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Mechanism Research On Adsorption And Catalytic Oxidation Of Hg~0 On Graphene Decorated By Single-atom Catalysts

Posted on:2022-09-11Degree:MasterType:Thesis
Country:ChinaCandidate:S P XuFull Text:PDF
GTID:2491306566975829Subject:Power Engineering and Engineering Thermophysics
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At present,coal-fired power station is the main form of coal consumption in China,and mercury pollution in coal-fired power plant seriously affects the atmospheric environment.Although the existing wet desulfurization technology and electrostatic precipitator can effectively remove Hg2+and Hgp,and the traditional activated carbon injection method and alkaline solution can remove part of elemental mercury(Hg0),but the removal of Hg0 is still very difficult due to the volatility and insoluble of Hg0.Therefore,this paper will try to search a new catalyst to realize the adsorption of Hg0 and catalytic oxidation and improve the removal capacity of existing pollutant removal equipment for Hg0.Based on density functional theory,the adsorption characteristics and catalytic oxidation of Hg0 on graphene based single-atom(Vanadium,Cadmium,Manganese,Cobalt,Palladium,Platinum)catalysts were studied.Firstly,24 kinds of catalyst models were constructed by combining 4 kinds of typical graphene substrates and 6 kinds of metal elements,and then study the adsorption configuration and adsorption energy of Hg0 on 24kinds of graphene based single-atom catalysts.The results showed that the distance between metal atoms and Hg0 after stable adsorption has a good linear relationship with the adsorption energy.The electron transfer analysis showed that Hg0 is the main electron acceptor,and graphene or metal atoms are the main electron donors.During the adsorption process,electrons accumulate between Hg0 and metal atom.The projected density of states analysis showed that the s and d orbitals of Hg0 play a role in the adsorption.The electron localization function analysis showed that the bonding type of Hg0 adsorption is non-covalent bond and the interaction force is van der Waals force which belongs to physical adsorption.The electrostatic potential analysis showed that the larger the positive electrostatic potential region corresponding to the active center is,the larger the adsorption energy is.The Fermi softness can be used as a good descriptor of Hg0 adsorption energy when the electron temperature of 16 kinds of transition metal monatomic catalysts is around 1 K and that of 8 kinds of noble metal monatomic catalysts is around 0.4 K.Secondly,the catalytic oxidation reaction mechanism of Hg0 on 8 kinds of monoatomic Cobalt and Palladium catalysts was studied,the catalytic oxidation reaction paths of Hg0 on different catalysts were calculated,and the structural parameters and reaction energy of each state in the reaction process were analyzed.Eley-Rideal mechanism is the dominant reaction mechanism for the catalytic oxidation of Hg0 on the catalyst.In the reaction process,the first Hg atom attacks the adsorbed oxygen to form the adsorbed mercury oxide,then the second Hg atom participates in the combination to form the chain mercury oxide clusters,and finally the chain mercury oxide clusters desorbed.By comparing the energy of the eight reaction paths,the determination steps of different catalysts in the catalytic oxidation reaction were determined.In addition,the product is easier to desorb on Palladium catalyst,which may have greater potential in practical application.In this paper,theoretical research methods provide effective guidance for the development of efficient graphene based monatomic catalyst for the removal of Hg0.
Keywords/Search Tags:Hg~0, graphene, single-atom catalyst, density functional theory, adsorption properties, catalytic oxidation
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