Theoretical Study Of Structure Regulation And Photo/electro Catalytic Performance Of Two-dimensional Materials

Energy crisis and environmental pollution prompt people to seek clean and alternative energy sources.If the abundant solar energy can be directly employed or converted into electric energy,it is of practical significance to solve the energy and environmental crisis by means of photochemistry or electrochemistry to promote energy conversion.Water splitting,fuel cells,and metal-air batteries are the key to energy storage and conversion technologies,in which hydrogen evolution,oxygen evolution,and oxygen reduction reactions play a key role.Catalyst is the key to the rate and efficiency of reaction,so it is necessary to rational design and develop catalysts.Based on first-principles method,in view of the wide forbidden band width and low visible light utilization efficiency of photocatalysts and the high cost,activity and selectivity can not be achieved simultaneously of electrocatalysts,through applying strain,electric field,metal,nonmetal,metal-nonmetal hybrid bi-atom,and metal-metal bi-atom anchoring to tune the electronic structure,we investigate and design a series of photocatalysts for hydrogen evolution and oxygen evolution reaction and electrocatalysts for hydrogen evolution,oxygen evolution,and oxygen reduction reaction,and explore the origin of catalytic activity.The main contents and achievements of this paper are summarized as follows:1.Biaxial strain and external electric field can regulate the structure and electronic properties of the catalyst without the introduction of foreign impurities.In this paper,Mn PS₃and Zn PS₃are used as simple models to compare the effect of biaxial strain and applied electric field on photocatalytic water splitting performance.By virtue of their wide band gaps,the photocatalytic ability of Mn PS₃and Zn PS₃for water splitting is subject to narrow visible light adsorption.Our theoretical calculations demonstrate that Mn PS₃under-10%biaxial strain,-5%biaxial strain and a 0.05 V/（?）electric field possess appropriate band gaps and band edge positions required for photocatalytic water splitting as well as pronounced absorbance in the visible and ultraviolet spectrum.Through the free energy change analysis,it is found that water splitting reactions on Mn PS₃under-10%biaxial strain as well as-5%biaxial strain can be thermodynamically spontaneous at p H=7-10 using natural sunlight.The oxygen evolution reaction on Mn PS₃under a 0.05 V/（?）electric field can be thermodynamically spontaneous at p H=7-14 using natural sunlight.Whereas,the band structures for Zn PS₃can not be altered significantly either by applying biaxial strain or electric field.2.Taking g-CN with a large hole and semiconductor properties as a simple model,the effect of 30 kinds of metal atoms anchoring on photocatalytic or electrocatalytic hydrogen evolution reaction performance is researched.It is found that Sc,Ti,V,Co,Ga,Rh,Pd,Ag,Sn,and Au anchored g-CN exhibit catalytic activity comparable to that of benchmark catalyst Pt（111）.Coupling conductivity and hydrogen evolution kinetics analysis,Sc,Ti,V,Ga,Sn,and Au anchored g-CN are considered to be promising hydrogen evolution reaction electrocatalysts under full p H conditions,while Co,Rh,and Pd anchored g-CN show excellent catalytic activity under acidic conditions.Through band structures and Gibbs free energy analysis,it is found that hydrogen evolution reaction on Ti,Ni,Ru,Pd,and Os anchored g-CN can be driven by photogenerated electrons to proceed under full p H conditions.Coupling with visible light absorption and proton reduction kinetics,Ti and Pd anchored g-CN can be regarded as excellent hydrogen evolution reaction photocatalysts.Aided by machine learning technique,it is found that the charge transfer between hydrogen and metal anchored g-CN plays a decisive role and a series of structural characteristics synergistically affect the catalytic activity.3.With the carrier of g-CN possessing a large hole and wide forbidden width characteristics,the effect of anchoring non-metal atoms on photocatalytic/electrocatalytic hydrogen evolution reaction performance is investigated.Coupling band structures and Gibbs free energy analysis,it is found that the hydrogen evolution reaction on B,C,O,Cl,and Br decorated g-CN can proceed spontaneously driven by photogenerated electrons at full p H conditions.In particular,Si decorated g-CN with visible light adsorption and low reaction barrier can be regarded as an excellent metal-free hydrogen evolution reaction photocatalyst.Combined with the conductivity and Gibbs free energy analysis,P decorated g-CN is a metal-free electrocatalyst with a reaction energy barrier of 0.25 e V.The introduction of P/Si with weaker electronegativity than N atoms can tune the coordination environment,and further weaken the strong adsorption for hydrogen on g-CN,rendering the hydrogen releasing process favorable.Taking the P and Si decorated g-CN as substrate,introducing 26 kinds of metal atoms to construct 52 kinds of metal-nonmetal hybrid bi-atom catalysts.Based on stability,Gibbs free energy,and electric conductivity analysis,6 kinds of catalysts including Ir-P,Cr-Si,Mn-Si,Co-Si,Rh-Si,and Au-Si anchored g-CN with better performance than benchmark catalyst Pt（111）are screened out.By means of machine learning technique,it is found that the catalytic activity is mainly influenced by valence electron of metal atoms and the spatial configuration for the adsorbed hydrogen.Based on the screened influential features,a universal prediction equation for metal-nonmetal hybrid bi-atom catalysts in terms of electrocatalytic hydrogen evolution reaction activity is constructed.4.Through high-throughput calculations,with the carrier of g-CN owning a large hole,26 kinds of homonuclear and 253 heteronuclear bi-atom catalysts are constructed,and proving that the catalytic activity and selectivity of hydrogen evolution,oxygen evolution,and oxygen reduction reactions can be tuned by regulating bi-atom combinations.In this study,it is found that homonuclear bi-atom catalysts could only improve hydrogen evolution catalytic activity,but did not significantly promote oxygen evolution or oxygen reduction activity.However,heteronuclear bi-atom catalysts can significantly regulate hydrogen evolution,oxygen evolution,and oxygen reduction reaction activity.Especially,Pd Ni and Ag Pt anchored g-CN possess the almost negligible hydrogen evolution reaction energy barrier,and Au Rh anchored g-CN owns the oxygen reduction reaction overpotential as 0.35 V.The overpotentials for oxygen evolution/oxygen reduction reaction on Ag Pd anchored g-CN are 0.43 and 0.48 V,respectively,whereas Au Co anchored g-CN exhibits trifunctional activities（the overpotentials for hydrogen evolution/oxygen evolution/oxygen reduction reaction are 0.05,0.52,and 0.48V,respectively）.With the help of machine learning technique,the inner relationship between the hydrogen evolution/oxygen evolution/oxygen reduction reaction catalytic activity for bi-atom catalysts and structural properties is revealed,the systems with small metal-metal distances and large metal-nitrogen bond lengths exhibit weak adsorption for reaction intermediates,thus improving reaction catalytic activity.