Environment-dependent distribution of the sediment nifH-harboring microbiota in the Northern South China Sea.

The South China Sea (SCS), the largest marginal sea in the Western Pacific Ocean, is a huge oligotrophic water body with very limited influx of nitrogenous nutrients. This suggests that sediment microbial N(2) fixation plays an important role in the production of bioavailable nitrogen. To test the molecular underpinning of this hypothesis, the diversity, abundance, biogeographical distribution, and community structure of the sediment diazotrophic microbiota were investigated at 12 sampling sites, including estuarine, coastal, offshore, deep-sea, and methane hydrate reservoirs or their prospective areas by targeting nifH and some other functional biomarker genes. Diverse and novel nifH sequences were obtained, significantly extending the evolutionary complexity of extant nifH genes. Statistical analyses indicate that sediment in situ temperature is the most significant environmental factor influencing the abundance, community structure, and spatial distribution of the sediment nifH-harboring microbial assemblages in the northern SCS (nSCS). The significantly positive correlation of the sediment pore water NH(4)(+) concentration with the nifH gene abundance suggests that the nSCS sediment nifH-harboring microbiota is active in N(2) fixation and NH(4)(+) production. Several other environmental factors, including sediment pore water PO(4)(3-) concentration, sediment organic carbon, nitrogen and phosphorus levels, etc., are also important in influencing the community structure, spatial distribution, or abundance of the nifH-harboring microbial assemblages. We also confirmed that the nifH genes encoded by archaeal diazotrophs in the ANME-2c subgroup occur exclusively in the deep-sea methane seep areas, providing for the possibility to develop ANME-2c nifH genes as a diagnostic tool for deep-sea methane hydrate reservoir discovery.

Template free synthesis of lithium doped three-dimensional macroporous graphitic carbon nitride for photocatalytic N2 fixation: the effect of Li-N active sites.

In this work, three-dimensional macroporous lithium doped graphitic carbon nitride was synthesized. XRD, N2 adsorption, SEM, XPS, UV-Vis spectroscopy, N2-TPD and photoluminescence were used to characterize the prepared catalysts. The result shows that lithium exists as a coordinative Li-N bond, which can chemisorb and activate N2 molecules, and promote the electron transfer from the catalyst to the nitrogen molecules. The as-prepared lithium doped g-C3N4 shows a NH4+ production rate of 4.8 mg L-1 h-1 gcat-1, which is 20 times that of bulk g-C3N4. Density functional theory (DFT) simulations show that lithium doping can not only increase the N[triple bond, length as m-dash]N bond length, which activates N2 molecules, but also promote the electron-hole separation efficiency of g-C3N4.

Fabrication of a full-spectrum-response Cu2(OH)2CO3/g-C3N4 heterojunction catalyst with outstanding photocatalytic H2O2 production performance via a self-sacrificial method.

Over the past few decades, near infrared light (NIR), as an important part of sunlight, has seldom been utilized in photocatalytic reactions. In this work, a full-spectrum-response Cu2(OH)2CO3/g-C3N4 photocatalyst with outstanding photocatalytic H2O2 production performance was synthesized. XRD, UV-Vis, N2 adsorption, XPS, PL, EIS and EPR are used to characterize the as-prepared catalysts. As a light absorber from UV to NIR, Cu2(OH)2CO3 can form more photogenerated electrons to recombine the holes in g-C3N4 through the "Z-scheme" mechanism. The as-prepared Cu2(OH)2CO3/g-C3N4 photocatalyst shows the H2O2 equilibrium concentration of 8.9 mmol L-1, over 16 and 26.9 times higher than that of neat g-C3N4 and Cu2(OH)2CO3. According to the Z-scheme mechanism, a "two channel route" to form H2O2 is proposed for the Cu2(OH)2CO3/g-C3N4 heterojunction catalyst.

One step synthesis of high-efficiency AgBr-Br-g-C3N4 composite catalysts for photocatalytic H2O2 production via two channel pathway.

In this work, a two-component modified AgBr-Br-g-C3N4 composite catalyst with outstanding photocatalytic H2O2 production ability is synthesized. XRD, UV-Vis, N2 adsorption, TEM, XPS, EPR and PL were used to characterize the obtained catalysts. The as-prepared AgBr-Br-g-C3N4 composite catalyst shows the highest H2O2 equilibrium concentration of 3.9 mmol L-1, which is 7.8 and 19.5 times higher than that of GCN and AgBr. A "two channel pathway" is proposed for this reaction system which causes the remarkably promoted H2O2 production ability. In addition, compared with another two-component modified catalyst, Ag-AgBr-g-C3N4, AgBr-Br-g-C3N4 composite catalyst displays the higher photocatalytic H2O2 production ability and stability.