Introduction of porosity and fluorescent properties into lanthanide metal-organic frameworks(MOFs)with rational design to achieve multifunctional use is of great significance from the energy and environmental viewpoin...Introduction of porosity and fluorescent properties into lanthanide metal-organic frameworks(MOFs)with rational design to achieve multifunctional use is of great significance from the energy and environmental viewpoint.In this study,a microporous Tb(Ⅲ)-based MOF with the formula of{[Tb2(oba)3(Phen)2](DMF)2(H2O)4}_n(1)was solvothermally prepared via using the mixed ligands of 1,10-phenanthroline(Phen)and 4,4'-oxybis(benzoic acid)(H_(2)oba)as organic connecters.The structural evaluation results indicate that complex 1 is composed of binuclear Tb2(CO_(2))6(Phen)2clusters which are extended by the oba^(2-)ligands to afford a two-fold interpenetrated framework with one-dimensional microporous channels along the b-axis.Gas sorption studies show that the activated 1 demonstrates a high ideal adsorption solution theory(IAST)sorption selectivity of 7.4 toward C_(2)H_(2)in a C_(2)H_(2)/CO_(2)gas mixture,which are further supported by the dynamic breakthrough experiments.The grand canonical Monte Carlo(GCMC)simulation results indicate that the synergistic effects of the H-bond interactions of C_(2)H_(2)with oba^(2-)ligands and the C-H…πinteractions with Phen ligand contribute to the strong binding of the framework toward C_(2)H_(2)molecules.What's more,the luminescent measurements reveal that the emission of 1 features both the characteristic peaks of Phen ligand and Tb(Ⅲ)ion,which could be further applied as a self-calibrating sensor for the Cr(Ⅵ)detection in water.To the best of our knowledge,complex 1 represents the first example of Tb-MOF holding such a high C_(2)H_(2)/CO_(2)selectivity together with ratiometric Cr(Ⅵ)detection performances.展开更多
It is known that gas flow rate is a key factor in controlling industrial plasma processing. In this paper, a 2D PIC/MCC model is developed for an rf hollow cathode discharge with an axial nitrogen gas flow. The effect...It is known that gas flow rate is a key factor in controlling industrial plasma processing. In this paper, a 2D PIC/MCC model is developed for an rf hollow cathode discharge with an axial nitrogen gas flow. The effects of the gas flow rate on the plasma parameters are calculated and the results show that： with an increasing flow rate, the total ion（N＋2, N＋） density decreases, the mean sheath thickness becomes wider, the radial electric field in the sheath and the axial electric field show an increase, and the energies of both kinds of nitrogen ions increase;and, as the axial ion current density that is moving toward the ground electrode increases, the ion current density near the ground electrode increases. The simulation results will provide a useful reference for plasma jet technology involving rf hollow cathode discharges in N2.展开更多
TiBCN films were deposited on Si(100) and cemented carbide substrates by using multi-cathodic arc ion plating in C_2H_2 and N_2atmosp^here. Their structure and mechanical properties were studied systematically under d...TiBCN films were deposited on Si(100) and cemented carbide substrates by using multi-cathodic arc ion plating in C_2H_2 and N_2atmosp^here. Their structure and mechanical properties were studied systematically under different N_2 flow rates. The results showed that the Ti BCN films were adhered well to the substrates. Rutherford backscattering sp^ectroscopy was employed to determine the relative concentration of Ti, B, C and N in the films.The chemical bonding states of the films were explored by X-ray photoelectron sp^ectroscopy, revealing the presence of bonds of Ti N, Ti(C,N), BN, pure B, sp^2C–C and sp^3C–C, which changed with the N_2 flow rate. Ti BCN films contain nanocrystals of Ti N/Ti CN and Ti B_2/Ti(B,C)embedded in an amorphous matrix consisting of amorphous BN and carbon at N_2 flow rate of up to 250 sccm.展开更多
Forming an ultrathin conducting layer on a fluorinated carbon(CFx)surface for reducing severe electrochemical polarization in lithium/fluorinated carbon primary batteries(Li/CF_(x))remains a considerable challenge for...Forming an ultrathin conducting layer on a fluorinated carbon(CFx)surface for reducing severe electrochemical polarization in lithium/fluorinated carbon primary batteries(Li/CF_(x))remains a considerable challenge for achieving batteries with excellent rate capability.Herein,CFxwas modified by using acetylene/argon mixture plasma combined with MnO_(2)particles.The CF_(x)/C/MnO_(2)composite effectively reduced the voltage hysteresis and improved the electrochemical performance of Li/CF_(x).The excellent rate performance of CF_(x)/C/MnO_(2)was due to the high electrochemical activity provided by the atomicscale conductive carbon layer and ultrafine MnO_(2)particles.Compared with pristine CF_(x),the charge transfer resistance of the optimized CF_(x)/C/MnO_(2)decreased from 218.5 to 48.2Ω,the discharge rate increased from 2C to 10C,and the power density increased from 3.11 to 13.44 kW·g^(-1),The intrinsic reason for the enhanced rate performance was attributed to the fact that the ultrathin carbon layer acted as a conductive bridge to reduce the voltage hysteresis at the initial stage of the Li/CF_(x)discharge,and the high electrochemical activity of the ultrafine MnO_(2)particles provided a faster lithium-ion diffusion rate.展开更多
The determination of trace element Pb in electrolyte MnSO_4H_2SO_4 was studied with differential pulse po-larography. The trace Pb was originated from new type Pb-Ag-Ca alloy anode being used in preduction processof e...The determination of trace element Pb in electrolyte MnSO_4H_2SO_4 was studied with differential pulse po-larography. The trace Pb was originated from new type Pb-Ag-Ca alloy anode being used in preduction processof electrolytic MnO_2 (EMD). The KCl was added as background of electrolyte. The differential pulse polarco-gram obtained for Pb(Ⅱ) is well in peak contour and is easy to determination. The peak potential is -0. 44 V(vs Ag-AgCl potential , experimental valuel). The Pb content may be determined by standard addition methodwhich is simple , reliable and fast. This study presents some foundamental data for Pb-Ag-Ca anode (abbreviated to PAC anede). The consuming rate for PAC anode is evaluated as 4. 82% annually.展开更多
Offset-tracking is an essential method for deriving glacier flow rates using optical imagery.Sentinel-2(S2)and Landsat-8/9(L8/9)are popular optical satellites or constellations for polar studies,offering high spatial ...Offset-tracking is an essential method for deriving glacier flow rates using optical imagery.Sentinel-2(S2)and Landsat-8/9(L8/9)are popular optical satellites or constellations for polar studies,offering high spatial resolution with relatively short revisit time,wide swath width,and free accessibility.To evaluate and compare the precision of offset-tracking results yielded with these two kinds of data,in this study S2 and L8/9 imagery observed in Petermann Glacier in Greenland,Karakoram in High-Mountains Asia,and Amery Ice Shelf in the Antarctic are analyzed.Outliers and various systematic error sources in the offset-tracking results including orbital and strip errors were analyzed and eliminated at the pre-process stage.Precision at the off-glacier(bare rock)region was evaluated by presuming that no deformation occurred;then for both glacierized and the off-glacier regions,precision of velocity time series was evaluated based on error propagation theory.The least squares method based on connected components was used to solve flow rates time series based on multi-pair images offset-tracking.The results indicated that S2 achieved slightly higher precision than L8/9 in terms of both single-pair derived displacements and least square solved daily flow rates time series.Generally,the RMSE of daily velocity is 26%lower for S2 than L8/9.Moreover,S2 provided higher temporal resolution for monitoring glacier flow rates.展开更多
Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electr...Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.展开更多
基金Project supported by the National Natural Science Foundation of China(U23A20579)。
文摘Introduction of porosity and fluorescent properties into lanthanide metal-organic frameworks(MOFs)with rational design to achieve multifunctional use is of great significance from the energy and environmental viewpoint.In this study,a microporous Tb(Ⅲ)-based MOF with the formula of{[Tb2(oba)3(Phen)2](DMF)2(H2O)4}_n(1)was solvothermally prepared via using the mixed ligands of 1,10-phenanthroline(Phen)and 4,4'-oxybis(benzoic acid)(H_(2)oba)as organic connecters.The structural evaluation results indicate that complex 1 is composed of binuclear Tb2(CO_(2))6(Phen)2clusters which are extended by the oba^(2-)ligands to afford a two-fold interpenetrated framework with one-dimensional microporous channels along the b-axis.Gas sorption studies show that the activated 1 demonstrates a high ideal adsorption solution theory(IAST)sorption selectivity of 7.4 toward C_(2)H_(2)in a C_(2)H_(2)/CO_(2)gas mixture,which are further supported by the dynamic breakthrough experiments.The grand canonical Monte Carlo(GCMC)simulation results indicate that the synergistic effects of the H-bond interactions of C_(2)H_(2)with oba^(2-)ligands and the C-H…πinteractions with Phen ligand contribute to the strong binding of the framework toward C_(2)H_(2)molecules.What's more,the luminescent measurements reveal that the emission of 1 features both the characteristic peaks of Phen ligand and Tb(Ⅲ)ion,which could be further applied as a self-calibrating sensor for the Cr(Ⅵ)detection in water.To the best of our knowledge,complex 1 represents the first example of Tb-MOF holding such a high C_(2)H_(2)/CO_(2)selectivity together with ratiometric Cr(Ⅵ)detection performances.
基金supported by the Natural Science Foundation of Hebei Province,China(No.A2012205072)
文摘It is known that gas flow rate is a key factor in controlling industrial plasma processing. In this paper, a 2D PIC/MCC model is developed for an rf hollow cathode discharge with an axial nitrogen gas flow. The effects of the gas flow rate on the plasma parameters are calculated and the results show that： with an increasing flow rate, the total ion（N＋2, N＋） density decreases, the mean sheath thickness becomes wider, the radial electric field in the sheath and the axial electric field show an increase, and the energies of both kinds of nitrogen ions increase;and, as the axial ion current density that is moving toward the ground electrode increases, the ion current density near the ground electrode increases. The simulation results will provide a useful reference for plasma jet technology involving rf hollow cathode discharges in N2.
基金supported by the National Natural Science Foundation of China(Nos.11375135 and 11275141)International Cooperation Program of the Ministry of Science and Technology of China(No.2015DFR00720)Fundamental Research Funds for the Central Universities
文摘TiBCN films were deposited on Si(100) and cemented carbide substrates by using multi-cathodic arc ion plating in C_2H_2 and N_2atmosp^here. Their structure and mechanical properties were studied systematically under different N_2 flow rates. The results showed that the Ti BCN films were adhered well to the substrates. Rutherford backscattering sp^ectroscopy was employed to determine the relative concentration of Ti, B, C and N in the films.The chemical bonding states of the films were explored by X-ray photoelectron sp^ectroscopy, revealing the presence of bonds of Ti N, Ti(C,N), BN, pure B, sp^2C–C and sp^3C–C, which changed with the N_2 flow rate. Ti BCN films contain nanocrystals of Ti N/Ti CN and Ti B_2/Ti(B,C)embedded in an amorphous matrix consisting of amorphous BN and carbon at N_2 flow rate of up to 250 sccm.
基金financially supported by the National Natural Science Foundation of China(No.51972045)the Fundamental Research Funds for the Chinese Central Universities,China(No.ZYGX2019J025)。
文摘Forming an ultrathin conducting layer on a fluorinated carbon(CFx)surface for reducing severe electrochemical polarization in lithium/fluorinated carbon primary batteries(Li/CF_(x))remains a considerable challenge for achieving batteries with excellent rate capability.Herein,CFxwas modified by using acetylene/argon mixture plasma combined with MnO_(2)particles.The CF_(x)/C/MnO_(2)composite effectively reduced the voltage hysteresis and improved the electrochemical performance of Li/CF_(x).The excellent rate performance of CF_(x)/C/MnO_(2)was due to the high electrochemical activity provided by the atomicscale conductive carbon layer and ultrafine MnO_(2)particles.Compared with pristine CF_(x),the charge transfer resistance of the optimized CF_(x)/C/MnO_(2)decreased from 218.5 to 48.2Ω,the discharge rate increased from 2C to 10C,and the power density increased from 3.11 to 13.44 kW·g^(-1),The intrinsic reason for the enhanced rate performance was attributed to the fact that the ultrathin carbon layer acted as a conductive bridge to reduce the voltage hysteresis at the initial stage of the Li/CF_(x)discharge,and the high electrochemical activity of the ultrafine MnO_(2)particles provided a faster lithium-ion diffusion rate.
文摘The determination of trace element Pb in electrolyte MnSO_4H_2SO_4 was studied with differential pulse po-larography. The trace Pb was originated from new type Pb-Ag-Ca alloy anode being used in preduction processof electrolytic MnO_2 (EMD). The KCl was added as background of electrolyte. The differential pulse polarco-gram obtained for Pb(Ⅱ) is well in peak contour and is easy to determination. The peak potential is -0. 44 V(vs Ag-AgCl potential , experimental valuel). The Pb content may be determined by standard addition methodwhich is simple , reliable and fast. This study presents some foundamental data for Pb-Ag-Ca anode (abbreviated to PAC anede). The consuming rate for PAC anode is evaluated as 4. 82% annually.
基金supported by the National Natural Science Foundation of China(Grant no.42371136)the Guangdong Basic and Applied Basic Research Foundation(Grant no.2021B1515020032)the Innovation Group Project of Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai)(Grant no.311022003).
文摘Offset-tracking is an essential method for deriving glacier flow rates using optical imagery.Sentinel-2(S2)and Landsat-8/9(L8/9)are popular optical satellites or constellations for polar studies,offering high spatial resolution with relatively short revisit time,wide swath width,and free accessibility.To evaluate and compare the precision of offset-tracking results yielded with these two kinds of data,in this study S2 and L8/9 imagery observed in Petermann Glacier in Greenland,Karakoram in High-Mountains Asia,and Amery Ice Shelf in the Antarctic are analyzed.Outliers and various systematic error sources in the offset-tracking results including orbital and strip errors were analyzed and eliminated at the pre-process stage.Precision at the off-glacier(bare rock)region was evaluated by presuming that no deformation occurred;then for both glacierized and the off-glacier regions,precision of velocity time series was evaluated based on error propagation theory.The least squares method based on connected components was used to solve flow rates time series based on multi-pair images offset-tracking.The results indicated that S2 achieved slightly higher precision than L8/9 in terms of both single-pair derived displacements and least square solved daily flow rates time series.Generally,the RMSE of daily velocity is 26%lower for S2 than L8/9.Moreover,S2 provided higher temporal resolution for monitoring glacier flow rates.
基金This work was supported by the University of Science and Technology Beijing.DG acknowledges the financial support from 111 Project(no.B170003)Foshan Science and Technology Innovation Project(no.2018IT100363).
文摘Electrochemical CO_(2)reduction to C_(2)H_(4)can provide a sustainable route to reduce globally accelerating CO_(2)emissions and produce energy-rich chemical feedstocks.However,the poor selectivity in C_(2)H_(4)electrosynthesis limits its implementation in industrially interesting processes.Herein,we report a composite structured catalyst composed of Ag and Cu_(2)O with different crystal faces to achieve highly efficient reduction of CO_(2)to C_(2)H_(4).The catalyst composed of Ag and octahedral Cu_(2)O enclosed with(111)facet exhibits the best CO_(2)electroreduction performance,with the Faradaic efficiency(FE)and partial current density reaching 66.8%and 17.8 mA cm2 for C_(2)H_(4)product at-1.2 VRHE in 0.5 M KHCO_(3),respectively.Physical characterization and electrochemical test analysis indicate that the high selectivity for C_(2)H_(4)product stems from the synergistic effect of crystal faces control engineering and tandem catalysis.Specifically,Ag can provide optimal availability of CO intermediate by suppressing hydrogen evolution;subsequently,C-C coupling is promoted on the intimate surface of Cu_(2)O with facetdependent selectivity.The insights gained from this work may be beneficial for designing efficient multicomponent catalysts for improving the selectivity of electrochemical CO_(2)reduction reaction to generate C2þproducts.
