Urea-assisted natural seawater electrolysis is an emerging technology that is effective for grid-scale carbon-neutral hydrogen mass production yet challenging.Circumventing scaling relations is an effective strategy t...Urea-assisted natural seawater electrolysis is an emerging technology that is effective for grid-scale carbon-neutral hydrogen mass production yet challenging.Circumventing scaling relations is an effective strategy to break through the bottleneck of natural seawater splitting.Herein,by DFT calculation,we demonstrated that the interface boundaries between Ni_(2)P and MoO_(2) play an essential role in the selfrelaxation of the Ni-O interfacial bond,effectively modulating a coordination number of intermediates to control independently their adsorption-free energy,thus circumventing the adsorption-energy scaling relation.Following this conceptual model,a well-defined 3D F-doped Ni_(2)P-MoO_(2) heterostructure microrod array was rationally designed via an interfacial engineering strategy toward urea-assisted natural seawater electrolysis.As a result,the F-Ni_(2)P-MoO_(2) exhibits eminently active and durable bifunctional catalysts for both HER and OER in acid,alkaline,and alkaline sea water-based electrolytes.By in-situ analysis,we found that a thin amorphous layer of NiOOH,which is evolved from the Ni_(2)P during anodic reaction,is real catalytic active sites for the OER and UOR processes.Remarkable,such electrode-assembled urea-assisted natural seawater electrolyzer requires low voltages of 1.29 and 1.75 V to drive 10 and600 mA cm^(-2)and demonstrates superior durability by operating continuously for 100 h at 100 mA cm^(-2),beyond commercial Pt/C||RuO_(2) and most previous reports.展开更多
The addition of early transition metals(ETMs)into Fe-based amorphous alloys is practically found to be effective in reducing theα-Fe grain size in crystallization process.In this paper,by using ab initio molecular dy...The addition of early transition metals(ETMs)into Fe-based amorphous alloys is practically found to be effective in reducing theα-Fe grain size in crystallization process.In this paper,by using ab initio molecular dynamics simulations,the mechanism of the effect of two typical ETMs(Nb and W)on nano-crystallization is studied.It is found that the diffusion ability in amorphous alloy is mainly determined by the bonding energy of the atom rather than the size or weight of the atom.The alloying of B dramatically reduces the diffusion ability of the ETM atoms,which prevents the supply of Fe near the grain surface and consequently suppresses the growth ofα-Fe grains.Moreover,the difference in grain refining effectiveness between Nb and W could be attributed to the larger bonding energy between Nb and B than that between W and B.展开更多
The adsorption and diffusion of F2 molecules on pristine graphene are studied by using first-principles calculations.For the diffusion of F2 from molecular state in gas phase to the dissociative adsorption state on gr...The adsorption and diffusion of F2 molecules on pristine graphene are studied by using first-principles calculations.For the diffusion of F2 from molecular state in gas phase to the dissociative adsorption state on graphene surface, a kinetic barrier is identified, which explains the inertness of graphene in molecular F2 at room temperature, and its reactivity with F2 at higher temperatures. Study of the diffusion of F2 molecules on graphene surface determines the energy barrier along the optimal diffusion pathway, which conduces to the understanding of the high stability of fluorographene.展开更多
In this paper, an improved incompressible multi-relaxation-time lattice Boltzmann-front tracking approach is proposed to simulate two-phase flow with a sharp interface, where the surface tension is implemented. The la...In this paper, an improved incompressible multi-relaxation-time lattice Boltzmann-front tracking approach is proposed to simulate two-phase flow with a sharp interface, where the surface tension is implemented. The lattice Boltzmann method is used to simulate the incompressible flow with a stationary Eulerian grid, an additional moving Lagrangian grid is adopted to track explicitly the motion of the interface, and an indicator function is introduced to update the fluid properties accurately. The interface is represented by using a four-order Lagrange polynomial through fitting a set of discrete marker points, and then the surface tension is directly computed by using the normal vector and curvature of the interface. Two benchmark problems, including Laplace's law for a stationary bubble and the dispersion relation of the capillary wave between two fluids are conducted for validation. Excellent agreement is obtained between the numerical simulations and the theoretical results in the two cases.展开更多
Numerical simulation of the mixed convection induced by buoyancy, crystal rotation, and also unbalanced surface tension at the melt-gas interface is conducted by means of the finite volume method in the model of the C...Numerical simulation of the mixed convection induced by buoyancy, crystal rotation, and also unbalanced surface tension at the melt-gas interface is conducted by means of the finite volume method in the model of the Czochralski crystal growth. The role of Marangoni convection in the heat and mass transfer is investigated by the comparison of the models with and without surface tension included, and our results indicate that Marangoni convection plays an important role in the heat and mass transfer near the interface of melt and crystal, and also the convection structure.展开更多
Two-dimensional (2D) multiferroics have attracted increasing interests in basic science and technological fields in recent years.However,most reported 2D magnetic ferroelectrics are based on the d-electron magnetism,w...Two-dimensional (2D) multiferroics have attracted increasing interests in basic science and technological fields in recent years.However,most reported 2D magnetic ferroelectrics are based on the d-electron magnetism,which makes them rather rare due to the empirical d^(0) rule and limits their applications for low magnetic phase transition temperature.In this work,we demonstrate that the ferroelectricity can coexist with the p-electron-induced ferromagnetism without the limitation of d^(0) rule and metallicity in a family of stable 2D MXene-analogous oxynitrides,X_(2)NO_(2) (X = In,Tl).Remarkably,the itinerant character of p electrons can lead to the strong ferromagnetic metallic states.Furthermore,a possible magnetoelectric effect is manifested in a Tl_(2)NO_(2)/WTe_(2) heterostructure through the interface engineering.Our findings provide an alternative possible route toward 2D multiferroics and enrich the concept of ferroelectric metals.展开更多
Emergent Dirac fermion states underlie many intriguing properties of graphene,and the search for them constitutes one strong motivation to explore two-dimensional(2D)allotropes of other elements.Phosphorene,the ultrat...Emergent Dirac fermion states underlie many intriguing properties of graphene,and the search for them constitutes one strong motivation to explore two-dimensional(2D)allotropes of other elements.Phosphorene,the ultrathin layers of black phosphorous,has been a subject of intense investigations recently,and it was found that other group-Va elements could also form 2D layers with similar puckered lattice structure.Here,by a close examination of their electronic band structure evolution,we discover two types of Dirac fermion states emerging in the low-energy spectrum.One pair of(type-I)Dirac points is sitting on high-symmetry lines,while two pairs of(type-II)Dirac points are located at generic k-points,with different anisotropic dispersions determined by the reduced symmetries at their locations.Such fully-unpinned(type-II)2D Dirac points are discovered for the first time.In the absence of spin-orbit coupling(SOC),we find that each Dirac node is protected by the sublattice symmetry from gap opening,which is in turn ensured by any one of three point group symmetries.The SOC generally gaps the Dirac nodes,and for the type-I case,this drives the system into a quantum spin Hall insulator phase.We suggest possible ways to realise the unpinned Dirac points in strained phosphorene.展开更多
基金supported by the Vietnam National University,Ho Chi Minh City (Grant No.TX2024-50-01)partial supported by National Natural Science Foundation of China (Grant No.22209186)。
文摘Urea-assisted natural seawater electrolysis is an emerging technology that is effective for grid-scale carbon-neutral hydrogen mass production yet challenging.Circumventing scaling relations is an effective strategy to break through the bottleneck of natural seawater splitting.Herein,by DFT calculation,we demonstrated that the interface boundaries between Ni_(2)P and MoO_(2) play an essential role in the selfrelaxation of the Ni-O interfacial bond,effectively modulating a coordination number of intermediates to control independently their adsorption-free energy,thus circumventing the adsorption-energy scaling relation.Following this conceptual model,a well-defined 3D F-doped Ni_(2)P-MoO_(2) heterostructure microrod array was rationally designed via an interfacial engineering strategy toward urea-assisted natural seawater electrolysis.As a result,the F-Ni_(2)P-MoO_(2) exhibits eminently active and durable bifunctional catalysts for both HER and OER in acid,alkaline,and alkaline sea water-based electrolytes.By in-situ analysis,we found that a thin amorphous layer of NiOOH,which is evolved from the Ni_(2)P during anodic reaction,is real catalytic active sites for the OER and UOR processes.Remarkable,such electrode-assembled urea-assisted natural seawater electrolyzer requires low voltages of 1.29 and 1.75 V to drive 10 and600 mA cm^(-2)and demonstrates superior durability by operating continuously for 100 h at 100 mA cm^(-2),beyond commercial Pt/C||RuO_(2) and most previous reports.
基金Project supported by the National Key Research and Development Program of China(Grant No.2016YFB0300502)the Shenzhen Municipal Fundamental Science and Technology Research Program,China(Grant No.JCYJ20170815162201821)the Fundamental Research Funds for Central Universities,China(Grant No.31020170QD102)
文摘The addition of early transition metals(ETMs)into Fe-based amorphous alloys is practically found to be effective in reducing theα-Fe grain size in crystallization process.In this paper,by using ab initio molecular dynamics simulations,the mechanism of the effect of two typical ETMs(Nb and W)on nano-crystallization is studied.It is found that the diffusion ability in amorphous alloy is mainly determined by the bonding energy of the atom rather than the size or weight of the atom.The alloying of B dramatically reduces the diffusion ability of the ETM atoms,which prevents the supply of Fe near the grain surface and consequently suppresses the growth ofα-Fe grains.Moreover,the difference in grain refining effectiveness between Nb and W could be attributed to the larger bonding energy between Nb and B than that between W and B.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11664003 and 11474285)the Natural Science Foundation of Guangxi Zhuang Autonomous Region,China(Grant No.2015GXNSFAA139015)the Scientific Research and Technology Development Program of Guilin,China(Grant No.2016012002)
文摘The adsorption and diffusion of F2 molecules on pristine graphene are studied by using first-principles calculations.For the diffusion of F2 from molecular state in gas phase to the dissociative adsorption state on graphene surface, a kinetic barrier is identified, which explains the inertness of graphene in molecular F2 at room temperature, and its reactivity with F2 at higher temperatures. Study of the diffusion of F2 molecules on graphene surface determines the energy barrier along the optimal diffusion pathway, which conduces to the understanding of the high stability of fluorographene.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10872222 and 50921063)the Specialized Research Fund for the Doctoral Program of Higher Education of China(Grant No.20110191110037)the Fundamental Research Funds for the Central Universities,China(Grant Nos.CDJXS11240011 and CDJXS10241103)
文摘In this paper, an improved incompressible multi-relaxation-time lattice Boltzmann-front tracking approach is proposed to simulate two-phase flow with a sharp interface, where the surface tension is implemented. The lattice Boltzmann method is used to simulate the incompressible flow with a stationary Eulerian grid, an additional moving Lagrangian grid is adopted to track explicitly the motion of the interface, and an indicator function is introduced to update the fluid properties accurately. The interface is represented by using a four-order Lagrange polynomial through fitting a set of discrete marker points, and then the surface tension is directly computed by using the normal vector and curvature of the interface. Two benchmark problems, including Laplace's law for a stationary bubble and the dispersion relation of the capillary wave between two fluids are conducted for validation. Excellent agreement is obtained between the numerical simulations and the theoretical results in the two cases.
文摘Numerical simulation of the mixed convection induced by buoyancy, crystal rotation, and also unbalanced surface tension at the melt-gas interface is conducted by means of the finite volume method in the model of the Czochralski crystal growth. The role of Marangoni convection in the heat and mass transfer is investigated by the comparison of the models with and without surface tension included, and our results indicate that Marangoni convection plays an important role in the heat and mass transfer near the interface of melt and crystal, and also the convection structure.
基金This work was supported by the Science and Technology Development Fund(FDCT)from Macao SAR(0081/2019/AMJ,0102/2019/A2,and 0154/2019/A3)。
文摘Two-dimensional (2D) multiferroics have attracted increasing interests in basic science and technological fields in recent years.However,most reported 2D magnetic ferroelectrics are based on the d-electron magnetism,which makes them rather rare due to the empirical d^(0) rule and limits their applications for low magnetic phase transition temperature.In this work,we demonstrate that the ferroelectricity can coexist with the p-electron-induced ferromagnetism without the limitation of d^(0) rule and metallicity in a family of stable 2D MXene-analogous oxynitrides,X_(2)NO_(2) (X = In,Tl).Remarkably,the itinerant character of p electrons can lead to the strong ferromagnetic metallic states.Furthermore,a possible magnetoelectric effect is manifested in a Tl_(2)NO_(2)/WTe_(2) heterostructure through the interface engineering.Our findings provide an alternative possible route toward 2D multiferroics and enrich the concept of ferroelectric metals.
基金supported by NSFC(Grant No.11374009,61574123 and 21373184)the National Key Basic Research Program of China(2012CB825700)+5 种基金SUTD-SRG-EPD2013062Singapore MOE Academic Research Fund Tier 1(SUTD-T1-2015004)A*STAR SERC 122-PSF-0017 and AcRF R-144-000-310-112support by Singapore National Research Foundation under NRF Award No.NRF-NRFF2013-03Special Program for Applied Research on Super Computation of the NSFC-Guangdong Joint Fund(the second phase)support from SR16000 supercomputing resources of the Center for Computational Materials Science,Tohoku University.
文摘Emergent Dirac fermion states underlie many intriguing properties of graphene,and the search for them constitutes one strong motivation to explore two-dimensional(2D)allotropes of other elements.Phosphorene,the ultrathin layers of black phosphorous,has been a subject of intense investigations recently,and it was found that other group-Va elements could also form 2D layers with similar puckered lattice structure.Here,by a close examination of their electronic band structure evolution,we discover two types of Dirac fermion states emerging in the low-energy spectrum.One pair of(type-I)Dirac points is sitting on high-symmetry lines,while two pairs of(type-II)Dirac points are located at generic k-points,with different anisotropic dispersions determined by the reduced symmetries at their locations.Such fully-unpinned(type-II)2D Dirac points are discovered for the first time.In the absence of spin-orbit coupling(SOC),we find that each Dirac node is protected by the sublattice symmetry from gap opening,which is in turn ensured by any one of three point group symmetries.The SOC generally gaps the Dirac nodes,and for the type-I case,this drives the system into a quantum spin Hall insulator phase.We suggest possible ways to realise the unpinned Dirac points in strained phosphorene.