M 2 tide and density residual currents in the Bohai Sea were examined using the Blumberg and Mellor 3D nonlinear numerical coastal circulation model incorporating Mellor and Yamada level 2.5 turbulent closure model. T...M 2 tide and density residual currents in the Bohai Sea were examined using the Blumberg and Mellor 3D nonlinear numerical coastal circulation model incorporating Mellor and Yamada level 2.5 turbulent closure model. The tidal results showed good agreement with previous work. The model results indicated that the density residual currents are robust in summer; and that at the transition zone between well-mixed and stratified water, the horizontal velocity is high and the vertical velocity is positive.展开更多
The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-...The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.展开更多
Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5...Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.展开更多
Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence...Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence of ultraviolet(UV)and electromagnetic wave radiation,the results indicate that the BAM target may undergo luminescent excitation due to collisions with electrons and ions.This led us to investigate the physical mechanism behind this plasma luminescence excitation phenomenon.A spectrometer was used to record the luminescent spectroscopy and peak light intensity.Under excitation by argon plasma,the BAM material emits a continuum spectrum from 400 nm to 550 nm,with the peak light intensity located at 462.58 nm,which is the same as the spectrum excited by UV torchlight.To identify the relationship between the plasma parameters and the luminescent intensity,Langmuir and Faraday probes were employed to determine the local plasma parameters such as electron density,electron temperature,and current density.After normalizing the peak light intensity to the plasma parameters,the most interesting point is that the current density is linearly correlated with the luminescent light intensity.To verify the repeatability and lifetime of the plasma-luminescence interaction,a 600 s lifetime test was conducted in a 200 W ICP discharge environment.The maximum difference for the peak light strength of the luminescent spectrum is 6.5%.From a voltage bias experiment and a theoretical derivation,we initially identified that bombardment by ions plays the dominant role in the luminescence excitation process,which also explains the mechanism by which the current density is proportional to the luminescence intensity.This new finding leads us to reconsider the possibility of applying this plasma luminescence phenomenon to optical plasma diagnostics.The BAM light intensity can potentially be used to predict the current density of a plasma beam for large-area two-dimensional(2D)measurements and can capture high spatial resolution in a single test.We believe that this method may lead to high-efficiency,spatially resolved plasma current density measurement.展开更多
The development of high-performance electrocatalysts with rapid mass and charge transfer for the hydrogen evolution reaction(HER)at high current densities is critical to enabling practical hydrogen production via alka...The development of high-performance electrocatalysts with rapid mass and charge transfer for the hydrogen evolution reaction(HER)at high current densities is critical to enabling practical hydrogen production via alkaline water electrolysis(AWE).Currently,important research advancements have been made in the rational design of ruthenium(Ru)-based electrocatalysts,aiming to satisfy the performance requirements of large-scale electrochemical hydrogen production.A timely summary of recent advances is pivotal for designing next-generation Ru-based electrocatalysts.Herein,we systematically examine key strategies for optimizing their electronic effect and water/bubble behaviors,alongside detailed discussions on recent breakthroughs in integrated Ru-based AWE systems.Furthermore,we outline the remaining bottlenecks and future directions for deploying Ru-based electrocatalysts in commercial applications.展开更多
Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of ac...Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of active sites caused by the blocked mass/charge transportation at this condition.Herein,we present a freestanding lamellar nanoporous Ni-Co-Mn alloy electrode(Lnp-NCM)designed by a refined variant of the“dealloying-coarsening-dealloying”protocol for highly efficient bifunctional electrocatalyst,where large porous channels distribute on the surface and small porous channels at the interlayer.With its 3D lamellar architecture regulating,the electrocatalytic properties of the electrodes with different distances between lamellas are compared,and faster energy conversion kinetics is achieved with efficient bubble transport channels and abundant electroactive sites.Note that the optimized sample(Lnp-NCM4)is expected to be a potential bifunctional electrocatalyst with low overpotentials of 258 and 439 mV at high current densities of 1000 and 900 mA·cm^(-2)for hydrogen and oxygen evolution reactions(HER and OER),respectively.During overall water splitting in a two-electrode cell with Lnp-NCM4 as cathode and anode,it only needs an ultralow cell voltage of 1.75 V to produce 100 mA·cm^(-2)with remarkable long-term stability over 50 h.This study on lamellar nanoporous electrode design approaches industrial water splitting requirements and paves a way for developing other catalytic systems.展开更多
Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance i...Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance is often limited by charge carrier recombination,resulting in unsatisfactory saturation current densities.To address this challenge,we present a novel strategy for achieving ultrahigh current density by incorporating a bridge layer between the Si substrate and the NiOOH cocatalyst in this paper.The optimal photoanode(TCO/n-p-Si/TCO/Ni)shows a remarkably low onset potential of 0.92 V vs.a reversible hydrogen electrode and a high saturation current density of 39.6 mA·cm^(-2),which is about 92.7%of the theoretical maximum(42.7 mA·cm^(-2)).In addition,the photoanode demonstrates stable operation for 60 h.Our systematic characterizations and calculations demonstrate that the bridge layer facilitates charge transfer,enhances catalytic performance,and provides corrosion protection to the underlying substrate.Notably,the integration of this photoanode into a PEC device for overall water splitting leads to a reduction of the onset potential.These findings provide a viable pathway for fabricating highperformance industrial photoelectrodes by integrating a substrate and a cocatalyst via a transparent and conductive bridge layer.展开更多
The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited ...The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited a high formate Faradaic efficiency(FE)of 97.45%(-0.9 V)and a large partial current density of-45.82 mA/cm^(2)(-1.2 V).The good performance benefits from the reconstruction of BiVO_(4)to generate active metal Bi sites,which results in the electron redistribution to boost the OCHO∗formation.In flow cells,near industrial current density of 183.94 mA/cm^(2)was achieved,with the FE of formate above 95%from 20mA/cm^(2)to 180mA/cm^(2).Our work provides a facily synthesized BiVO_(4)precatalyst for CO_(2)electroreduction.展开更多
A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate...A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate the equilibrium current density in a ribbon-shaped system within the AHE regime,consisting of two sets of counterpropagating channels arranged in a zebra stripes pattern.While the middle channels are susceptible to scattering,the edge channels remain relatively robust.Despite this difference,all channels exhibit the same differential current density when subjected to a differential voltage across the two ends of the ribbon.When a differential voltage is applied to both sides of the ribbon,it results in a snaking pattern of differential current density forming across it.Furthermore,in a four-terminal device comprising the ribbon and two normal leads,it is found that Hall conductance is independent of ribbon width within certain scattering strengths due to the differences in robustness between middle and edge channels.These findings disclose the details of the AHE transport in a finite-sized system under weak scattering.展开更多
Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/mo...Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/molybdenum nitride rod-shaped structures(denoted Co/Mo_(2)N)via ammonia-assisted reduction,which effectively modulating the HER performance.The optimized Co/Mo_(2)N-500,characterized by 3%tensile lattice strain,demonstrates exceptional HER activity with lower overpotentials of140 mV and 184 mV at high current density of 1000 mA cm^(-2)in alkaline freshwater and seawater electrolytes,respectively.Co/Mo_(2)N also exhibits excellent long-term durability even at a high current density of 300 mA cm^(-2),surpassing its counterparts and benchmark Pt/C catalyst.Density functional theory calculations validate that the tensile strain optimizes the d-band states,water dissociation,and hydrogen adsorption kinetics of the strained Mo_(2)N in Co/Mo_(2)N,thereby improving its catalytic efficacy.This work provides valuable insights into controlling lattice strain to develop highly efficient electrocatalysts towards advanced electrocatalytic applications.展开更多
Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density o...Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.展开更多
Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique...Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique. The effects of current density on the chemical composition, electrocatalytic activity, and stability of the composite anode material were investigated by energy dispersive X-ray spectroscopy（EDXS）, anode polarization curves, quasi-stationary polarization（Tafel） curves, electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM）, and X-ray diffraction（XRD）. Results reveal that the composite electrode obtained at 1 A/dm2 possesses the lowest overpotential（0.610 V at 500 A/m2） for oxygen evolution, the best electrocatalytic activity, the longest service life（360 h at 40 °C in 150 g/L H2SO4 solution under 2 A/cm2）, and the lowest cell voltage（2.75 V at 500 A/m2）. Furthermore, with increasing current density, the coating exhibits grain growth and the decrease of content of Mn O2. Only a slight effect on crystalline structure is observed.展开更多
AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer betwee...AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer between GaAs layers, potential wells beside the two sides of barrier are deepened, resulting in an increase of the peak-to-valley current ratio （PVCR） and a peak current density. A special shape of collector is designed in order to reduce contact resistance and non-uniformity of the current;as a result the total chrrent density in the device is increased. The use of thin barriers is also helpful for the improvement of the PVCR and the peak current density in DBRTDs. The devices exhibit a maximum PVCR of 13.98 and a peak current density of 89kA/cm^2 at room temperature.展开更多
The electrocatalytic reduction of nitrate to ammonia(NO_(3)^(−)RR)offers a sustainable alternative to energy-intensive industrial NH3 synthesis.Tandem catalysis has shown promise in overcoming the multi-step complexit...The electrocatalytic reduction of nitrate to ammonia(NO_(3)^(−)RR)offers a sustainable alternative to energy-intensive industrial NH3 synthesis.Tandem catalysis has shown promise in overcoming the multi-step complexity of NO_(3)^(−)RR,yet challenges remain in optimizing performance and elucidating tandem mechanisms.Herein,we report a Cu@Co/CoFe-P tandem electrocatalyst featuring a phosphorus-doped heterostructure with dual active sites(Cu-P and Co/CoFe-P).This catalyst achieves an exceptional NH_(3)yield of 175.40 mg h^(−1)cm^(−2)and a record-high current density exceeding 2 A cm^(−2),with the electro-synthesized NH3 directly converted into NH4Cl.In situ spectroscopic analysis and density functional theory(DFT)calculations reveal a novel desorption-reactivation tandem mechanism:(1)the Cu-P domain preferentially reduces NO_(3)^(−)to*NO_(2),which desorbs as stable NO_(2)^(−);(2)the Co/CoFe-P domain subsequently reactivates NO_(2)^(−),and converts it efficiently into NH3.Moreover,phosphorus doping enhances*H supply,while Fe alloying with Co promotes NO_(2)^(−)hydrogenation,ensuring an efficient and synchronized tandem pathway for NO_(3)^(−)RR.The proposed*NO_(2)desorption-reactivation mechanism deepens the understanding of NO_(3)^(−)RR tandem process,thereby paving the way for designing more efficient tandem electrocatalysts.展开更多
The metallic Ni catalyst suffers from strong binding with the*CO intermediate,resulting in poisoning of the catalyst surface.It is feasible to facilitate the generation of CO by alleviating the binding strength of the...The metallic Ni catalyst suffers from strong binding with the*CO intermediate,resulting in poisoning of the catalyst surface.It is feasible to facilitate the generation of CO by alleviating the binding strength of the*CO intermediate on the Ni metal surface through a lattice expansion strategy.Here,Ni_(3)ZnC_(0.7)@C with lattice expansion was synthesized by co-doping with Zn and interstitial C through high-temperature pyrolysis.Structural characterization confirms that the lattice of Ni_(3)ZnC_(0.7)expands by 5.47%compared to Ni due to the co-doping of Zn and interstitial C.The Ni_(3)ZnC_(0.7)@C possesses excellent catalytic performance with Faradaic efficiency(FE)of CO exceeding 90%over a wide potential range from−0.8 to−1.4 V versus reversible hydrogen electrode(vs.RHE)with a peak FECO of 96.6%at−1.0 V vs.RHE.In membrane electrode assembly(MEA)testing,Ni_(3)ZnC_(0.7)@C achieves a FECO of 81.4%at the industrial-level current density of 400 mA cm^(−2).In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS)and density functional theory(DFT)calculations reveal that the co-introduction of Zn and interstitial C in the Ni crystal can significantly promote the desorption of*CO intermediate,which facilitates the generation of CO.This study demonstrates a viable way for designing efficient transition metal catalysts for CO_(2)electroreduction through lattice strain engineering.展开更多
Economical,stable,and corrosion-resistant catalytic electrodes are still urgently needed for the oxygen evolution reaction(OER)in water and seawater.Herein,a mild electroless plating strategy is used to achieve large-...Economical,stable,and corrosion-resistant catalytic electrodes are still urgently needed for the oxygen evolution reaction(OER)in water and seawater.Herein,a mild electroless plating strategy is used to achieve large-scale preparation of the“integrated”phosphorus-based precatalyst(FeP-NiP)on nickel foam(NF),which is in situ reconstructed into a highly active and corrosion-resistant(Fe)NiOOH phase for OER.The interaction between phosphate anions(PO_(x)^(y-))and iron ions(Fe^(3+))tunes the electronic structure of the catalytic phase to further enhance OER kinetics.The integrated FeP-NiP@NF electrode exhibits low overpotentials for OER in alkaline water/seawater,requiring only 275/289,320/336,and 349/358 mV to reach 0.1,0.5,and 1.0 A cm^(−2),respectively.The in situ reconstructed PO_(x)^(y-)anion electrostatically repels Cl−in seawater electrolytes,allowing stable operation for over 7 days at 1.0 A cm^(−2) in extreme electrolytes(1.0 M KOH+seawater and 6.0 M KOH+seawater),demonstrating industrial-level stability.This study overcomes the complex synthesis limitations of P-based materials through innovative material design,opening new avenues for electrochemical energy conversion.展开更多
The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly...The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly monsoon in summer induces a clockwise circulation in the Beibu Gulf, and the density gradient induces a counter-clockwise one; but the density current is more intense than the wind- driven one in summer, espeially in surface layer. In addition, the northeasterly monsoon in winter in- duces a counter-clockwise circulation. The simulated results don't support the traditional condusion that there is a clockwise circulation in the Beibu Gulf in summer and a counter-clockwise one in winter, but support the statement that a counterclockwise circulation exists in the Beibu Gulf all year round.展开更多
Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxid...Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.展开更多
Developing highly effective and stable non-noble metalbased bifunctional catalyst working at high current density is an urgent issue for water electrolysis(WE).Herein,we prepare the N-doped graphene-decorated NiCo all...Developing highly effective and stable non-noble metalbased bifunctional catalyst working at high current density is an urgent issue for water electrolysis(WE).Herein,we prepare the N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet grown on 3D nickel foam(NiCo@C-NiCoMoO/NF)for water splitting.NiCo@C-NiCoMoO/NF exhibits outstanding activity with low overpotentials for hydrogen and oxygen evolution reaction(HER:39/266 mV;OER:260/390 mV)at±10 and±1000 mA cm^(−2).More importantly,in 6.0 M KOH solution at 60℃ for WE,it only requires 1.90 V to reach 1000 mA cm−2 and shows excellent stability for 43 h,exhibiting the potential for actual application.The good performance can be assigned to N-doped graphene-decorated NiCo alloy and mesoporous NiCoMoO nano-sheet,which not only increase the intrinsic activity and expose abundant catalytic activity sites,but also enhance its chemical and mechanical stability.This work thus could provide a promising material for industrial hydrogen production.展开更多
In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed ...In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed void shapes: circular, ellipse, and cardioid. Void morphological evolution is governed by the competition between the electric field and surface capillary force. In the developed model, both the electric field and capillary force on the void's surface are solved analytically. Based on the mass conversation principle, the normal velocity on the void surface during diffusion is obtained. The void morphological evolution behavior is investigated, and a physical model is developed to predict void collapse to a crack or to split into sub-voids under electric current. It is noted that when the electric current is being applied from the horizontal direction, a circular void may either move stably along the electric current direction or collapse to a finger shape, depending on the relative magnitude of the electric current and surface capillary force. However, the elliptical-shaped void will elongate along the electric current direction and finally collapse to the finger shape. On the other hand, the cardioid-shaped void could bifurcate into two sub-voids when the electric current reaches a critical value. The theoretical predictions agree well with the experimental observations.展开更多
文摘M 2 tide and density residual currents in the Bohai Sea were examined using the Blumberg and Mellor 3D nonlinear numerical coastal circulation model incorporating Mellor and Yamada level 2.5 turbulent closure model. The tidal results showed good agreement with previous work. The model results indicated that the density residual currents are robust in summer; and that at the transition zone between well-mixed and stratified water, the horizontal velocity is high and the vertical velocity is positive.
基金sponsored by the National Natural Science Foundation of China(Nos.5210125 and 52375422)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069,B2020208083 and E202320801).
文摘The stability and electrocatalytic efficiency of transition metal oxides for water splitting is determined by geometric and electronic structure,especially under high current densities.Herein,a newly designed lamella-heterostructured nanoporous CoFe/CoFe_(2)O_(4) and CeO_(2−x),in situ grown on nickel foam(NF),holds great promise as a high-efficient bifunctional electrocatalyst(named R-CoFe/Ce/NF)for water splitting.Experimental characterization verifies surface reconstruction from CoFe alloy/oxide to highly active CoFeOOH during in situ electrochemical polarization.By virtues of three-dimensional nanoporous architecture and abundant electroactive CoFeOOH/CeO_(2−x) heterostructure interfaces,the R-CoFe/Ce/NF electrode achieves low overpotentials for oxygen evolution(η_(10)=227 mV;η_(500)=450 mV)and hydrogen evolution(η_(10)=35 mV;η_(408)=560 mV)reactions with high normalized electrochemical active surface areas,respectively.Additionally,the alkaline full water splitting electrolyzer of R-CoFe/Ce/NF||R-CoFe/Ce/NF achieves a current density of 50 mA·cm^(−2) only at 1.75 V;the decline of activity is satisfactory after 100-h durability test at 300 mA·cm^(−2).Density functional theory also demonstrates that the electron can transfer from CeO_(2−x) by virtue of O atom to CoFeOOH at CoFeOOH/CeO_(2−x) heterointerfaces and enhancing the adsorption of reactant,thus optimizing electronic structure and Gibbs free energies for the improvement of the activity for water splitting.
基金supported by the National Natural Science Foundation of China(Nos.52305349,52305423 and 51635005)CGN-HIT Advanced Nuclear and New Energy Research Institute(No.CGN-HIT202305).
文摘Electrically assisted forming(EAF)is a reliable method of reducing the deformation resistance of metallic materials and enhancing their formability.In this study,the mechanical properties and microstructure of Al_(0.5)CoCrFeNi high-entropy alloy(HEA)under electrically assisted compression(EAC)were investigated.The results showed that the flow stress decreased with increasing current density in the EAC.Specifically,the flow curves exhibited S-shaped softening at a higher current density,which was dominated by the non-uniform distribution of the Joule heating temperature during EAC.When the flow stress was fixed at 500 MPa and 80 A·mm^(−2),compressible deformation amounts of 63.7%were observed at a strain rate of 1 s−1,indicating full compression of Al_(0.5)CoCrFeNi HEA at low-stress levels.Based on the microstructure,the flowability of Al_(0.5)CoCrFeNi HEA was improved during EAC,and the flow direction shifted from 45°to the horizontal direction.The current density,which influences the Joule heating temperature and strain rate,synergistically affects the stacking fault energy(SFE)and critical resolved shear stress(CRSS),which affect the tendency for twinning behavior.Thererfore,deformation nanoscale twins(DTs)were observed,indicating a shift in the deformation mechanisms from dislocation slip domination to a mixed pattern of dislocation slip and twinning.This study confirmed the deformability of Al_(0.5)CoCrFeNi HEA during EAC and provided an experimental foundation and theoretical support for the formation of HEAs.
基金partly supported by National Natural Science Foundation of China(Nos.52302464 and 52177128)supported by the Key Scientific Research Project for Institutions of Higher Education of Henan Province(No.22B140002).
文摘Recently,it has been observed that during the operation of an inductively coupled plasma(ICP),a luminescent target(BAM,BaMgAl10O17:Eu)can interact with the plasma beam and emit blue light.After excluding the influence of ultraviolet(UV)and electromagnetic wave radiation,the results indicate that the BAM target may undergo luminescent excitation due to collisions with electrons and ions.This led us to investigate the physical mechanism behind this plasma luminescence excitation phenomenon.A spectrometer was used to record the luminescent spectroscopy and peak light intensity.Under excitation by argon plasma,the BAM material emits a continuum spectrum from 400 nm to 550 nm,with the peak light intensity located at 462.58 nm,which is the same as the spectrum excited by UV torchlight.To identify the relationship between the plasma parameters and the luminescent intensity,Langmuir and Faraday probes were employed to determine the local plasma parameters such as electron density,electron temperature,and current density.After normalizing the peak light intensity to the plasma parameters,the most interesting point is that the current density is linearly correlated with the luminescent light intensity.To verify the repeatability and lifetime of the plasma-luminescence interaction,a 600 s lifetime test was conducted in a 200 W ICP discharge environment.The maximum difference for the peak light strength of the luminescent spectrum is 6.5%.From a voltage bias experiment and a theoretical derivation,we initially identified that bombardment by ions plays the dominant role in the luminescence excitation process,which also explains the mechanism by which the current density is proportional to the luminescence intensity.This new finding leads us to reconsider the possibility of applying this plasma luminescence phenomenon to optical plasma diagnostics.The BAM light intensity can potentially be used to predict the current density of a plasma beam for large-area two-dimensional(2D)measurements and can capture high spatial resolution in a single test.We believe that this method may lead to high-efficiency,spatially resolved plasma current density measurement.
基金National Natural Science Foundation of China(22472049)Natural Science Foundation of Wuhan(2024040801020308)+3 种基金Postdoctor Project of Hubei Province(2024HBBHCXB001)China Postdoctoral Science Foundation(2024M750846)Provincial Natural Science Foundation of Hunan(2025JJ20013)Changsha Natural Science Foundation(kq2402051)。
文摘The development of high-performance electrocatalysts with rapid mass and charge transfer for the hydrogen evolution reaction(HER)at high current densities is critical to enabling practical hydrogen production via alkaline water electrolysis(AWE).Currently,important research advancements have been made in the rational design of ruthenium(Ru)-based electrocatalysts,aiming to satisfy the performance requirements of large-scale electrochemical hydrogen production.A timely summary of recent advances is pivotal for designing next-generation Ru-based electrocatalysts.Herein,we systematically examine key strategies for optimizing their electronic effect and water/bubble behaviors,alongside detailed discussions on recent breakthroughs in integrated Ru-based AWE systems.Furthermore,we outline the remaining bottlenecks and future directions for deploying Ru-based electrocatalysts in commercial applications.
基金supported by the National Natural Science Foundation of China(No.52101251)the Science Research Project of Hebei Education Department(No.BJK2023058)the Natural Science Foundation of Hebei Province(Nos.E2020208069 and B2020208083).
文摘Retaining satisfactory electrocatalytic performance under high current density plays a crucial role in industrial water splitting but is still limited to the enormous energy loss because of insufficient exposure of active sites caused by the blocked mass/charge transportation at this condition.Herein,we present a freestanding lamellar nanoporous Ni-Co-Mn alloy electrode(Lnp-NCM)designed by a refined variant of the“dealloying-coarsening-dealloying”protocol for highly efficient bifunctional electrocatalyst,where large porous channels distribute on the surface and small porous channels at the interlayer.With its 3D lamellar architecture regulating,the electrocatalytic properties of the electrodes with different distances between lamellas are compared,and faster energy conversion kinetics is achieved with efficient bubble transport channels and abundant electroactive sites.Note that the optimized sample(Lnp-NCM4)is expected to be a potential bifunctional electrocatalyst with low overpotentials of 258 and 439 mV at high current densities of 1000 and 900 mA·cm^(-2)for hydrogen and oxygen evolution reactions(HER and OER),respectively.During overall water splitting in a two-electrode cell with Lnp-NCM4 as cathode and anode,it only needs an ultralow cell voltage of 1.75 V to produce 100 mA·cm^(-2)with remarkable long-term stability over 50 h.This study on lamellar nanoporous electrode design approaches industrial water splitting requirements and paves a way for developing other catalytic systems.
基金supported by Multi-Year Research Grants from the University of Macao(MYRG-GRG2023-00010-IAPME,MYRG-GRG2024-00038-IAPME,MYRG2022-00026-IAPME)the Science and Technology Development Fund(FDCT)from Macao SAR(0023/2023/AFJ,0050/2023/RIB2,006/2022/ALC,0087/2024/AFJ,0111/2022/A2).
文摘Photoelectrochemical(PEC)water splitting holds significant promise for sustainable energy harvesting that enables efficient conversion of solar energy into green hydrogen.Nevertheless,achievement of high performance is often limited by charge carrier recombination,resulting in unsatisfactory saturation current densities.To address this challenge,we present a novel strategy for achieving ultrahigh current density by incorporating a bridge layer between the Si substrate and the NiOOH cocatalyst in this paper.The optimal photoanode(TCO/n-p-Si/TCO/Ni)shows a remarkably low onset potential of 0.92 V vs.a reversible hydrogen electrode and a high saturation current density of 39.6 mA·cm^(-2),which is about 92.7%of the theoretical maximum(42.7 mA·cm^(-2)).In addition,the photoanode demonstrates stable operation for 60 h.Our systematic characterizations and calculations demonstrate that the bridge layer facilitates charge transfer,enhances catalytic performance,and provides corrosion protection to the underlying substrate.Notably,the integration of this photoanode into a PEC device for overall water splitting leads to a reduction of the onset potential.These findings provide a viable pathway for fabricating highperformance industrial photoelectrodes by integrating a substrate and a cocatalyst via a transparent and conductive bridge layer.
基金financially supported by the Fundamental Research Funds for the Central Universities of Central South University(No.2022ZZTS0579).
文摘The large current density of electrochemical CO_(2)reduction towards industrial application is challenging.Herein,without strong acid and reductant,the synthesized BiVO_(4)with abundant oxygen vacancies(Ovs)exhibited a high formate Faradaic efficiency(FE)of 97.45%(-0.9 V)and a large partial current density of-45.82 mA/cm^(2)(-1.2 V).The good performance benefits from the reconstruction of BiVO_(4)to generate active metal Bi sites,which results in the electron redistribution to boost the OCHO∗formation.In flow cells,near industrial current density of 183.94 mA/cm^(2)was achieved,with the FE of formate above 95%from 20mA/cm^(2)to 180mA/cm^(2).Our work provides a facily synthesized BiVO_(4)precatalyst for CO_(2)electroreduction.
基金supported by the National Natural Science Foundation of China(Grant No.12304062)supported by the National Natural Science Foundation of China(Grant No.12074107)+1 种基金the Program of Outstanding Young and Middle-aged Scientific and Technological Innovation Teams of Colleges and Universities in Hubei Province(Grant No.T2020001)the Innovation Group Project of the Natural Science Foundation of Hubei Province of China(Grant No.2022CFA012)。
文摘A finite equilibrium current density arises in the anomalous Hall effect(AHE)as a result of time-reversal symmetry breaking,affecting both the differential current density and total current.In this paper,we illustrate the equilibrium current density in a ribbon-shaped system within the AHE regime,consisting of two sets of counterpropagating channels arranged in a zebra stripes pattern.While the middle channels are susceptible to scattering,the edge channels remain relatively robust.Despite this difference,all channels exhibit the same differential current density when subjected to a differential voltage across the two ends of the ribbon.When a differential voltage is applied to both sides of the ribbon,it results in a snaking pattern of differential current density forming across it.Furthermore,in a four-terminal device comprising the ribbon and two normal leads,it is found that Hall conductance is independent of ribbon width within certain scattering strengths due to the differences in robustness between middle and edge channels.These findings disclose the details of the AHE transport in a finite-sized system under weak scattering.
基金supported by the Hunan Joint International Laboratory of Advanced Materials and Technology for Clean Energy(2020CB1007)Fundamental Research Funds for the Central Universities and Guangxi Key Laboratory of Information Materials and Guilin University of Electronic Technology,China(231002-K)+4 种基金Natural Science Foundation of Guangxi Zhuang Autonomous Region(2022GXNSFAA035467)Guangxi Science and Technology Program(Guike AD21220067)National Natural Science Foundation of China(22369002)Nationally Funded Postdoctoral Researcher Program(GZC20230756)China Postdoctoral Science Foundation(2024M750858)。
文摘Lattice-strain engineering has demonstrated its capability to influence the electronic structure and catalytic performance of electrocatalysts.Herein,we present a facile method for inducing thermal strain in cobalt/molybdenum nitride rod-shaped structures(denoted Co/Mo_(2)N)via ammonia-assisted reduction,which effectively modulating the HER performance.The optimized Co/Mo_(2)N-500,characterized by 3%tensile lattice strain,demonstrates exceptional HER activity with lower overpotentials of140 mV and 184 mV at high current density of 1000 mA cm^(-2)in alkaline freshwater and seawater electrolytes,respectively.Co/Mo_(2)N also exhibits excellent long-term durability even at a high current density of 300 mA cm^(-2),surpassing its counterparts and benchmark Pt/C catalyst.Density functional theory calculations validate that the tensile strain optimizes the d-band states,water dissociation,and hydrogen adsorption kinetics of the strained Mo_(2)N in Co/Mo_(2)N,thereby improving its catalytic efficacy.This work provides valuable insights into controlling lattice strain to develop highly efficient electrocatalysts towards advanced electrocatalytic applications.
基金Project(51371039)supported by the National Natural Science Foundation of China
文摘Plasma electrolytic oxidation (PEO) ceramic coatings were fabricated in a silicate-based electrolyte with the addition of potassium fluorozirconate (K2ZrF6) on 6063 aluminum alloy, and the effects of current density on microstructure and properties of the PEO coatings were studied. It was found that pore density of the coatings decreased with increasing the current density. The tribological and hardness tests suggested that the ceramic coating produced under the current density of 15 A/dm2showed the best mechanical property, which matched well with the phase analysis. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization curves proved that the coating obtained under 15 A/dm2 displayed the best anti-corrosion property, which was directly connected with morphologies of coatings.
基金Projects(51004056,51004057)supported by the National Natural Science Foundation of ChinaProject(KKZ6201152009)supported by the Opening Foundation of Key Laboratory of Inorganic Coating Materials,Chinese Academy of Sciences+2 种基金Project(2010ZC052)supported by the Applied Basic Research Foundation of Yunnan Province,ChinaProject(20125314110011)supported by the Specialized Research Fund for the Doctoral Program of Higher Education,ChinaProject(2010247)supported by Analysis&Testing Foundation of Kunming University of Science and Technology,China
文摘Al/conductive coating/α-Pb O2-Ce O2-Ti O2/β-PbO 2-MnO 2-WC-Zr O2 composite electrode material was prepared on Al/conductive coating/α-PbO 2-Ce O2-Ti O2 substrate by electrochemical oxidation co-deposition technique. The effects of current density on the chemical composition, electrocatalytic activity, and stability of the composite anode material were investigated by energy dispersive X-ray spectroscopy（EDXS）, anode polarization curves, quasi-stationary polarization（Tafel） curves, electrochemical impedance spectroscopy（EIS）, scanning electron microscopy（SEM）, and X-ray diffraction（XRD）. Results reveal that the composite electrode obtained at 1 A/dm2 possesses the lowest overpotential（0.610 V at 500 A/m2） for oxygen evolution, the best electrocatalytic activity, the longest service life（360 h at 40 °C in 150 g/L H2SO4 solution under 2 A/cm2）, and the lowest cell voltage（2.75 V at 500 A/m2）. Furthermore, with increasing current density, the coating exhibits grain growth and the decrease of content of Mn O2. Only a slight effect on crystalline structure is observed.
文摘AlAs/GaAs/In0.1Ga0.9As/GaAs/AlAs double-barrier resonant tunneling diodes （DBRTDs） grown on a semi-insulated GaAs substrate with molecular beam epitaxy is demonstrated. By sandwiching the In0.1 Ga0.9 As layer between GaAs layers, potential wells beside the two sides of barrier are deepened, resulting in an increase of the peak-to-valley current ratio （PVCR） and a peak current density. A special shape of collector is designed in order to reduce contact resistance and non-uniformity of the current;as a result the total chrrent density in the device is increased. The use of thin barriers is also helpful for the improvement of the PVCR and the peak current density in DBRTDs. The devices exhibit a maximum PVCR of 13.98 and a peak current density of 89kA/cm^2 at room temperature.
基金supported financially by the Key Project of the National Ministry of Science and Technology (No.2022YFC3705005)the Open Foundation of Key Laboratory of Industrial Ecology and Environmental Engineering,MOE (KLIEEE-22-05)
文摘The electrocatalytic reduction of nitrate to ammonia(NO_(3)^(−)RR)offers a sustainable alternative to energy-intensive industrial NH3 synthesis.Tandem catalysis has shown promise in overcoming the multi-step complexity of NO_(3)^(−)RR,yet challenges remain in optimizing performance and elucidating tandem mechanisms.Herein,we report a Cu@Co/CoFe-P tandem electrocatalyst featuring a phosphorus-doped heterostructure with dual active sites(Cu-P and Co/CoFe-P).This catalyst achieves an exceptional NH_(3)yield of 175.40 mg h^(−1)cm^(−2)and a record-high current density exceeding 2 A cm^(−2),with the electro-synthesized NH3 directly converted into NH4Cl.In situ spectroscopic analysis and density functional theory(DFT)calculations reveal a novel desorption-reactivation tandem mechanism:(1)the Cu-P domain preferentially reduces NO_(3)^(−)to*NO_(2),which desorbs as stable NO_(2)^(−);(2)the Co/CoFe-P domain subsequently reactivates NO_(2)^(−),and converts it efficiently into NH3.Moreover,phosphorus doping enhances*H supply,while Fe alloying with Co promotes NO_(2)^(−)hydrogenation,ensuring an efficient and synchronized tandem pathway for NO_(3)^(−)RR.The proposed*NO_(2)desorption-reactivation mechanism deepens the understanding of NO_(3)^(−)RR tandem process,thereby paving the way for designing more efficient tandem electrocatalysts.
基金financial support from the National Natural Science Foundation of China(No.22478278,22308246)the Central Government Guides the Local Science and Technology Development Special Fund(No.YDZJSX20231A015)the Fundamental Research Program of Shanxi Province(No.202203021212266).
文摘The metallic Ni catalyst suffers from strong binding with the*CO intermediate,resulting in poisoning of the catalyst surface.It is feasible to facilitate the generation of CO by alleviating the binding strength of the*CO intermediate on the Ni metal surface through a lattice expansion strategy.Here,Ni_(3)ZnC_(0.7)@C with lattice expansion was synthesized by co-doping with Zn and interstitial C through high-temperature pyrolysis.Structural characterization confirms that the lattice of Ni_(3)ZnC_(0.7)expands by 5.47%compared to Ni due to the co-doping of Zn and interstitial C.The Ni_(3)ZnC_(0.7)@C possesses excellent catalytic performance with Faradaic efficiency(FE)of CO exceeding 90%over a wide potential range from−0.8 to−1.4 V versus reversible hydrogen electrode(vs.RHE)with a peak FECO of 96.6%at−1.0 V vs.RHE.In membrane electrode assembly(MEA)testing,Ni_(3)ZnC_(0.7)@C achieves a FECO of 81.4%at the industrial-level current density of 400 mA cm^(−2).In situ attenuated total reflection surface-enhanced infrared absorption spectroscopy(ATR-SEIRAS)and density functional theory(DFT)calculations reveal that the co-introduction of Zn and interstitial C in the Ni crystal can significantly promote the desorption of*CO intermediate,which facilitates the generation of CO.This study demonstrates a viable way for designing efficient transition metal catalysts for CO_(2)electroreduction through lattice strain engineering.
基金funding support from Natural Science Foundation of Shanghai(Grant No.23ZR1443900)the National Natural Science Foundation of China(Grant Nos.22178309,22476131 and 22176127)。
文摘Economical,stable,and corrosion-resistant catalytic electrodes are still urgently needed for the oxygen evolution reaction(OER)in water and seawater.Herein,a mild electroless plating strategy is used to achieve large-scale preparation of the“integrated”phosphorus-based precatalyst(FeP-NiP)on nickel foam(NF),which is in situ reconstructed into a highly active and corrosion-resistant(Fe)NiOOH phase for OER.The interaction between phosphate anions(PO_(x)^(y-))and iron ions(Fe^(3+))tunes the electronic structure of the catalytic phase to further enhance OER kinetics.The integrated FeP-NiP@NF electrode exhibits low overpotentials for OER in alkaline water/seawater,requiring only 275/289,320/336,and 349/358 mV to reach 0.1,0.5,and 1.0 A cm^(−2),respectively.The in situ reconstructed PO_(x)^(y-)anion electrostatically repels Cl−in seawater electrolytes,allowing stable operation for over 7 days at 1.0 A cm^(−2) in extreme electrolytes(1.0 M KOH+seawater and 6.0 M KOH+seawater),demonstrating industrial-level stability.This study overcomes the complex synthesis limitations of P-based materials through innovative material design,opening new avenues for electrochemical energy conversion.
基金This study was supported by the Youth Ocean Sience Funds of State Oceanic Administration under contract No. 97301.
文摘The Casulli's difference scheme was introduced into the three-dimensional ocean model in the present paper, and the wind-driven current and thermohaline current were simulated. The results show that, southwesterly monsoon in summer induces a clockwise circulation in the Beibu Gulf, and the density gradient induces a counter-clockwise one; but the density current is more intense than the wind- driven one in summer, espeially in surface layer. In addition, the northeasterly monsoon in winter in- duces a counter-clockwise circulation. The simulated results don't support the traditional condusion that there is a clockwise circulation in the Beibu Gulf in summer and a counter-clockwise one in winter, but support the statement that a counterclockwise circulation exists in the Beibu Gulf all year round.
基金Project(20080505)supported by Science and Technology Department of Jilin Province,China
文摘Oxide coatings were prepared on magnesium alloys in electrolyte solution of Na2SiO3 at different current densities(3,4 and 5 A/cm 2 )with micro-arc oxidation process.X-ray diffractometry(XRD)results show that the oxide coatings formed on magnesium alloys are mainly composed of MgO and MgAl2O4 phases;in addition,the content of MgO increases with increasing the current density.The morphology and surface roughness of the coatings were characterized by confocal laser scanning microscopy (CLSM).The results show that the surface roughness(Ra)decreases with increasing the current density.Moreover,the electrochemical corrosion results prove that the MgO coating produced in the electrolyte Na2SiO3 at current density of 5 A/cm 2 shows the best corrosion resistance.
基金supported by the National Natural Science Foundation of China(21872040)the Hundred Talents Program of Guangxi Universitiesthe Excellent Scholars and Innovation Team of Guangxi Universities。
文摘Developing highly effective and stable non-noble metalbased bifunctional catalyst working at high current density is an urgent issue for water electrolysis(WE).Herein,we prepare the N-doped graphene-decorated NiCo alloy coupled with mesoporous NiCoMoO nano-sheet grown on 3D nickel foam(NiCo@C-NiCoMoO/NF)for water splitting.NiCo@C-NiCoMoO/NF exhibits outstanding activity with low overpotentials for hydrogen and oxygen evolution reaction(HER:39/266 mV;OER:260/390 mV)at±10 and±1000 mA cm^(−2).More importantly,in 6.0 M KOH solution at 60℃ for WE,it only requires 1.90 V to reach 1000 mA cm−2 and shows excellent stability for 43 h,exhibiting the potential for actual application.The good performance can be assigned to N-doped graphene-decorated NiCo alloy and mesoporous NiCoMoO nano-sheet,which not only increase the intrinsic activity and expose abundant catalytic activity sites,but also enhance its chemical and mechanical stability.This work thus could provide a promising material for industrial hydrogen production.
基金supported by the National Natural Science Foundation of China (Grant 11572249)the Aerospace Technology Foundation (Grant N2014KC0068)the Aeronautical Science Foundation of China (Grant N2014KC0073)
文摘In this work, analysis of electromigration-induced void morphological evolution in solder interconnects is performed based on mass diffusion theory. The analysis is conducted for three typical experimentally observed void shapes: circular, ellipse, and cardioid. Void morphological evolution is governed by the competition between the electric field and surface capillary force. In the developed model, both the electric field and capillary force on the void's surface are solved analytically. Based on the mass conversation principle, the normal velocity on the void surface during diffusion is obtained. The void morphological evolution behavior is investigated, and a physical model is developed to predict void collapse to a crack or to split into sub-voids under electric current. It is noted that when the electric current is being applied from the horizontal direction, a circular void may either move stably along the electric current direction or collapse to a finger shape, depending on the relative magnitude of the electric current and surface capillary force. However, the elliptical-shaped void will elongate along the electric current direction and finally collapse to the finger shape. On the other hand, the cardioid-shaped void could bifurcate into two sub-voids when the electric current reaches a critical value. The theoretical predictions agree well with the experimental observations.
