Theoretical Study Of Water Gas Shift Reaction On Ir-Fe₃O₄ Catalysts

The water gas shift reaction not only plays an important role in the catalytic industry,but also serves as key reaction in the production of hydrogen.With the evolution of society or science and technology,more and more people are keeping eye on the evolution of energy.At present,fossil fuels still play a significant role in human life.However,with the exploitation of mountainous fossil energy,the storage of fossil energy on the earth cannot be able to meet human needs.In order to satisfy the requirements of human life,scientists began to pay attention to clean energy such as hydrogen energy,solar energy,and wind energy.In many energy sources,hydrogen energy has become a focus attention for its high calorific value,non-pollution,and reproducibility.Fe₃O₄ catalyst is an important catalyst in the water gas shift reaction,and the content of iron on the earth accounts for 4.75%,which ranks the fourth in the earth's crust.Moreover,the iron is extraordinarily inexpensive and accessible to get.This paper mainly studies the Fe₃O₄ catalysts in the water-gas shift reaction,analyzing the adsorption properties of the transition metal elements such as Ir on the catalyst and the reaction mechanism of the water gas shift reaction on the catalyst.The specific content and results are as follows:Firstly,the adsorption sites of a single Ir atom on the Fe₃O₄?111?surface were systematically analyzed,and the most stable adsorption site and adsorption configuration of a single Ir atom on the Fe₃O₄?111?surface was also found.At the same time,the Bader charge analysis was used to analyze the charge transfer between the adsorbed atoms and the termination.It was found that there was a charge transfer between the termination and the adsorbed atoms.The charge transfer direction was related to the electronegativity of the atoms around the adsorbed atoms.In order to study the regularity of the transition metal atoms on the Fe₃O₄ termination,we systematically analyzed the adsorption conditions of the VIII transition metal elements?Ru,Os,Co,Rh,Ir,Ni,Pd,Pt?on the surface.Secondly,the clustering effect of free Ir_x?x=1-4?clusters was studied.The linear Ir2 clusters,the positive triangle Ir₃ clusters and the regular tetrahedral Ir₄ clusters were analyzed.It was found that there exist a positive relationship between adhesion energy and cluster size.The change rule of Ir_x?x=1-4?clusters with the cluster size on the termination was also studied.It was discovered that there was a positive relationship between the adhesion energy of the adsorbed clusters on the surface and the cluster size.The amount of charge transfer calculated by the Bader charge analysis also showed a certain correlation with the cluster size.Then the properties of free and adsorbed Ir_x?x=1-4?clusters were also compared with each other.Finally,the reaction mechanism of water gas shift reaction on the Fe₃O₄?111?termination was studied.The pathway of each elementary reaction on the surface was systematically analyzed.It was found that the OH fragment is the most difficult to dissociate on the Fe_oct2 termination and it is the decisive step for the entire elementary reaction,which can provide the guidance information for the design of the catalyst in the water gas reaction.