Theoretical Research And Design Of Low Dimensional Electrocatalytic Hydrogen Evolution Materials

The further deterioration of the global environment puts forward new requirements for environmental protection.Among them,the development of environment-friendly energy technology has aroused great interest.Among all kinds of energy,hydrogen（H₂）energy is the most likely new energy to replace the traditional non-renewable energy because of its high energy density,renewable and low-carbon characteristics.Among many methods for preparing hydrogen,electrolytic water is an effective,simple and clean method for hydrogen production,which has attracted more and more attention.At present,noble metal platinum（Pt）is considered to be the most effective hydrogen evolution reaction（HER）catalyst because of its high exchange current density,stability and small Tafel slope.However,the high cost and scarcity of precious metals limit their further wide application.Therefore,the development of low-cost,efficient and stable non noble metal-based hydrogen evolution electrocatalysts is very important in the field of hydrogen production from electrolytic water.Although researchers have made great efforts in the past few decades,so far,there is still no catalyst that can meet the needs of commercial applications.At present,layered two-dimensional materials stand out among many types of catalysts because of their many advantages.On the other hand,with the continuous improvement of computer performance and the rapid development of relevant theories and numerical algorithms,computing based on first principles plays a more and more important role in scientific research,including the search and design of catalysts.Based on two-dimensional materials and density functional theory,this paper studies and designs a high-efficiency electrocatalyst for electrochemical hydrogen evolution reaction.The specific research contents are as follows:（1）Four doping structures were constructed on the surface of Fe PS₃monolayer,which were boron（B）and carbon（C）instead of phosphorus（P）,Nitrogen（N）and oxygen（O）instead of sulfur（S）.The catalytic activities of the four doped structures were compared,and the effect of doping on the catalytic activity was further discussed.The activity differences of these five systems are explored through density functional theory calculation,and the action mechanism of non-metallic atom doping in the influencing factors of electrocatalytic activity is clarified.It is proved that B and C doping will cause a transformation of Fe PS₃ from semiconductor to metal,which will enhance the conductivity of materials and greatly improve the electrocatalytic activity.（2）The density functional theory is used to calculate the HER properties of Cr Se₂/Sn S₂ transverse heterojunction and Fe Se₂/Ni Se₂transverse heterojunction,study whether the construction of transverse heterojunction can improve the HER properties of these four materials,and further explore the action mechanism of transverse heterojunction.It is found that the transverse heterojunction has the best catalytic activity because a strong charge transfer between the heterogeneous interfaces will cause the charge redistribution between the interfaces,resulting in the obvious improvement of HER performance.（3）Among various surface control methods,defect is also a common and extremely effective means.Sn Se is a typical two-dimensional material.We introduce a Sn hole into the single-layer structure of Sn Se to see the improvement of hydrogen evolution performance by the introduction of Sn hole,and use electron density of states analysis to explore the reason why defective holes improve hydrogen evolution performance.Gibbs free energy shows an obvious decrease of Gibbs free energy on the surface of Sn vacancy.The reason for the decrease is explained by the density of States,which is mainly due to the acceleration of electron transmission efficiency and the improvement of hydrogen evolution performance caused by the introduction of additional electronic states.