Ammonia borane(AB)is an excellent candidate for the chemical storage of hydrogen.However,its practical utilization for hydrogen production is hindered by the need for expensive noble-metal-based catalysts.Herein,we re...Ammonia borane(AB)is an excellent candidate for the chemical storage of hydrogen.However,its practical utilization for hydrogen production is hindered by the need for expensive noble-metal-based catalysts.Herein,we report Co-Co3O4 nanoparticles(NPs)facilely deposited on carbon dots(CDs)as a highly efficient,robust,and noble-metal-free catalyst for the hydrolysis of AB.The incorporation of the multiinterfaces between Co,Co3O4 NPs,and CDs endows this hybrid material with excellent catalytic activity(rB=6816 mLH2 min^-1 gCo^-1)exceeding that of previous non-noble-metal NP systems and even that of some noble-metal NP systems.A further mechanistic study suggests that these interfacial interactions can affect the electronic structures of interfacial atoms and provide abundant adsorption sites for AB and water molecules,resulting in a low energy barrier for the activation of reactive molecules and thus substantial improvement of the catalytic rate.展开更多
The lifting efficiency and stability of gas lift well are affected by the socalled slippage-loss effect in gas-liquid two-phase flow.The existing studies on this subject have generally been based on vertical and horiz...The lifting efficiency and stability of gas lift well are affected by the socalled slippage-loss effect in gas-liquid two-phase flow.The existing studies on this subject have generally been based on vertical and horizontal wells.Only a few of them have considered inclined pipes.In the present work a new focused study is presented along these lines.More specifically,we use the non-slip pressure drop model with Flanigan’s fluctuation correction coefficient formula(together with the parameters of slippage density,slippage pressure drop and slippage ratio)to analyze the influence of the inclination angle on slippage loss for different conditions(different gas-liquid superficial velocity and pipe diameters).Moreover,the“standard regression coefficient method”is used for multi-factor sensitivity analysis.The experimental results indicate that slippage loss is affected by multiple factors,and the influence of the inclination angle on slippage loss is less significant than other factors.The change of the slippage pressure drop with the superficial velocity of gas-liquid is similar to that of the total pressure drop.The inclination angles of 45°and 60°have the greatest influence on slippage loss.The correlation between slippage density and slippage ratio is not obvious.Using the so-called slippage ratio seems to be a more accurate option to evaluate the degree of slippage loss.展开更多
Water electrolysis is considered as one most promising technique for hydrogen production.The high efficiency electrocatalyst is the key to accelerating the sluggish kinetics of the hydrogen evolution reaction(HER) in ...Water electrolysis is considered as one most promising technique for hydrogen production.The high efficiency electrocatalyst is the key to accelerating the sluggish kinetics of the hydrogen evolution reaction(HER) in alkaline media.In this work,an efficient HER electrocatalyst with hetero-interfacial metal-metal oxide structure was constructed through a redox solid phase reaction(SPR) strategy.During the annealing process under Ar atmosphere,RuO_(2) and WS_(2)in RuO_(2)/WS_(2)precursor were converted to Ru nanoparticles(NPs) and WO3in situ,where tiny Ru NPs and oxygen vacancies were uniformly distributed onto the newly formed WO3nanosheets.Different characterization techniques were adopted to confirm the successful formation of Ru/WO_(3)electrocatalyst(RWOC).The optimized RWOC sample annealed at 400℃ exhibited the low overpotential value of 13 mV at a current density of 10 mA cm^(-2)and strong durability under the alkaline condition.Density functional theoretical calculations further revealed that the promoted adsorption/desorption rate of reaction intermediates and the accelerated kinetics of HER process were deduced to the synergistic effect between Ru and WO_(3)in electrocatalyst.This work provides a feasible method to fabricate highly efficient HER electrocatalysts.展开更多
The defect-free structure of Mo-based materials is a“double-edged sword”,which endows the material with excellent stability,but limits its chemical versatility and application in electrochemical hydrogen evolution r...The defect-free structure of Mo-based materials is a“double-edged sword”,which endows the material with excellent stability,but limits its chemical versatility and application in electrochemical hydrogen evolution reaction(HER).Carbon doping engineering is an attractive strategy to effectively improve the performance of Mo-based catalyst and maintain their stability.Herein,we report a cross-linked porous carbon-doped MoO_(2)(C–MoO_(2))-based catalyst Ru/C–MoO_(2) for electrochemical HER,which is prepared by the convenient redox solid-phase reaction(SPR)of porous RuO_(2)/Mo_(2)C composite precursor.Theoretical studies reveal that due to the presence of carbon atoms,the electronic structure of C–MoO_(2) has been properly adjusted,and the loaded small Ru nanoparticles provide a fast water dissociation rate and moderate H adsorption strength.In electrochemical studies under a pH-universal environment,Ru/C–MoO_(2) electrocatalyst exhibits a low overpotential at a current density of 10 mA cm^(-2) and has a low Tafel slope.Meanwhile,Ru/C-MoO_(2) has excellent stability for more than 100 h at an initial current density of 100 mA cm^(-2).展开更多
Bismuth-based compounds with high capacity and durability are still challenging in Li-ion batteries(LIBs).In this article,Bi_(2)S_(3)nanorods hosted on reduced graphene oxide nanosheets(Bi_(2)S_(3)/rGO,BSG)are success...Bismuth-based compounds with high capacity and durability are still challenging in Li-ion batteries(LIBs).In this article,Bi_(2)S_(3)nanorods hosted on reduced graphene oxide nanosheets(Bi_(2)S_(3)/rGO,BSG)are successfully prepared using molecular precursor pyrolysis strategy.1D nanorod architecture possesses preeminent kinetic characteristics,shortening the ion diffusion path and increasing the contact area between electrode and electrolyte.The large specific surface area and charge polarization of rGO at the interface promote charge transfer.The capacity of material(BSG-400)reaches 558.4 m Ah g^(-1)at 0.2 A g^(-1)after 200 cycles.The anode properties of the composite outperform those of pristine Bi_(2)S_(3).The introduction of graphene enables the interfacial interaction between rGO and Bi_(2)S_(3).The closely contact interface improves the conductivity and lithium storage performances of Bi_(2)S_(3).The regulatory effect of rGO on the electronic density of states and band gap of Bi_(2)S_(3)has been demonstrated by theoretical calculation.The synthetic approach has the advantages of universality,simple operation procedure,and strong repeatability.This research provides some ideas for the preparation of other metal sulfides/rGO nanomaterials and their application in battery research.展开更多
Boron hydrides release an abundant amount of hydrogen in the presence of a suitable catalyst.Accelerating bimolecular activation kinetics is the key to designing cost-effective catalysts for borohydride hydrolysis.In ...Boron hydrides release an abundant amount of hydrogen in the presence of a suitable catalyst.Accelerating bimolecular activation kinetics is the key to designing cost-effective catalysts for borohydride hydrolysis.In this study,the bimolecular activation of a polar O-Co-P site demonstrated superior hydrogen-generation kinetics(turnover frequency,TOF=37 min−1,298 K)and low activation energy(41.0 kJ mol^(−1))close to that of noble-metal-based catalysts.Through a combination of experiments and theoretical calculations,it was revealed that the activated dangling oxygen atom in the Co–O precursor effectively replaced via surface-phosphorization because of strong electronic interactions between the dangling oxygen and P atoms.This substitution modulated the local coordination environment and electronegativity around the surface Co sites and formed a new polar O-Co-P active site for optimizing the activation kinetics of ammonia borane and water.This strategy based on bimolecular activation may create new avenues in the field of catalysis.展开更多
In this paper, we demonstrate a color tunable white organic light-emitting devices （WOLEDs） based on the two complementary color strategies by introducing two-dimensional （2-D） dual periodic gratings. It is possib...In this paper, we demonstrate a color tunable white organic light-emitting devices （WOLEDs） based on the two complementary color strategies by introducing two-dimensional （2-D） dual periodic gratings. It is possible to tune the color in a range between cold-white and warmwhite by simply operating the polarization of polarizer in front of the microstructured WOLEDs. Experimental and numerical results demonstrate that color tunability of the WOLEDs comes from the effect of the 2-D dual periodic gratings by exciting the surface plasmon-polariton （SPP） resonance associated with the cathode/organic interface. The electroluminescence （EL） performance of the WOLEDs have also been improved due to the effective light extraction by excitation and out-coupling of the SPP modes, and a 39.65% enhancement of current efficiency has been obtained compared to the conventional planar devices.展开更多
Due to the abuse of antibiotics,antibiotic residues can be detected in both natural environment and various industrial products,posing threat to the environment and human health.Here we describe the design and impleme...Due to the abuse of antibiotics,antibiotic residues can be detected in both natural environment and various industrial products,posing threat to the environment and human health.Here we describe the design and implementation of an engineered Escherichia coli capable of degrading tetracycline(Tc)-one of the commonly used antibiotics once on humans and now on poultry,cattle and fisheries.A Tcdegrading enzyme,TetX,from the obligate anaerobe Bacteroides fragilis was cloned and recombinantly expressed in E.coli and fully characterized,including its Km and kcat value.We quantitatively evaluated its activity both in vitro and in vivo by UVeVis spectrometer and LC-MS.Moreover,we used a tetracycline inducible amplification circuit including T7 RNA polymerase and its specific promoter PT7 to enhance the expression level of TetX,and studied the dose-response of TetX under different inducer concentrations.Since the deployment of genetically modified organisms(GMOs)outside laboratory brings about safety concerns,it is necessary to explore the possibility of integrating a kill-switch.Toxin-Antitoxin(TA)systems were used to construct a mutually dependent host-plasmid platform and biocontainment systems in various academic and industrious situations.We selected nine TA systems from various bacteria strains and measured the toxicity of toxins(T)and the detoxifying activity of cognate antitoxins(A)to validate their potential to be used to build a kill-switch.These results prove the possibility of using engineered microorganisms to tackle antibiotic residues in environment efficiently and safely.展开更多
Human mobility trajectories are fundamental resources for analyzing mobile behaviors in urban computing applications.However,these trajectories,typically collected from location-based services,often suffer from sparsi...Human mobility trajectories are fundamental resources for analyzing mobile behaviors in urban computing applications.However,these trajectories,typically collected from location-based services,often suffer from sparsity and irregularity in time.To support the development of mobile applications,there is a need to recover or estimate missing locations of unobserved time slots in these trajectories at a fine-grained spatial–temporal resolution.Existing methods for trajectory recovery rely on either individual user trajectories or collective mobility patterns from all users.The potential to combine individual and collective patterns for precise trajectory recovery remains unexplored.Additionally,current methods are sensitive to the heterogeneous temporal distributions of the observable trajectory segments.In this paper,we propose CLMove(where CL stands for contrastive learning),a novel model designed to capture multilevel mobility patterns and enhance robustness in trajectory recovery.CLMove features a two-stage location encoder that captures collective and individual mobility patterns.The graph neural network based networks in CLMove explore location transition patterns within a single trajectory and across various user trajectories.We also design a trajectory-level contrastive learning task to improve the robustness of the model.Extensive experimental results on three representative real-world datasets demonstrate that our CLMove model consistently outperforms state-of-the-art methods in terms of trajectory recovery accuracy.展开更多
基金financially supported by the National Natural Science Foundation of China(21774041 and 51433003)the China Postdoctoral Science Foundation(2018M640681 and 2019T120632)。
文摘Ammonia borane(AB)is an excellent candidate for the chemical storage of hydrogen.However,its practical utilization for hydrogen production is hindered by the need for expensive noble-metal-based catalysts.Herein,we report Co-Co3O4 nanoparticles(NPs)facilely deposited on carbon dots(CDs)as a highly efficient,robust,and noble-metal-free catalyst for the hydrolysis of AB.The incorporation of the multiinterfaces between Co,Co3O4 NPs,and CDs endows this hybrid material with excellent catalytic activity(rB=6816 mLH2 min^-1 gCo^-1)exceeding that of previous non-noble-metal NP systems and even that of some noble-metal NP systems.A further mechanistic study suggests that these interfacial interactions can affect the electronic structures of interfacial atoms and provide abundant adsorption sites for AB and water molecules,resulting in a low energy barrier for the activation of reactive molecules and thus substantial improvement of the catalytic rate.
基金supported by National Natural Science Foundation of China(No.61572084)the National Key Research and Development Program of China(2017ZX05030-005,2019D-4413).
文摘The lifting efficiency and stability of gas lift well are affected by the socalled slippage-loss effect in gas-liquid two-phase flow.The existing studies on this subject have generally been based on vertical and horizontal wells.Only a few of them have considered inclined pipes.In the present work a new focused study is presented along these lines.More specifically,we use the non-slip pressure drop model with Flanigan’s fluctuation correction coefficient formula(together with the parameters of slippage density,slippage pressure drop and slippage ratio)to analyze the influence of the inclination angle on slippage loss for different conditions(different gas-liquid superficial velocity and pipe diameters).Moreover,the“standard regression coefficient method”is used for multi-factor sensitivity analysis.The experimental results indicate that slippage loss is affected by multiple factors,and the influence of the inclination angle on slippage loss is less significant than other factors.The change of the slippage pressure drop with the superficial velocity of gas-liquid is similar to that of the total pressure drop.The inclination angles of 45°and 60°have the greatest influence on slippage loss.The correlation between slippage density and slippage ratio is not obvious.Using the so-called slippage ratio seems to be a more accurate option to evaluate the degree of slippage loss.
基金supported by the grants from the Research Grants Council of the Hong Kong Special Administrative Region,China (Project No. 16205721)Guangdong Basic and Applied Basic Research Foundation (Project No.2021A1515011815)Poly U Start-up Fund (Project No. 1-BDC4)。
文摘Water electrolysis is considered as one most promising technique for hydrogen production.The high efficiency electrocatalyst is the key to accelerating the sluggish kinetics of the hydrogen evolution reaction(HER) in alkaline media.In this work,an efficient HER electrocatalyst with hetero-interfacial metal-metal oxide structure was constructed through a redox solid phase reaction(SPR) strategy.During the annealing process under Ar atmosphere,RuO_(2) and WS_(2)in RuO_(2)/WS_(2)precursor were converted to Ru nanoparticles(NPs) and WO3in situ,where tiny Ru NPs and oxygen vacancies were uniformly distributed onto the newly formed WO3nanosheets.Different characterization techniques were adopted to confirm the successful formation of Ru/WO_(3)electrocatalyst(RWOC).The optimized RWOC sample annealed at 400℃ exhibited the low overpotential value of 13 mV at a current density of 10 mA cm^(-2)and strong durability under the alkaline condition.Density functional theoretical calculations further revealed that the promoted adsorption/desorption rate of reaction intermediates and the accelerated kinetics of HER process were deduced to the synergistic effect between Ru and WO_(3)in electrocatalyst.This work provides a feasible method to fabricate highly efficient HER electrocatalysts.
基金This work was financially supported by the National Natural Science Foundation of China (52122308,21905253,51973200)the Natural Science Foundation of Henan (202300410372).
文摘The defect-free structure of Mo-based materials is a“double-edged sword”,which endows the material with excellent stability,but limits its chemical versatility and application in electrochemical hydrogen evolution reaction(HER).Carbon doping engineering is an attractive strategy to effectively improve the performance of Mo-based catalyst and maintain their stability.Herein,we report a cross-linked porous carbon-doped MoO_(2)(C–MoO_(2))-based catalyst Ru/C–MoO_(2) for electrochemical HER,which is prepared by the convenient redox solid-phase reaction(SPR)of porous RuO_(2)/Mo_(2)C composite precursor.Theoretical studies reveal that due to the presence of carbon atoms,the electronic structure of C–MoO_(2) has been properly adjusted,and the loaded small Ru nanoparticles provide a fast water dissociation rate and moderate H adsorption strength.In electrochemical studies under a pH-universal environment,Ru/C–MoO_(2) electrocatalyst exhibits a low overpotential at a current density of 10 mA cm^(-2) and has a low Tafel slope.Meanwhile,Ru/C-MoO_(2) has excellent stability for more than 100 h at an initial current density of 100 mA cm^(-2).
基金Financial supports from the National Natural Science Foundation of China(no.21401168)Dalian Institute of Chemical Physics(no.N-19-11)
文摘Bismuth-based compounds with high capacity and durability are still challenging in Li-ion batteries(LIBs).In this article,Bi_(2)S_(3)nanorods hosted on reduced graphene oxide nanosheets(Bi_(2)S_(3)/rGO,BSG)are successfully prepared using molecular precursor pyrolysis strategy.1D nanorod architecture possesses preeminent kinetic characteristics,shortening the ion diffusion path and increasing the contact area between electrode and electrolyte.The large specific surface area and charge polarization of rGO at the interface promote charge transfer.The capacity of material(BSG-400)reaches 558.4 m Ah g^(-1)at 0.2 A g^(-1)after 200 cycles.The anode properties of the composite outperform those of pristine Bi_(2)S_(3).The introduction of graphene enables the interfacial interaction between rGO and Bi_(2)S_(3).The closely contact interface improves the conductivity and lithium storage performances of Bi_(2)S_(3).The regulatory effect of rGO on the electronic density of states and band gap of Bi_(2)S_(3)has been demonstrated by theoretical calculation.The synthetic approach has the advantages of universality,simple operation procedure,and strong repeatability.This research provides some ideas for the preparation of other metal sulfides/rGO nanomaterials and their application in battery research.
基金H.Z.and K.Z.contributed equally to this work.Financial supports from the National Natural Science Foundation of China (nos.22075254,52071135,51871090,U1804135,21805071,51671080,and 21401168)Plan for Scientific Inno-vation Talent of Henan Province (no.194200510019)Key Project of Educa-tional Commission of Henan Province (no.19A150025)are acknowledged.
文摘Boron hydrides release an abundant amount of hydrogen in the presence of a suitable catalyst.Accelerating bimolecular activation kinetics is the key to designing cost-effective catalysts for borohydride hydrolysis.In this study,the bimolecular activation of a polar O-Co-P site demonstrated superior hydrogen-generation kinetics(turnover frequency,TOF=37 min−1,298 K)and low activation energy(41.0 kJ mol^(−1))close to that of noble-metal-based catalysts.Through a combination of experiments and theoretical calculations,it was revealed that the activated dangling oxygen atom in the Co–O precursor effectively replaced via surface-phosphorization because of strong electronic interactions between the dangling oxygen and P atoms.This substitution modulated the local coordination environment and electronegativity around the surface Co sites and formed a new polar O-Co-P active site for optimizing the activation kinetics of ammonia borane and water.This strategy based on bimolecular activation may create new avenues in the field of catalysis.
基金The authors gratefully acknowledge support from the National Basic Research Program of China （973 Program） （No. 2013CBA01700）, the National Natural Science Foundation of China （NSFC） （Grant Nos. 61322402, 91233123 and 61177024）.
文摘In this paper, we demonstrate a color tunable white organic light-emitting devices （WOLEDs） based on the two complementary color strategies by introducing two-dimensional （2-D） dual periodic gratings. It is possible to tune the color in a range between cold-white and warmwhite by simply operating the polarization of polarizer in front of the microstructured WOLEDs. Experimental and numerical results demonstrate that color tunability of the WOLEDs comes from the effect of the 2-D dual periodic gratings by exciting the surface plasmon-polariton （SPP） resonance associated with the cathode/organic interface. The electroluminescence （EL） performance of the WOLEDs have also been improved due to the effective light extraction by excitation and out-coupling of the SPP modes, and a 39.65% enhancement of current efficiency has been obtained compared to the conventional planar devices.
基金the National Key R&D Program of China(2016YFA0501502,2016YFA0502400)the National Science Foundation of China(91313301,21325211)。
文摘Due to the abuse of antibiotics,antibiotic residues can be detected in both natural environment and various industrial products,posing threat to the environment and human health.Here we describe the design and implementation of an engineered Escherichia coli capable of degrading tetracycline(Tc)-one of the commonly used antibiotics once on humans and now on poultry,cattle and fisheries.A Tcdegrading enzyme,TetX,from the obligate anaerobe Bacteroides fragilis was cloned and recombinantly expressed in E.coli and fully characterized,including its Km and kcat value.We quantitatively evaluated its activity both in vitro and in vivo by UVeVis spectrometer and LC-MS.Moreover,we used a tetracycline inducible amplification circuit including T7 RNA polymerase and its specific promoter PT7 to enhance the expression level of TetX,and studied the dose-response of TetX under different inducer concentrations.Since the deployment of genetically modified organisms(GMOs)outside laboratory brings about safety concerns,it is necessary to explore the possibility of integrating a kill-switch.Toxin-Antitoxin(TA)systems were used to construct a mutually dependent host-plasmid platform and biocontainment systems in various academic and industrious situations.We selected nine TA systems from various bacteria strains and measured the toxicity of toxins(T)and the detoxifying activity of cognate antitoxins(A)to validate their potential to be used to build a kill-switch.These results prove the possibility of using engineered microorganisms to tackle antibiotic residues in environment efficiently and safely.
基金supported by the National Natural Science Foundation of China(Nos.62072115 and 61971145)the Shanghai Science and Technology Innovation Action Plan Project,China(No.22510713600)。
文摘Human mobility trajectories are fundamental resources for analyzing mobile behaviors in urban computing applications.However,these trajectories,typically collected from location-based services,often suffer from sparsity and irregularity in time.To support the development of mobile applications,there is a need to recover or estimate missing locations of unobserved time slots in these trajectories at a fine-grained spatial–temporal resolution.Existing methods for trajectory recovery rely on either individual user trajectories or collective mobility patterns from all users.The potential to combine individual and collective patterns for precise trajectory recovery remains unexplored.Additionally,current methods are sensitive to the heterogeneous temporal distributions of the observable trajectory segments.In this paper,we propose CLMove(where CL stands for contrastive learning),a novel model designed to capture multilevel mobility patterns and enhance robustness in trajectory recovery.CLMove features a two-stage location encoder that captures collective and individual mobility patterns.The graph neural network based networks in CLMove explore location transition patterns within a single trajectory and across various user trajectories.We also design a trajectory-level contrastive learning task to improve the robustness of the model.Extensive experimental results on three representative real-world datasets demonstrate that our CLMove model consistently outperforms state-of-the-art methods in terms of trajectory recovery accuracy.
