CO Oxidation Catalyzed By The Metal-embedded Hexagonal Boron Nitride Nanosheet: A First-principles Investigation

With the rapid development of modern industry and transportation industry,a large number of poisonous and harmful substances are discharged into the air,causing great harm to the environment of human survival.CO,one of the main pollutants,is colorless,tasteless,poisonous gas,poisoning people easily.So how to eliminate the CO effectively becomes an urgent matter.At present,one of the most effective methods is by catalytic oxidation,making it valuable and significant for us to search for the cheap and efficient catalyst under the conditions of low temperature.Based on density functional theory,this paper has studied the adsorption properties of different small molecules on metal doped h-BN and the catalytic oxidation of CO in metal doped h-BN system.The main research work and results are as follows:1.Have studied the adsorption properties of small molecules?CO,O₂,NO,SO₂,H₂,H₂S and so on?in Co embedded h-BN system.The research results show that: the Co can change the curvature of the surface of the BN,and the anchored site and the redistribution of the surrounding atom charge,contribute to that some gas molecules,as CO,NO,SO₂,H₂S,will be adsorbed on the top position of Co and its nearest neighbor six element ring.Co-BN showed its good adsorption and activation characteristics for the above several kinds of gas molecules,providing a theoretical basis for the large-scale application of the related energy equipment such as gas sensing element and non-noble metal catalyst for CO catalytic oxidation.2.We investigate the CO catalytic oxidation in the system of Co embedded h-BN.The results indicates that: for the Langmuir-Hinshelwood?LH?mechanism,the first step in catalytic oxidation reaction of CO?CO+O₂?CO₂+O?by overcoming a small energy barrier of 0.17 eV to form an intermediate state OCOO.Then overcome an energy barrier of 0.55 eV to dissociate into CO and O.Lastly,the second CO react with the remaining O atom to form CO₂ and then release out with an energy barrier of 0.16 eV.For the Eley-Rideal?ER?mechanism,the whole energy barrier of the rate-limiting-step is 0.89 eV,the corresponding reaction process is CO+O₂?CO₃.The TER mechanism is that O₂ molecule is activated by two pre-adsorbed CO molecules to form an intermediate OCO-Co-OCO,which the rate-limiting-step is 0.41 eV,the corresponding reaction process is 2CO?ad?+O₂?OCO-Co-OCO.3.We investigate the CO catalytic oxidation in the system of Co embedded h-BN.The results indicates that: under the Eley-Rideal?ER?mechanism,the effect of the catalysts for CO oxidation is very good,and the reaction CO+O₂?CO₃ needs overcome an energy barrier of 0.16 eV to happen,and CO₃?CO₂+O reaction needs to overcome an energy barrier of 0.01 eV.The energy barrier of the rate-limiting-step is 0.19 eV.The reaction is also easy to occur by the LH mechanism,the energy barrier of the rate-limiting-step is little higher than ER mechanism,which is 0.37 eV.The energy barrier of the rate-limiting-step is 0.67 e V via TER mechanism.