Error Mechanism And Application Of Gear Measuring Center Based On VGMC

Ammonia is one of the most important raw materials in human industrial production and agricultural life.The demand for ammonia is also increasing with the rapid development of society.At present,the production of ammonia in the industry depends on the Haber-Bosch process,which requests high temperatures and high pressure by consuming many fossil fuels.Thus,this leads to the serious environment pollution.Energy and environmental issues have become serious in recent years.As a major industrial country,China has been paying attention to environmental protection for a long time.After President Xi proposed"carbon neutrality,emission peak",it is more important to use cleaner and environmentally friendly energy to reduce carbon emissions.Thus,it is important to find a cleaner and environmentally friendly way to synthesize ammonia.At present,the electrocatalytic nitrogen reduction reaction（NRR）can use nitrogen and water as reactants,then use electricity generated from clean energy to synthesize ammonia.It is considered as one of the promising ways of ammonia production and has made great progress in recent years.The main reason why electrocatalytic ammonia synthesis is difficult to achieve large-scale industrial application up to now is that the catalyst used for the reaction is difficult to achieve high activity and high selectivity.The rapid development of two-dimensional materials in recent years shows that they can be widely used in catalysis,energy storage,and other aspects.Thus,starting from the most important catalysts in the electrocatalytic synthesis of ammonia,this paper explores the application of two-dimensional boron-containing materials in the electrocatalytic synthesis of ammonia via density functional theory（DFT）,deeply discusses the mechanism of two-dimensional boron-containing materials catalyzing N₂ and NO synthesis of ammonia with the theoretical calculation,and selects efficient catalysts.It is mainly divided into the following aspects:（1）In the first work,two-dimensional（2D）Mo B was used as a catalyst to explore the feasibility of activating N₂ and synthesizing ammonia.By stripping Al atoms from Mo₂Al B₂,2D Mo B structures were obtained,and N₂ molecules were absorbed at different positions on the surface of Mo Al B.It was found that not only N₂ molecules could be effectively activated but also the adsorption angle and activation degree of N₂ molecules changed with the change in the number of Mo atoms.Then,the reaction process of hydrogen synthesis of ammonia by N₂molecules with different adsorption configurations was studied.When nitrogen molecules coordinate with two Mo atoms,N₂ molecules are adsorbed on the surface of 2D Mo B.The rate-limiting potential of ammonia synthesis is only 0.50 e V,and the rate-limiting potential of hydrogen evolution reaction（HER）reaches 0.57 e V at this time.This indicates that 2D Mo B can effectively promote NRR reactions and inhibit HER reactions.Therefore,2D Mo B is an effective catalyst for the electrocatalytic reduction of N₂ at normal temperature and pressure.（2）According to previous work,we believe that the application of two-dimensional transition metal borides（MBenes）in electrocatalytic ammonia synthesis has high feasibility,considering the extremely strong N≡N bond of N₂ is difficult to be activated.Therefore,NO was used as a nitrogen source,and the feasibility of MBenes（Cr B,Mn B,Mo B,Hf B,and WB）for nitric oxide electrocatalytic ammonia synthesis was studied through theoretical calculations.On the surface of these materials,all NO molecules tend to adsorb on the surface of MBenes in a lateral configuration.Subsequently,the hydrogenation of activated NO molecules to NH₃was explored through association and dissociation.The lowest overpotentials are 0.00 and 0.37 e V for the associated and dissociated paths,which occur on Mn B and WB surfaces,respectively.（3）Considering that the surface structure of MBenes is not perfect in actual production,in this chapter,d-MBenes containing transition metal defects were constructed as catalysts,and researched the coexistence of N₂ and NO on the catalyst surface.The high catalytic activity of d-MBenes enables NO molecules to directly dissociate,and the isolated O atoms generated on the catalyst surface can promote the dissociation of N₂ molecules,change the rate-limiting step of ammonia synthesis and reduce the rate-limiting potential in the subsequent ammonia synthesis process.This work shows that the coexistence of O atoms can promote the dissociation of N₂ and the synthesis of ammonia by nitrogen.（4）Single atom catalyst（SAC）,which can improve the utilization rate of catalysts and improve the efficiency of ammonia production,has been a research focus on electrocatalytic ammonia synthesis in recent years.In this chapter,a monatomic catalyst model of transition metal monitor embedded in h-BN was built,combined with the characteristics of high activity of NO molecules in previous studies.The feasibility of NO as a nitrogen source to synthesize ammonia on its surface was studied.The nitric oxide reduction reaction（NORR）process on M@B₂N₂ was studied by theoretical calculation and all possible reaction paths for the optimal adsorption configuration were discussed.For the NORR reaction process,Pd@B₂N₂ shows the best catalytic activity,and the whole reaction follows the path of*NO→*NOH→*HNOH→*NH→*NH₂→*NH₃,corresponding rate-limiting step is only 0.55 e V.This result points out a way to explore a new method of ammonia synthesis,which can not only achieve ammonia production,but also effectively reduce environmental pollution,and has important application value.