Study On The Reaction Mechanism Of Graphene-based Single Atom Ni Catalyzed Oxidation Of NO And SO₂

Due to our country’s energy structure with‘rich coal,poor oil and less gas’,coal-fired power generation still occupies a dominant position in our country’s electricity production.The harmful pollutant gases produced in the process of energy and power production are mainly NOx and SOx.The annual emissions of these two types of gases in 2019 were 1.14 million tons and 1.2 million tons,respectively.These pollutant gases have caused great harm to the environment.The existing removal technology in coal-fired power plants has disadvantages such as complex system and large equipment area.Therefore,this article is looking for a new type of catalyst to achieve the catalytic oxidation of NO_x and SO_x in order to improve the processing capacity of existing equipment for NO and SO₂.Based on the first principles and density functional theory,this paper carries out VASP simulation calculations,constructs eleven graphene-based single-atom Ni catalysts,and studies the single/double vacancies and nitrogen-doped graphene-based single-atom Ni catalysts for the adsorption characteristics of NO,NO₂,SO₂ and SO₃.The research results show that the supported Ni atom is the active center of the catalyst,and the catalytic activity of the catalyst can be improved by changing the metal coordinated C atom to N atom.The adsorption energy of the single-vacancy type catalyst increases significantly with the increase of the number of doped N atoms;while in the double-vacancy type catalyst,the adsorption energy changes little with the increase of the number of N atoms.Bader charge analysis shows that Ni atoms act as donors to transfer charges to the graphene substrate and gas during the adsorption process;EDD and PDOS show that the bonding mechanism between Ni and gas in the process of gas adsorption is the result of the combined effect of ionic bonds and covalent bonds.Finally,the thermodynamic analysis is carried out in this paper,and the calculation results show that temperature inhibits gas adsorption.In this paper,four representative graphene-based single-atom Ni catalysts are selected to study the reaction mechanism of NO and SO₂ on the catalysts,namely single-vacancy(Ni _SA/SV),single-vacancy doping with three nitrogen atoms(Ni _SA/SV)-N3),double vacancy(Ni _SA/DV)and double vacancy doping with four nitrogen atoms(Ni _SA/DV-N4)four kinds of catalysts.In the process of transition state exploration,CINEB’s computational simulation method is used,and the Eley-Rideal（E-R）reaction mechanism is mainly used to study the reaction path of NO and SO₂ on the catalyst surface.Combined with the comprehensive analysis of the reaction energy barrier and the reaction heat data,the catalytic effects of the four catalysts on NO are Ni _SA/DV-N4>Ni _SA/DV>Ni _SA/SV>Ni _SA/SV-N3;the catalytic effects of the four catalysts on SO₂are Ni _SA/DV>Ni _SA/DV-N4>Ni _SA/SV>Ni _SA/SV-N3.By researching the reaction mechanism of NO and SO₂ on the surface of the four catalysts,this paper proves that graphene-based single-atom nickel catalysts can catalyze NO and SO₂.This article provides theoretical support for further optimization of the catalyst for the catalytic oxidation of NO and SO₂.