 and 30 gN/(m2 x a). Soil fauna was sampled after 6, 9, 13 and 16 months of treatment in three soil depths (0-5 cm, 5-10 cm, 10-15 cm). Soil available N increased in correspondence with the increasing N treatment, whereas soil pH decreased. Bacterial and fungal densities were elevated by the N treatment. Soil fauna increased in the lower nitrogen treatments but decreased in the higher N treatments, which might indicate that there was a threshold around 10 gN/(m2 x a) for the stimulating effects of N addition. The N effects were dependent on the soil depth and sampling time. The data also suggested that the effects of the different N treatments were related to the level of N saturation, especially the concentration of NO3- in the soil.

Roots of pioneer trees in the lower sub-tropical area of Dinghushan, Guangdong, China.

Representative pioneer tree root systems in the subtropical area of South China were examined with regard to their structure, underground stratification and biomass distribution. Excavation of skeleton roots and observation of fine roots of seven species including the Euphorbiaceae, Theaceae, Melastomataceae, Lauraceae and Fagaceae families was carried out. The results showed that: (1) Pioneer tree roots in the first stage of natural succession were of two types, one characterized by taproot system with bulky plagiotropic branches; the other characterized by flat root system with several tabular roots. The late mesophilous tree roots were characterized by one obvious taproot and tactic braches roots up and down. Shrub species roots were characterized by heart fibrous root type featured both by horizontally and transversally growing branches. Root shapes varied in different dominant species at different stages of succession. (2) Roots of the different species varied in the external features-color, periderm and structure of freshly cut slash. (3) In a set of successional stages the biomass of tree roots increased linearly with the age of growth. During monsoon, the total root biomass amounted to 115.70 t/ha in the evergreen broad-leaved forest; 50.61 t/ha in needle and broad-leaved mixed forest dominated by coniferous forest; and 64.20 t/ha in broad-and needle-leaved mixed forest dominated by broad-leaved heliophytes, and are comparable to the underground biomass observed in similar tropical forests. This is the first report about roots characteristics of forest in the lower sub-tropical area of Dinghushan, Guangdong, China.

Dynamics of soil inorganic nitrogen and their responses to nitrogen additions in three subtropical forests, south China.

Three forests with different historical land-use, forest age, and species assemblages in subtropical China were selected to evaluate current soil N status and investigate the responses of soil inorganic N dynamics to monthly ammonium nitrate additions. Results showed that the mature monsoon evergreen broadleaved forest that has been protected for more than 400 years exhibited an advanced soil N status than the pine (Pinus massoniana) and pine-broadleaf mixed forests, both originated from the 1930's clear-cut and pine plantation. Mature forests had greater extractable inorganic N pool, lower N retention capacity, higher inorganic N leaching, and higher soil C/N ratios. Mineral soil extractable NH4(+)-N and NO3(-)-N concentrations were significantly increased by experimental N additions on several sampling dates, but repeated ANOVA showed that the effect was not significant over the whole year except NH4(+)-N in the mature forest. In contrast, inorganic N (both NH4(+)-N and NO3(-)-N) in soil 20-cm below the surface was significantly elevated by the N additions. From 42% to 74% of N added was retained by the upper 20 cm soils in the pine and mixed forests, while 0%-70% was retained in the mature forest. Our results suggest that land-use history, forest age and species composition were likely to be some of the important factors that determine differing forest N retention responses to elevated N deposition in the study region.