Theoretical Simulation Of CO Oxidation In Non Noble Single-Atom Catalysts On 2-D Materials

With the environment pollution getting worse,the transformation and elimination of waste gases become particularly important.The emission of untreated carbon monoxide?CO?is harm to human body and the environment.Also the presence of CO will reduce the activity of catalyst and thus affect the catalytic reaction.At present,the most effective way to eliminate CO is to convert it into carbon dioxide?CO₂?.A large number of theoretical and experimental studies have shown that traditional catalysts such as Au,Pd,Pt,and other noble metals can catalyze CO oxidation,but their high cost and low catalytic efficiency need to be solved urgently.Single atom catalyst?SAC?can dope or support on the substrate materials basing on the atomic levels?including noble and non-noble metals?,which can greatly reduce the cluster problem and significantly improve the activity and catalytic efficiency.In recent years,single atom catalytic systems formed by doping two-dimensional materials and loading metal atoms have been studied extensively.Based on density functional theory?DFT?,the oxidation of CO by two different kinds of single atom catalysts were studied systematically.Details are as follows:?1?Penta-graphene?PG?as a new allotrope of carbon has been studied due to its excellent physical and chemical properties.In order to explore the mechanism of CO oxidation and develop the application of PG in the field of SAC,series of metals doped PG were examined to catalyze CO oxidation with the aid of first-principles calculations.Theoretical calculations show that Fe doped at 3-coordinated carbon site of PG is found favorable with large binding energy of-12.73 eV,more importantly,exhibits high affinity to the CO and O2.Furthermore,CO oxidation via Eley-Rideal?ER?mechanism is prior compare with Langmuir-Hinshelwool?LH?mechanism,the first CO molecule oxidation is the rate-determining step?RDS?with the energy barrier of 0.51 eV,which is comparable with other catalysts.In the case of Fe doped at 4-coordinated carbon site,ER and LH mechanisms are almost the same because of the similar energy barrier?0.60 eV and 0.59 eV?.Compared with other SACs especially graphene and its deravetives,Fe-PG system possesses high catalytic activity for CO oxidation.The results show that CO can be effectively eliminated and transformed by the SAC basis of a new allotrope of carbon.?2?MoS₂ has attracted great attention due to its unique physical,electrical,and optical characteristics and has been used in catalysis field extensively.MoS2 also has been proved to catalyze hydrogen evolution reaction?HER?effectively.To explore its catalytic effect on CO oxidation,a series of metals are choosen to dope into MoS₂ to form SACs.Calculation results show that Al can combine well with MoS2 and have relative strong adsorption ability of O2and CO gases.Al doped MoS₂ is proven to be the most promising SAC.In Eley-Rideal?ER?mechanism,the energy barrier of the rate-determining step?RDS?is as low as 0.19 eV,which is lower than that of Langmuir-Hinshelwool?LH?mechanism?0.39 eV?.Very interestingly,in the last step of the ER mechanism,the second CO₂ cannot be dissociated spontaneously because of the strong interaction between CO2 and Al-MoS2 with the Ead of-0.78 eV,until another O₂ was adsorbed to weaken their interaction resulting in the energy barrier of 0.01 eV.Then the left adsorbed O2 will continue the reaction via ER mechanism.Our results demonstrate that Al-MoS₂ is a promising SAC for CO oxidation.It has positive significance to solve the problem of waste gas pollution.