Theoretical Study On Hydrogen Permeability At The Interface Of Vanadium Based Alloys

Hydrogen energy technology involves multiple fields,including hydrogen production,storage,transportation,filling,and fuel cells.The research and development of this technology will promote the application of the entire industry chain,creating many employment opportunities and economic benefits for society.Metal vanadium(V)hydrogen purification is a promising technology for producing high-purity hydrogen,which can effectively remove carbon monoxide,sulfides,and other trace pollutants in hydrogen.At the same time,the relatively low cost and high scalability of metal V hydrogen purification make it suitable for both small-scale fuel cells and large-scale industrial hydrogen production.However,during the hydrogen purification process,V is prone to hydrogen embrittlement and contamination oxidation,which limits its application in the hydrogen purification industry.Studies have shown that depositing a catalytic layer on the surface to form a composite membrane can prevent V surface oxidation and poisoning,and improve the efficiency of hydrogen dissociation and recombination.In order to gain a deeper understanding of the effect of interface formation on hydrogen permeation performance in V-based composite membranes and promote the development of more efficient and stable hydrogen separation technologies,this paper takes V-based matrix as the research object and explores the stability and hydrogen permeation properties of V combined with several materials to form composite interfaces based on first-principles theoretical research methods.The specific research content is as follows:Firstly,in order to better understand the relationship between the interface structure and hydrogen absorption/diffusion properties at the interface between the catalytic palladium(Pd)layer and the metal film,and to explore methods to improve the ability of the alloy film to purify hydrogen,the hydrogen adsorption/diffusion behavior at the Pd/V metal composite membrane interface was explored using a first-principles method based on density functional theory.The results show that the charge at the Pd/V interface increases with Pd/V bonding,causing the dissolution energy of hydrogen atoms(H)to increase as the interface is approached,with the highest dissolution energy near the Pd/V interface.The calculation of hydrogen migration energy barriers shows that compared with the maximum migration barrier(0.64 e V)of H diffusing along the Pd/V interface,the barrier for H diffusing perpendicularly along the Pd/V interface(0.56 e V)is smaller,so H tends to migrate perpendicularly to the Pd/V interface and diffuse from the Pd layer to the V matrix side because the hydrogen dissolution energy(0.238 e V)of the Pd layer at the Pd/V interface is higher than that on the V membrane side(-0.165 e V),and H will accumulate on the V membrane side of the interface,which is prone to hydrogen embrittlement.The calculation of V-based composite membranes doped with Pd/Fe shows that compared with the undoped barrier(0.56 e V),the maximum barrier(0.45/0.54 e V)in the diffusion path of the doped barrier is significantly reduced,which is conducive to hydrogen permeation and diffusion,and the doped interface can to a certain extent inhibit the mutual diffusion of V and catalytic Pd layers,improving the structural stability of the composite membrane.Secondly,depositing copper(Cu)and Pd together on V to form composite hydrogen permeable membranes can solve the problem of hydrogen embrittlement in the Pd membrane and reduce costs.Therefore,in this paper,the cohesive energy,hydrogen solubility,hydrogen permeation,and hydrogen-induced interfacial strength of the two body-centered cubic Pd Cu/V interfaces were studied after Pd/Cu alloying followed by membrane deposition with V,using first-principles calculations.The results show that due to the denser Pd-V bonds in the interface area,the Pd Cu(100)/V(100)interface is more thermodynamically stable than the Pd Cu(110)/V(110)interface,with a lower interface energy and higher separation work.In addition,due to the increased interface charge density,the hydrogen dissolution energy on both sides of the interface is higher than that of the corresponding Pd Cu bulk and V bulk,so the formation of the interface hinders hydrogen dissolution.The maximum diffusion energy barrier of the Pd Cu(100)/V(100)interface is smaller than that of the Pd Cu(110)/V(110)interface,so the hydrogen permeation performance of the Pd Cu(100)/V(100)interface is better.Finally,to explore new,palladium-free catalytic layers for V-based hydrogen permeation membranes,the dissolution energy,adsorption energy,and H diffusion energy barriers of nitrogenized titanium(Ti N)in bulk,surface,and grain boundaries were calculated using density functional theory,to understand the importance of different diffusion processes.The results show that the dissolution energy and diffusion energy barrier of H in Ti N bulk are 2.15 e V and 0.72 e V,respectively,making it difficult for H to diffuse through Ti N bulk.The most stable adsorption position of H on the Ti N(001)surface is the top position connected to Ti atoms,and H can easily diffuse on the Ti N surface along the path connecting Ti atoms.In the grain boundary,the energy barrier for H diffusion along the grain boundary channel is 0.61 e V.When there are N vacancies in the grain boundary,the diffusion energy barrier is greatly reduced to 0.24 e V.Therefore,the main transmission mechanism of H through Ti N nanocrystals prepared by magnetron sputtering on the V surface is diffusion in the grain boundary space.In this paper,the stability and hydrogen permeability characteristics of the composite interface formed by V and several materials are systematically studied through the firstprinciples calculation method,and the basic physical data of this research group project are completed.The preparation provides the necessary theoretical basis.