Design of novel transition-metal-doped C_(4)N_(4) as highly effective electrocatalysts for nitrogen fixation with a new intrinsic descriptor

Electrocatalytic nitrogen reduction reaction(NRR) is an efficient and green way to produce ammonia,which offers an alternative option to the conventional Haber-Bosch process.Unfortunately,the large-scale industrial application of NRR processes is still hindered by poor Faraday efficiency and high overpotential,which need to be overcome urgently.Herein,combined with density functional theory and particle swarm optimization algorithm for the nitrogen carbide monolayer structural search(C_mN_(8-m),m=1-7),the surprising discovery is that single transition metal-atom-doped C_(4)N_(4) monolayers(TM@C_(4)N_(4)) could effectively accelerate nitrogen reduction reaction.TM@C_(4)N_(4)(TM=29 transition metals) as single-atom catalysts are evaluated via traditional multi-step screening method,and their structures,NRR activity,selectivity and solvation effect are investigated to evaluate their NRR performance,Through the screening steps,W@C_(4)N_(4) possesses the highest activity for NRR with a very low limiting potential of-0.29 V.Moreover,an intrinsic descriptor φ is proposed with machine learning,which shortens the screening process and provides a new idea for finding efficient SACs.This work not only offers promising catalysts W@C_(4)N_(4) for NRR process but also offers a new intrinsic and universal descriptor φ.

Building up a general selection strategy and catalytic performance prediction expressions of heteronuclear double-atom catalysts for N_(2)reduction

The severe environmental problems and the demand for energy urgently require electrocatalysis to replace Haber-Bosch for the nitrogen reduction reaction(NRR).The descriptors and important properties of single-atom and homonuclear double-atom catalysts have been preliminarily explored,but the relationship between the inherent properties and catalytic activity of heteronuclear double-atom catalysts with better performance remains unclear.Therefore,it is very significant to explore the prediction expressions of catalytic activity of heteronuclear double-atom catalysts based on their inherent properties and find the rule for selecting catalytic centers.Herein,by summarizing the free energy for the key steps of NRR on 55 catalysts calculated through the first-principle,the expressions of predicting the free energy and the corresponding descriptors are deduced by the machine learning,and the strategy for selecting the appropriate catalytic center is proposed.The selection strategy for the central atom of heteronuclear double-atom catalysts is that the atomic number of central B atom should be between group VB and VIIIB,and the electron difference between central A atom and B atom should be large enough,and the selectivity of NRR or hydrogen evolution reaction(HER)could be calculated through the prediction formula.Moreover,five catalysts are screened to have low limiting potential and excellent selectivity,and are further analyzed by electron transfer.This work explores the relationship between the inherent properties of heteronuclear double-atom catalysts and the catalytic activity,and puts forward the rules for selecting the heteronuclear double-atom catalytic center,which has guiding significance for the experiment.

大学生网络交往系统“搭瓣”的设计与实现

目的:很多大学生的学习负担重、业余活动种类与次数少、缺乏同兴趣爱好的圈子。为了丰富大学生的生活,增加大学生交友圈子和活动范围,我们建立了大学生网络交流平台“搭瓣”,让大学生找到志趣相同的人与他们一起学习、旅游、活动,丰富其大学生活。方法:基于用户兴趣和社交信任的聚类推荐,基于位置设计网络的地点推荐和基于双边兴趣的社交网络好友推荐。结果:成功登陆搭瓣系统之后,系统根据大学生所填的真实信息用匹配算法对数据库中已有的大学生进行信息的匹配,将推荐与该大学生志趣相投的人、活动、地点等。结论:大学生网络交往系统“搭瓣”通过好友推荐、地点推荐、兴趣推荐等方式匹配到同一时间去做同一件事的同学,使用简便、便于维护和扩展。

大学生手机使用现状及对睡眠质量的影响

目的:探讨大学生手机使用现状及对睡眠质量的影响状况。方法:应用匹兹堡睡眠量表(PSQI)及手机成瘾量表对银川市某高校300名在校大学生进行调查分析。结果:睡眠量表结果显示,PSQI总分小于等于8的有171人,占84.2%;大于8的有32人,占15.8%。不同性别对睡眠质量影响差异无统计学意义;年级,夜晚使用手机时间,使用后身体状况及手机成瘾性对睡眠质量影响有统计学意义。结论:多数大学生晚上都有长时间使用手机的习惯,使用手机后睡眠质量有所下降。

Rational design of porous carbon allotropes as anchoring materials for lithium sulfur batteries

The shuttle effect seriously impedes the development and practical application of lithium sulfur(Li-S)batteries.It is still a long-term challenge to find effective anchoring materials to hinder the shuttle effect of Li-S batteries.Using carbon allotrope as anchoring materials is an effective strategy to alleviate the shuttling effect.However,the influence factors of carbon allotrope on the adsorption performance of LIPSS at the atomic level are not clear,which limits the application of carbon allotrope in Li-S batteries.Herein,using first-principles simulations,a systematical calculation of carbon allotropes with various ring size(6 ≤S≤16) and shape is conducted to understand the adsorption mechanism.The results show that the T-G monolayers with suitable ring structure and high charge transfer can significantly enhance the interaction between the monolayer and LiPSs,allowing them to have high capacity and high coulombic efficiency.Further diffusion studies show that LiPSs on the T-G monolayer have the low diffusion barriers,which ensures the charging and discharging rate of batteries.Our studies could provide material design principles of carbon allotrope monolayers used as anchoring materials of the high performance Li-S batteries.

Spontaneously enhanced visible-light-driven photocatalytic water splitting of type Ⅱ PG/AlAss van der Waal heterostructure:A first-principles study

To solve the problem of energy scarcity and widespread environmental contamination,it is necessary to design green and low-cost photocatalysts for water splitting.In this paper,a new penta-graphene/AlAs_(5)(PG/AlAss)van der Waals(vdW)heterostructure is proposed and its performance for photocatalytic hydrolysis is calculated using the first-principles method.The findings suggest that the PG/AIAss heterostructure belong to type-ll indirect semiconductor,and the edge position and band gap width of this heterostructure satisfy the requests of redox reaction.Furthermore,the oxidation reaction(OER)on the AIAss side and the hydrogen evolution reaction(HER)on the PG side are thermodynamically spontaneous under different conditions.Surprisingly,the introduction of strain engineering has changed the position of the band edge and light absorption performance of PG/AlAss heterostructure,which is powerful for the performance of photocatalytic water splitting.The PG/AlAs_(5) vdw heterostructure exhibits well visible light absorption intensity without applying strain and biaxial strain of 2%.In conclusion,the findings suggest that the PG/AlAss vdW heterostructure is a prospecting catalyst for visible-light hydrolysis.

Effects of long-term fertilization with different substitution ratios of organic fertilizer on paddy soil

In recent years,the abuse of chemical fertilizers has caused numerous environmental problems,such as soil acidification and compaction.Replacing chemical fertilizers with organic fertilizers can effectively alleviate these problems.However,the effects of alternative organic fertilizers remain unclear.To explore the effects of organic fertilizer substitution on rice yield and paddy soil physicochemical properties and bacterial community structure,we conducted a 5-year experiment using different proportions of organic fertilizer substitution in a double-cropping rice field in Jiangxi,China.Our results showed that replacing chemical fertilizers with organic fertilizers can reduce soil acidification,increase soil organic matter content,nutrient contents,and enzyme activities,improve soil physicochemical properties and microbial community,and enhance soil metabolism.Appropriate organic substitution also had positive effects on rice production.These findings enhance our understanding of the effects of different alternative organic fertilization methods and have important theoretical significance for the promotion of the use of organic fertilizers in the future.

Selectively enhancing radiosensitivity of cancer cells via in situ enzyme-instructed peptide self-assembly

The radiotherapy modulators used in clinic have disadvantages of high toxicity and low selectivity.For the first time,we used the in situ enzyme-instructed self-assembly(EISA)of a peptide derivative(Nap-GDFDFpYSV)to selectively enhance the sensitivity of cancer cells with high alkaline phosphatase(ALP)expression to ionizing radiation(IR).Compared with the in vitro pre-assembled control formed by the same molecule,assemblies formed by in situ EISA in cells greatly sensitized the ALPhigh-expressing cancer cells to y-rays,with a remarkable sensitizer enhancement ratio.Our results indicated that the enhancement was a result of fixing DNA damage,arresting cell cycles and inducing cell apoptosis.Interestingly,in vitro pre-formed assemblies mainly localized in the lysosomes after incubating with cells,while the assemblies formed via in situ EISA scattered in the cell cytosol.The accumulation of these molecules in cells could not be inhibited by endocytosis inhibitors.We believed that this molecule entered cancer cells by diffusion and then in situ self-assembled to form nanofibers under the catalysis of endogenous ALP.This study provides a successful example to utilize intracellular in situ EISA of small molecules to develop selective tumor radiosensitizers.

Rational design of a novel two-dimensional porous metal-organic framework material for efficient benzene sensor

As a common volatile organic compound,benzene(C_(6)H_(6)) exists in home decoration pollution gas widely,which causes great harm to the environment and human health.Therefore,it is necessary to rationally design advanced materials with high selectivity to detect and capture C_(6)H_(6).Herein,combined with the d-band center theory and cohesive energy,a new two-dimensional metal-organic framework material,Ni-doped hexaaminobenzene-based coordination polymer(Ni-HAB-CP)is designed,and its application potential as a C_(6)H_(6) sensor are systematically investigated by using first principles calculation.The result shows that Ni-HAB-CP has a strong adsorption for C_(6)H_(6) without any additional method.In addition,NiHAB-CP can maintain good conductivity before and after adsorption,and C_(6)H_(6) can be easily desorbed from the surface of Ni-HAB-CP by charge control.Moreover,the I-V curve calculated by Atomistix Toolkit(ATK)reveals that Ni-HAB-CP has high sensitivity and selectivity to C_(6)H_(6).Hence,Ni-HAB-CP is expected to be used as a potential material for a highly efficient and recyclable C_(6)H_(6) sensor in the future.The calculation and analysis methods used in this paper could provide a certain theoretical basis and reference for the future research of gas sensors.

Fatigue evaluation of steel-concrete composite deck in steel truss bridge—A case study

An innovative composite deck system has recently been proposed for improved structural performance.To study the fatigue behavior of a steel-concrete composite bridge deck,we took a newly-constructed rail-cum-road steel truss bridge as a case study.The transverse stress history of the bridge deck near the main truss under the action of a standard fatigue vehicle was calculated using finite element analysis.Due to the fact that fatigue provision remains unavailable in the governing code of highway concrete bridges in China,a preliminary fatigue evaluation was conducted according to the fib Model Code.The results indicate that flexural failure of the bridge deck in the transverse negative bending moment region is the controlling fatigue failure mode.The fatigue life associated with the fatigue fracture of steel reinforcement is 56 years.However,while the top surface of the bridge deck concrete near the truss cracks after just six years,the bridge deck performs with fatigue cracks during most of its design service life.Although fatigue capacity is acceptable under design situations,overloading or understrength may increase its risk of failure.The method presented in this work can be applied to similar bridges for preliminary fatigue assessment.

The InSe/g-CN van der Waals hybrid heterojunction as a photocatalyst for water splitting driven by visible light

Designing and developing the highly efficient photocatalysts is full of significance to achieve spontaneous photolysis water.In this work,using the first-principles calculations,we have performed a systematic theoretical study of water splitting photocatalytic activity of the InS e/g-CN heterojunction.It is concluded that the In Se/g-CN heterojunction is a typical type-II semiconductor,whose electrons and holes can be effectively separated.And the potential of the conduction band minimum(CBM)and valence band maximum(VBM)satisfy the requirements for photolysis water.Moreover,the changes of Gibbs free energy(ΔG)of the oxygen evolution reaction(OER)and the hydrogen evolution reaction(HER)are calculated to investigate thermodynamic sustainability of photolysis water.The results show that when pH=7,the potential driving force provided by the InSe/g-CN heterojunction can ensure the spontaneous progress of HER and OER.In addition,it is found that the solar conversion efficiency(η;)of the In Se/g-CN heterojunction is up to 13.7%,which indicates it has broad commercial application prospects.Hence,the In Se/g-CN heterojunction is expected to be an excellent candidate for photolysis water.