Potential-dependent insights into the origin of high ammonia yield rate on copper surface via nitrate reduction:A computational and experimental study

Focusing on revealing the origin of high ammonia yield rate on Cu via nitrate reduction(NO3RR),we herein applied constant potential method via grand-canonical density functional theory(GC-DFT)with implicit continuum solvation model to predict the reaction energetics of NO3RR on pure copper surface in alkaline media.The potential-dependent mechanism on the most prevailing Cu(111)and the minor(100)and(110)facets were established,in consideration of NO_(2)_(−),NO,NH_(3),NH_(2)OH,N_(2),and N_(2)O as the main products.The computational results show that the major Cu(111)is the ideal surface to produce ammonia with the highest onset potential at 0.06 V(until−0.37 V)and the highest optimal potential at−0.31 V for ammonia production without kinetic obstacles in activation energies at critical steps.For other minor facets,the secondary Cu(100)shows activity to ammonia from−0.03 to−0.54 V with the ideal potential at−0.50 V,which requires larger overpotential to overcome kinetic activation energy barriers.The least Cu(110)possesses the longest potential range for ammonia yield from−0.27 to−1.12 V due to the higher adsorption coverage of nitrate,but also with higher tendency to generate di-nitrogen species.Experimental evaluations on commercial Cu/C electrocatalyst validated the accuracy of our proposed mechanism.The most influential(111)surface with highest percentage in electrocatalyst determined the trend of ammonia production.In specific,the onset potential of ammonia production at 0.1 V and emergence of yield rate peak at−0.3 V in experiments precisely located in the predicted potentials on Cu(111).Four critical factors for the high ammonia yield and selectivity on Cu surface via NO3RR are summarized,including high NO3RR activity towards ammonia on the dominant Cu(111)facet,more possibilities to produce ammonia along different pathways on each facet,excellent ability for HER inhibition and suitable surface size to suppress di-nitrogen species formation at high nitrate coverage.Overall,our work provides comprehensive potential-dependent insights into the reaction details of NO3RR to ammonia,which can serve as references for the future development of NO3RR electrocatalysts,achieving higher activity and selectivity by maximizing these characteristics of copper-based materials.

Vertical plane depth-resolved surface potential and carrier separation characteristics in flexible CZTSSe solar cells with over 12% efficiency

Cu2ZnSn(S,Se)4(CZTSSe)solar cells have resource distribution and economic advantages.The main cause of their low efficiency is carrier loss resulting from recombination of photo-generated electron and hole.To overcome this,it is important to understand their electron-hole behavior characteristics.To determine the carrier separation characteristics,we measured the surface potential and the local current in terms of the absorber depth.The elemental variation in the intragrains(IGs)and at the grain boundaries(GBs)caused a band edge shift and bandgap(Eg)change.At the absorber surface and subsurface,an upward Ec and Ev band bending structure was observed at the GBs,and the carrier separation was improved.At the absorber center,both upward Ec and Ev and downward Ec-upward Ev band bending structures were observed at the GBs,and the carrier separation was degraded.To improve the carrier separation and suppress carrier recombination,an upward Ec and Ev band bending structure at the GBs is desirable.

Ab initio potential energy surface and anharmonic vibration spectrum of NF_(3)^(+)

Potential energy surfaces(PESs), vibrational frequencies, and infrared spectra are calculated for NF_(3)^(+) using ab initio calculations, based on UCCSD(T)/cc-p VTZ combined with vibrational configuration interaction(VCI). Based on an iterative algorithm, the surfaces(SURF) program adds automatic points to the lattice representation of the potential function, the one-dimensional and two-dimensional PESs are calculated after reaching a convergence threshold, finally the smooth image of the potential energy surface is fitted. The PESs accurately account for the interaction between the different modes, with the mode q_(6) symmetrical stretching vibrations having the greatest effect on the potential energy change of the whole system throughout the potential energy surface shift. The anharmonic frequencies are obtained when the VCI matrix is diagonalized. Fundamental frequencies, overtones, and combination bands of NF_(3)^(+) are calculated, which generate the degenerate phenomenon between their frequencies. Finally, the calculated anharmonic frequency is used to plot the infrared spectra.Modal antisymmetric stretching ν_(5) and symmetric stretching ν_(6) exhibit a phenomenon of large-intensity borrowing. This study can provide data to support the characterization in the laboratory.

Impressive strides in amelioration of corrosion behavior of Mg-based alloys through the PEO process combined with surface laser process: A review

The unsatisfactory corrosion properties of Mg-based alloys pose a significant obstacle to their widespread application. Plasma electrolytic oxidation(PEO) is a prevalent and effective coating method that produces a ceramic-like oxide coating on the surface of Mg-based alloys,enhancing their resistance to corrosion. Research has demonstrated that PEO treatment can substantially improve the corrosion performance of alloys based on magnesium in the short term. In an effort to enhance the corrosion resistance of PEO coatings over an extended period of time, researchers have turned their attention to the use of laser processes as both pre-and post-treatments in conjunction with the PEO process. Various laser processes, such as laser shock melting(LSM), laser shock adhesion(LSA), laser shock texturing(LST), and laser shock peening(LSP), have been investigated for their potential to improve PEO coatings on Mg substrates and their alloys. These laser melting processes can homogenize and alter the microstructure of Mg-based alloys while leaving the bulk material unchanged, thereby modifying the substrate surface. However, the porous and rough structure of PEO coatings, with their open and interconnected pore structure, can reduce their long-term corrosion resistance. As such, various laser processes are well-suited for surface modification of these coatings. This study will first examine the PEO process and the various types of laser processes used in this process, before investigating the corrosion behavior of PEO coatings in conjunction with laser pre-and post-treatment processes.

Path-Following Control With Obstacle Avoidance of Autonomous Surface Vehicles Subject to Actuator Faults

This paper investigates the path-following control problem with obstacle avoidance of autonomous surface vehicles in the presence of actuator faults,uncertainty and external disturbances.Autonomous surface vehicles inevitably suffer from actuator faults in complex sea environments,which may cause existing obstacle avoidance strategies to fail.To reduce the influence of actuator faults,an improved artificial potential function is constructed by introducing the lower bound of actuator efficiency factors.The nonlinear state observer,which only depends on measurable position information of the autonomous surface vehicle,is used to address uncertainties and external disturbances.By using a backstepping technique and adaptive mechanism,a path-following control strategy with obstacle avoidance and fault tolerance is designed which can ensure that the tracking errors converge to a small neighborhood of zero.Compared with existing results,the proposed control strategy has the capability of obstacle avoidance and fault tolerance simultaneously.Finally,the comparison results through simulations are given to verify the effectiveness of the proposed method.

Global Potential Energy Surface for the H＋CH4←→H2＋CH3 Reaction using Neural Networks

A globla potential energy surface （PES） for the H＋CH4←→H2＋CH3 reaction has been constructed using the neural networks method based on 47783 high level ab initio geometry points. Extensive quasi-classical trajectories and quantum scattering calculations were carried out to check the convergence of the PES. This PES, fully converged with respect to the fitting procedure and the number of ab initio points, has a very small fitting error, and is much faster on evaluation than the modified Shepard interpolating PES, representing the best available PES for this benchmark polyatomic system.

Theoretical Study on Dissociation Potential Energy Surface of Peroxynitric Acid

The lowest energy structures of peroxynitric acid have been studied with B3LYP/6-311＋ G（2d,2p） method. The potential energy surfaces （PES） along the O-N and O-O bonds have been scanned at CCSD（T）/aug-cc-pVDZ level, respectively. The calculated results show that on the O-N PES, the O3-N4 bond length of the loose transition state is 2.82A^° and the corresponding energy barrier is 25.6 kcal/mol, while on the O-O PES, the loose transition state with of O2-O3 bond length of 2.35A^° has the energy barrier of 37.4 kcal/mol. Thus the primary reaction path for peroxynitric acid is the dissociation into HO2 and NO2.

Effect of Surface Potential Barrier on the Electron Energy Distribution of NEA Photocathodes

By calculating the energy distribution of electrons reaching the photocathode surface and solving the Schrodinger equation that describes the behavior of an electron tunneling through the surface potential barrier,we obtain an equation to calculate the emitted electron energy distribution of transmission-mode NEA GaAs photocathodes. Accord- ing to the equation,we study the effect of cathode surface potential barrier on the electron energy distribution and find a significant effect of the barrier-Ⅰ thickness or end height,especially the thickness,on the quantum efficiency of the cath- ode. Barrier Ⅱ has an effect on the electron energy spread, and an increase in the vacuum level will lead to a narrower electron energy spread while sacrificing a certain amount of cathode quantum efficiency. The equation is also used to fit the measured electron energy distribution curve of the transmission-mode cathode and the parameters of the surface barri- er are obtained from the fitting. The theoretical curve is in good agreement with the experimental curve.

Structure characterization of the oxide film on FGH96 superalloy powders with various oxidation degrees

The structure of the oxide film on FGH96 alloy powders significantly influences the mechanical properties of superalloys.In this study,FGH96 alloy powders with various oxygen contents were investigated using high-resolution transmission electron microscopy and atomic probe technology to elucidate the structure evolution of the oxide film.Energy dispersive spectrometer analysis revealed the presence of two distinct components in the oxide film of the alloy powders:amorphous oxide layer covering the γ matrix and amorphous oxide particles above the carbide.The alloying elements within the oxide layer showed a laminated distribution,with Ni,Co,Cr,and Al/Ti,which was attributed to the decreasing oxygen equilibrium pressure as oxygen diffused from the surface into the γ matrix.On the other hand,Ti enrichment was observed in the oxide particles caused by the oxidation and decomposition of the carbide phase.Comparative analysis of the oxide film with oxygen contents of 140,280,and 340 ppm showed similar element distributions,while the thickness of the oxide film varies approximately at 9,14,and 30 nm,respectively.These findings provide valuable insights into the structural analysis of the oxide film on FGH96 alloy powders.

Sensitivity impacts owing to the variations in the type of zero-range pairing forces on the fission properties using the density functional theory

Using the Skyrme density functional theory,potential energy surfaces of^(240)Pu with constraints on the axial quadrupole and octupole deformations(q_(20)and q_(30))were calculated.The volume-like and surface-like pairing forces,as well as a combination of these two forces,were used for the Hartree–Fock–Bogoliubov approximation.Variations in the least-energy fission path,fission barrier,pairing energy,total kinetic energy,scission line,and mass distribution of the fission fragments based on the different forms of the pairing forces were analyzed and discussed.The fission dynamics were studied based on the timedependent generator coordinate method plus the Gaussian overlap approximation.The results demonstrated a sensitivity of the mass and charge distributions of the fission fragments on the form of the pairing force.Based on the investigation of the neutron-induced fission of^(239)Pu,among the volume,mixed,and surface pairing forces,the mixed pairing force presented a good reproduction of the experimental data.

Generalized Mechanism for the Solid Phase Transition of M_(2)O_(3)(M=Al,Ga)Featuring Single Cation Migration and Martensitic Lattice Transformation

Al_(2)O_(3)and Ga_(2)O_(3)exhibit numerous crystal phases with distinct stabilities and materialproperties.However,the phase transitions among thosematerialsare typicallyundesirable in industrial applications,making it imperative to elucidate the transition mechanisms between these phases.The configurational similarities between Al_(2)O_(3)and Ga_(2)O_(3)allow for the replication of phase transition pathways between these materials.In this study,we investigate the potential phase transition pathway of alumina from the 0-phase to the α-phase using stochastic surface walking global optimization based on global neural network potentials,while extending an existing Ga_(2)O_(3)phase transition path.Through this exploration,we identify a novel single-atom migration pseudomartensitic mechanism,which combines martensitic transformation with single-atom diffusion.This discovery offers valuable insights for experimental endeavors aimed at stabilizing alumina in transitional phases.

LSDA-APF:A Local Obstacle Avoidance Algorithm for Unmanned Surface Vehicles Based on 5G Communication Environment

In view of the complex marine environment of navigation,especially in the case of multiple static and dynamic obstacles,the traditional obstacle avoidance algorithms applied to unmanned surface vehicles(USV)are prone to fall into the trap of local optimization.Therefore,this paper proposes an improved artificial potential field(APF)algorithm,which uses 5G communication technology to communicate between the USV and the control center.The algorithm introduces the USV discrimination mechanism to avoid the USV falling into local optimization when the USV encounter different obstacles in different scenarios.Considering the various scenarios between the USV and other dynamic obstacles such as vessels in the process of performing tasks,the algorithm introduces the concept of dynamic artificial potential field.For the multiple obstacles encountered in the process of USV sailing,based on the International Regulations for Preventing Collisions at Sea(COLREGS),the USV determines whether the next step will fall into local optimization through the discriminationmechanism.The local potential field of the USV will dynamically adjust,and the reverse virtual gravitational potential field will be added to prevent it from falling into the local optimization and avoid collisions.The objective function and cost function are designed at the same time,so that the USV can smoothly switch between the global path and the local obstacle avoidance.The simulation results show that the improved APF algorithm proposed in this paper can successfully avoid various obstacles in the complex marine environment,and take navigation time and economic cost into account.

Experimental investigation of the effects of oil asphaltene content on CO_(2) foam stability in the presence of nanoparticles and sodium dodecyl sulfate

Foam stability tests were performed using sodium dodecyl sulfate(SDS)surfactant and SiO2 nanoparticles as foaming system at different asphaltene concentrations,and the half-life of CO_(2) foam was measured.The mechanism of foam stability reduction in the presence of asphaltene was analyzed by scanning electron microscope(SEM),UV adsorption spectrophotometric concentration measurement and Zeta potential measurement.When the mass ratio of synthetic oil to foam-formation suspension was 1:9 and the asphaltene mass fraction increased from 0 to 15%,the half-life of SDS-stabilized foams decreased from 751 s to 239 s,and the half-life of SDS/silica-stabilized foams decreased from 912 s to 298 s.When the mass ratio of synthetic oil to foam-formation suspension was 2:8 and the asphaltene mass fraction increased from 0 to 15%,the half-life of SDS-stabilized foams decreased from 526 s to 171 s,and the half-life of SDS/silica-stabilized foams decreased from 660 s to 205 s.In addition,due to asphaltene-SDS/silica interaction in the aqueous phase,the absolute value of Zeta potential decreases,and the surface charges of particles reduce,leading to the reduction of repulsive forces between two interfaces of thin liquid film,which in turn,damages the foam stability.

Wind dynamic environment and wind-sand erosion and deposition processes on different surfaces along the Dunhuang–Golmud railway,China

The Dunhuang–Golmud railway passes through different deserts in arid areas,especially drifting-sand desert and sandy-gravel Gobi.The near-surface wind environment and wind-sand transport process vary due to different external factors,such as topography,vegetation,and regional climate,resulting in evident spatial differences in surface erosion and deposition.Consequently,the measures for preventing wind-sand hazards will differ.However,the mechanism and control theory of sand damage remain poorly understood.In this study,we used meteorological observation,three-dimensional(3D)laser scanning,and grain-size analysis to compare and evaluate the spatial distribution of wind conditions,sand erosion and deposition patterns,and grain composition in the drifting-sand desert and sandy-gravel Gobi along the Dunhuang–Golmud railway in China.Results show that the annual mean wind speed,the frequency of sand-driving wind,and the drift potential of sandy-gravel Gobi are higher than those of drifting-sand desert,indicating a greater wind strength in the sandy-gravel Gobi,which exhibits spatial heterogeneity in wind conditions.The major sediment components in sandy-gravel Gobi are very fine sand,fine sand,and medium sand,and that in drifting-sand desert are very fine sand and fine sand.We found that the sediment in the sandy-gravel Gobi is coarser than that in the drifting-sand desert based on mean grain size and sediment component.The spatial distributions of sand erosion and deposition in the sandy-gravel Gobi and drifting-sand desert are consistent,with sand deposition mainly on the west side of the railway and sand erosion on the east side of the railway.The area of sand deposition in the drifting-sand desert accounts for 75.83%of the total area,with a mean deposition thickness of 0.032 m;while the area of sand deposition in the sandy-gravel Gobi accounts for 65.31%of the total area,with a mean deposition thickness of 0.028 m,indicating greater deposition amounts in the drifting-sand desert due to the presence of more fine sediment components.However,the sand deposition is more concentrated with a greater thickness on the embankment and track in the sandy-gravel Gobi and is dispersed with a uniform thickness in the drifting-sand desert.The sand deposition on the track of the sandy-gravel Gobi mainly comes from the east side of the railway.The results of this study are helpful in developing the preventive measures and determining appropriate selection and layout measures for sand control.

Growth behavior and resource potential evaluation of gas hydrate in core fractures in Qilian Mountain permafrost area, Qinghai-Tibet Plateau

The Qilian Mountain permafrost area located in the northern of Qinghai-Tibet Plateau is a favorable place for natural gas hydrate formation and enrichment,due to its well-developed fractures and abundant gas sources.Understanding the formation and distribution of multi-component gas hydrates in fractures is crucial in accurately evaluating the hydrate reservoir resources in this area.The hydrate formation experiments were carried out using the core samples drilled from hydrate-bearing sediments in Qilian Mountain permafrost area and the multi-component gas with similar composition to natural gas hydrates in Qilian Mountain permafrost area.The formation and distribution characteristics of multi-component gas hydrates in core samples were observed in situ by X-ray Computed Tomography(X-CT)under high pressure and low temperature conditions.Results show that hydrates are mainly formed and distributed in the fractures with good connectivity.The ratios of volume of hydrates formed in fractures to the volume of fractures are about 96.8%and 60.67%in two different core samples.This indicates that the fracture surface may act as a favorable reaction site for hydrate formation in core samples.Based on the field geological data and the experimental results,it is preliminarily estimated that the inventory of methane stored in the fractured gas hydrate in Qilian Mountain permafrost area is about 8.67×1013 m3,with a resource abundance of 8.67×108 m3/km2.This study demonstrates the great resource potential of fractured gas hydrate and also provides a new way to further understand the prospect of natural gas hydrate and other oil and gas resources in Qilian Mountain permafrost area.

Surface Characterization and Tribology Behavior of PMMA Processed by Excimer Laser

Polyoxymethylene methacrylate (PMMA) is widely used in ophthalmic biomaterials. Misuse of PMMA in extreme environments is likely to damage the ocular surface and intraocular structures. The surface characterization and tribological behavior of PMMA processed using an excimer laser were investigated in this study by contrasting diferent lubrication conditions and friction cycles. The results show that the roughness of the material surface increases with laser processing, which changes its physical structure. Under lubrication, the laser-treated PMMA exhibits better hydrophilicity, especially during the use of eye drops. No obvious relationship exists between the laser-processing time and friction behavior. However, the laser treatment may contribute to the formation of friction and wear mechanisms of PMMA materials. Laser-treated PMMA in saline solution exhibits better abrasive resistance by showing a lower wear rate than that in eye drops, although it has a higher friction coefcient. In this study, the diferent friction stages in laser-treated PMMA were clarifed under two lubrication conditions. The wear rates of the laser-treated PMMA were found to decrease with the number of cycles, and the friction coefcient has a similar variation tendency. The wear behavior of the laser-treated PMMA is dominated by the main abrasive wear and secondary transferred flm formation. This study provides a theoretical basis for the development and application of ophthalmic biomaterials in complex environments by examining the material surface interface behavior and wear mechanism after laser processing using PMMA as the research matrix.

An accurate analytical surface potential model of heterojunction tunnel FET

Based on the accurate and efficient thermal injection method, we develop a fully analytical surface potential model for the heterojunction tunnel field-effect transistor(H-TFET). This model accounts for both the effects of source depletion and inversion charge, which are the key factors influencing the charge, capacitance and current in H-TFET. The accuracy of the model is validated against TCAD simulation and is greatly improved in comparison with the conventional model based on Maxwell–Boltzmann approximation. Furthermore, the dependences of the surface potential and electric field on biases are well predicted and thoroughly analyzed.

Refinement of an Analytical Approximation of the Surface Potential in MOSFETs

A refinement of an analytical approximation of the surface potential in MOSFETs is proposed by introducing a high-order term. As compared to the conventional treatment with accuracy between 1nV and 0. 03mV in the cases with an oxide thickness tox = 1 ～ 10nm and substrate doping concentration Na = 1015 ～ 1018 cm-3 , this method yields an accuracy within about 1pV in all cases. This is comparable to numerical simulations, but does not require trading off much computation efficiency. More importantly, the spikes in the error curve associated with the traditional treatment are eliminated.

Three-dimensional Potential Energy Surface and Bound States of the Ar2-Ne Complex

The first three-dimensional interaction potential energy surface （PES） of the Ar2-Ne complex is developed using the single and double excitation coupled cluster theory with noniterative treatment of triple excitations CCSD（T）. The aug-cc-pVQZ basis sets are employed for all atoms, including an additional （3s3p2d2flg） set of midpoint bond functions. The calculated single point energies are fitted to an analytic two-dimensional potential model at each of seven fixed rAr~ values. The seven model potentials are then used to construct the three- dimensional PES by interpolating along （r-re） using a sixth-order polynomial. The PES is used in the following rovibrational energy levels calculations. The comparisons of theoretical transition frequencies and spectroscopic constants with the experimental results are given.

The effect of sea surface temperature increase on the potential habitat of Ommastrephes bartramii in the Northwest Pacific Ocean

In the Northwest Pacific Ocean, the squid jigging fisheries from China, Japan and other countries and regions have targeted the west winter-spring cohort of neon flying squid（Ommastrephes bartramii） from August to November since the 1970 s. This squid is a short-lived ecological opportunist with a life-span of about one year,and its population is labile and recruitment variability is driven by the environment or climate change. This variability provides a challenge for ones to forecast the key habitats affected by climate change. The catch data of O. bartramii from Chinese squid jigging fishery and the satellite-derived sea surface temperature（SST） data are used in the Northwest Pacific Ocean from August to November of 1998 to 2004, the SST preferences of O.bartramii corresponding to high values of catch per fishing day（CPUE） are determined and monthly potential habitats are predicted using a histogram analysis of the SST data. The possible changes in the potential habitats of O. bartramii in the Northwest Pacific Ocean are estimated under four climate change scenarios based on the Fourth Assessment Report（AR4） of the Intergovernmental Panel on Climate Change, i.e., 0.5, 1, 2 and 4°C increases in the SST because of the climate change. The results reveal an obvious poleward shift of the potential habitats of O. bartramii in the Northwest Pacific Ocean.