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The structures, semiconductor and photocurrent response properties of three 1,4-diazabicyclo[2.2.2]octane derivative-templated iodobismuthates, (Et2DABCO)3(BiI6)2 (1), (i-Pr2DABCO)2(Bi2I10) (2), [(Me2DABCO)2(Bi2I10)2]n (3) (Et2DABCO2+ = N,N′-diethyl-1,4-diazabicyclo[2.2.2] octane, i-Pr2DABCO2+ = N,N′-diisoproyl-1,4-diazabicyclo[2.2.2] octane, Me2DABCO2+ = N,N′-dimethyl-1,4-diazabicyclo[2.2.2] octane), are reported. Based on the templates with different substitutents on 1,4-diazabicyclo[2.2.2]octane, mono-nuclear ((BiI6)3− for 1), dimer ((Bi2I10)4− for 2) and 1-D chain ((BiI5)n2n− for 3) can be obtained. C-H···I hydrogen bonds contribute to the structural extension to 2-D layer (for 2) and 3-D network (for 3). Their absorption spectra were investigated, and energy band gaps of 2.24/1.73/1.44 eV indicate their narrow-gap semiconductor natures. Their photocurrent response properties were also discussed. Finally, theoretical calculation was executed to give structure-properties correlation. [ABSTRACT FROM AUTHOR]

A new iodobismuthate-based hybrid (Me2DABCO)7(BiI6)2(Bi2I9)2.2I3 (1) (Me2DABCO2+ = N,N′-dimethyl-1,4- diazabicyclo[2.2.2] octane) has been structurally determined. The highly interesting feature of 1 lies in its presence of mixed types of iodobismuthate clusters, i.e. mononuclear (BiI6)3− and (Bi2I9)3− dimer in one crystal lattice templated by Me2DABCO2+ cation, which is the first example of mixed iodobismuthate clusters in one lattice. Its absorption zone can be broadened compared with other single iodobismuthate cluster-containing analogy compounds. And due to the strong I···I interactions, an optical gap of 1.61 eV can be observed. The photocurrent response properties before and after heating were discussed, which suggests that the device can be potentially used as temperature-response switch. [ABSTRACT FROM AUTHOR]

A well-connected and high-porosity current collector layer fabricated at a low temperature of 550 °C is designed for metal-supported solid oxide fuel cells (SOFCs). Reduced Mn 1.5 Co 1.5 O 4 (MCO) powders are used as the binder through the reforming of MCO in the air atmosphere. A high conductivity phase La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3 (LSCF) is added to keep the porous frame microstructure and decease the ohmic polarization of the current collector layer. Three current collector layers are prepared: MCO, MCO/LSCF, and LSCF. The working state of each current collector layer in planar SOFC stack is reproduced by special experimental design; the performance is tested in the range of 550–750 °C. The results show that the current collector layer for SOFC is achieved at low temperatures using the reduction-oxidation properties of MCO, and the performance is improved by adding high conductivity phase LSCF. The gas distribution at the cathode side is also simulated for designing a high performance SOFC. • A high-porosity current collector layer is fabricated at 550°C. • The real working state of the current collector layer is reproduced. • The gas distribution is simulated for designing a current collector layer. [ABSTRACT FROM AUTHOR]

The water-sediment regulation scheme (WSRS) in the Yellow River has been adjusted annually to maintain the optimal capacity of the Xiaolangdi Reservoir via the scouring of deposits downstream before the rainy season. The high-intensity sediment scouring in a short time has given rise to elevated dissolved inorganic carbon (DIC) exportation; however, the source of the DIC is still unclear. Here, we hypothesized that sediment scouring released porewater DIC into the river water, increasing the riverine DIC concentration and enhancing CO 2 outgassing during the adjustment of the WSRS. To test this hypothesis, we used the isotopic composition of the DIC (δ13C DIC) to constrain the sources and transformations of the DIC. River water samples were collected below the Xiaolangdi Reservoir dam before, during, and after the adjustment of the WSRS. In these three stages, the pH of the river water decreased from 8.2 to 8.0 and then increased to 8.4; and the DIC concentrations increased from 185.30 to 216.37 mg L−1, and then decreased to 199.93 mg L−1. The δ 13C DIC values decreased from −7.01 to −11.53‰ and then increased to −6.82‰; and the partial pressure of the CO 2 increased from 5.21 × 10−3 to 35.30 × 10−3 atm, and then decreased to 3.40 × 10−3 atm. The increase in the DIC concentrations with negative δ 13C DIC values during the adjustment of the WSRS resulted from the release of porewater DIC due to the sediment scouring, which was derived from the anaerobic oxidation of organic matter in the permeable sediment environment. More broadly, the sedimentary organic carbon-derived DIC released into the ocean would counteract CO 2 drawdown via the burial of organic carbon in the geological timescales. [Display omitted] • Artificial sediment scouring increased DIC concentrations and flux during the WSRS. • Riverine δ 13C DIC values were negative during the WSRS. • DO concentrations were as low as 1.6 mg/L, and d -excess values increased to 9‰ during the WSRS. • Porewater mixing has resulted in negative δ 13C DIC values and increased DIC concentrations. [ABSTRACT FROM AUTHOR]

Piedmont alluvial fans have, for a long time, supported clean groundwater for human development worldwide. Rapid urbanization in China has over-exploited groundwater and resulted in severe groundwater nitrate pollution in piedmont alluvial fans, which has led to both human health concerns and clean water shortages, especially in rural residential areas where drinking water is mainly derived from shallow groundwater. However, sources of nitrate in groundwater and their pathways are still unclear. In this study, we hypothesized that untreated manure and domestic sewage are the primary nitrate sources in a residential area, and that an unconfined aquifer would be more vulnerable to nitrate pollution than a confined aquifer due to nitrate infiltration via the vadose zone. To verify this hypothesis, groundwater nitrate pollution in a well-characterized piedmont alluvial fan was studied through hydrochemical composition and multi-isotope (δ 15N NO3 , δ 34S SO4 , δ 18O SO4 , δ 13C DIC) data over four seasons. Seasonal variations for both NO 3 − concentrations and δ 15N NO3 values in unconfined groundwater (UGW) and confined groundwater (CGW) were observed. Mixing of nitrate sourced from manure/sewage, precipitation, soil nitrogen, and synthetic fertilizer controlled the groundwater nitrate level, and manure/sewage contributed 52.4%, 32.4%, and 33.7% nitrate to UGW, CGW, and surface water (SFW), respectively, based on Stable Isotope Mixing Models in R (SIMMR) analysis. Denitrification had a minor effect on groundwater nitrate levels in a residential area, and nitrate pollution in CGW was partly due to nitrate migration through geological faults and fracture zones in a piedmont alluvial fan. Nitrate pollution sources and pathways in residential areas were confirmed through multiple isotopes (δ 15N NO3 , δ 13C DIC , δ 34S SO4 , and δ 18O SO4). Collectively, these results highlight the roles of the hydrogeological setting and anthropogenic activities in groundwater N pollution beneath piedmont alluvial fans. • Hydrogeological controls play a key role in nitrate levels in groundwater. • Elevated nitrate levels in groundwater are closely linked with manure/sewage. • Unconfined groundwater is more vulnerable to nitrate pollution than confined groundwater. • Multiple isotope data confirms nitrate sources and transformations in groundwater. [ABSTRACT FROM AUTHOR]