Ab initio study of anisotropic mechanical and electronic properties of strained carbon-nitride nanosheet with interlayer bonding

Due to the noticeable structural similarity and being neighborhood in periodic table of group-IV and-V elemental monolayers,whether the combination of group-IV and-V elements could have stable nanosheet structures with optimistic properties has attracted great research interest.In this work,we performed first-principles simulations to investigate the elastic,vibrational and electronic properties of the carbon nitride(CN)nanosheet in the puckered honeycomb structure with covalent interlayer bonding.It has been demonstrated that the structural stability of CN nanosheet is essentially maintained by the strong interlayerσbonding between adjacent carbon atoms in the opposite atomic layers.A negative Poisson’s ratio in the out-of-plane direction under biaxial deformation,and the extreme in-plane stiffness of CN nanosheet,only slightly inferior to the monolayer graphene,are revealed.Moreover,the highly anisotropic mechanical and electronic response of CN nanosheet to tensile strain have been explored.

A general strategy via photoelectrocatalytic oxygen reduction for generating singlet oxygen with carbon bridged carbon-nitride electrode

With the ever-growing demand of clean water for the healthy world,water purification has become an urgent global issue.Singlet oxygen(^(1)O_(2))as unique non-radical derivative of oxygen,possessing unoccupiedπ*orbital and exhibiting high selectivity towards electron-rich organic pollutants.Nevertheless,most of the approaches suffer from low-efficiency or biotoxicity,which severely restrict their potential applications.Therefore,in this work,we propose a general strategy via photoelectrocatalytic for selectively reducing oxygen to^(1)O_(2)with designed carbon bridged carbon nitride(CBCN).This work highlights the important role of synergistic photo-electro-catalytic effect for selectively generating the^(1)O_(2)via oxygen reduction pathway,which can be a promising way especially for degrading electron-rich pollutants.

Facile synthesis and enhanced photocatalytic H_2-evolution performance of NiS_2-modified g-C_3N_4 photocatalysts

NiS2 is a promising cocatalyst to improve the photocatalytic performance of g-C3N4 for the production of H2.However,the synthesis of the NiS2 cocatalyst usually requires harsh conditions,which risks destroying the microstructures of the g-C3N4 photocatalysts.In this study,a facile and low-temperature（80 ℃） impregnation method was developed to prepare NiS2/g-C3N4 photocatalysts.First,the g-C3N4 powders were processed by the hydrothermal method in order to introduce oxygen-containing functional groups（such as-OH and-C0NH-） to the surface of g-C3N4.Then,the Ni^2＋ ions could be adsorbed near the g-C3N4 via strong electrostatic interaction between g-C3N4 and Ni^2＋ ions upon the addition of Ni（NO3）2 solution.Finally,NiS2 nanoparticles were formed on the surface of g-C3N4 upon the addition of TAA.It was found that the NiS2 nanoparticles were solidly and homogeneously grafted on the surface of g-C3N4,resulting in greatly improved photocatalytic H2production.When the amount of NiS2 was 3 wt%,the resultant NiS2/g-C3N4 photocatalyst showed the highest H2 evolution rate（116.343 μmol h^-1 g^-1）,which is significantly higher than that of the pure g-C3N4（3 μmol h^-1 g^-1）.Moreover,the results of a recycling test for the NiS2/g-C3N4（3 wt%）sample showed that this sample could maintain a stable and effective photocatalytic H2-evolution performance under visible-light irradiation.Based on the above results,a possible mechanism of the improved photocatalytic performance was proposed for the presented NiS2/g-C3N4 photocatalysts,in which the photogenerated electrons of g-C3N4 can be rapidly transferred to the NiS2 nanoparticles via the close and continuous contact between them;then,the photogenerated electrons rapidly react with H2O adsorbed on the surface of NiS2,which has a surficial metallic character and high catalytic activity,to produce H2.Considering the mild and facile synthesis method,the presented low-cost and highly efficient NiS2-modified g-C3N4 photocatalysts would have great potential for practical use in photocatalytic H2 production.

SIMULATION OF WELD THERMAL CYCLE USING THE MODEL OF CARBONITRIDE PARTICLES PRECIPITATION

Based on the chasteal nucleation theory, the kinetic precipitation model of carbon - nitride particles in weld HAZ is proposed. Using the model,welding simulation technology and the quantitative metallo- graphic analysis,the precipitation transformation temperatue (PTT) curve is obtained.The data from the simulated welds are in good apreement with the value that the PTT curves predicated.