Carbonate chemistry and the anthropogenic CO_2 in the South China Sea

In order to understand the water mass exchange between the South China Sea and the West PhilippineSea, and to study the dissolved carbonate system in the seas surrounding Taiwan Island, we participated in five WOCEcruises (Cruises 257, 262, 266, 287 and 316) aboard R/V Ocean Researcher 1. The areas studied were the South ChinaSea, the West Philippine Sea and the Bashi Channel. Temperature, salinity, pH, alkalinity and total CO2 were measured.Our data indicate that because of the interference of the submarine topography and the Kuroshio axis, there existsa 'front' south of the Lanyu Islet. East of it, the water mass belongs to the West Philippine Sea, on the west in themixed water of the South China Sea and the West Philippine Sea.The South China Sea deep water should have the characteristics similar to the water at about 2 200 m in the WestPhilippine Sea. The calculated results from the residence time, the inorganic carbon dissolution rate and the organic carbon decomposition rate show that the differences between these two water masses should be between 0. 008～0. 023 inpH, 5. 2～15. 0 μmol/kg in apparent oxygen utilization, 3. 6～10. 2 μmol/kg in alkalinity and 6. 4～18. 4 μmol/kg intotal CO2, respectively. The measured results show that there are no distinguishable differences between these two watermasses, implying a short deep water residence time of approximately 40 a.The anthropogenic CO2 penetrates to roughly 500 m, slightly shallower than found in the West Philippine Sea. Theentire South China Sea contains (0. 38±0. 1 ) × 1015 g excess CO2.

Selective electroreduction of carbon dioxide to formic acid on electrodeposited SnO_2@N-doped porous carbon catalysts

Electrocatalytic reduction of CO_2 is a promising route for energy storage and utilization. Herein we synthesized SnO_2 nanosheets and supported them on N-doped porous carbon (N-PC) by electrodeposition for the first time. The SnO_2 and N-PC in the SnO_2@N-PC composites had exellent synergistic effect for electrocatalytic reduction of CO_2 to HCOOH. The Faradaic efficiency of HCOOH could be as high as 94.1% with a current density of 28.4 mA cm-2 in ionic liquid-MeCN system. The reaction mechanism was proposed on the basis of some control experiments. This work opens a new way to prepare composite electrode for electrochemical reduction of CO_2.